the application of measurement science to environmental analytical ... j c... · environmental...

The Application of Measurement Science to Environmental Analytical Chemistry

for Air Quality Studies

Dr Richard J. C. Brown ARCS DIC CChem CSci EurChem FRSC Analytical Science Division

National Physical Laboratory

Submitted for the award of the Doctor of Science degree

from Imperial College London

February 2012

http://www3.imperial.ac.uk/

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Contents

Page no.

Contents 2

Curriculum vitae 3

Preface 5

List of publications submitted 7

D.Sc. statement: The Application of Measurement Science to Environmental Analytical Chemistry for Air Quality Studies

10

- Sub-area: Mercury vapour measurement in ambient air 10

- Sub-area: The chemical composition of particulate matter in ambient air 14

- Sub-area: Novel measurement and data analysis techniques 17

- Summary of personal contributions 19

Reprints of publications submitted 20

Annex: Peer-reviewed publications list a - j

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Curriculum Vitae Name: Dr Richard J. C. Brown ARCS DIC CChem CSci EurChem FRSC Date of Birth: 14th December 1975 Employer: National Physical Laboratory Position: Head of Trace Chemical Analysis & Principal Research Scientist Section: Analytical Science Division E-mail: [email protected] Direct line: 020 8943 6409 Mobile: 07718 195299 Higher Education: 1994-1997 B.Sc. Chemistry (1st class), Imperial College, London. Awarded the Governors’ Prize in Chemistry for the top 1st class degree.

Associate of the Royal College of Science. 1997-2000 PhD Physical Chemistry, Imperial College, London.

Awarded the Final Year Research Prize. Diploma of Imperial College. Summary of professional experience, responsibilities and achievements: National Physical Laboratory (NPL) career history and internal awards:

2000 Joined the Environmental Standards Section at NPL 2002 Promoted to Senior Research Scientist 2004 Promoted to Principal Research Scientist (fastest ever promotion to this position) 2004 Appointed Head of Trace Chemical Analysis • Winner of the Rayleigh award for NPL’s best peer-reviewed paper (2003), & three

times runner-up (2006, 2007 & 2010). • Three times winner of NPL’s Silver Medal for outstanding scientific achievement

(2001, 2005 and 2008) • Winner of the inaugural NPL Measurement Services Innovation Award (2010) • Serco Divisional Commendation for Excelling at Innovation (2011) External awards and positions held:

• Winner of the 34th SAC Silver Medal by the Royal Society of Chemistry (2009). The citation read: “Distinguished for his excellence in the application of measurement science to a variety of analytical chemistry problems. In particular the areas of: environmental analytical chemistry, electroanalysis and SERS”

• Winner of the CITAC Award for the Most Important Paper on Metrology in Chemistry (2008) for pioneering work on providing SI traceability for mercury vapour measurements

• Academic visitor at the then Faculty of Physical Sciences at Imperial College, London (2005-2007)

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Professional qualifications, memberships and designations:

• Fellow of the Royal Society of Chemistry (FRSC) – 2009 (aged 33); RSC member since 1994

• Holder of the European Chemist designation (EurChem) – 2006 • Chartered Chemist (CChem), Chartered Scientist (CSci) – 2005 • Member of the Society of Chemical Industry since 1998 • Member of the EPSRC Peer Review College • Member of the Organising Committee for the 11th International Conference on

Mercury as a Global Pollutant Relevant external committee representation:

• BIPM Consultative Committee for Amount of Substance (CCQM) – UK representative • BIPM CCQM Electrochemical Analysis Working Group – UK representative • BSI EH/2/3, ‘Ambient Atmospheres’ – Secretary • BSI EH/2, ‘Ambient Air’ • CEN/TC264/WG20, ‘Deposition of metals’ – UK representative • CEN/TC264/WG21, ‘Measurement of benzo[a]pyrene in ambient air’ – UK

representative • CEN/TC264/WG25, ‘Measurement of mercury in ambient air’ – Co-convenor • CEN/TC264/WG34, ‘Measurement of anions and cations in ambient air – UK

representative • IUPAC sub-committee on pH measurement – UK representative • Royal Society of Chemistry Electroanalytical Group Committee • Royal Society of Chemistry Analytical Methods Committee • Society of Chemical Industry Electrochemical Technology Group Committee (Past

Treasurer) • EPSRC Peer Review College Publications (2001 to 2012 inclusive):

• Peer reviewed publications: 111 (excluding refereed conference proceedings) • Other publications: 55 (including trade journal articles, NPL reports, conference

proceedings, etc). • Documentary Standards: 8 co-authored CEN standards on air quality measurement • Books: Co-editor of “Mercury: Sources, Applications and Health Impact" to be

published by Nova in 2012. • Book chapters: co-author of “Fundamentals of polymer electrolyte membrane and

direct methanol fuel cell technology” in ‘Functional materials for energy applications’ to be published by Woodhead in 2012.

Peer reviewed journals editorship:

• Editor in chief: The Scientific World Journal – Environmental and Analytical Chemistry Domains (Hindawi)

• Editorial Board member: Analytical Methods (RSC), Environmental Monitoring and Assessment (Springer), The Open Spectroscopy Journal (Bentham).

• Special issue guest editorship: The Scientific World Journal on ‘Emerging measurement techniques for airborne pollutants’

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Preface

Despite improvements in air quality over recent decades, the air we breathe still contains a variety of pollutants at levels that are harmful to human health and environmental sustainability. In particular, air pollution remains a serious problem in highly industrialised and developing countries. In developed countries pollutants such as particulates with their varying chemical compositions, and mercury vapour have emerged as more recent threats to air quality.

As a result of these threats a number of international protocols, national and continental legislations is in place to limit the emissions of pollutants from various processes and their eventual concentration in ambient air. Many countries have therefore established air quality monitoring networks to measure the exposure of their populations to harmful substances in air and to assess compliance with relevant legislation and the effectiveness of abatement policies. Furthermore as the global nature and long range transport of pollutants such as mercury vapour is increasingly recognised, the case for international cooperation becomes even more pressing.

In this context the requirement for a robust measurement science infrastructure becomes even more important in order to:

Ensure measurement methods are appropriate and properly validated;

Ensure measurement results are properly traceable to the SI system of units;

Ensure the quality of the very large data sets produced by air quality studies.

In particular it is clear that measurement science has a role to play in establishing SI traceability of measurement values in order to ensure that air quality data are:

Comparable across measurement locations;

Stable with reference to a fixed point, so trends over time may be properly gauged;

Coherent, so that results made with different measurement methods are comparable.

These requirements are not currently in place universally, and are especially lacking for emerging pollutants and such measurands as the chemical composition of particles and for mercury vapour. Therefore relevant stakeholders, often through government (UK Departments such as BIS and Defra) but also via other NGOs, UK Research Councils and industry, have funded work to address these deficiencies and put in place a measurement research infrastructure to underpin these scientific endeavours. The output of such research undertaken by the candidate forms the basis of this DSc submission. Following the award of BSc and PhD degrees from Imperial College the candidate, Dr Richard J. C. Brown, joined the National Physical Laboratory (NPL) in Teddington in 2000 and has since worked on a variety of analytical chemistry problems such as pH metrology, electroanalytical chemistry, surface enhanced Raman spectroscopy, low reflectance surfaces (resulting in the much-publicised ‘NPL Super Black’) and complex data analysis techniques – making significant contributions to each. However his most important and substantial contributions over the last decade have focussed on the application of measurement science principles to environmental analytical chemistry for air quality studies.

The candidate has published over 110 peer-reviewed papers during this period (not including refereed conference proceedings). He is NPL’s most prolific author of peer-reviewed papers over the last decade. He has also published over 55 non-peer reviewed works (including conference proceedings, NPL reports, and European and International

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documentary standards) and has been a co-author on 8 European standards for air quality measurement which are now adopted across the European Union. This submission concentrates on the 21 most significant peer-reviewed publications over this period of time relating to the overarching theme of the application of measurement science to environmental analytical chemistry for air quality studies.

The candidate’s role in all cases has been to lead the scientific research and the publication of results, lead authoring the majority of the papers. All the papers presented in this portfolio have been led and published by the candidate’s group either exclusively or with minor contributions from collaborators. The experimentally intensive nature of the work means that in most cases this has been delivered by NPL colleagues under the candidate’s direction and supervision. External contributions are highlighted in the relevant text.

