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Standard Operating Procedure
 

for the X-Ray Fluorescence Analysis
 

of Particulate Matter Deposits on Teflon Filters
 

Environmental and Industrial Measurements Division
 

RTI International*
 

Research Triangle Park, North Carolina
 

Prepared by 11- (((tAL Date: ~/27/01 ----­

__ Date: <6/~1/c1 f

I 

Date:¢7/0f I 

Reviewed by:_--:::;.~'.!Z!:.~-'-,..<~~~~~

Approved by :-H-t-h'-----N-''---IF--r-~'--''--------'-..L--/----

~RTI INTERNATIONAL 

* RTI International is a trade name of Research Triangle Institute. 
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Contents 

1.0 Scope and Application .........................................................................................................3 

1.1 Principle ...................................................................................................................3 

1.2 Method Overview ....................................................................................................4 

2.0 Safety ...................................................................................................................................5 

3.0 Filter Sample Considerations...............................................................................................5 

4.0 Interferences and Intensity Corrections ...............................................................................5 

4.1 Spectral Interferences ..............................................................................................5 

4.2 Background Correction............................................................................................6 

4.3 Particle Size Effects .................................................................................................6 

4.4 Attenuation Correction ............................................................................................6 

5.0 Instruments...........................................................................................................................6 

6.0 Instrument Calibration .........................................................................................................7 

6.1 Standards..................................................................................................................7 

6.2 Method Setup...........................................................................................................7 

6.3 Calibration Frequency..............................................................................................9 

7.0 Filter Handling.....................................................................................................................9 

8.0 Filter Preparation and Analysis..........................................................................................10

8.1 Preparation .............................................................................................................10 

8.2 Analysis .................................................................................................................10

9.0 Data Acquisition and Calculations ....................................................................................10 

10.0 Quality Control ..................................................................................................................11 

11.0 Data Review and Validation ..............................................................................................12

11.1 Level 0 Validation .................................................................................................12 

11.2 Level 1 Validation .................................................................................................12 

12.0 XRF Round-Robin Comparison Program..........................................................................16 

12.1 Selection of Filters .................................................................................................16 

12.2 Distribution of Filters, Data Tracking, and Reporting...........................................16 

12.3 Interpretation of Results and Corrective Actions ..................................................17 
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Standard Operating Procedure 

for the X-ray Fluorescence Analysis 

of PM Deposits on Teflon Filters 

1.0 Scope and Application 

This standard operating procedure addresses the application of energy dispersive X-ray 

fluorescence (EDXRF) spectrometry to the determination of trace elements in particulate matter 

(PM) deposits on Teflon filters. This technique is capable of quantitative analysis of elements 

with atomic numbers 11 (sodium) through 92 (uranium). The 33 elements specific to this project 

are listed in Table 1. 

Table 1. Project-Specific Elements Analyzed for the PM Speciation Program 

Element Element Element Element 

Sodium (Na) Titanium (Ti) Arsenic (As) Indium (In) 

Magnesium (Mg) Vanadium (V) Selenium (Se) Antimony (Sb) 

Aluminum (Al) Chromium (Cr) Bromine (Br) Cesium (Cs) 

Silicon (Si) Manganese (Mn) Rubidium (Rb) Barium (Ba) 

Phosphorus (P) Iron (Fe) Strontium (Sr) Cerium (Ce) 

Sulfur (S) Cobalt (Co) Zirconium (Zr) Lead (Pb) 

Chlorine (Cl) Nickel (Ni) Silver (Ag) 

Potassium (K) Copper (Cu) Cadmium (Cd) 

Calcium (Ca) Zinc (Zn) Tin (Sn) 

1.1 Principle 

The basis of X-ray fluorescence (XRF) spectrometry is the interaction of X-ray photons from a 

separate excitation source with atoms of the elements of interest found in the sample (filter 

deposit). When these excitation photons interact with the atoms in the sample, the photons cause 

the ejection of inner shell electrons. Outer shell electrons then fall into these vacancies. These 

transitions result in the emission of X-rays that are characteristic of the element. The energy of 

the characteristic X-ray is equal to the difference in the electron-binding energies of the two 

electron shells involved in the transition. Because the electron-binding energies are a function of 

the atomic number, the energy of the X-ray is characteristic of the element. The number or 

intensity of X-rays produced at a given energy provides a measure of the amount of the element 

present by comparisons with standards. 
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The X-rays are detected with a semiconductor material, lithium-drifted silicon. The X-ray 

passing into the detector produces a pulse of electrical current; the more energetic the X-ray, the 

larger the pulse of electrical current. The electrical pulses are measured and counted with 

appropriate electronics. These analyzer electronics further process the signals and display the 

