chem 699 izzat
TRANSCRIPT
-
8/3/2019 Chem 699 Izzat
1/35
1
Selective method for the analysis of perchloratein drinking waters at nanogram per liter levels,using two-dimensional ion chromatography with
suppressed conductivity detection
CHEM 699
Izzat w. Kazi
-
8/3/2019 Chem 699 Izzat
2/35
outline
Introduction
Experimental
InstrumentationResult & Discussion
Conclusion
Recommendation
2
-
8/3/2019 Chem 699 Izzat
3/35
3
Introduction
Perchlorate can interfere with the uptake of iodide by thethyroid gland
Health effects associated with the presence of perchloratein various food products and drinking water is a cause of
concern since certain populations are particularlysusceptible, such as pregnant women and infants
High doses of perchlorate can affect metabolism, growthand development of the body.
Early in 2005, the National Academy of Sciencesrecommended a maximum perchlorate dose of0.7 mg kg1body weight per day from all sources, including water,milk, vegetables and prepared food
Office of Environmental Health Hazard Assessment, March 11, 2004,http://www.oehha.ca.gov/public info/facts/faqperchlorate.html.National Academy of Science, January 10, 2005, http://www4.nationalacademies.org/news.nsf/isbn/0309095689?OpenDocument
http://www.oehha.ca.gov/public%20info/facts/faqperchlorate.htmlhttp://www.oehha.ca.gov/public%20info/facts/faqperchlorate.html -
8/3/2019 Chem 699 Izzat
4/35
4
Introduction contd
Until recently, U.S. EPA method 314.0 was used fordetermining the level of perchlorate in drinking andgroundwaters
Excellent utility at 4 mg l1 or higher concentration levels,
But Requires offline sample pretreatment using solid phase
extraction (SPE) cartridges
Difficult to determine perchlorate at low levels.
High levels of matrix ions chloride, sulfate or bicarbonate
Labor intensive and cumbersome sample pretreatment
Safe Drinking Water Act Analytical Methods and Laboratory Certification
-
8/3/2019 Chem 699 Izzat
5/35
5
Introduction contd
In order to eliminate these more laborintensive procedures, EPAs Office of GroundWater and Drinking Water (OGWDW) and
National Exposure Research Laboratory,initiated method development projects toincrease sensitivity and selectivity using
direct injection techniques for the analysisof perchlorate in drinking water and insimulated high ionic strength matrices.
-
8/3/2019 Chem 699 Izzat
6/35
6
Introduction contd
Two-dimensional ion chromatography (2D-IC) with suppressed conductivity detectionmet all OGWDW requirements for
selectivity
sensitivity
precision
accuracy and
method robustness
-
8/3/2019 Chem 699 Izzat
7/35
7
Introduction contd
This is essentially an automated heart-cutting, columnconcentration and matrix elimination technique withsecond column confirmation
In the first dimension, a large sample volume is injected
onto a first separation column and the matrix ions arediverted to waste, while the perchlorate and a smallamount of other anions that elute within the cut windoware diverted and trapped onto a concentrator column
In the second dimension, the contents of the concentrator
column are eluted off and diverted onto a secondanalytical, smaller diameter (higher resolution) column forseparation and quantitation of perchlorate.
-
8/3/2019 Chem 699 Izzat
8/35
8
Introduction contd
Dionex Corporation and OGWDW worked in partnership todevelop a 2D-IC method in order to simplify the Method
Development of this new
highly sensitive and selective 2D-IC, suppressed conductivitymethod
Drinking water Lowest Concentration Minimum ReportingLevel (LCMRL) of55 ng/L, and has
comparable sensitivity and selectivity
simpler and more economical than IC-MS or ICMSMS techniques.
Revisions to the Unregulated Contaminant Monitoring Regulation for Public Water Systems, Proposed Rule, EPA document #815-R-05-006, November 2004 (http://www.epa.gov/safewater/methods/pdfs/method lcmrl.pdf).
http://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdfhttp://www.epa.gov/safewater/methods/pdfs/method_lcmrl.pdf -
8/3/2019 Chem 699 Izzat
9/35
Experimental
ReagentsAll solutions and all dilutions were prepared
using purified reagent water (RW) 18 MW
filtered with a 0.2 mm filter and did not contain any
measurable quantity of the target analyte orinterfering compound
laboratory synthetic sample matrix (LSSM)
fortified with 1000 mg/L of chloride, bicarbonate and
sulfate
This solution was used to simulate a drinking watermatrix containing a total of 3000 mg/L of theseanions
9
-
8/3/2019 Chem 699 Izzat
10/35
Standard and sample preparation
Calibration standards,
Continuing calibration check standards and
Perchlorate spiking solutions
prepared using a 1000 mg/L perchlorate (ClO4)
standard stock solution prepared from solid sodium
perchlorate (Sigma, Milwaukee, WI).