The candidate’s work in this area has already received substantial recognition via the Royal Society of Chemistry’s 34th SAC Silver Medal and the 2008 CITAC (Cooperation on International Traceability in Analytical Chemistry) award for the “Most Important Paper on Metrology in Chemistry”. Furthermore, the recent International Benchmarking of NPL’s science (similar to the RAE for universities) overseen by the Royal Society / Royal Academy of Engineering Panel which ensures the quality of NPL’s output, rated Dr Brown’s work as “Internationally Leading” (the top category) for both “Science Quality” and “Impact”. The candidate has also won numerous internal NPL awards for the quality of his work – a considerable achievement when this work is being compared across the whole of NPL’s output, most of which is physics-based.

The 21 publications forming this submission are grouped according to sub-area, of which three are considered: ‘Mercury vapour measurement in ambient air’, ‘The chemical composition of particulate matter in ambient air’, and ‘Novel measurement and data analysis techniques’. (Publications considered particularly significant are marked: , next to the publication’s title.) All of these publications are peer-reviewed, and none of these papers has been used for the purpose of obtaining any other degree. For completeness the candidate’s full peer-reviewed publications list appears in the Annex to this submission following the reprints of the papers submitted for consideration. This provides access to other publications in the environmental analytical chemistry area not offered for examination here, and additionally gives an overview of the candidate’s simultaneous contributions to other scientific fields.

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List of publications submitted

The following list of 21 publications is sorted firstly by subject sub-area (as described in the accompanying statement), then by whether the work is as sole author or as conjoint work, and finally chronologically. Publications considered particularly significant are marked: . Sub-area: Mercury vapour measurement in ambient air Conjoint work: 1) “A practical uncertainty budget for ambient mercury vapour measurement” Brown, R J C; Brown, A S; Yardley, R E; Corns, W T; Stockwell, P B Atmospheric Environment, 2008, 42, 2504–2517 2) “Establishing SI traceability for measurements of mercury vapour” Brown, A S; Brown, R J C; Corns, W T; Stockwell, P B Analyst, 2008, 133, 946-953 3) “Accurate calibration of mercury vapour measurements” Brown, R J C; Brown, A S Analyst, 2008, 133, 1611-1618 4) “Temperature propagation through a mercury vapour calibration source and assessment of possible analytical biases caused by measurement of temperature variations” Brown, R J C; Wang, J; Brown, A S Measurement, 2010, 43, 1291-1298 5) “Elemental mercury vapour in air: the origins and validation of the ‘Dumarey equation’ describing the mass concentration at saturation” Dumarey, R; Brown, R J C; Corns, W T; Brown, A S; Stockwell, P B Accreditation and Quality Assurance, 2010, 15, 409-414 6) “Standardisation of a European measurement method for the determination of total gaseous mercury: results of the field trial campaign and determination of a measurement uncertainty and working range” Brown, R J C; Pirrone, N; van Hoek, C; Sprovieri, F; Fernandez, R; Toté, K Journal of Environmental Monitoring, 2010, 12, 689-695 7) “A novel automatic method for the measurement of mercury vapour in ambient air, and comparison of uncertainty with established semi-automatic and manual methods” Brown, A S; Brown, R J C; Dexter, M A; Corns, W T; Stockwell, P B Analytical Methods, 2010, 2, 954-966 8) “Memory effects on adsorption tubes for mercury vapour measurement in ambient air: elucidation, quantification and strategies for mitigation of analytical bias” Brown, R J C; Kumar, Y; Brown, A S; Kim, K-H Environmental Science & Technology, 2011, 45, 7812–7818

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9) “Field comparison of manual and semi-automatic methods for the measurement of total gaseous mercury in ambient air and assessment of equivalence” Brown, R J C; Kumar, Y; Brown, A S; Dexter, M A; Corns, W T Journal of Environmental Monitoring, 2012, 14, 657-665 Sub-area: The chemical composition of particulate matter in ambient air Conjoint work: 10) “Sample matrix and critical interference effects on the recovery and accuracy of concentration measurements of arsenic in ambient particulate samples using ICP-MS” Brown, R J C; Yardley, R E; Brown, A S; Milton, M J T Journal of Analytical Atomic Spectroscopy, 2004, 19, 703-705 11) “A novel calibration procedure for trace analytical measurements: application to the analysis of polybrominated diphenyl ethers by GC-MS” Brown, A S; Brown, R J C; Robinson, R A Analyst, 2007, 132, 922-928 12) “Twenty-five years of nationwide ambient metals measurement in the United Kingdom: concentration levels and trends” Brown, R J C; Yardley, R E; Muhunthan, D; Butterfield, D M; Williams, M; Woods, P T; Brown, A S; Goddard S L Environmental Monitoring and Assessment, 2008, 142, 127-140 13) “Measurement of anions in ambient particulate matter by ion chromatography: a novel sample preparation technique and development of a generic uncertainty budget” Brown R J C; Edwards, P R Talanta, 2009, 80, 1020-1024 14) “Spatial inhomogeneity of metals in particulate matter on ambient air filters determined by LA-ICP-MS and comparison with acid digestion ICP-MS” Brown, R J C; Jarvis, K E; Disch, B A; Goddard, S L; Brown, A S Journal of Environmental Monitoring, 2009, 11, 2022-2029 15) “Comparison of ED-XRF and LA-ICP-MS with the European reference method for the measurement of metals in ambient particulate matter” Brown, R J C; Jarvis, K E; Disch, B A; Goddard, S L; Adriaenssens, E; Claeys, N Accreditation and Quality Assurance, 2010, 15, 493-502 16) “Spatial inhomogeneity of anions in ambient particulate matter collected on air filters: determination using a drift-corrected ion chromatography technique” Brown, R J C; Keates, A C Talanta, 2011, 84, 918–923

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Sub-area: Novel measurement and data analysis techniques

Sole author work: 17) “Benford's law and the screening of analytical data: the case of pollutant concentrations in ambient air” Brown, R J C Analyst, 2005, 130, 1280-1285 18) “The use of Zipf's law in the screening of analytical data: a step beyond Benford” Brown, R J C Analyst, 2007, 132, 344-349 19) “Comparison of estimated annual emissions and measured annual ambient concentrations of metals in the United Kingdom 1980-2007” Brown, R J C Journal of Environmental Monitoring, 2010, 12, 665-671 Conjoint work: 20) “Using principal component analysis to detect outliers in ambient air monitoring studies” Brown, R J C; Goddard, S L; Brown, A S International Journal of Environmental Analytical Chemistry, 2010, 90, 761-772. 21) “Comparison of averaging techniques for the calculation of the ‘European average exposure indicator’ for particulate matter” Brown, R J C; Woods, P T Journal of Environmental Monitoring, 2012, 14, 165-171.

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D.Sc. Statement: The Application of Measurement Science to Environmental Analytical Chemistry for Air Quality Studies

Sub-area: Mercury vapour measurement in ambient air

Mercury vapour is acknowledged as a particularly important emerging pollutant because of its combined qualities of toxicity and propensity for bioaccumulation in terrestrial and aquatic ecosystems. Furthermore its long-range transport makes it a truly global pollutant. Emitted mainly by fossil fuel combustion there are also a number of other significant sources in developing countries, such as artisan gold production, and in developed countries from crematoria and hazardous waste disposal. Until recently no measurement science infrastructure existed in this area, and the work presented in this section has led the world in underpinning global measurement science and traceability for mercury vapour measurement – in particular to establish confidence in the equation used to describe the concentration of mercury vapour in air, and the saturated mercury vapour in air apparatus, which is used to calibrate all measurements. Conjoint work: 1) “A practical uncertainty budget for ambient mercury vapour measurement” Brown, R J C; Brown, A S; Yardley, R E; Corns, W T; Stockwell, P B Atmospheric Environment, 2008, 42, 2504–2517

This paper presented for the first time a full measurement equation and uncertainty budget for the measurement of mercury in ambient air. This paper outlined all the aspects that need to be considered during this measurement, including the first incidence of discussion of the correctness of the mercury vapour equation used for calibration, and produced estimates of the uncertainty of these components and how they combined to provide an overall uncertainty for the measurement. Since publication it has been extensively cited within the field and has become a template for others to calculate their uncertainty. Our industrial collaborators provided the loan of equipment for this research and were included as co-authors. NPL colleagues performed the experimental work under my direction. 2) “Establishing SI traceability for measurements of mercury vapour” Brown, A S; Brown, R J C; Corns, W T; Stockwell, P B Analyst, 2008, 133, 946-953

This paper won the CITAC (Cooperation on International Traceability in Analytical Chemistry) award for the “Most Important Paper on Metrology in Chemistry”. For the first time it established that the ‘Dumarey’ equation used for calibrating measurement of mercury vapour in air, was consistent with SI traceable mass measurements. This gave air quality practitioners confidence that current and historical measurements were correct. It also showed that those not using the Dumarey equation for the calibration should start doing so, and as such improved global comparability of these measurements. This paper has inspired a flurry of activity surrounding the accuracy of this equation, with attempts to drive the uncertainty of its SI realisation down further, and as a result has been highly cited within the field. Our industrial collaborators provided the loan of equipment for this research and were included as co-authors. Authorship of the paper was led jointly with Dr A. S. Brown. NPL colleagues performed the experimental work under my direction.