X-ray energy spectrum (numbers of X-rays versus energy) on a personal computer (PC). The 

computer software determines the energy and intensity of the characteristic X-ray peaks, and 

then calculates the elemental concentrations through comparison to calibration parameters. The 

analysis of PM filter deposits is based on the assumption that the thickness of the deposit is small 

with respect to the analyte characteristic X-ray transmission thickness. It is assumed that the 

overall production of fluorescence X-rays is equivalent for PM samples and thin film, elemental 

standards. Therefore, the concentration of analytes in an unknown sample is determined by first 

calibrating the spectrometer with thin-film standards to determine sensitivity factors, and then 

analyzing the unknown samples under identical excitation conditions as used to determine the 

calibration factors. 

1.2 Method Overview 

The first step is to check the energy calibration to ensure that peak energies are accurately tied to 

specific elements. Energy adjustment is performed using a ThermoNoran copper (Cu) calibration 

standard. This procedure is run every day before any analysis is performed. The energy 

adjustment involves measuring the Cu K" line (8041), and then determining the difference 

between the measured peak energy value and the ideal value and if any adjustments are required, 

the instrument software performs it automatically. 

Filter samples are removed from cold storage and are loaded into the sample cups. Sample 

information is entered into the instrument logbook. The filters (in their sample cups) are loaded 

into the XRF sample tray in the same order as they are written into the instrument logbook. The 

instrument is then prepared for analysis by entering each filter aliquot number into the Method 

Tray List within the WinTrace software. The PM filter deposit analysis is then initiated. 

This analysis protocol consists of each filter being analyzed five separate times using five 

different excitation conditions (See Section 6.2, Method Setup). The specific excitation 

conditions have been optimized for specific groups of elements listed in Table 1. The different 

excitation conditions are used to maximize the sensitivity of the measurement of the different 

groups of elements, which fluoresce over a wide range of excitation energies. Each analytical 

run, which includes nine samples, has a multi-element thin film standard to verify overall 

method and instrumentation performance. 

Quantitative calibration for the elements is based on the use of thin film, elemental standards 

available from Micromatter, Inc. Recalibration of the instrument is required when the quality 

control samples or the National Institute of Standards and Technology standard falls outside their 

acceptance limits, when the detector or tube is replaced, or when the instrument undergoes 

significant repair or other changes in the hardware. Typical recalibration frequency is on the 

order of once every 6 to 12 months. 
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2.0 Safety 

Operating the ThermoNoran QuanX XRF analyzer under normal operations and following Good 

Laboratory Practices to provide a safe working environment, but the following cautions should 

be noted. 

ThermoNoran QuanX XRF analyzer operators are protected from accidental exposure to X-rays 

by a lid lock and front and back door interlocks when the instrument is in operation. Monthly the 

RTI Radiation Safety Officer performs area monitoring around each instrument to check for any 

leaking radiation. Also, the operator wears one to monitor his or her exposure. If any problems 

arise with the “X-RAYS ON” indicator light on the sample chamber lid or the interlock system, 

contact the instrument service engineer. 

A beryllium (Be) window is present to separate the sample chamber from the X-ray tube and 

detector. Because this window is fragile and brittle, do not allow sample or debris to fall onto the 

window and avoid using compressed air to clean the window because it will cause the window to 

rupture. If the window should rupture, it is important to note that Be metal is poisonous. Use 

extreme caution when collecting pieces of Be and consult the instrument service engineer for 

advice on cleaning up the broken window and replacing it. 

3.0 Filter Sample Considerations 

It is assumed that the PM material is uniformly deposited on the filter and that the position of the 

PM filter and the standards in the instrument is the same. It is important that care be taken when 

loading filters into the sample cups so that the deposit is not scraped, smudged, or smeared in 

any way. Care also needs to be taken to assure that the filters are placed flat in the sample cups 

and that these cups rest flat on the instrument sample-positioning wheel. 

