Document NGRa1pe3EMBQmEMdkbJboD8zR

58 & * r u.s. d epar t men t o f c o mmer c e National Technical Information Sareice PFI-294 860 Lead Analysis of Ambient Air Particulates; Interlaboratory Evaluation of ERA Lead Reference Method (U.S.) Environmental Monitoring and Support Lob, Research Triangle Pork, NC Jan 79 K f- *rtr*\ `-yafr-n TEH 0532331 N33801 TECHNICAL REPORT DATA (Please react Instructions onjhc reverse before completing) 1. REPORT NO. EPA-600/J-79-006 .2. JOURNAL ARTICLE * PB 294860 4.. TI7L.S AND SUSTIT LE . ,,. . Lead Analysis of Ambient Air Particulates: Inter- S. REPORT OAT laboratory Evaluation of EPA Lead Reference Method 6. PERFORMING ORGANIZATION CODE 7. AUTWOFt(S) Sharon J. long. Jack C. Suggs, and Joseph F. Walling 8, PERFORMING ORGANIZATION REPORT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS environmental Monitoring and Support Laboratory Research Triangle Park* North Carolina 10. PROGRAM . EM ENT NO. 11. CONTRACT/GRANT NO. 12. SPONSORING AGENCY NAME AND ADDRESS Environmental Protection Agency Washington, D. C* 13. TYPE OF REPORT ANO PERIOD COVERED .14, SPONSORING AGENCY CODE 15. SUPPLEMENTARY NOTES Published in J. Air Poll. Cont, Assn. 29(1), 28-31, 1979. 16. ABSTRACT 1 ' '--"--1 -- The evaluation of the U. S, Environmental Protection Agency's "Reference Method for the Determination of Lead in Suspended Particulate Matter Collected from Ambient Air" among four laboratories and the quantitation by additional techniques are summarized. Coefficients of variation of 10% for the lead reference method were obtained. Optical emission spectrometry produced data that are statistically indistinguishable from data obtained from the reference atomic absorption spec trometry technique. DESCRIPTORS Air pollution Particulates Measurements 3. OJSTRieUTlON STATEMENT Unrestricted EPA Form 2220-1 (9-73J KEY WORDS AND DOCUMENT ANALYSIS b.IDENTIFIERS/OPEN ENPED TERMS C. COSATI I'klWf'GtOUp Ambient Air Lead r epr o duc ed bt NATIONAL TECHNICAL INFORMATION SSIVICE U.S. DEPRRrREHT Of COMMERCE _____5PRIMGEIELD, VA. W 19. SECURITY CLASS (This Report) Unclassified 20. SECURITY CLASS (This paw) Unclassified 68A t;21. NO. OF PAGES i niL.c K tyc'j/ijFF/o / TEH 0532332 DUP050033420 t EPA-6 00/J-79-0C 6 JOURNAL ARTICLE ** Lead Analysis of Ambient Air Particulates: Interiabcraftoiy Evaluation of EPA Lead Reference Method Sharon J. Long, Jack C, Suggs, and Joseph F. Walling U. S-Environmental Protection Agency I ! ' The evaluation of the U. S. Environmental Protection Agency's "Reterenee Method tor the Determination of Lead In Suspended Particulate Matter Collected from Ambient Air" among four laboratories and the quantitation by additional techniques are summarized. Coefficients of variation ot 10% for the lead reterenee method were obtained. Opticalemission spectrometry produced data that are statistically indistinguishable from data obtained irom the reference atomic absorption spectrometry tectinlqu e. The U. S. Environmental Protection Agency (EPA) was required to set a standard for the lead content of ambient air and, consequent'}', to select suitable collection and analysis techniques for lead-1-2 Since it has been estimated that nearly 90% of tht- ambient atmospheric Pb burden results frpm particulate emissions from mobile sources.11 the utilization ofalready existing particulate sampling devices (hi-voiume samplers will, glass-fiber filters)4 and analysis of the collected total suspended particulate ) (TSP) by acid extraction and atomic, absorption spectrophotometry were selected as the reference methods.' Al ternative procedures will eventually be identified as equivalent methods