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3) “Accurate calibration of mercury vapour measurements” Brown, R J C; Brown, A S Analyst, 2008, 133, 1611-1618

This paper discusses the thermodynamic and kinetic considerations that must be taken into account when using the ‘bell-jar apparatus’ for calibrating measurements of mercury vapour in air, provides the theoretical basis for understanding the operation of the bell-jar, and presents experimental data demonstrating the systematic biases which may be obtained if the bell-jar is used incorrectly. These biases depend on the temperature difference between the mercury vapour in the bell-jar and the syringe used to remove the mercury vapour from the bell-jar, but they may be well in excess of 10% under some operating conditions. The results from this study have been used to propose best practice solutions for mercury vapour calibrations using the bell-jar and have since been adopted as best practice in the air quality field and are now incorporated in European documentary standards (EN 15852 & EN 15853) and are hence used for all measurements of mercury vapour conducted by European air quality Networks. NPL colleagues performed the experimental work under my direction. 4) “Temperature propagation through a mercury vapour calibration source and assessment of possible analytical biases caused by measurement of temperature variations” Brown, R J C; Wang, J; Brown, A S Measurement, 2010, 43, 1291-1298

Following on from previous work on the bell jar calibration apparatus for mercury vapour measurement, this key paper demonstrated theoretically and experimentally that external temperature variations propagate very quickly within mercury vapour calibration apparatus, and thus any internal temperature inhomogeneities may be largely neglected. However the study has shown that the response time of the temperature measuring device used to make readings within the mercury vapour calibration apparatus can impose a bias as a result of the device’s inability to respond quickly to changes in temperature within the mercury vapour calibration apparatus. This work has disseminated further improvements in calibration techniques which have minimised bias and reduced uncertainty on global determinations of mercury vapour. NPL colleagues performed the experimental work under my direction. 5) “Elemental mercury vapour in air: the origins and validation of the ‘Dumarey equation’ describing the mass concentration at saturation” Dumarey, R; Brown, R J C; Corns, W T; Brown, A S; Stockwell, P B Accreditation and Quality Assurance, 2010, 15, 409-414

A key reference text, lead authored by the candidate and in collaboration with Dr Ronny Dumarey, where the original data underpinning the ‘Dumarey’ equation for the saturated mass concentration of mercury in air is summarised and re-analysed and comprehensive validation data is presented. The paper also elucidates deficiencies of other approaches for calculating saturated mercury concentration in air, and sets out the key criteria for using the Dumarey equation accurately. This has provided increased confidence in the comparability of mercury vapour measurements globally and has helped to settle the international debate on the correct equation to use to describe the saturated mass concentration of mercury in air. The co-authors provided commentary on the draft manuscript, but the work was led throughout by the candidate.

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6) “Standardisation of a European measurement method for the determination of total gaseous mercury: results of the field trial campaign and determination of a measurement uncertainty and working range” Brown, R J C; Pirrone, N; van Hoek, C; Sprovieri, F; Fernandez, R; Toté, K Journal of Environmental Monitoring, 2010, 12, 689-695

This collaborative work, led by Dr Brown, described an extensive field trial of co-located automatic mercury vapour measurement instruments, and performed a statistical analysis of the results which a) demonstrated compliance of these instruments with the European Air Quality Directive data quality objectives, b) validated the proposed European standard method, and c) allowed a robust uncertainty budget for the method to be produced. These data were included in the documentary European standard for the measurement of mercury vapour in air (EN 15852) and are now used for all measurements of mercury vapour conducted by European air quality Networks. NPL and collaborative colleagues performed the experimental work under my direction. 7) “A novel automatic method for the measurement of mercury vapour in ambient air, and comparison of uncertainty with established semi-automatic and manual methods” Brown, A S; Brown, R J C; Dexter, M A; Corns, W T; Stockwell, P B Analytical Methods, 2010, 2, 954-966

This paper presented a novel and innovative automatic method for such in situ measurements of mercury vapour in ambient air using atomic fluorescence spectrometry, where calibration, sampling and analysis are all performed fully automatically without manual intervention. This work provided a new, fully validated method, with which to perform air quality assessments that have been adopted by many in the ambient air arena, and also in areas such as continuous emissions monitoring for crematoria and natural gas possessing facilities. The technique allows reduced cost, unattended measurement, with no reduction in measurement quality, thereby making this technique suitable for remote locations. This work was jointly lead-authored with Dr A. S. Brown. Our industrial collaborators provided the loan of equipment for this research and were included as co-authors. 8) “Memory effects on adsorption tubes for mercury vapour measurement in ambient air: elucidation, quantification and strategies for mitigation of analytical bias” Brown, R J C; Kumar, Y; Brown, A S; Kim, K-H Environmental Science & Technology, 2011, 45, 7812–7818

Possible bias in measurements of mercury vapour on adsorption tubes from both short-term and long-term memory effects was highlighted in this work. The origins of the biases were elucidated and strategies for reducing their effect in routine measurements were described. This work has great significance for global measurements made using the trap-and-desorb adsorption tube approach and adds to the understanding of the uncertainty in the measurement and how this may be reduced to ensure better comparability going forward. It has given clear guidance to increase the quantity of mercury collected on these tubes prior to analysis by either increasing sampling rates or increasing sampling time in order to minimise the bias from this effect. These proposal are now in use throughout the relevant UK air quality network. NPL colleagues performed the experimental work under my direction.

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9) “Field comparison of manual and semi-automatic methods for the measurement of total gaseous mercury in ambient air and assessment of equivalence” Brown, R J C; Kumar, Y; Brown, A S; Dexter, M A; Corns, W T Journal of Environmental Monitoring, 2012, 14, 657-665

This key paper has for the first time compared manual and semi-automatic methods for the measurement of total gaseous mercury in ambient air in a field trial. The comparison results have shown that whilst the expected random scatter is present, there was no significant systematic bias between the two methods, whose operational differences have also been outlined and analysed in this work. This has had significant implications for the operation of the mercury vapour measurement network in the UK since it has proved de facto equivalence between the two methods to the standards required by the European Commission, thereby providing the evidence base for the UK to continue manual sampling and analysis at 25 locations across the UK. This has in addition saved the UK approximately £ 500,000 in costs that would have been required to purchase automatic samplers for each monitoring station. Our industrial collaborators provided the loan of equipment for this research and were included as co-authors. NPL colleagues performed the experimental work under my direction.

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Sub-area: The chemical composition of particulate matter in ambient air It has been known for many years that particles in ambient air contain toxic compounds such as ‘heavy’ metals and organic compounds, many of these resulting from anthropogenic sources. The requirement to perform accurate measurements has been brought into sharp focus in recent years with accompanying epidemiological studies that have proven the links between these compounds and damage to human health. Moreover legislation which now limits the allowable concentration of species such as polycyclic aromatic hydrocarbons and ‘heavy’ metals such as Pb, Ni, Cd and As is now in force in Europe. Furthermore new requirements to measure the anionic content of particulate matter have recently emerged, because these are precursors for acid rain, or are formed from other gaseous pollutants such as SO2, NO and NO2 and are of interest when performing particulate matter mass closure studies. Similarly to the case of mercury vapour, rigorous validated measurement procedures have been lacking in this area, and the implications for the accuracy and comparability of air quality data in this arena are serious. The work detailed below has led the field in providing measurement science solutions for many of these issues. Conjoint work: 10) “Sample matrix and critical interference effects on the recovery and accuracy of concentration measurements of arsenic in ambient particulate samples using ICP-MS” Brown, R J C; Yardley, R E; Brown, A S; Milton, M J T Journal of Analytical Atomic Spectroscopy, 2004, 19, 703-705 Arsenic is a key ambient metalloid because of its toxic properties. Its accurate measurement using high-throughput unit resolution inductively coupled plasma-mass spectrometry is a challenge because of the isobaric interference which occurs between 75As and 40Ar35Cl. Because of the mono-isotopic nature of arsenic this is a difficult problem to resolve. Therefore this paper presents a detailed investigation of isobaric and molecular interferences in the measurement of arsenic in complex environmental matrices. It is shown that the positive bias on arsenic recovery data may be due to persistent interferences that may not be completely eliminated by the use of arithmetic corrections or reaction cell strategies but can be removed by careful optimisation of the nebuliser gas flow. Practical solutions to ensure the validity and accuracy of such routine analytical measurements are proposed, and these have been taken forward by many European laboratories performing this measurement, and as a result the work has received a number of citations. Furthermore reference to this issue has been included in the European documentary standard EN 14902, which is followed by all European air quality networks making these measurements. NPL colleagues performed the experimental work under my direction. 11) “A novel calibration procedure for trace analytical measurements: application to the analysis of polybrominated diphenyl ethers by GC-MS” Brown, A S; Brown, R J C; Robinson, R A Analyst, 2007, 132, 922-928