4.0 Interferences and Intensity Corrections 

The following sections describe potential sources of error in the procedure: 

4.1 Spectral Interferences 

Spectral interferences with analyte line intensity determination include elemental peak overlap, 

escape peak, and sum peak interferences. These interferences are automatically corrected within 

the method program. No action is required by the XRF operator once these interferences have 

been addressed within the method. 
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4.2 Background Correction 

The laboratory background correction is determined using 10 blank, unused Teflon filters. These 

filters are analyzed on the XRF instrument for the 33 elements. Only those elements for which 

the average laboratory blanks values is above three times the uncertainty calculated by 

ThermoNoran software are subjected to background correction. A median value is determined 

for each of the select elements with a background above three times the uncertainty, and this 

median value is subtracted from the measured value for each of these elements to make the 

corrections. The correction values are entered into the software for automatic correction of field 

sample data. 

4.3 Particle Size Effects 

The X-ray production efficiency is affected by particle size for the lightest elements, such as 

aluminum; however, PM particle size effects are substantially less than 1 percent for most 

elements. Because the true particle size distribution cannot be determined for any given filter 

without microscopic analysis of that filter, no correction for particle size is performed. 

4.4 Attenuation Correction 

X-ray attenuation occurs when incoming (excitation) x-ray photons are absorbed by the sample 

before causing the desired fluorescence and when outgoing (fluorescent) photons are absorbed 

by the sample before escaping the sample. The net effect is that the instrument detects less signal 

from an element than would be expected if there is no attenuation correction; smaller values 

indicate a greater attenuation effect. RTI Attenuation correction software accounts for the 

excitation energies used in the RTI ThermoNoran QuanX XRF instruments. The software, which 

is a modification of a routine used by EPA, determines attenuations and their uncertainties for 

both thin, homogeneous deposits principally from aerosol condensation and also from deposits 

that contain particles with diameters in the high end of the PM2.5 size range. The software is 

applied to RTI’s XRF data post measurement to correct for the attenuation before that data is 

posted in the AQS. 

5.0 Instruments 

Three ThermoNoran QuanX XRF analyzers (i.e., bench top, laboratory grade, EDXRF 

spectrometers) are used for this procedure. Each instrument uses a high flux rhodium anode 

X-ray tube, which is positioned to direct excitation X-rays through one of five preselected filters 

onto the sample. Standard equipment for each instrument includes an electronically cooled 

lithium-drifted silicon (Si[Li]) solid-state X-ray detector, a 10-position sample filter wheel, and 

pulse-processing electronics that communicate spectral data to a PC, which displays and 

processes spectral information and outputs elemental concentration data. Each analyzer contains 

the following major components: 

 ThermoNoran QuanX cabinet that contains the detector, X-ray tube, and sample changer 

and electronics for system control and signal processing. 
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 PC with the ThermoNoran WinTrace software. 

 Vacuum pump. 

 Printer for analysis reports. 

 Uninterruptible power supply, which supplies the instrument, PC, and the vacuum pump 

with 6 hours of uninterruptible power. 

6.0 Instrument Calibration 

6.1 Standards 

Standards used for calibration consist of single or two non-interfering elements deposited as thin 

film standards from Micromatter, Inc; the standards are prepared by vacuum deposition resulting 

in highly uniform deposits. The 31 Micromatter standards used for calibration at RTI are listed in 

Table 2. 

Table 2. Micromatter Calibration Standards 

Analyte Analyte Analyte Analyte 

Sodium or chlorine as 

NaCl 

Titanium as Ti metal Zinc as ZnTe Indium as In metal 

Magnesium as Mg 

metal 

Vanadium as V metal Arsenic as GaAs Tin as Sn metal 

Aluminum as Al metal Chromium as Cr metal Selenium as Se metal Antimony as Sb metal 

Silicon as SiO Manganese as Mn 

metal 

Bromine or cesium as 

CsBr 

Cesium as CsF2

Phosphorus or gallium 

as GaP 

Iron as Fe metal Rubidium as RbI Barium as Ba F2

Sulfur as CuSx Cobalt as Co metal Strontium as Sr F2 Cerium as CeF3

Potassium as KI Nickel as Ni metal Silver or mercury as 

Ag-Hg Amalgam 

Lead as Pb metal 

Calcium as Ca F2 Copper as Cu metal Cadmium or selenium 

as CdSe 

6.2 Method Setup 

The standardization procedure consists of following steps: 

 Set up reference peak spectra: Acquisition of reference spectra is required when 

performing calibration. As long as no processing methods have changed, these peak 

shape references remain valid. The procedure of acquiring reference spectra consists of 

analyzing thin film standards or pure element material (as listed in Table 2) and acquiring 

individual elemental spectra that are stored in the Method File with each of the analytical 

conditions. The reference spectra must be interference free, and the peak count for the 
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reference spectra must be greater than 30,000 counts. These reference spectra are used in 

the standard deconvolution and mathematical separation of overlapping peaks of the 

unknown spectra. 