after passing specific tests. Those equivalency tests have recently been proposed/' The purpose of this paper is to ' present a summary of the important results to date of those investigations surrounding the reference method as well as some alternative quantitationtechniques. Preliminary Studies of Ihe Reference Method A procedural write-up was prepared by FPA which combined the experi ence's of two lalioratories gained through t'J?3'A>r FnliirtiMnf'nnsrol thousands of Pb analyses of TSP, The procedure consisted of an acid extrac tion of the particulate, conducted wit h either boiling nitric acid or with cold nitric acid and ultrasonic energy, and quantitation of the resulting extract from either procedure by flame atomic absorption spectrometry. The write-up was sent to approxi mately 100 laboratories engaged in work with air particulate for comments. Slightly less than halfof the laboratories responded. Comments received and some limited additional work in one laboratory led to modifications of the original write-up, most importantly the inclusion of an ultrasonic extraction procedure using mixed nitric-hydro chloric acids. EPA activities to date have net in cluded an evaluation of the sensitivity of parameter variations. Rather, it has consisted of a limited interlaboratory comparison of the [INOa write-up ap plied by several laboratories to split samples of real atmospheric particulate with which they were provided. These data, when subjected to an analysis of variance, provide a reasonable basis for expectations about the performance of this method when it is applied on a large scale. In addition, all lour of the labo ratories in this inlerlahoratory com parison analyzed the same HN'0:i ex tracts using optical emission spectrom eters having different excitation sources. One of the laboratories went further subjecting these same extracts to other analytical methods of anodic stripping voltammetry (ASV), fiameless atomic absorption (FAA), and spark excitation optical emission spectrometry (SE OES). Finally, in a more limited evaluation. two laboratories tested the ap plication of ultrasonic energy with a mixed HNOa-HCl extraction medium, quantitating by the same techniques utilized for the HNOs extract. The pro cedures used, the results obtained, and the statistical analyses ofthese various activities constitute the remainder of this paper, Interlabqratdry Comparison of the Reference Method and Alternative Analytical Techniques Four laboratories who commented on the write-up volunteered to participate in this portion of the study. All four laboratories received the same materials and instructions which requested their application of the proposed reference procedure using the nitric acid extrac tions to the material supplied with quantitation via the reference atomic absorption and optical emission spec trometry techniques. Two of these lab oratories had previously participated in studies that included blind quality control strips provided by the Quality Assurance Branch, Environmental Monitoring and Support Laboratory, Environmental Protection Agency. Re search Triangle Park, KC. These strips had been processed by methods identi cal to the boiling and ultrasonic HNO-, reference methods and had shown an averaze bias from the expected value of Reprinted from APCA JOURNAL, IVj. gg, No f, January 1979 TEH 0532333 DUP050033421 \\ Tablet, Lead data Crura nitric arid extraction reference procedure: flarae atomic Precision of a measurement method generally refers to the closeness of re Extraction Lob.No. (V) 1 Filter number o 34 5 67 peated measurements when the method Is applied to the