The measurement of polybrominated diphenyl ethers (PBDEs) in ambient air by gas chromatography–mass spectrometry is known to be highly challenging due to existence of the analytes at trace levels and the instability of the higher molecular weight PBDEs. These properties make accurate analysis especially problematic when utilising a low-resolution ‘bench-top’ GC–electron impact (EI) mass spectrometer. This key paper presented a novel

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solution for calibration in these circumstances which involved a ‘mixed calibration procedure’ (a combination of standard addition and working curve calibration) that allowed analyses to be performed that would not be possible using traditional calibration techniques. A full uncertainty analysis of the technique was also developed. The procedure is also applicable to many other environmental analytical situations. This paper was jointly lead-authored with Dr A. S. Brown. NPL colleagues performed the experimental work under my direction. 12) “Twenty-five years of nationwide ambient metals measurement in the United Kingdom: concentration levels and trends” Brown, R J C; Yardley, R E; Muhunthan, D; Butterfield, D M; Williams, M; Woods, P T; Brown, A S; Goddard S L Environmental Monitoring and Assessment, 2008, 142, 127-140

This reference text on ambient metals concentrations in the UK reviewed and provided critical examination of concentrations and trends over a quarter of a century. It is seen as a seminal reference document in the area which has since been cited by many in the field, and received significant publicity in the media – indeed, such reviews are now required by Defra from all operators of UK air quality monitoring networks! Furthermore for the first time the use of principal component analysis for the source apportionment of metals in UK air was presented and this was demonstrated to be a good tool in assessing the effect of abatement legislation on measured concentrations. The co-authors provided comments on draft manuscripts but the work was led throughout by the nominee. 13) “Measurement of anions in ambient particulate matter by ion chromatography: a novel sample preparation technique and development of a generic uncertainty budget” Brown R J C; Edwards, P R Talanta, 2009, 80, 1020-1024

This paper outlined a novel sample preparation technique for extracting the anionic content of particulate matter directly into the eluant solution used for the subsequent ion chromatography analysis. This allowed the dual benefits of increasing the extraction efficiency of the analyte in question and improving the accuracy of low retention time analytes by removal of the ‘water dip’ observed for samples with an aqueous matrix. Furthermore the paper presented the first fully validated uncertainty budget for this measurement, which has since been incorporated into the European technical specification (TR 16269) for this measurement. This is used by all air quality networks in the continent. NPL colleagues performed the experimental work under my direction. 14) “Spatial inhomogeneity of metals in particulate matter on ambient air filters determined by LA-ICP-MS and comparison with acid digestion ICP-MS” Brown, R J C; Jarvis, K E; Disch, B A; Goddard, S L; Brown, A S Journal of Environmental Monitoring, 2009, 11, 2022-2029

This work provided a fundamental understanding of how the possible inhomogeneous distribution of particulate-bound pollutants on sampled ambient air filters may bias measured mass concentration values of the pollutants if sub-sampling of these filters occurs prior to analysis. This is especially a problem when filter-based samples are sub-divided in order to analyse for multiple pollutants by different techniques. For the first time laser ablation ICP-MS was used to profile spatially the distribution of metals on an air filter. Therefore, this study ensured the accuracy of measured pollutant values in ambient air in the context of increasing requirements to maximise the data obtained from air quality networks and sampling campaigns by making analyses for multiple pollutants from the same

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air sample. The best practice guidelines laid down by this paper are used widely in UK filter-based air quality networks and are being increasing taken up in Europe. Our collaborators at Imperial College (Silwood Park) provided the LA-ICP-MS measurements for this study and are therefore included as co-authors. NPL colleagues performed the other experimental work under my direction. 15) “Comparison of ED-XRF and LA-ICP-MS with the European reference method for the measurement of metals in ambient particulate matter” Brown, R J C; Jarvis, K E; Disch, B A; Goddard, S L; Adriaenssens, E; Claeys, N Accreditation and Quality Assurance, 2010, 15, 493-502

This important work presented a comparison study of the measurement of metals in ambient particulate matter collected on air filters, using energy-dispersive X-ray fluorescence (ED-XRF), laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) and wet chemical digestion followed by ICP-MS analysis according to the European ‘reference method’ EN14902. The uncertainty of each analysis has been estimated and compared with the data quality objectives for uncertainty specified in the relevant European air quality legislation. The work has shown that improvements in repeatability and calibration methods for both ED-XRF and LA-ICP-MS would be needed before these methods were truly applicable for routine use in air quality measurements of this type. In particular the lack of independent traceability routes for the non-reference methods was highlighted. This study has fed into the forthcoming revision of the European Air Quality Directive in 2013 in terms of the allowable analytical techniques that may be used. Our collaborators at Imperial College (Silwood Park) and VMM in Belgium provided the LA-ICP-MS and ED-XRF measurements, respectively, for this study and are therefore included as co-authors. NPL colleagues performed the other experimental work under my direction. 16) “Spatial inhomogeneity of anions in ambient particulate matter collected on air filters: determination using a drift-corrected ion chromatography technique” Brown, R J C; Keates, A C Talanta, 2011, 84, 918–923

Similarly to the study presented above for metallic components within particulate matter this work elucidated for the first time the likely variations in the spatial distribution of anions in particulate matter on filters. Importantly this study showed that this distribution was a complex function of particle size, sampler type and sampling time. Best practice solutions were presented for the sub-sampling of these filters in order to minimise bias. This work was incorporated in the relevant European standard describing the measurement of anions in particulate matter and now underpins the operation of these measurements on the UK Particles Network. NPL colleagues performed the experimental work under my direction.

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Sub-area: Novel measurement and data analysis techniques

A feature of multi-site, multi-species air quality networks is that they require very large numbers of analyses, and produce very large and complex data sets: for example the UK Heavy Metals Monitoring Network produces in excess of 19000 independent analytical values every year. With such large data sets there is a pressing need to ensure the quality of the analytical values produced and to determine how best to extract as much information as possible from these data. This is especially difficult since it is usually not possible to examine every value produced individually. Therefore, this requires several different challenges to be addressed:

a) the development and review of new techniques for the production and analysis of traceable analytical data at low concentration levels such as in the air quality arena; b) effective screening of large data sets for outlying data, which may require further investigation; c) new data analysis techniques to add value when expressing and interpreting the data produced.

The publications described below have made significant contributions to these areas, and have set out a framework for ensuring high quality accurate data from air quality networks around the world. Sole author work: 17) “Benford's law and the screening of analytical data: the case of pollutant concentrations in ambient air” Brown, R J C Analyst, 2005, 130, 1280-1285

Benford’s Law is the empirical observation that the digits 1 to 9 are not equally likely to appear as the initial digit in multi-digit numbers. For the first time, this paper demonstrates the application of Benford’s Law to the screening of analytical data, here from air quality networks. The work has shown that even small changes in the deviation of a data set from Benford’s Law may indicate the introduction of errors during data processing. In this way, Benford’s Law provides a sensitive technique for identifying data mishandling in large data sets. This innovative study has provided another data screening technique for analytical chemists and has been cited by the seminal Nigrini ‘Forensics Analytics’ book on the applications of Benford’s Law and other similar phenomena. 18) “The use of Zipf's law in the screening of analytical data: a step beyond Benford” Brown, R J C Analyst, 2007, 132, 344-349

This study advanced the use of Benford’s Law for the analysis of outliers in data sets by using Zipf’s Law – essentially a generalised form of Benford’s Law. It was shown that the advantage of using Zipf’s Law is that it may be ‘calibrated’ to take account of the likely distribution of a validated data set, and therefore is more sensitive to outliers. In the case of pollutant concentrations in ambient air, the multivariate nature of the measurement, and the relationship between the measured values of these multivariate quantities are the characteristics that allow a Zipf’s law approach to data screening to be successful. Furthermore, it was shown that Zipf’s law has advantages over other novel data screening