 Select acquisition conditions and analysis technique: Five different excitation conditions 

are performed during the analysis, as shown in Table 3. The specific excitation 

conditions have been optimized for specific groups of elements listed in Table 1. The 

different excitation conditions are used to maximize the sensitivity of the measurement of 

the different groups of elements, which fluoresce over a wide range of energies. When 

creating the excitation conditions, there are two operational parameters that are typically 

used and need to be considered (as shown in Table 4). These are determination of live 

time and atmospheric conditions, which will depend on the elements of concern and the 

detection limits that need to be achieved. Typically, for the lighter the elements, the live 

time is set to 300, and the atmospheric condition is set to vacuum. 

Table 3. Excitation Conditions 

Condition Filter Atmospheric 

Conditions 

Voltage 

(kV) 

Current 

(mA) Analytes* 

1 Low Za None Vacuum 4 1.98 Na and Mg 

2 Low Zb Graphite Vacuum 10 1.98 Al, Si, P, S Cl, K, and Ca 

3 Mid Za Pd thin Vacuum 30 1.66 Ti, V, Cr, Mn, Fe, Co, Ni, 

Cu, Zn, Cs, Ba, and Ce 

4 Mid Zc Pd thick Vacuum 50 1.00 As, Se, Br, Rb, Sr, and Pb 

5 High Za Cu thin Vacuum 50 1.00 Zr, Ag, Cd, In, Sn, and Sb 

Cs, Ba, Ce, Pb, are quantified from L-lines; all other elements are quantified from the K-lines. 

Table 4. Operational Parameters

Parameter Description 

Live time This is pre-set in the Method File; for the unknown samples, each excitation 

condition is set to between 200 and 300 seconds live time 

Atmosphere This is pre-set in the Method File; for the unknown samples, each excitation 

condition will operate under vacuum 

 Set up standards file: The Micromatter standards listed in Table 2 are manually entered 

into a Standards Library and imported into the Method File. The information provided in 

the Standards Library is the standard name, identification number, and certified 

concentration of the particular standard. The software will not allow the measurement of 
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the standards until the standard file is imported into the Method File. 

 Measurement of standards: After the Standards Library is imported into the Method File, 

the analyst proceeds with calibration by clicking the calibrate icon. The software will 

prompt to acquire all spectra for the standards. Verify that the standards are placed in the 

sample tray correctly, then start the acquisition. The software will acquire all the 

necessary spectra to perform the calibration. Because the method is quantifying for 33 

elements and the sample tray is for 10 samples, the software will prompt for the next tray 

to be loaded after finishing the first 10 standards. 

 Determine background correction: Laboratory background correction is determined using 

10 blank, unused Teflon filters. These filters are analyzed for the 33 elements. Only the 

elements for which the average laboratory blank value is above three times the 

uncertainty calculated by ThermoNoran software are subjected to background correction. 

A median value is determined for the select elements with background levels above three 

times the uncertainty, and this median value is subtracted from the measured value for 

each of these elements to make the correction. The correction is manually added into the 

software under the Coefficients view, for automatic correction of the data. 

 Validate calibration: After the standards and reference spectra have been acquired and the 

background correction has been applied, the round-robin samples (See Section 12 

regarding the round-robin program) and the NIST 1832, along with Micromatter 

standards (as unknowns) are analyzed to verify calibration and check recoveries for each 

element of concern. A typical adjustment to the calibration is due to the +/- 5% error with 

the Micromatter standards. If an element’s recovery is too high or low when the standard 

has been analyzed as an unknown, then an adjustment is made within the Coefficients 

view of the Method File to accurately correct for the error with the standard. 

 Run unknowns: After the instrument has successfully performed calibration, quantitative 

analysis can be performed on real-world samples. 

6.3 Calibration Frequency 

Calibration is performed only when the quality assurance/quality control (QA/QC) limits are 

exceeded or if there is a change in the excitation and/or detection conditions, such as a change in 

the tube, detector, X-ray filters, or signal processor. Calibrations are typically valid for 6 months 

to 1 year. 

