united states environmental protection agencyx-ray fluorescence (fpxrf) analysis procedures for soil...

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION 5

_ _i-rj-^ 77 WEST JACKSON BOULEVARD\, _,^ CHICAGO, IL 60604-3590

REPLY TO THE ATTENTION OF:

SQ-14J

MEMORANDUM

DATE: JUN 07 1993

SUBJECT: Approval of the Standard Operating Procedure(SOP) for Portable X-Ray Fluorescence Analysisfor Field Analytical Supporjtr-Projects (FASPs)

FROM: Curris Ross, ActiQuality Assurance Mana

TO: Charles Elly,central Regional Laboratory Director

I am providing approval of the SOP for Portable X-Ray

Fluorescence Analysis for Field Analytical Support Projects. The

SOP was received by Quality Assurance Section on May 25, 1993.

The signed approval page is attached to the memorandum.

Printod on flecyc/sd Pa

SOP Number:FASP-XRF-00Revision Number: 0Revision Date:5/93Supersedes: NonePage 1 of 16

E8AT REGION VSTANDARD OPERATING PROCEDURES FOR FIELD ANALYTICAL SUPPORT PROJECTS

TITLE:

STANDARD OPERATING PROCEDURE FOR ESAT FIELD-PORTABLE X-RAY FLUORESCENCEANALYSIS

Approvals:

Dennis MillerLockheed ESAT Region VTeam Manager

Charles EllyCentral Regional LaboratcDirector

0.Lewis KranzLockheed ESAT Region VQA/QC Coordinator

Curtis RossRegional Quality AssuramManac


Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1 PRINCIPLE AND METHOD SUMMARY . . . . . . . . . . . . . . . 41.1 Principle . . . . . . . . . . . . . . . . . . . . . 41.2 Method summary . . . . . . . . . . . . . . . . . . 4

2 SAMPLE SIZE, PRESERVATION, AND HANDLING . . . . . . . . . 5

3 SAMPLE PREPARATION AND PROCEDURE . . . . . . . . . . . . . 53.1 Sample Preparation: Discrete Samples . . . . . . . 63.2 Sample Preparation: In-Situ Samples . . . . . . . . 7

4 CALIBRATION PROCEDURE . . . . . . . . . . . . . . . . . . 7

5 INTERFERENCES AND CORRECTIVE MEASURES . . . . . . . . . . .95.1 Interelement Interferences . . . . . . . . . . . . . 95.2 Variations in Element Concentration . . . . . . . 95.3 Operating Conditions . . . . . . . . . . . . . . . . 10

6 EQUIPMENT AND MAINTENANCE . . . . . . . . . . . . . . . . 106.1 Equipment . . . . . . . . . . . . . . . . . . . . . 106.2 Equipment Maintenance . . . . . . . . . . . . . . . 11

7 PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . 117.1 Office Preparation: Pre-Sampling . . . . . . . . . 117.2 Field Preparation: Pre-Survey . . . . . . . . . . . 127.3 FPXRF Measurement Procedure . . . . . . . . . . . . 12

8 DATA TREATMENT AND DELIVERABLES . . . . . . . . . . . . . 13

9 QUALITY CONTROL AND QUALITY ASSURANCE MEASURES ...... 139.1 Precision . . . . . . . . . . . . . . . . . . . . . 139.2 Accuracy . . . . . . . . . . . . . . . . . . . . . 149.3 Representativeness and Confirmation . . . . . . . 14

10 LOGBOOK . . . . . . . . . . . . . . . . . . . . . . . . . 15

11 HEALTH AND SAFETY . . . . . . . . . . . . . . . . . . . . 15

12 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . 16


STANDARD OPERATING PROCEDURE FOR ESAT FIELD-PORTABLE X-RAYFLUORESCENCE (FPXRF) ANALYSIS

Scope: This SOP contains sample preparation and field-portableX-ray fluorescence (FPXRF) analysis procedures for soiland sediment samples in addition to appropriate qualityassurance measures, guidance for appropriatedocumentation of field activities and recommendationsfor personal protection. The utilization of this SOPis limited to the X-MET 880 FPXRF system manufacturedby Outokumpu.