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techniques in terms of sensitivity and scope. This work therefore presented yet another novel technique for the screening of outlying data values for air quality scientists. 19) “Comparison of estimated annual emissions and measured annual ambient concentrations of metals in the United Kingdom 1980-2007” Brown, R J C Journal of Environmental Monitoring, 2010, 12, 665-671

This paper presented a novel method to compare emissions and measured concentrations of a suite of metals in UK ambient air over the last 28 years. It has provided the first assessment for the ambient air and atmospheric chemistry community of the sensitivity of ambient concentrations to emitted levels, and why this sensitivity may vary between metals and over time. The results presented have helped in the planning of national air quality networks and in assessing the effect on the continuity of data caused by changing monitoring locations. In addition, this work has helped to benchmark the accuracy of national emissions inventories for metals – finding discrepancies for vanadium, which have since been taken up by the UK National Emissions Inventory Team and revised values have been published. Conjoint work 20) “Using principal component analysis to detect outliers in ambient air monitoring studies” Brown, R J C; Goddard, S L; Brown, A S International Journal of Environmental Analytical Chemistry, 2010, 90, 761-772.

This paper outlined a novel method for the detection of possible outliers in multivariate sets of air quality monitoring data, in this case the metals content of ambient particulate matter, using principal component analysis. This technique took advantage of the expected correlation between metals concentrations at individual monitoring sites to produce a summary statistic based on the deviation of each observation from the expected pattern, which can then be interrogated using one-dimensional robust statistical techniques to identify possible outliers. This sophisticated and highly sensitive technique is now in use on the UK Metals and PAH air quality Networks to screen the multivariate data produced prior to publication. The co-authors provided comments on the draft manuscript but the work was led throughout by the nominee. 21) “Comparison of averaging techniques for the calculation of the ‘European average exposure indicator’ for particulate matter” Brown, R J C; Woods, P T Journal of Environmental Monitoring, 2012, 14, 165-171.

The European ‘average exposure indicator’ (AEI) has recently been introduced to assess whole population exposure to PM2.5 in ambient air. This key paper has compared various averaging techniques to calculate the AEI. The results have shown that use of the geometric mean and weighted means in the calculation produces significantly lower AEI values within the required three year averaging periods and slightly lower changes in the AEI value between the three year averaging periods than the use of the arithmetic mean. The results may have significant implications for how the legislation is interpreted across Europe. We expect this study to feed into the forthcoming revision of the European Air Quality Directive in 2013 in order to make the guidance for calculation of the AEI more explicit and comparable across the whole of Europe. The co-author provided comments on the draft manuscript but the work was led throughout by the nominee.

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Summary of personal contributions The range of original and innovative work presented above helps to demonstrate the candidate’s extensive and significant contributions to the application of measurement science to environmental analytical chemistry for air quality studies across a number of years and in a variety of different areas. The work presented in this submission has helped to advance significantly the measurement science base in the air quality arena by:

providing accurate and reliable data to assess the exposure of the general population and the environment to dangerous pollutants where it was previously lacking;

putting in place mechanisms to provide SI traceability for key pollutants, especially mercury vapour, to ensure the comparability of these measurements over time and between locations and to ensure results are coherent regardless of the method of measurement;

developing novel analytical techniques for the measurement of current and emerging pollutants to work towards future improvements in air quality, public health and environmental sustainability;

developing a number of novel data analysis techniques to ensure the accuracy and validity of the very large data sets produced by current air quality measurement networks and analytical instrumentation.

The submission has highlighted, within this overarching theme, three sub-areas: mercury vapour measurement, the chemical composition of particulate matter, and novel measurement and data analysis techniques, where significant contributions to the advancement of the science in these areas have been made. Through these published works the meritorious contributions of the candidate to the field of air pollution studies have been demostrated, in particular the acknowledged world-leading role in ensuring the accuracy and traceability of these measurements in ambient air. The impact of the published work has been considerable, and is demonstrated through the various mechanisms of uptake and impact such that the published work has:

become highly cited in the field

been included in European and International documentary standards that are in use globally

informed policy makers and influenced revision of legislation

stimulated additional research in new areas that have been suggested as a result of the work

been adopted for use in air quality networks in the UK and around Europe The collection of papers presented in support of this submission for the Doctor of Science degree provides evidence of these significant contributions to the application of measurement science to environmental analytical chemistry for air quality over a prolonged period.

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Reprints of publications submitted The following pages contain reprints of the 21 publications submitted for consideration by the candidate. These are arranged in the same order with the same numbering as in the sections above. Each reprint is preceded by a title page giving the number of the publication in the top right-hand corner.

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Annex: Peer-reviewed publications list 111. Assessment of the effect of degradation by atmospheric gaseous oxidants on measured annual average benzo[a]pyrene mass concentrations Brown, R J C; Brown, A S Chemosphere, submitted, 2012 110. Characterization of unidentified particulate components (UPC) in at an urban monitoring station in Seoul, Korea Kim, Y-H; Kim, K-H; Ma, C-J; Shon, Z-H; Park, C G; Song, S-K; Ro, C U; Brown R J C Atmospheric Environment, submitted, 2012 109. Silver-decorated Cylindrical Nanopores: Combining the Third Dimension with Chemical Enhancement for Efficient Trace Chemical Detection with SERS Kodiyath, R; Papadopoulos, T A; Wang, J; Combs, Z A; Li, H; Brown, R J C; Brédas, J-L; Tsukruk V V Journal of Physical Chemistry C, submitted, 2012 108. Comparison of quantification strategies for one-point standard addition calibration: The heteroscedastic case Brown, R J C; Gillam, T P S Measurement, submitted, 2012 107. An Improved Approach for Fabricating Ag/AgCl Electrodes Brewer, P J; Leese, R J; Brown, R J C Electrochimica Acta, submitted, 2012 106. A simple approach for measuring emission patterns of vapour phase mercury from soil under temperature-controlled conditions Kim, K-H; Yoon, H-O; Jung, M-C; Oh, J-M; Brown, R J C Atmospheric Environment, submitted, 2012. 105. Principal component analysis as an outlier detection tool for polycyclic aromatic hydrocarbon concentrations in ambient air Brown, R J C; Brown, A S Water, Air & Soil Pollution, submitted, 2012. 104. Distribution, sources, and association of PAHs, black carbon, and total organic carbon in size-segregated soil samples along a background-urban-rural transect in Delhi, India Ray, S; Khillare, P S; Kim, K-H; Brown R J C Environmental Engineering Science, submitted, 2012. 103. Current status of trace metal pollution in soils affected by industrial activities Kabir, E; Ray, S; Kim, K-H; Kim, Y-S; Cho, Y-S; Yoon, H-O; Yun, S-T; Brown, R J C The Scientific World Journal, in press, 2012. 102. Comparison of averaging techniques for the calculation of the ‘European Average Exposure Indicator’ for particulate matter Brown, R J C; Woods, P T Journal of Environmental Monitoring, 2012, 14 (1), 165-171. doi:10.1039/C1EM10751H 101. Field comparison of manual and semi-automatic methods for the measurement of total gaseous mercury in ambient air and assessment of equivalence Brown, R J C; Kumar, Y; Brown, A S; Dexter, M A; Corns, W T Journal of Environmental Monitoring, 2012, 14 (2), 657-665. doi:10.1039/C2EM10719H.