10
-
8/3/2019 Chem 699 Izzat
11/35
Instrumentation
Dionex Model ICS-3000 dual system Dual pump (DP) module
Eluent generator (EG) module
Detector/chromatography (DC) module
Autosampler (AS)
Continuously-regenerated anion trap columns,
Suppressors Carbonate removal devices
Dual conductivity detectors, and
Computer-based data acquisition and controls stem.
11
-
8/3/2019 Chem 699 Izzat
12/35
Instrumental conditions and equipment forfirst dimensions
12
Ion chromatograph Dionex ICS-3000 dual system
Sample loop 2.0 or 4.0 mLLoad volume 4.7 mL
Eluent generator Dionex ICS-3000 eluent generator (EG) with dual channel EluGen Catridges
EluentIsocratic 35 mM potassium hydroxide ramped to 100 mM potassium hydroxide
following the elution of perchlorate
(when injection valve system #2 is switched to the inject position)
Eluent flow 1.0 mL/min
AutosamplerAutosampler module (AS) with sequential injection, sample preparation options and
a large volume (8.2 mL) sample needle assembly
Columns Dionex IonPac AG 20 (4 mm 50 mm) Dionex IonPac AS 20 (4 mm 250 mm)
Typical system back-
pressure2500 psi
Conductivitysuppressor
Dionex ASRS Ultra II, 4-mm with 4-mm carbonate removal device (CRD)
Chromatography
module DC-Module maintained at 30 C
Detector Conductivity detector (CD) with integrated cell held at 35 C
Total analysis time 45 min
-
8/3/2019 Chem 699 Izzat
13/35
Instrumental conditions and equipment forsecond dimensions
13
Ion chromatograph Dionex ICS-3000 dual system
Sample loop Dionex UTAC ULP1, 5 mm 23 mm, concentrator column
Load volume Cut-window time set per procedures
Eluent generator Dionex ICS-3000 eluent generator (EG) with dual channel EluGen Catridges
Eluent Isocratic 65 mM KOH
Eluent flow 0.25 mL/min
Autosampler Autosampler module (AS)
Columns Dionex IonPac AG 16 (2 mm 50 mm) Dionex IonPac AS 16 (2 mm 250 mm)
Typical system back-
pressure2500 psi
Conductivity
suppressorDionex ASRS Ultra II, 2-mm with 2-mm carbonate removal device (CRD)
Chromatography
module DC-Module maintained at 30 C
Detector Conductivity detector (CD) with integrated cell held at 35 C
Total analysis time45 min
-
8/3/2019 Chem 699 Izzat
14/35
14
Fig. 1 Scheme of 2-D IC. Acronyms defined in above Table
-
8/3/2019 Chem 699 Izzat
15/35
Results and discussion
Two complete IC systems are integrated toprovide a single IC
Automated analyses that incorporate heart-
cutting, column concentration Matrix elimination techniques
Single injection for the analysis
can accommodate a large sample injectionvolume (up to 4.0-mL)
greatly increases sensitivity
refocus the perchlorate peak that is partially
resolved in the first15
-
8/3/2019 Chem 699 Izzat
16/35
Setting the cut window
window must be set to ensure that theperchlorate is completely eluted from thecolumn and that the amount of other
potentially interfering species, which mayalso elute during this time, are kept to aminimum
Ideally, a surrogate would be included inthe method to monitor and ensure that thecut window is functioning properly
16
-
8/3/2019 Chem 699 Izzat
17/35
Setting the start time for the cut window inthefirstdimension
Since 2D-IC utilizes a large volume injection (up to4 mL)
high ionic matrix concentration on the retention time isa critical factor
address when setting the cut window
injection volume is also a critical factor
retention time for perchlorate determined in
1000 mg/L (LSSM) to set the start time of the cut window and
RW
to set the stop time of the cut window17
-
8/3/2019 Chem 699 Izzat
18/35
The start time for the cut window 2.0 mL of a 50 mg/L perchlorate standard
prepared in the 1000 mg/L LSSM
injection valve #2 on system #2 is switchedto the load position
pressure spike
baseline deflection occurs after about 30 sstart time for the cut window
1 min before the rise in baseline for the
perchlorate peak in the 1000 mg/L LSSM.18
-
8/3/2019 Chem 699 Izzat
19/35
Fig 2: start time for the cut window using a 2.0-mL injection volume of a50 mg/L ClO4
fortification in the 1000 mg/L LSSM.
19
-
8/3/2019 Chem 699 Izzat
20/35
To ensure the start time is set using theperchlorate peak, not this earlier baselinedeflection
2.0-mL injection of the blank 1000 mg/L LSSM(without the perchlorate) also be injected.