same chemical sample or different specimens from the same t 1233nm) 0.11.6 10.88 0.154 10.94 1.42 2220 1.44 2.16 0.251 15.08 0.268 15.08 6.36 6.40 chemically homogeneous material. The two terms used here to describe preci lUlIl 10.93 1.43 2.14 0.258 15.09 6.40 sion are "within-laboratnry standard *5 <0.20 12.90 1.50 .2.00 <0.200 14.30 6.00 deviation," denoted by c,, and "be- < 2 (283 nml <0.2(1 11.40 1.50 <0/200 14.30 6.00 tween-laboratory standard deviation," *E <0.20 11,30 .60 2.20 <0.200 6.00 6.00 denrted by aL. The within-laboratory 2 0.20 11.30 1.53 2.21 0.36 15.00 6.96 Standard deviation is a measure char 3 (283 nm) 0.27 11.32 1.84 2.32 0.44 15.07 7.09 acterizing a single laboratory or operator 0.36 11.29 1.72 2.42 051 15.18 7.17 and is based on repeated observations. 4 (217 nm) 0.20 0.20 0.18 10.80 11.00 1C.SO 1.40 1.40 1.40 2.10 2.10 2.10 0.26 15.20 6.50 0.29 15.20 6.50 0.29 15.10 6.50 On the average, two observations will not differ by more than 2.77 <rr more than 5% of the time due to chance alone. The between-laboratory standard de 0.110 10.40 1.36 2.03 0.221 14.77 6.38 viation is a measure of laboratory bias. g i (283 nm) 0.085 10-45 1.37 2.01 0.229 14.65 6.39 When combined with the within-labo- 2 0.091 10.45 1.38 2.05 0.236 14.72 6.37 rato.-y standard deviation, a value is < 0.30 10.00 2.00 50 0150 15.00 < .20 obtained such that on the average, two 2 (283nm) ,0.30 10.00 1.70 2.00 0.50 14,00 < .20 observations should not differ by more 0.50 9.60 1,30 1.90 <0.20 14.00 < .20 than 2.77 times this value more than T3 0.21 11.45 1.54 2.25 0.29 15.04 6.78 5% of the time due to chance alone re & 3 (283 nm) 0.23 11.58 1.62 2.37 0:37 15.02 6.9) gardless from which laboratory the two C 1 0.37 0.20 11.55 11.20 1,69 1.40 2.39 2.20 0.47 0.26 IMS 15.20 6.90 6.5 observations are taken. AH the estimates of precision may be expressed as a per- ** 4 (217 nm) 0.20 11.30 1.40 2.20 0.26 15.30 6J> cent of the average concentration. 0.20 11.50 MO 2.20 0:26 15.10 6.6 The results of these computations for X = wavelength utilized the HNOn reference procedure and op tical emission procedures are shown in Tables III and IV, The indicated values were excluded due to analytical dif --1,5% (for 284 strips) and --3.0% (for 40 derived from the data under the as ficulties. The tables of precision esti strips), respectively, over the concen sumption that the four participating mates demonstrate the usual behavior tration range of 0 to 2000 pg lead/ laboratories were asample from a larger of techniques of this kind where, at strip. group of equally competent laborato concentrations less than approximately All laboratories were provided with ries. 10 times the limiting noise, the noise portions of exposed glass-fiber filters containing real ambient particulate which had been collected by hi-vot samplers over 24 hr periods. Seven such filters were ..cut into 8 strips each with physically adjacent strips being paired Table II. !.ead data from nitric acid extraction reference procedure: optical emission spectrometry quantitation. (mg.Ph/l). in order on each filter. Thus, 4 pairs of strips were available from each filter. Pairswere randomly assigned to each pf Extraction Lab No. (X)" 1 Filter number 2 34 5 67 the laboratories to ensure that strip bias was negligible. Kach laboratory was re quested to extract one strip of each pair with the boiling HNOa procedure and the other with the ultrasonic HNOj i procedure. Ail extracts were to be ana lyzed three times in random order by both the reference atomic absorption and optical emission spectrometry techniques. As analyses were to be per formed using the laboratory's