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100. Some insights into the relationship between urban air pollution and noise levels Ho, D X; Kim, K-H; Brown, R J C; Park, C K; Ryu, I C Atmospheric Environment, submitted, 2012. 99. Partitioning of dioxins (PCDDs/Fs) in ambient air at four urban residential locations in Seoul, Korea Rahman, M M; Shon, Z-H; Ma, C-J; Brown, R J C; Pandey, S K; Park, C G; Kim, K H Chemosphere, submitted, 2012. 98. Correlations in polycyclic aromatic hydrocarbon concentrations in UK ambient air and implications for source apportionment Brown, A S; Brown, R J C Journal of Environmental Monitoring, submitted, 2012. 97. Comparison of quantification strategies for one-point standard addition calibration: the homoscedastic case Brown, R J C; Gillam, T P S Analytica Chimica Acta, 2012, 716, 108-111. doi:10.1016/j.aca.2011.12.041 96. On the generalised case of sequential standard addition calibration Brown, R J C; Gillam, T P S Chemometrics and Intelligent Laboratory Systems, 2012, 110, 97-101. doi:10.1016/j.chemolab.2011.10.004 95. An investigation of calibration materials for the measurement of metals in ambient particulate matter on filters by LA-ICP-MS Brown, R J C; Jarvis, K E; Disch, B A; Goddard, S L International Journal of Environmental Analytical Chemistry, in press, 2012. doi:10.1080/03067319.2011.592950 94. Emerging measurement techniques for airborne pollutants Brown, R J C; Kim, K-H. The Scientific World Journal, 2011, 11, 2599-2601. doi:10.1100/2011/274710. 93. SERS Effects in Silver-Decorated Cylindrical Nanopores Kodiyath, R; Wang, J; Combs, Z A; Chang, S; Gupta, M K; Anderson, K D; Brown, R J C; Tsukruk, V V Small, 2011, 7 (24), 3452-3457. doi:10.1002/smll.201101936. 92. Influence of fabrication procedure on the electrochemical performance of Ag/AgCl reference electrodes Stoica, D; Brewer, P J; Brown, R J C; Fisicaro, P Electrochimica Acta, 2011, 56 (27), 10009-10015. doi:10.1016/j.electacta.2011.08.089 91. The modern paradox of unregulated cooking activities and indoor air quality Kim, K-H; Pandey, S K; Kabir, E; Susaya, J; Brown, R J C Journal of Hazardous Materials, 2011, 195, 1-10. doi:10.1016/j.jhazmat.2011.08.037 90. Sensitivities of Key Parameters in the Preparation of Silver / Silver Chloride Electrodes used in Harned Cell Measurements of pH Brewer, P J; Stoica, D; Brown, R J C Sensors, 2011, 11 (8), 8072-8084. doi:10.3390/s110808072 89. Memory effects on adsorption tubes for mercury vapour measurement in ambient air: elucidation, quantification and strategies for mitigation of analytical bias Brown, R J C; Kumar, Y; Brown, A S; Kim, K-H Environmental Science & Technology, 2011, 45 (18), 7812–7818. doi:10.1021/es201454u

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88. A review of techniques for the determination of polycyclic aromatic hydrocarbons (PAHs) in air Pandey, S K; Kim, K-H; Brown, R J C Trends in Analytical Chemistry, 2011, 30 (11), 1716-1739. doi:10.1016/j.trac.2011.06.017 87. Comment on “Recommendations on quantities, symbols and measurement units for publications in ACQUAL: preparation of tables and graphs” Brown, R J C Accreditation and Quality Assurance, 2011, 16, 271-272. doi:10.1007/s00769-011-0758-1. 86. Application of a GaPO4 microbalance for the detection of coke formation in high temperature reactors and solid oxide fuel cells Millichamp, J; Brandon, N P; Brown, R J C; Kalyvas, C; Manos, G; Brett, D J L Industrial & Engineering Chemistry Research, 2011, 50 (13), 8371–8375. doi:10.1021/ie200188z 85. Improvements to standard methodologies for the analytical determination of metals in stationary-source emissions samples Brown, R J C; Goddard, S L; Blakley, K C; Brown, A S Journal of the Air and Waste Management Association, 2011, 61, 764-770. doi:10.3155/1047-3289.61.7.1 84. Optimised determinations of water in ethanol by encoded photometric near-infrared spectroscopy: a special case of sequential standard addition calibration Brown, R J C; Keates, A C; Brown, A S Analytical Chimica Acta, 2011, 690, 47-52. doi:10.1016/j.aca.2011.02.002. 83. Comparison of the extrapolation precision of sequential and conventional standard addition calibrations Brown, R J C Measurement, 2011, 44, 1487-1490. doi:10.1016/j.measurement.2011.05.005. 82. Spatial inhomogeneity of anions in ambient particulate matter collected on air filters: determination using a drift-corrected ion chromatography technique Brown, R J C; Keates, A C Talanta, 2011, 84, 918–923. doi:10.1016/j.talanta.2011.02.032. 81. A study or relative performance between direct injection and thermal desorption for several volatile organic acids and reference VOCs by gas chromatography – mass spectrometry Kim, K-H; Susaya, J; Sohn, J. R; Brown, R J C Fresenius Environmental Bulletin, 2011, 20 (11), 2875-2882. 80. Measurement techniques for Hg species in ambient air Pandey, S K; Kim, K-H; Brown, R J C Trends in Analytical Chemistry, 2011, 30, 899-917. doi:10.1016/j.trac.2011.01.017. 79. Lithographical gap-size engineered nanoarrays for surface-enhanced Raman probing of biomarkers Stosch, R; Yaghobian, F; Weimann, T; Brown, R J C; Milton, M J T; Güttler, B Nanotechnology, 2011, 22, 105303 (6pp). doi:10.1088/0957-4484/22/10/105303. 78. Interlaboratory comparison exercise for the determination of As, Cd, Ni and Pb in PM10 in Europe Gerboles, M; Buzica, D; Brown, R J C; Yardley, R E; Hanus-Illnar, A; Salfinger, M; Vallant, B; Adriaenssens, E; Claeys, N; Vercauteren, J; Sega, K; Jurasovic, J; Rychlik, S; Rabinak, E; Tanet, G; Passarella, R; Pedroni, V; Karlsson, V; Alleman, L; Pfeffer, U; Gladtke, D; Olschewski, A; O'Leary, B; Pockeviciute, D; Biel-Cwikowska, J; Tursic, J Atmospheric Environment, 2011, 45, 3488-3499. doi:10.1016/j.atmosenv.2010.12.020.

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77. Uncertainty-weighted time-averaging of mercury vapour concentrations in ambient air: application to measurements in the United Kingdom Brown, RJC; Muhunthan, D TheScientificWorldJOURNAL, 2011, 11, 242-252. doi:10.1100/tsw.2011.37

76. Sensitivities of a standard test method for the determination of the pHe of bioethanol and suggestions for improvement Brown, R J C; Keates, A C; Brewer, P J Sensors, 2010, 10, 9982-9993. doi:10.3390/s101109982. 75. High-accuracy stable gas flow dilution using an internally calibrated network of critical flow orifices Brewer, P J; Goody, B A; Gilham, T; Brown, R J C; Milton, M J T Measurement Science and Technology, 2010, 21, 115902 (8pp). doi:10.1088/0957-0233/21/11/115902. 74. Temperature propagation through a mercury vapour calibration source and assessment of possible analytical biases caused by measurement of temperature variations Brown, R J C; Wang, J; Brown, A S Measurement, 2010, 43, 1291-1298. doi:10.1016/j.measurement.2010.07.004 73. Effect of Silver Annealing Conditions on the Performance of Electrolytic Silver/Silver Chloride Electrodes used in Harned Cell Measurements of pH Brewer, P J; Brown, R J C Sensors, 2010, 10, 2202-2216. doi:10.3390/s100302202. 72. A novel automatic method for the measurement of mercury vapour in ambient air, and comparison of uncertainty with established semi-automatic and manual methods Brown, A S; Brown, R J C; Dexter, M A; Corns, W T; Stockwell, P B Analytical Methods, 2010, 2, 954-966. doi:10.1039/C0AY00058B. 71. Comparison of ED-XRF and LA-ICP-MS with the European reference method for the measurement of metals in ambient particulate matter Brown, R J C; Jarvis, K E; Disch, B A; Goddard, S L; Adriaenssens, E; Claeys, N Accreditation and Quality Assurance, 2010, 15, 493-502. doi:10.1007/s00769-010-0668-7. 70. Standardisation of a European measurement method for the determination of mercury in deposition: results of the field trial campaign and determination of a measurement uncertainty and working range Brown, R J C; Pirrone, N; van Hoek, C; Horvat, M; Kotnik, J; Wangberg, I; Corns, W T; Bieber, E Accreditation and Quality Assurance, 2010, 15, 359-366. doi:10.1007/s00769-010-0636-2. 69. Standardisation of a European measurement method for the determination of total gaseous mercury: results of the field trial campaign and determination of a measurement uncertainty and working range Brown, R J C; Pirrone, N; van Hoek, C; Sprovieri, F; Fernandez, R; Toté, K Journal of Environmental Monitoring, 2010, 12, 689-695. doi:10.1039/B924955A. 68. CCQM-P111 study on Traceable determination of Practical Salinity and mass fraction of major seawater components Seitz, S; Spitzer, P; Brown, R J C Accreditation and Quality Assurance, 2010, 15, 9-17. doi:10.1007/s00769-009-0578-8 67. Comparison of estimated annual emissions and measured annual ambient concentrations of metals in the United Kingdom 1980-2007 Brown, R J C Journal of Environmental Monitoring, 2010, 12, 665-671. doi:10.1039/b920843g