7.0 Filter Handling 

Teflon filters are received from RTI’s Gravimetric Laboratory after being weighed to determine 

the mass (loading) of the filter. Custody of the Teflon filters is transferred to RTI’s XRF 

Laboratory by signing the appropriate chain-of-custody forms. The filters are placed in cold 

storage (refrigerator in Building 6) until they are scheduled for analysis. Note that the filters are 

analyzed at room temperature and under vacuum conditions. 
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8.0 Filter Preparation and Analysis 

8.1 Preparation 

Filters scheduled for analysis are removed from cold storage and are allowed to come to room 

temperature. With a 10-tray autosampler, the QA standard will always be loaded into position 

10, and the unknowns will start out with position 1 and will continue to position 9. The analyst 

will wear powder-free gloves when working with the filters and samples holders. Before any 

filters are loaded into the sample cups, the cups must be wiped with a Kimwipe to remove any 

residue left behind from the previous filters. This will eliminate potential cross-contamination. 

To load a filter into a sample cup, first remove the top of the Petri slide. Next, turn over the Petri 

slide into the sample cup with the exposed area of the filter now face down in the cup and ready 

for analysis. The filter will gently fall from the Petri slide into the cup. If a filter is stuck in the 

Petri slide, cleaned forceps are used to gently grab the filter by the outer ring and to place it face 

down into the sample cup. Place the sample cup in the next available tray position and write 

down the filter aliquot number in the instrument’s logbook. Recording the tray position and filter 

aliquot number in the logbook will allow the operator to cross check the information when 

entering the filter information into the WinTrace software for analysis. No other preparation of 

the samples is required. 

8.2 Analysis 

After the filters are loaded into the sample cups and loaded into the sample tray, a Method Tray 

List is created in Acquisition Manager within the WinTrace software. The Method Tray List will 

allow for automated quantitative analysis in conjunction with a Method File. The Method Tray 

List is created by entering the first sample identification and choosing the Method File from the 

directory. After the Method File is opened by Acquisition Manager and the sample position is 

verified in the tray as being correct, then proceed to enter the next sample on the next line. The 

program automatically fills in the Method File specified for the previous sample. 

After the Method Tray List is set up, click the spectrum icon on the toolbar to start the 

acquisition. The chamber lid will latch and the “X-RAYS ON” warning light will illuminate and 

the vacuum pump will click on. After a 300-second warm up, acquisition will begin starting with 

the lowest power condition. 

9.0 Data Acquisition and Calculations 

After all the spectra have all been acquired (they are saved in the respective Method File), 

Method Explorer will process the spectrums and display the analytical results in a specific 

format. The instrumental analysis report details the analyte, concentration, uncertainty, peak 

counts per second (cps), and background cps. 

To obtain the analytical results of the unknowns, go into Method Explorer and open the 

respective Method File. Under sample lists, identify the samples needed, and then click on the 

analysis report item to obtain the results in an rtf format. Save the report onto the hard drive. The 
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results file must be converted from the rtf format to a csv format to be able to upload to the RTI 

XRF database. ThermoNoran provided RTI with an external program to complete the 

conversion. After the data has been converted, it is an acceptable format to upload into the RTI 

XRF database for report generation, uncertainty determinations, attenuation correction through 

EPA provided software, and perform QC analysis. During report generation, the unit 

concentration μg/cm2

 is multiplied by the sample area, 11.3 cm2, to obtain the value for μg/filter. 

The WinTrace XRF software does not calculate uncertainty values when the peak and 

concentration result is zero (i.e., peak area ≤ background area). To obtain the uncertainty values 

for when the result is zero, a calculation is performed during the import into the RTI XRF 

database. The calculation is 

Uncertainty = Slope * A * sqrt (3 * sqrt (B * t) + B * t)/t 

Where: 

Slope is the response slope calculated in the method 

B = Background count rate (cps) 

A = Scaling factor for converting to μg/cm2

t = Live time 

10.0 Quality Control 

Several different QC activities are performed as part of the analysis procedure. These activities, 

their frequency, the measures of acceptable performance, and action if the item fails performance 

standards are provided in Table 5. 
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Table 5. Quality Control Procedures 