routine 0.16 10.76 1.42 2.19 0.26 14.94 6.49 X 1 (405 nro) 0.17 10.72 1.43 2.16 0.25 14,97 6.1.2 o 0.12 10.70 1.43 2.09 0.21 14.86 6.23 . *c 0.15 .10.81 1.49 2.20 0.26 14.40 6.36 o 2 (220 rml 0.15 10.76 1.48 2.20 0.23 14.30 6.36 t 0-15 10.75 1.48 2.21 0.26 14.30 6.36 2 0.137 (1.40 1.49 2.14 0.264 15.60 7.23 c " ,220 nm) 0.111 11.50 1210 2.17 0.207 15.70 7.14 M 0.134 11.60 1.44 2.15 0.215 15.30 7.31 0.33 10.00 1.70 2.10 0.32 16.00 6.6 4 (283 ran) 0.30 ,10.10 1.70 2.00 0.32 15.80 6.6 analytical procedures, no instructions were given nor requirements made on the instrument parameters to be utilized in quantitation of the extracts other than those outlined in the reference procedure. The data which resulted from this effort are shown in Tables.! and 11. Reference Method Using analysis f variance tech 0-14 10.31 1.35 2.01 0.27 15.00 6.41 .1 (405 *tm) 0.16 10.31 1.3.5 2.06 0.26 14.93 6.43 0.15 10.08 135 1,96 0,23 14.46 6.40 0.130 10.36 1.45 2.18 0.26 14.84 0.38 iz 2 (220 nm) 0.230 10.36 1.45 2.18 0.26 14.87 B.trr z 0.120 10.33 1.45 2.20 0.26 14,78 fi.36 0.128 11.80 1.41 2.10 0.207 15.40 6.94 3 (220 nm) 0.158 11.50 1.40 2.10 o.2v: |5.f!0 6,92 i 0.150 12.00 ISO 2.15 0.205 15.60 7.09 4 (2*3 nml 0.20 0.20 10.40 10.50 1.60 1,60 1.90 1.80 0.H2 0,33 (5,50 15.70 fi.r, 6.5 niques,6 estimates of precision were X wavelength utilized January 1979 Volume 29, No. 1 29 TEH 0532334 DUP050033422 Table 11.^ Precision estimates of nitric acid extraction reference procedure and flame atomic absorption spectrometry quantitation. (Numbers in parentheses a. e ratiosof the precision estimates expressed as a percent of the average.) Tiller Concentration number average (mg Bh/f) Boiling Nitric Acul (%CV,J <Tra <%cv,> 1 0.218 0.06 JJ8) 0.04 (18) 0.07 5 0.305 0.10 (33) 0.04 U3> 0.11 3 1.456 0.15 (IQ) 0.24 U6> 0.28 4 2.148 0.13 . (.6) 0.19 ( 9) 0-23 ? .550 0.44 ( 7) 0.05 ( 1) 0.45 2 U.0U 0.38 < 3) 0.15 ( 4) 0.59 6 14.897 V*.34> i: 2) 0.06* (-4) 0.37 it - Bctween-Iaboratory standard deviation. at * tVi.lhin-Iaboratury standard deviation. ay " (c/.2 + .ar2i:,2a b laboratory 2 was excluded from the analysis. * The value 6.0 ag/ml reported by laboratory 2 was excluded. (%CVv) (32) (36) (19) un ( 7) t 5) ( 2) o.io 0.06 o.i i 0.08 025 0,77 0.35 (%CVtl (46) 420) ( 7) < 4) ( 4) < 7) ( 2) Ultrasonic. ar (%ev,j (%CVv) 0.07 0.09 0.18 0.16 0.06h 0.14 0.30 (32) (30) (12) ( 81 ( 1) < l) ilU 0.13 O.M 0.2) 0.18 0.25 0.73 0.46 (60) (36) (14) ( 8) < 4) ( 7) (3) S becomes an ever increasing part of the determination- This nearly constant limit can be estimated by determining the standard deviation of repeated measurements on a given solution for a series of solutions increasingly more dilute in the constituent of interest. In both of these tables it can be seen that the limiting noise is on the order of 0.1 mg/1, implying that limiting noise is an important part of the lowest two filter concentrations. Discarding the two lowest concentrations and averaging the coefficients of variation over the re maining five concentration levels gives a rough idea of the degree of precision which could he anticipated from using the reference HNOa method- In com paring individual resulls from a single laboratory, one can anticipate that, on the average, two observations will not differ by more than 17% of the concen tration level more than f>% of the time due to chance alone. In dealing with averages, this value is decreased by a i factor of 1/Vn. For example, two aver ages, each based on lf> observations, will not differ by more than 4.25% of the ! concentration level. When comparing individual observations between labo ratories, this value is increased to 