This SOP provides pertinent practical information forthe calibration and analytical use of the X-MET 880system; however, the complete calibration/measurementprocess will not be provided due to the detailed natureof the X-MET 880's analytical software. Instead, theX-MET 880 user manual (1) is frequently referencedbecause it contains the required detail justificationand options necessary for properly making measurementswith the instrument. In addition, this SOP does notinclude sample survey procedures or the procedures forthe collection of representative soil or sedimentsamples.

Purpose: To standardize the procedures for the preparation andanalysis of soil and/or sediment samples for selectedinorganic elements by FPXRF. These inorganic elementsvary from potassium (Z * 19) to uranium (Z - 92) andthe detection limits and quantitation ranges forspecific elements are very dependent upon the samplematrix and cross-element interference. FPXRF analysisdata can be used to identify "hot spots11 ofcontamination and recommend appropriate sample sizes ordilution factors for samples selected for confirmatorylaboratory analyses.


PRINCIPLE AND METHOD SUMMARY

1.1 Principle

Analysis of soil and/or sludge samples for inorganic elements byFPXRF can provide real-time data for a specific range ofelements. The FPXRF instrument described in this SOP is aportable (i.e., hand carried) model X-MET 880 manufactured byOutokumpu which can be operated on or near the site of interestin a discrete-sample mode or can also be used to make in-situmeasurements.

In XRF analysis, primary X-rays emitted from a radioisotopesource are used to irradiate the sample. These primary X-rayscause the sample to emit fluorescence X-rays characteristic ofthe element and with intensities related to the concentrations ofemitting elements in their the sample. For the X-MET 880, two X-ray sources are used (Cs-244 and Am-241) and the associatedinternal instrument software accommodates the scanning of asample for up to 10 elements and quantitation of up to 6elements.

1.2 Method summary

The application of FPXRF at any site in either in-situ ordiscrete-sample mode requires the steps of (1) instrumentcalibration, (2) sample preparation, and (3) sample measurement.

Instrument calibration for either in-situ or discrete-samplemeasurements requires the usa of standard (pure) elementmeasurement for the target elements and measurement of site-specific samples with accompanying confirmatory AA/ICP data forthe target elements. The standard-element measurement providesthe instrument with spectra of the particular elements and theirinterferences while the site-specific calibration samples (SSCSs)provide the data necessary to model the matrix interferencesunique to the site* With standard element and SSCS spectraloaded into the instrument, a unique model is generated toaccommodate the site-specific matrix effects to be encounteredwhile measuring unknown samples from the site.

The preparation of site-specific samples requires a collectedsample to be dried completely, ground, and sieved to provide afine-grained portion representative of the sample. Five to sixgrams of this fine-grained aliquot are then placed in a 31 mm


diameter cup and covered with Mylar or polypropylene throughwhich the measurement can be made. In-situ sample preparationrequires the clearing of organic matter and large debris from anarea approximately 1 square foot at the location to be sampled.The remaining fine-grained material is then smoothed using atrowel and sample measurement is conducted on the smoothedsurface.

Sample measurement is conducted in the same manner for either in-situ or discrete samples. The analyst determines both ameasurement time (typically 30 to 200 seconds) and the number ofreadings that will be averaged (typically 5 measurements for in-situ and three measurements for discrete samples). Theinstrument probe is placed in contact with the sample and thesample is irradiated. The measurement readings and averaging areconducted and displayed by the instrument.

2 SAMPLE SIZE, PRESERVATION, AND HANDLING

The collected soil or sediment SSCS or site survey sample willconsist of a sufficient volume to provide a minimum of 15 gramsof sieved sample. Typical soil and sediment samples arecollected in four to eight ounce glass jars with teflon-linedlids if samples are to be shipped, or quart- or gallon-sizedplastic bags can be used for on-site analysis. The samplesshould be free of organic matter and of large (greater than 2 mm)matter.