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66. Elemental mercury vapour in air: the origins and validation of the ‘Dumarey equation’ describing the mass concentration at saturation Dumarey, R; Brown, R J C; Corns, W T; Brown, A S; Stockwell, P B Accreditation and Quality Assurance, 2010, 15, 409-414. doi:10.1007/s00769-010-0645-1 65. Novel method for producing uncertainty-weighted averages from a time series of ambient air measurements Brown, R J C International Journal of Environment and Pollution, 2010, 41, Nos. 3/4, 355-368. 64. Using principal component analysis to detect outliers in ambient air monitoring studies Brown, R J C; Goddard, S L; Brown, A S International Journal of Environmental Analytical Chemistry, 2010, 90, 761-772. doi:10.1080/03067310903094545

63. Spatial inhomogeneity of metals in particulate matter on ambient air filters determined by LA-ICP-MS and comparison with acid digestion ICP-MS Brown, R J C; Jarvis, K E; Disch, B A; Goddard, S L; Brown, A S Journal of Environmental Monitoring, 2009, 11, 2022-2029. doi:10.1039/b911441f 62. An electrochemical quartz crystal microbalance study of platinum phthalocyanine thin films Brown, R J C; Brett, D J L; Kucernak, A R J Journal of Electroanalytical Chemistry, 2009, 633, 339-346. doi:10.1016/j.jelechem.2009.07.002 61. Measurement of anions in ambient particulate matter by ion chromatography: a novel sample preparation technique and development of a generic uncertainty budget Brown R J C; Edwards, P R Talanta, 2009, 80, 1020-1024. doi:10.1016/j.talanta.2009.07.042 60. Systematic Error Arising from ‘Sequential’ Standard Addition Calibrations. 2: Determination of analyte mass fraction in blank solutions Brown, R J C Analytica Chimica Acta, 2009, 648, 153-156. doi:10.1016/j.aca.2009.06.061 59. A simple method for excluding self-citation from the h-index: the b-index Brown, R J C Online Information Review, 2009, 33, (6), 1129-1136. doi:10.1108/14684520911011043 58. The rise of environmental analytical chemistry as an inter disciplinary activity Brown, R J C TheScientificWorldJOURNAL, 2009, 9, 536-538. doi:10.1100/tsw.2009.78 57. Microelectrode voltammetry as a high accuracy method for determination of diffusion coefficients Brown, R J C; Brett, D J L Microchimica Acta, 2009, 164, 337-344. doi:10.1007/s00604-008-0062-x. 56. Stripping voltammetry using sequential standard addition calibration with the analytes themselves acting as internal standards Brown, R J C; Roberts, M R; Brett, D J L Analytica Chimica Acta, 2009, 635, (1), 1-5. doi:10.1016/j.aca.2009.01.014 55. Long-term equilibrium potential and electrochemical impedance study of Ag/AgCl electrodes used in Harned Cell measurements of pH Brown, R J C; Brewer, P J; Brett, D J L Accreditation and Quality Assurance, 2009, 14, (3),139-145. doi:10.1007/s00769-009-0487-x

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54. Effect of Structural Design of Silver/Silver Chloride Electrodes on Stability and Response Time and the Implications for Improved Accuracy in pH Measurement Brewer, P J; Brown, R J C Sensors, 2009, 9, (1), 118-130. doi:10.3390/s90100118 53. Explaining the distinction between accuracy and reliability in scientific measurement Brown, R J C School Science Review, 2009, 91, (335), 24-28.

52. Synthesis and Raman Spectroscopic Characterisation of Carbon Nanoscrolls Roy, D; Angeles-Tactay, E; Brown, R J C; Spencer, S J; Fry, T; Dunton, T A; Young, T; Milton, M J T Chemical Physics Letters, 2008, 465, (4-6), 254-257. doi:10.1016/j.cplett.2008.09.044 51. The Use and Abuse of Limits of Detection in Environmental Analytical Chemistry Brown, R J C The Scientific World Journal, 2008, 8, 796-801. doi:10.1100/tsw.2008.107 50. Consistency of practical salinity measurements, traceable to primary conductivity standards: EUROMET project 918 Seitz, S; Spitzer, P; Brown, R J C Accreditation and Quality Assurance, 2008, 13 (10), 601-605. doi:10.1007/s00769-008-0444-0. 49. Accurate calibration of mercury vapour measurements Brown, R J C; Brown, A S Analyst, 2008, 133, 1611-1618. doi:10.1039/B806860G 48. Accurate calibration of mercury vapour indicators for occupational exposure measurements using a dynamic mercury vapour generator Brown, R J C; Brown, A S; Corns, W T; Stockwell, P B Instrumentation Science & Technology, 2008, 36, 611-622. doi:10.1080/10739140802448309 47. A Practical Method to Fabricate Gold Substrates for Surface-Enhanced Raman Spectroscopy Tantra, R; Brown, R J C; Milton M J T; Gohil, D Applied Spectroscopy, 2008, 62, (9), 992-1000. 46. A study of the critical uncertainty contributions in the analysis of PCBs in ambient air Brown, A S; Brown, R J C Journal of Automated Methods and Management in Chemistry, 2008, Volume 2008, Article ID 179498, 14 pages. doi:10.1155/2008/179498 45. Establishing SI traceability for measurements of mercury vapour Brown, A S; Brown, R J C; Corns, W T; Stockwell, P B Analyst, 2008, 133, (6), 946-953. doi:10.1039/B803724H 44. Quantities and units in analytical chemistry Brown, R J C International Journal of Environmental Analytical Chemistry, 2008, 88, 681-687. doi:10.1080/03067310801899722 43. The effect of isotopic composition on the uncertainty of routine metal mass concentration measurements in ambient air Brown, R J C; Goddard, S L; Brown, A S; Yardley, R E Journal of Automated Methods and Management in Chemistry, 2008, Volume 2008, Article ID 504092, 6 pages. doi:10.1155/2008/504092

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42. Nano-structures and nano-structured substrates for Surface Enhanced Raman Spectroscopy (SERS) – a review Brown, R J C; Milton, MJT Journal of Raman Spectroscopy, 2008, 39, (10), 1313 - 1326. doi:10.1002/jrs.2030 41. On the Optimum Sampling Time for the Measurement of Pollutants in Ambient Air Brown, R J C; Hood, D; Brown, A S Journal of Automated Methods and Management in Chemistry, 2008, Volume 2008, Article ID 814715, 6 pages. doi:10.1155/2008/814715 40. A practical uncertainty budget for ambient mercury vapour measurement Brown, R J C; Brown, A S; Yardley, R E; Corns, W T; Stockwell, P B Atmospheric Environment, 2008, 42, (10), 2504–2517. doi:10.1016/j.atmosenv.2007.12.012 39. Twenty-five years of nationwide ambient metals measurement in the United Kingdom: concentration levels and trends Brown, R J C; Yardley, R E; Muhunthan, D; Butterfield, D M; Williams, M; Woods, P T; Brown, A S; Goddard S L Environmental Monitoring and Assessment, 2008, 142, (1-3), 127-140. DOI: 10.1007/s10661-007-9914-9 38. The Mechanisms in Place for Separating Teams with Identical Records in English football Leagues and International football Competitions Brown, A S; Brown R J C International Journal of Sports Science and Engineering, 2008, 2, (1), 23-28. 37. New developments in accurate and traceable chemical measurements Brown, R J C; Milton, M J T Chemical Society Reviews, 2007, 36, (6), 904-913. doi:10.1039/B507452P 36. Intelligent routes to the controlled synthesis of nanoparticles Krishnadasan, S; Brown, R J C; deMello, A J; deMello, J C Lab on a Chip, 2007, 7, (11), 1434-1441. doi:10.1039/B711412E 35. A novel calibration procedure for trace analytical measurements: application to the analysis of polybrominated diphenyl ethers by GC-MS Brown, A S; Brown, R J C; Robinson, R A Analyst, 2007, 132, (9), 922-928. doi:10.1039/B707924A 34. Systematic error arising from 'sequential' standard addition calibrations: quantification and correction Brown, R J C; Roberts, M R; Milton, M J T Analytica Chimica Acta, 2007, 587, 158-163. doi:10.1016/j.aca.2007.01.064 33. Stripping voltammetry as a possible primary method for amount of substance Brown, R J C, Milton, M J T IEEE Transactions on Instrumentation and Measurement, 2007, 56, (2), 280-283. doi:10.1109/TIM.2007.891159 32. The use of Zipf's law in the screening of analytical data: a step beyond Benford Brown, R J C Analyst, 2007, 132, (4), 344-349. doi:10.1039/B618255K 31. Errors in the Analysis of Minor Components within Environmental Samples Caused by the Physical Matrix Effect: Implications for Automated Analysis and Standardised Methods Brown, R J C