Item 

Inspection 

Frequency Inspection Parameter 

Action If Item 

Fails Inspection 

Documentation 

Required 

Energy calibration Daily Wavelength alignment 

of the instrument 

This is an 

automated 

process 

Document in the 

instrument’s run 

logbook 

Monthly Percentage of recovery 

of seven elements on 

thin-film National 

Institutes of Standards 

and Technology 

reference materials 

Document in the 

instrument’s run 

logbook; results 

stored in the XRF 

database 

Calibration 

verification 

Monthly 90% to 110% recovery 

analyzing the PM2.5 

calibration standards as 

unknowns 

Adjust 

instrument 

calibration 

factors 

Results stored in 

instrument’s 

method file 

Ongoing 

calibration 

verification 

Run with 

every tray of 

samples 

90% to 110% recovery 

using a multi-element 

sample containing Ti, 

Fe, Cd, Se, Pb, and SiO 

deposits of 5-10μg/cm2

Re-check 

instrument 

calibration and 

adjust if 

necessary; reanalyze samples 

Document in the 

instrument’s run 

log book 

Background 

Determination 

Monthly Analysis of 10 blank, 

unused Teflon filters. 

All elements below 

three times the 

uncertainty 

Adjust 

instrument 

background 

values 

Documented in 

instruments run 

logbook 

11.0 Data Review and Validation 

The analytical dataset undergoes Level 0 and Level 1 validations. These levels of validation will 

ensure that the dataset being reported will be of good quality. 

11.1 Level 0 Validation 

A Level 0 validation begins with the analyst, who identifies any problems related to the chain-ofcustody, the filter, or any mechanical or software problems that might have occurred during the 

analysis of the filters. If such items are identified, the analyst notes any problems in the 

instrument logbook, which is reviewed by the Technical Area Supervisor. 

11.2 Level 1 Validation 

A Level 1 validation is a more technical review of the analytical data. This review starts with the 

analyst, but it will primarily be performed by the Technical Area Supervisor. Using the review 

criteria developed by the QA Manager, the responsibilities of the analyst and the Technical Area 

Supervisor are provided in Table 6. 
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If any discrepancies are noted by the analyst or the Technical Area Supervisor, they will be 

reported on their respective checklist (Figure 1 and Figure 2). 

Table 6. Level 1 Validation Responsibilities 

Analyst Technical Area Supervisor 

Verify proper custody documentation is 

provided in batch folder 

Ensure analytical dataset is complete and the 

proper procedures were followed to analyze 

the filters 

Check sample identifications against COC 

forms and proper number of samples match 

given COC 

Check that proper paperwork is provided in the 

batch folder and for any notations regarding 

the analysis of the batch or flaws with the 

filters that were analyzed 

Confirm mass values for each sample are 

present on final report 

Review precision, accuracy, and replicate data 

for acceptable limits 

Make sure sample identifications are consistent 

between final report versus pre-attenuation 

report 

Check data for any inconsistencies or trends 

and report to QA Manager 

Review pre and post attenuation reports for 

disparity with attenuated data 

Apply flags to data , if applicable 

After two levels of review have been performed on the analytical dataset, it is ready to be 

submitted for upload into the CSN database. 
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Batch Creation Date:______________ Batch ID Number:________________ 

Number of Samples:_________ 

(circle one, if no leave comment why) 

Item #1: Custody Documentation 

Chain-of-Custody form present Yes No 

Signed By:_______________ 

Dated:___________________ 

Sample Identification 

No. of samples matches number on COC form Yes No 

ID#s on COC match Id #s on samples Yes No 

Item #2: Attenuation Correction 

Sample IDs consistent with pre-attenuation report Yes No 

Mass values present on report Yes No 

Item #3: Data Comparison Pre-attenuation vs Attenuated Data 

Results consistent between pre and post attenuation Yes No 

Comments Regarding Data:______________________________________________________________ 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

___________________________________________________________________________________ 

Reviewer Signature:___________________________ Date Signed:_______________ 

Figure 1. EDXRF Analysis Analyst Checklist. 
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COC Form No. Report Date: 

 

Data Review: 

Sample Filter No. Comments: 

 

Sample Filter No. Comments: 

Sample Filter No. Comments: 

Sample Filter No. Comments: 

Sample Filter No. Comments: 

Sample Filter No. Comments: 

Quality Control Review: 

Precision Data Acceptable? Yes No Notes: 

 

Accuracy Data Acceptable? Yes No Notes: 

Replicate Data Acceptable? Yes No Notes: 