Preservation and handling requirements for the samples are notextensive. Samples anlayzed on site do not require specialhandling other than normal procedures used to ensure theintegrity and safe handling of the sample. Samples collected forconfimatory laboratory analysis should be stored and shipped at4°C and chemical preservation of either on-site or shippedsamples is not required or recommended. Shipping and handling ofthe samples should be conducted according to the proceduresoutlined in EPA Region V Technical Support Service's SOP forSample Packaging and Shipping (2).

3 SAMPLE PREPARATION AND PROCEDURE

Both in-situ and discrete samples require specific but differentpreparation. The intent of the sample preparation is to providea homogenous fine-grained sample representative of the samplelocation. The end result of this preparation is a 5-gram sample


cup for the discrete sample and a cleared and homogenous soilsurface for the in-situ sample.

3.1 Sample Preparation: Discrete Samples

Site-specific discrete samples used for both calibration andsurvey measurements require the same preparation. The followingdescribes field preparation of discrete samples:

i) Oven dry the sample by emptying the sample onto a paperplate and placing in a microwave oven or drying oven.Dry the sample by operating the microwave for 3 to 10minutes at the highest power setting or operating thedrying oven at 105CC until the sample is dry. (Noteregarding sample dryness: the field preparation of thesample requires that the sample be dry enough toproduce the dry fine-grained material- to be measured.As a result, the dryness of the sample is notquantified as a percent moisture but rather determinedvisually and by the ability to provide the dry fine- *grained material. Typical sample drying byconventional oven at 105 °C requires 24 hours of dryingtime.) If the sample is to be analyzed by AA/ICP orfor mercury by cold vapor, homogenize the sample anddivide it into appropriate sample sizes for theanalyses prior to drying but do not dry the mercury orAA/ICP fractions.

ii) Grind the dried FPXRF sample by placing another paperplate over the sample and rolling with a rolling pin orby using a laboratory grinding mill. Another option isto transfer the dried sample from the paper plate to asheet of wax paper and placing another sheet of waxpaper on top of the sample. The sample can then betreated with a rolling pin as described for the paperplates.

iii) Thoroughly sieve the sample through a standard 10 mesh(2 mm) sieve onto a clean plate or into a plastic bag.

iv) Homogenize the sieved sample by tilting the plate orbag and rolling the soil to the center. This rollingshould be conducted 20 times to ensure thoroughhomogenization.

v) Using a clean spoon or spatula, transfer 5 to 6 gramsof the homogenized sample into a 3lmm SPEX cup (the cup

SOP Number :FASP-XRF-00Revision Number: 0Revision Date:5/93Supersedes: NonePage 7 of 16

should be 80% to 90% full) , cover with eitherpolypropylene or Mylar, and label.

3.2 Sample Preparation: In-Situ Samples

In-situ sampling provides the most rapid application of FPXRF,however, it is limited to drier in-situ soils and cannot beapplied to sediments. The following steps describe thepreparation of in-situ samples:

i) With the sample location determined, ensure the soilsof the location are not wet since water in the samplewill scatter the X-rays and bias results.

ii) Clear a one-foot square area of the sample location ofall organic debris and large (>2 mm) soil matter andstones .

iii) Smooth and level the remaining soil matter using aclean trowel or spoon. This smoothed soil will bemeasured directly by the FPXRF instrument as describedin Section 7.3.

4 CALIBRATION PROCEDURE

The calibration of FPXRF instrument requires the use of both pureelement standards and site-specific standards (with associatedconfirmatory AA/ICP data) and is an iterative and multivariateprocedure. The resulting calibration for either in-situ samplesor discrete samples is a mathematical model that accommodatesmatrix effects and interelement interferences of the soil orsediment samples. Potentially, more than one model may berequired to provide acceptable measurements over the range oftarget elements and concentrations. Model parameters can be mosteasily optimized if a minimum of 10 SSCSs are used for 2 to 3target elements and an additional 2 SSCSs for each target elementbeyond 3 (these SSCSs should include variations in elementconcentration as described in Section 5.2). The X-MET 880manufacturer's us^r manual, which provides a complete method forcalibration and model generation, is summarized in the followingbrief outline.