28%. Average coefficients of variation from the optical emission techniques are similar though slightly smaller. Statis tical tests based on the analysis of vari ance' indicate that differences between the methods used to extract the Pb and differences between the methods used to quantitate the Pb are not signifi cant. Alternative Analytical and Mixed Acid Extraction Techniques Two laboratories participated in this study. Each laboratory received strips from two different hi-volume filters, with nominal Pb concentrations of 7.5 mg/1 and 2.0 mg/1, to assess whether or riot the addi tion of hydrochloric acid to the ultrasonic extraction medium would alter the amount of Pb extracted. The HNO,i was replaced by a mixed acid of similar nitric acid concentration and a HNO.)-HCl ratio of two/' Though more limited in scope and materials, the pro cedure was carried out in a fashion analogous to the original study and with similar conclusions. Based on an -.nalysis of variance, the addition ot HE! does not alter the amount of Pb extracted when compared to the results of the reference- method. This is concluded with reference to"a large body of labo ratories of which the two participants are a sample. On the average it was de termined that no two individual extracts should differ by more than 6% of the concentration level about 5% of the time, regaruless of which laboratory makes the measurements end independent of the extraction method used. . One laboratory analyzed the extracts from both interlaboratory studies via three other techniques whose parame ters are outlined in Table V. The in struments were calibrated using solu tions whose acid composition matched those-of the extracted Samples. The results from the reference atomic ahsorption procedure were not statisti cally different from this laboratory's results of the inductively coupled argon plasma optical emission spectroscopy (ICAP OES) for all extraction medium and filters tested. The other techniques in this laboratory's hands, however, were distinguishable from the above in that they were all less precise than the flame AA and the ICAP OES. Typical coeffi cients of variation for repeating a single measurement were 2% fur ICAP OES, 3% for flame AA, 6% for nameless AA, 10% for ASV and 15% for spark excited OES, Overall Conclusions Results from this study indicate the Table IV. Precision estimates of p;tric acid extraction reference procedure and optical emission spectroscopy quantitation. (Numbers jn parentheses are ratio, of the.precision estimates expressed as a percent of llie average. 1____________ Filter CotieCnttatmn number average (mu I'M) i 0.175 5 0.2G3 3 1.4*5 4 2.095 7 6.598 0 10.732 fi 15.156 hi* 0.08 0.03 an 0.05 0.44 0.56 0.67 Boiling Nilric Acid <%CV/.) Tf ,cv,.) *v (46) (in < 7) ( 21 ( 7) ( 5) ( 4) 0.02 0.02 0.02 0.03 0.11 0.06 0.13 (in 1 8) (n ( l) ( 2) . < 1) (n 0.07 0.0-1 o.n 0.06 0.46 0.57 0.63 0S4-V,) (40) (15) ( 7) ( 3) ( 71 ( 5) ( 4) 0.01 0.04 0.09 0.14 0.29 0.74 0.35 ou;v/.) ( 6) (IS) ( 6) i 7) ( 41 ( 7l ( 21 Ultrasonic f>rm ( u:v,j 0.03 n.oa 0.03 004 0.05 0.15 0.23 (17) (in ( 2) < 21 ( I) (u ( 2) 17v* (W.'W) 0.04 0,06 0.10 0.15 0.30 0.76 0.42 (23) (23) ( 71 ( 7) ( 4) ( 7) ( 3) * n;. " Fl.etVret*n-.lalM)ratnry standard deviation. it " Within-laboratorysuindard deviation. iy = (Sj,3 + O,3)1'3 TEH 0532335 J :\ \ ) t < .i DUP050033423 i> * <* Vn-1 Table V. Al.;tlvt idl conditions of candidate.methods. Healed vaporization Iftamelesx) atomic absorption spectroscopy Spectrophotometer Porkin-Klmer Model 4011 Lamp atomic abiorptiun* Analytical Line 283.3.nm Slit width Atomizer Perkin-Klmer Heated Purge gas Atomizer Model 2100 