Retention time
19.5 min and, therefore, the cut window starttime was set at
18.5 min.20
-
8/3/2019 Chem 699 Izzat
21/35
Setting the stop time for the cut window
The stop time for the cut window 2.0 mL of a 25 mg/L perchlorate standard prepared in
the RW
stop time for the cut window is also the time atwhich injection valve #2 on system #2 is switchedto the inject position
elution of perchlorate must be completed at least 60 sbefore injection valve #2 is switched into the injectposition
perchlorate peak returned to baseline at 22.5 min andthe stop time for the cut window was established at23.5 min.
21
-
8/3/2019 Chem 699 Izzat
22/35
Fig. 3. Setting the stop time for the cut window using a 2.0-mL injectionvolume of a 25mg/L ClO4
fortification in RW.
22
-
8/3/2019 Chem 699 Izzat
23/35
Fig. 4. First- and second-dimension chromatogram using a 2.0-mLinjection volume of a 25mg/L ClO4
fortification in RW.
23
-
8/3/2019 Chem 699 Izzat
24/35
Incorporating QC standards to monitor the cutwindow
Column performance can deteriorate aschromatographic columns age
Should monitored on a daily basis, with the use of QC
standardsHighest calibration standard should be prepared in
the 1000 mg/L LSSM as a continuing calibrationcheck standard (CCC)
to ensure the perchlorate is being trapped within the setcut window.
-
8/3/2019 Chem 699 Izzat
25/35
. Demonstration of method performance using a2.0-mL injection volume
Instrument calibration standards prepared in RW
0.025, 0.050, 0.10, 0.30, 0.50,1.0, 3.0, 5.0 and 10g/L
correlation coefficient was 0.99956LCMRL determination
LCMRL is the lowest true concentration
between 50 and 150% recovery with 99% confidence
seven individual, sterile filtered replicates
0.050, 0.10, 0.20 and 0.30g/L perchlorate fortifiedRW samples
LCMRL of 0.055g/L25
-
8/3/2019 Chem 699 Izzat
26/35
Precision and accuracy (P&A) data
26
Table 2Precision and accuracy (P&A) data (n = 7) using 2.0-
mL injection volume
Matrix
Native
concentration
(
g/L)
Fortified
concentration (
g/L)
Precision
(%RSD)
Accuracy
(%recovery)Reagent
water
-
8/3/2019 Chem 699 Izzat
27/35
27
Table 3
Precision and accuracy (P&A) data (n = 7) using 4.0-mL injection volume
Matrix
Native
concentratio
n (g/L)
Fortified
concentration
(g/L)
Precision
(%RSD)
Accuracy
(%recovery)
Reagent water
-
8/3/2019 Chem 699 Izzat
28/35
Demonstration of method performance using a4.0-mL injection volume
Larger injection volume increases sensitivity.
dramatic effect on retention
Resetting cut window using a 4.0- mLinjection
start time for the cut window was established at20.0 min
stop time was set at 26.0 min
LCMRL is 0.041g/L
28
-
8/3/2019 Chem 699 Izzat
29/35
Fig. 5. Setting the start time for the cut window in the first dimensionusing a 4.0-mL injection volume of a 25mg/L ClO4
fortification in the1000 mg/L LSSM.
29
-
8/3/2019 Chem 699 Izzat
30/35
Fig. 6. Setting the stop time for the cut window in the first dimensionusing a 4.0-mL injection volume of a 10mg/L ClO4
fortification in RW
30
-
8/3/2019 Chem 699 Izzat
31/35
Precision and accuracy data
31
Table 3
Precision and accuracy (P&A) data (n = 7) using 4.0-mL injection volume
Matrix
Native
concentration
(g/L)
Fortified
concentration
(g/L)
Precision
(%RSD)
Accuracy
(%recovery)
Reagent water
-
8/3/2019 Chem 699 Izzat
32/35
Comparison of 2.0 and 4.0 mL injection volumes
Peak areas for the 4.0-mL injection volume
2.0 to 2.1 times the peak area than the 2.0-mLinjection volume for the
low, mid and high-level CCC standards (n 5)
LCMRL was also slightly improved
native concentrations in the three drinking
water matrices ranged from 0.199 to 0.742mg/L
statistically equivalent (95% confidence interval) in
both injection volumes32
-
8/3/2019 Chem 699 Izzat
33/35
Conclusions
The new two-dimensional IC method withsuppressed conductivity detection
excellent sensitivity
Selectivity
precision
accuracy and
method robustness
Simpler and more economical than IC-MS orIC- MSMS techniques
33
-
8/3/2019 Chem 699 Izzat
34/35
Recommendation
Apply method for the determination of otherion like
Bromate (elutes just before chloride)
Nitrate (elutes just after chloride) etc.
In sea water or high matrix water
Simplification of the instrumentation
Replacing two-6port valve by single 10portvalve
Eliminating CD-134
-
8/3/2019 Chem 699 Izzat
35/35
35