i) Use collected soil or sediment samples that representthe matrix, target elements, and concentration rangesto be encountered throughout the site.


ii) Homogenize and split the samples into two portions,prepare one portion for FPXRF analysis (see Section3.1) and package/preserve the other portion laboratoryanalysis. The laboratory analysis should consist oflaboratory-grade XRF screening to determine the targetelements and AA/ICP analysis to determine theconcentrations of the target elements. (Note: thesample can be split into additional portions if thesample is to be analyzed for other elements orcompounds or if aliquots will be archived)

iii) Set the measurement time using the M.TIME key to 200seconds for the calibration.

iv) Select a model (numbered 1 to 32) using the MODEL keyin which the calibration will be contained.

v) Measure the pure element standards for the targetelements of the survey, including Fe and Bs(backscatter) using the >PUR command. Thesemeasurements will provide spectra for the elementswhich allow the channel limits of the element to bedetermined for the model.

vi) Measure the site-specific discrete samples using the>CAL command. The instrument will retain the spectrumfor each sample.

vii) Enter the site-specific discrete sample AA/ICP datausing the >ASV command. This gives the instrumentanalyte values to perform a regression againstcorresponding intensities during the modeling process.

viii) Construct the regression model using the >MOD command.This model construction is described in the user manualand is an iterative and multivariate approach whichminimizes the interelement interferences. In additionto the site-specific discrete samples used in themodel, splits of the site-specific discrete samplesshould be spiked with varying concentrations of thetarget elements (see Section 4) to provide additionalmodel data points to investigate the interelementinterferences.

ix) Verify the model by measuring the SSCSs used in themodel generation. The model should provide results

SOP Number :FASP-XRF-00Revision Number: 0Revision Date: 5/93Supersedes: NonePage of 16

within ±35% RSD (see Section 9.1) of the AA/ICPresults.

5 INTERFERENCES AND CORRECTIVE MEASURES

Interferences typically encountered during FPXRF measurementsinclude interelement interferences (absorption-enhancementeffects) in the samples, variations in element concentrations,and effects of changes in operating conditions.

5.1 Interelement Interferences

As part of the generation of the model, anticipated interelementinterferences resulting in high or low bias from absorption orenhancement must be stated in order to allow the model toaccommodate the interferences. These interelement absorption-enhancement interferences result from elements with X-rayemissions just above the target element enhancing the targetelement emissions and elements just below the target elementabsorbing target element emissions (e.g., zinc enhances copperemissions (bias high) and nickel absorbs copper emissions (biaslow)). These interelement interferences are entered in theDEFINE INDEPENDENTS portion of the >MOD command. The user manualdescribes in detail the method for determining the independents,but some iteration is required to determine the propercombination of element to element, element to backscatter, andsole elemental interferences.

5.2 Variations in Element Concentration

Typical SSCSs do not provide a sufficient range of concentrationsfor all of the target elements. As a result, additional SSCSsmust be prepared with spiked concentrations of particularelements to include the anticipated concentration range of thesite. For instance, if the AA/ICP data for the target element Cuis consistently under 100 mg/kg, SSCSs may be spiked with Cu toprovide the model with site-specific matrix data for Cu at the1000, 5000, 10000, and 15000 mg/kg levels.

Site-specific calibrations samples should also be spiked toensure the variable levels of target elements do not produceemission interferences. This emission interference can occurwhen the concentration of one target element is increased ordecreased in reference to another or other target elements. As


an example, AA/ICP data from SSCSs may show that the targetelement Zn is always high in comparison to the target element Pb,A site specific calibration sample spiked with Pb at a higherconcentration than Zn should be prepared to provide the modelwith a high Zn/high Pb data point and the associatedinterference. (Note that both types of spikes may beaccommodated efficiently if the SSCSs to be spiked are chosencarefully)

5.3 Operating Conditions

The user manual states the ranges of environmental conditions(temperature, humidity, etc.) and interferences (high voltage,etc.) that may bias or interfere with proper sample measurement.