Dry 100*C for w see Atomization tube Char 500C for 20 see Cooling water Atomize 2500*Cfor Msec Injection Perkin-Elmer Automatic Aliquot Sampler*! Sample Matrix 0.225 M HNO Spark ezcitatioii optics.' e/nixxiwt spcc(r<Kiwpy Spectrometer Applied Research laboratory Model ynO'jPreductitin Control Cuaiitometer* Analytical Line 263.3 tint Entrance blit 20 pm Exit blit 75 am Soaking Time 30 sec Pre-sparking Time 12 sec Sample Matrix 4.5 M HNO:,, 2% LiCI, 100 mg In/1 Source Amperage Upper ' electrode laower rotrode Cleclrode &P Integration time Anodic stripping vottammetrv Analyzer Environmental Sciences Associate.-! Model 2014 Multiple Anodic Stripping AnaUzer" Sweep Kate + 82.5 and + GO mV/sec Sweep Hold Purge Gas -30 mV at 5 psig Sample Matrix 1 M NaC.H.Ojor 1 M NaC-H.iO, anil 0.2 M NaC! at pH 5.4 Plating Time Plating Potential Initial Potential Sample Aliquot Fb EDI. at 9 watts 0.7 nm Ar at 50 units and 20 psig Graphite 1.51/min 20 mI High Voltage Spark 4.0 ASTM C 1 ASTMD5 3 mnr. .16 sec 15 min -900 niV -900 mV 50 (.1 Mention ofcommercial or trade names does not cnnsliture anendorsement or recmnmcmJrtiiin fornse. Monitoring and Support Laboratory, Environmental Protection Agency, Re search Triangle Park, NC. for his nitric acid ultrasonic procedure and Dr. Anna Yoakutit of Stewart Laboratories. Knoxville, TN, for the mass transport step of the boiling nitric acid procedure. We would also like to thank John Margeson of the Quality Assurance Branch, Environmental Monitoring and Support Laboratory, Environmental Protect ion Agency, Research Triangle Park, NC, for his administrative handling of the collaborative study. ' 1 References 1. Federal Register <2: 63O7G-63082 (De cember 14: 1977). 2. Federal Register 42: 63US2-63087 (De cember 14.1977). 3. "Air Quality Criteria for Lead--Volume 1." ERA Report No. 600-8-77-017, U. S. Environmental Protection Agency Washington, >). C., December 1977, pp. 5-6 and 5-7. 4. "Reference. Method for the.Determination of Suspended Particulates in the Atmo sphere (High Volume Method)." Code of Federal Regulations. Title 40. Part 50, Appendix B, July 1.1975 pp. 12-1B. 5. Federal Register 43:45248-46277 (Octo bers, 1978). 6. J. M,'Mantlet. "Repeatability and repro. ducibiiily," Materials Research and Standards II (8k 8 (August 19711. following: extraction of lead front at mospheric particulate occurs equally well under mild and severe oxidizing conditions in nitric acid or mixed ni tric-hydrochloric acids: that from alt tha laboratories which may use-the method as written, the effect due to extraction technique is not significant with regard to bias and precision: the precision of data generated by any given laboratory utilizing the reference flame atomic absorption method is such that two measurements are expected to differ by more than 17"v only fi>. of the time due to chance alone, and 2S% when measuremenlsare compared be tween labo ratories. Modern optical emission spectrometry produces results ofsimilar quality to flame atomic absorption. For samples collected and prepared by the lead reference procedure. it is expected that no two measurements should differ by more than even if the measure ments are from different laboratories using different analytical techniques as long as the concentrations are larger than 0.5 ug Pb/ra* air sampled. Acknowledgments The authors would like to acknowl edge the technical contribution of Dr, Richard J. Thompson. Analytical Chemistry Branch, Environmental The nutlvrs .are in the .Environ mental Moniturihg anri Support 1-ahnratnry. U. S. Kmironmenta! Protection Aeeivcv. Researth Trian gle Park. NT 27711. TEH 0532336 DUP050033424