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Journal of Liquid Chromatography & Related Technologies, 2007, 30, (16), 2445-2457. doi:10.1080/10826070701465779 30. Electromagnetic modelling of Raman enhancement from nanoscale structures as a means to predict the efficacy of SERS substrates Brown, R J C; Wang, J; Milton, M J T Journal of Nanomaterials, 2007, Article ID 12086, 10 pages. doi:10.1155/2007/12086 29. Strategy to improve the reproducibility of colloidal SERS Tantra, R; Brown, R J C; Milton, M J T Journal of Raman Spectroscopy, 2007, 38, (11), 1469-1479. doi:10.1002/jrs.1797 28. Double anonymity in peer review within the chemistry periodicals community Brown, R J C Learned Publishing, 2007, 20, 131-137. doi:10.1087/174148507X185108 27. Electromagnetic modelling of Raman enhancement from nanoscale substrates: a route to estimation of the magnitude of the chemical enhancement mechanism in SERS Brown, R J C; Wang, J; Tantra, R; Yardley, R E; Milton, M J T Faraday Discussions, 2006, 132, 201-213. doi:10.1039/B506751K 26. The effect of the physical matrix on accurate measurements using fixed volume analytical techniques Brown, R J C; Edwards, P R Journal of Separation Science, 2006, 29, (13), 2072-2077. doi:10.1002/jssc.200600098 25. Analytical methodologies with very low blank levels: implications for practical and empirical evaluations of the limit of detection Brown, R J C; Yardley, R E; Brown, A S; Edwards, P R; Rivier, C; Yardin, C Analytical Letters, 2006, 39, (6), 1229-1241. doi:10.1080/00032710600622563 24. Practical methodology for the solubility speciation analysis of ambient dust deposits for heavy metals: application to a 6-month measurement campaign Brown, R J C; Shaw, M C; Roberts, M R International Journal of Environmental Analytical Chemistry, 2006, 86, (6), 453-460. doi:10.1080/03067310500291627 23. Electrochemical study of biotin-modified self-assembled monolayers: recommendations for robust preparation Brown, R J C; Brett, D J L The Scientific World Journal, 2006, 6, 20-29. doi:10.1100/tsw.2006.20 22. The risk of meeting a hazard. Brown, R J C School Science Review, 2006, 88, (322), 17 21. Double anonymity and the peer review process Brown, R J C The Scientific World Journal, 2006, 6, 1274-1277. doi:10.1100/tsw.2006.228 20. Analytical techniques for trace element analysis: an overview Brown, R J C; Milton, M J T Trends in Analytical Chemistry, 2005, 24, (3), 266-274. doi:10.1016/j.trac.2004.11.010

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19. Benford's law and the screening of analytical data: the case of pollutant concentrations in ambient air Brown, R J C Analyst, 2005, 130, 1280-1285. doi:10.1039/B504462F 18. The photoelectrochemistry of platinum phthalocyanine films in aqueous media Brown, R J C; Kucernak, A R Journal of Solid State Electrochemistry, 2005, 9 (6), 459-468. doi:10.1007/s10008-004-0583-0 17. Optical second harmonic generation at platinum phthalocyanine-modified platinum electrodes Brown, R J C; Taylor, A G Thin Solid Films, 2005, 476 (2), 373-378. doi:10.1016/j.tsf.2004.10.008 16. The micro-porous structure of silver/silver chloride electrodes and the implications for Harned cell operation Brown, R J C; Milton, M J T Accreditation and Quality Assurance, 2005, 10, (7), 352-355. doi:10.1007/s00769-005-0014-7 15. Resonance contributions to anti-Stokes/Stokes ratios under surface enhanced Raman scattering conditions Maher, R C; Hou, J; Cohen, L F; Le Ru, E C; Hadfield, J M; Harvey, J E; Etchegoin, P G; Liu, F M; Green, M; Brown, R J C; Milton, M J T Journal of Chemical Physics, 2005, 123, 084702. doi:10.1063/1.2004841 14. The use of double anonymity in peer review: a decision whose time has come? Brown, R J C Quality Assurance: Good Practice, Regulation and Law, 2005, 11, (2-4), 103-109. doi:10.1080/10529410500481983 13. Sample matrix and critical interference effects on the recovery and accuracy of concentration measurements of arsenic in ambient particulate samples using ICP-MS Brown, R J C; Yardley, R E; Brown, A S; Milton, M J T Journal of Analytical Atomic Spectroscopy, 2004, 19, 703-705. doi:10.1039/b316628g 12. Spectroscopic and electrochemical studies on platinum and palladium phthalocyanines Brown, R J C; Long, N J; Mongay-Batalla, C New Journal of Chemistry, 2004, 28 (6), 676-680. doi:10.1039/b401880j 11. Localized plasmon resonances in inhomogeneous metallic nanoclusters Etchegoin, P; Cohen, L F; Hartigan, H; Brown, R J C; Milton, M J T; Gallop, J C Chemical Physics Letters, 2004, 383, 577-583. doi:10.1016/j.cplett.2003.12.001 10. Stokes/anti-stokes anomalies under surface enhanced Raman scattering conditions Maher, R C; Cohen, L F; Etchegoin, P; Hartigan, H J N; Brown, R J C; Milton, M J T Journal of Chemical Physics, 2004, 120 (24), 11746-11753. doi:10.1063/1.1739398 9. Physics of single molecule fluctuations in surface enhanced Raman spectroscopy active liquids Maher, R C; Dalley, M; Le Ru, E C; Cohen, L F; Etchegoin, P G; Hartigan, H; Brown, R J C; Milton, M J T Journal of Chemical Physics, 2004, 121 (18), 8901-8910. doi:10.1063/1.1804178 8. Observation of a combined dilution and salting effect in buffers under conditions of high dilution and high ionic strength Brown, R J C; Milton, M J T Accreditation and Quality Assurance, 2003, 8, (11), 505-510. doi:10.1007/s00769-003-0689-6

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7. Observation of dynamic oxygen release in hemoglobin using surface Raman scattering Etchegoin, P; Liem, H; Maher, R C; Cohen, L F; Brown, R J C; Milton, M J T; Gallop, J C Chemical Physics Letters, 2003, 367 (1-2), 223-229. doi:10.1016/S0009-2614(02)01705-0 6. New limits in ultrasensitive trace detection by surface enhanced Raman scattering (SERS) Etchegoin, P; Maher, R C; Cohen, L F; Hartigan, H; Brown, R J C; Milton, M J T; Gallop, J C Chemical Physics Letters, 2003, 375 (1-2), 84-90. doi:10.1016/S0009-2614(03)00821-2 5. Electromagnetic contribution to surface enhanced Raman scattering revisited Etchegoin, P; Cohen, L F; Hartigan, H; Brown, R J C; Milton, M J T; Gallop, J C Journal of Chemical Physics, 2003, 119 (10), 5281-5289. doi:10.1063/1.1597480 4. The physical and chemical properties of electroless nickel phosphorus alloys and low reflectance nickel phosphorus black surfaces Brown, R J C; Brewer, P; Milton, M J T Journal of Materials Chemistry, 2002, 12 (9), 2749-2754. doi:10.1039/b204483h 3. A novel amplification mechanism for surface enhanced Raman scattering Etchegoin, P; Liem, H; Maher, R C; Cohen, L F; Brown, R J C; Hartigan, H; Milton, M J T; Gallop, J C Chemical Physics Letters, 2002, 366 (1-2), 115-121. doi:10.1016/S0009-2614(02)01551-8 2. Butyl-3-methylimidazolium cobalt tetracarbonyl [bmin][Co(CO)4]: a catalytically active organometallic ion liquid Brown, R J C; Dyson, P J; Ellis, D J; Welton, T Chemical Communications, 2001, 1862-1863. doi: 10.1039/b104601m 1. The electrochemistry of platinum phthalocyanine microcrystals - electrochemical behaviour in aqueous electrolytes Brown, R J C; Kucernak, A R Electrochimica Acta, 2001, 46, 2573-2582. doi:10.1016/S0013-4686(01)00469-8

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