6 EQUIPMENT AND MAINTENANCE

6.1 Equipment

Equipment or site information required for FPXRF measurements isas follows:

User manual and SOPSampling and Analysis PlanHealth and Safety PlanSample location mapSafety equipment as specified in the Health and Safety PlanFPXRF instrument (X-MET 880)Laptop computerPure element standardsSite-specific calibration standards with AA/ICP dataSample(s) (previously collected)Drying oven (microwave or conventional drying oven)Rolling pin or mortar and pestlePaper platesWax paperPlastic bags (ziploc preferred)31 mm sample cups with Mylar coversBaby wipes for decontaminationPaper towelsThermometerLogbookCalculatorLabels


Cooler with iceChain-of-custody forms (if needed)Decontamination supplies and equipment

6.2 Equipment Maintenance

Most of the sampling equipment is relatively maintenance-free butsemi-annual testing for radiation leakage is required by theNuclear Regulatory Commission (NRC). Additional care andmaintenance required for the X-MET 880 FPXRF instrument isoutlined in the Outokumpu user manual.

7 PROCEDURES

The procedures for applying FPXRF to a survey include pre-surveyoffice and field preparation, sample collection and measurementprocedures, and post-sampling office and field procedures.

7.1 office Preparation: Pre-Sampling

Pre-survey office preparation includes the following:

i) The review of the approved site Sampling and AnalysisPlan to determine the data quality objectives andspecifics related to the collection of soil or sedimentsamples.

ii) The review of the approved site Health and Safety Planincluding site history.

iii) Procurement of the necessary SSCSs, sample preparation,monitoring, safety, and decontamination equipmentlisted in Section 6.1.

iv) Assurance that all equipment is in proper working orderand that the FPXRF instrument is calibrated correctlyor properly.

v) Prepare schedules and itineraries for staff* Arrangeshipping contact for equipment and samples, ifnecessary.


7.2 Field Preparation: Pre-Survey

Pre-survey field preparation includes the following:

i) Identify local suppliers of expendables and overnightshipping (if needed).

ii) Ensure equipment is decontaminated and working.

iii) Perform a general site overview to become familiar withthe site and identify any potential hazards.

7.3 FPXRF Measurement Procedure

The following procedure can be used for either in-situ ordiscrete samples*

i) Enter the desired measurement time (30 to 200 seconds)by using the MTIME key. Shorter measurement times (30.to 60 seconds) can be used if 5 or more measurementsare made for a sample while longer measurement times(100 to 200 seconds) are required for 3 to 4measurements.

ii) Place the sample in contact with the FPXRF probe windoweither by placing the probe on the prepared in-situsurface or by inverting the probe and then placing thesample cup (mylar down) on the probe window.

iii) Enter AMS and press the YES/CONT key. Pull the probetrigger after the instrument states MEASURE SAMPLE andhold the trigger open for the stated measurement time(the instrument will count down the seconds).

iv) After the measurement time has elapsed, the instrumentwill print the values for the target elements on thescreen and again state the prompt MEASURE SAMPLE.Additional measurements may be collected at this pointsimply by holding the trigger open as stated in (ii)above. Typically, sample cups are analyzed 3 times andin-situ measurements are performed 5 to 7 times (theprepared surface is measured at 5 to 7 locations; onceat each corner of a square or hexagon and once in themiddle).


v) After the measurement or measurements are complete,press the NO/END key to average the multiplemeasurements (if multiple measurements were made) andreturn to the prompt. Transcribe results to hard copysince no data storage is available for the instrument.Additional measurements are conducted by followingsteps iii, iv, and v above.

8 DATA TREATMENT AND DELIVERABLES

The treatment of the data collected will be a function of theparticular deliverable requirements as stated in the work planand the data quality objectives for the site sample analyses.

9 QUALITY CONTROL AND QUALITY ASSURANCE MEASURES

Quality control and quality assurance measures originate fromdata quality objectives and are required to ensure data of knownquality. Precision, accuracy, representativeness, completeness,and comparability are pertinent quality control and qualityassurance elements and specific samples are used to determine therange of these elements and gauge their acceptability.