Chain-of-Custody Data Cover Letter Yes No Notes: 

Filter-Loading Masses: Yes No Notes: 

 

Reviewed by: 

 Date 

Figure 2. EDXRF Analysis Technical Area Supervisor Checklist. 
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12.0 XRF Round-Robin Comparison Program 

The XRF Round-Robin Filter Exchange Program is intended to provide an ongoing comparison 

of analysis results generated by the two laboratories that analyze XRF samples for the Chemical 

Speciation Network (CSN) Program. Exposed (real-world) filters obtained from the CSN archive 

are used to provide the most realistic samples possible. According to the contract with EPA, 

filters and aliquots must be kept for 5 years in case the state monitoring agencies want to 

re-analyze them or have them returned to the respective agency. 

12.1 Selection of Filters 

To find filters that are likely to yield the most useful data, the database is periodically searched 

for filter samples that have the following characteristics: 

 Represents a range of different elements at levels above the analytical uncertainties 

(queries have been designed to select filter sets that maximize the number of different 

measurable elements) 

 Represents a range of different concentrations, from low to high (but above the 

uncertainty levels) 

 No data validity flags or codes 

 In good condition by visual inspection. 

12.2 Distribution of Filters, Data Tracking, and Reporting 

The selected filters in their Petri slides are in the CSN archive based on their box numbers, 

which can be obtained from the CSN database. Filters are already in Petri slides and are marked 

by their original aliquot numbers (assigned when the filter was received from the field). Filters 

are visually inspected before further processing, and any defective filters are not used as round 

robins. Filters are assigned a new aliquot number and are transferred into new Petri slides labeled 

with new barcode stickers. This is conducted to make the sample partially blind to the 

laboratories when they are re-analyzed; however, filters are identified as round-robin samples so 

that laboratories operating two or more XRF instruments for the CSN Program can analyze them 

on all of their instruments before sending them back to RTI. 

The aliquot number is linked in the database to measurement request ID number R28598T. 

Using a special measurement request ID allows data to be easily retrieved after the round-robin 

filters have been analyzed. 

The filters are incorporated into normal shipments to the participating XRF laboratories, 

including RTI. On average, at least two round-robin filters per month are analyzed by each 

laboratory. Laboratories with multiple XRF instruments analyze the round-robin filters on each 

instrument 

Each round-robin filter should be analyzed at least once by every participating laboratory (and 

instrument). Analysis of the same filter multiple times by the same laboratory is not considered 
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to be a problem; however, filters are rotated out of use after approximately 6 months of use and 

are replaced by new round-robin filters selected as described in Section 12.1 above. 

Data are reported back from the participating XRF laboratories, including RTI, along with all the 

regular data. The round-robin data are uploaded into the CSN database, along with all the regular 

data. Round-robin results are ignored by the data-processing routines used for validating and 

reporting routine and blank filter data. The round-robin data are accessible in the CSN database 

using the unique measurement request number assigned to the Round-Robin Program. 

Database queries have been developed that extract the round-robin XRF data, as well as the 

original values reported for the filter, and report them in a tabular format suitable for importing 

into Microsoft Excel or another data management and analysis tool. 

12.3 Interpretation of Results and Corrective Actions 

The most effective means of interpreting the results has been found to be plots of individual 

round-robin results versus the median of results for all reporting laboratories and instruments. 

The original result is usually included in the dataset from which the median is determined. 

Systematic problems are defined as particular element/laboratory/instrument combinations that 

are consistently above the median by a significant amount. This amount is assessed relative to 

the uncertainty values that are reported along with the concentration data. Identification of 

problems is similar to the technique used with control charts: a potential problem would be 

indicated under the following conditions, where “1-sigma” is the uncertainty value for the 

element reported by the laboratory: 

 One sample beyond 3-sigma. 

 Two samples beyond 2-sigma (both in the same direction). 

 Five samples beyond 1-sigma (all in the same direction). 

Whenever an element or a set of elements appears to be systematically high or low relative to the 

median results as previously described, the laboratory with the bias (same procedures for all 

participating XRF laboratories, including RTI) is contacted and is asked to recalibrate the 

instrument and/or to review its QC data for the time period during which the questioned roundrobin samples were analyzed. If the laboratory identifies a problem that requires recalibration, it 

will recalculate all data for the affected elements during the questioned time period and will 

resubmit the data to RTI, where it will be uploaded into the CSN database, replacing the 

previous data.