9.1 Precision

Precision defines the ability to reproduce a measurement undergiven conditions (3)* For an FPXRF measurement, sampling andanalytical factors comprise precision, with analytical factorsbeing most easily identified and accommodated. Sampling factorsthat contribute to precision and which are of concern includesample collection, sample handling, and heterogeneities in thesample population. For the analytical influence on precision,repeated measurements of a low-concentration SSCS at thebeginning and after every tenth sample will provide the datanecessary to monitor gain changes and baseline drift along with amid-range SSCS and an SSCS near the action level (e.g., 500 mg/kgfor lead). The precision objective of this repeated measurementshould be ±20% relative standard deviation as determined by thefollowing equation:

SOP Number:FASP-XRF-00Revision Number: 0Revision Date:5/93Supersedes: HonePage 14 of 16

Standard DeviationM x 100

M = Mean value of the low-concentration SSCSmeasurements and the Standard Deviation iscomputed as follows:

Standard Deviation = £i-l(X, •N • 1

whereXj = FPXRF measurement of the low-concentration SSCSM » average FPXRF measurement of the

low-concentration SSCSN = number of measurements

9.2 Accuracy

Accuracy is a measure of the combined sampling and analyticalsystem bias to produce consistently higher or lower values thanactual values (1). Although the sampling component of accuracyis not the concern of this SOP, analytical accuracy can bedetermined by the FPXRF measurement of low-, medium-, and high-concentration SSCSs and the comparison of these measurements withAA/ICP data* These accuracy measurements should be conductedonce every two hours of operation time. The standard deviationof the measurements should be ±20% (see Section 9.1).

9.3 Representativeness and Confirmation

Representativeness describes how well the collected data reflectsthe variable(s) of concern and confirmation relates the FPXRFmeasurements to accepted AA/ICP analyses. Representativeness in


analysis is accommodated in the calibration by using SSCSs andensuring the concentration ranges and interferences of the targetelements are included in the calibration model. Confirmation isaccommodated by analyzing a minimum of 10% of the samples byconventional AA/ICP. The correlation coefficient between theFPXRF measurements and the AA/ICP data should be > 0.7 ascalculated by the following equation:

ffE r (vL \" vi-i a

i-l i«l

wherer is the correlation coefficient

X, and MX are the FPXRF measurement and the averageFPXRF measurement for a particular element

Y{ and MY are the AA/ICP measurement and the averageAA/ICP measurement for a particular element

10 LOGBOOK

A bound field notebook will be maintained by field personnel torecord daily activities. Included in these activities will beambient temperature and sample collection and trackinginformation with a separate entry identification number made foreach sample collected. These entries should include informationfrom the sample label and any additional site-specific orlocation-specific information. Sample measurements may beincluded in this logbook or transcribed to an additional sample-only logbook,

11 HEALTH AND SAFETY

The health and safety issues should be covered completely in theSite Health and Safety Plan. Review of this plan should be


conducted with emphasis on hazards and protection-for direct-contact tasks and radiation hazards. The plan should include butnot be limited to the following items:

i) No in-situ measurements should be conducted withoutinitially and continually screening the sample areawith an appropriate organic vapor and radiationmonitoring instrument (e.g., HNu 101, OVA 128, andRadMini).

ii) All operators and individuals working in closeproximity to the XRF instrument should be badged with aradiation monitoring badge.

iii) The XRF probe shutter should not be opened unless asample is in place or the probe is contacting theground surface during in-situ sampling.

iv) The XRF probe should be locked whenever it isunattended or not in use.

v) The FPXRF instrument cannot be checked as airlineluggage due to the 100 mCi source. Also, do notsubject the source to X-ray radiation such as found atairport luggage screening.

12 REFERENCES

(1) Outokumpu X-MET 880 User Manual.

(2) U.S. EPA Region V Standard Operation Procedures: SampleHandling and Packaging (currently in review).

(3) Miller, J.C.; Miller, J.N. Statistics for AnalyticalChemistry; Ellis Horwood Limited: England, 1984; p 38.

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