Document KR0GYp9xv9YdqqN7XN7LxM3GQ

INDUSTRIAL HYGIENE REPORT DOW CHEMICAL U.&A. ` AN OPERATING UNIT Of THE OOW CHEMICAL COMPANY OCNkKTMENT H&ES Industrial Hygiene Laboratory TITU LA*0*AT0AY AtPOAI COpt HEH2.12-39-3(11) OATf SSUflT ACCOUNT NO 1855 RAOSUM NUUWN 178-0000301 RESULTS OF THE 1984 ANALYTICAL PROFICIENCY TESTING ROUND ROBIN FOR CHLORINATED METHANES AUTHOR (SI StONATUNC (SI R. M. A. Hahne MCvewCA* M3MATUMS D. R. Branson. M, j %!h DESCRIPTIVE SUMMARY WITH CONCLUSIONS ii Five laboratories participated in the Analytical Proficiency Testing Round Robin for the.chlorinated methanes. Each laboratory analyzed six charcoal tubes (two tubes at each of three different levels). The tubes were prepared by passing compressed nitrogen containing the four compounds through charcoal sorbent tubes for different lengths of time. The data have been treated statistically in a manner consistent with th soon-tobe distributed Industrial Hygiene Procedure No. 101 -- "Statistical Treatment of APT/Round Robin Data." The mean percent of actual values reported were 99, 101, 101, and 81 for methyl chloride, methylene chloride, chloroform, and carbon tetra-chlorlde, respectively, with relative standard deviations of 23, 37, 24, and 28 percent for the same four compounds respectively. The accuracy goal for this study Is that the results reported for each laboratory fall showed between 86% and 114% of the actual value for methyl chloride, between 90% and 110% for methylene chloride, between 87% and 113% for chloroform, and between 86% and 114% for carbon tetrachloride with a goal for precision of jT0% for each chemical. Although some laboratories met the goal for accuracy or pre cision for at least one of the chemicals, none of the laboratories met the goals for accuracy and precision for all the chemicals. There may have been a variety of reasons for not meeting the goals, which should be addressed on a case-by-case basis. j DISTRIBUTION *F. D. Axe, Pittsburg, CA *G. D. Ballantyne, Hong Kong D. L. Bosatra, Horgen *P. T. Canete, Santiago *H. A, Celedon, Sao Paulo 3. Coates, Plaquemine R. L. Daniel, Freeport *R. L. Egedahl, Sarnia C. E. Halphen, Plaquemine C. W. Heurtevant, Plaquemine H. Koppelmann, Stade *3. E. LeBeau, 1803 G* L. Meier, Strongsvill ` S. K. Norwood, 1803 R. D. Olson, 1803 L. W. Rampy, 1803 A. W. Schaffer, 2030 E. 3. Schneider, 1803 G. L. Wasserman, 474 Cover sheet only RESTRICTED: for um within The Dow Chemical Company only. DO 105984 CONFIDENTIAL - 2 INTRODUCTION One of the components of a good quality assurance program in an analytical laboratory is the analysis of extramural proficiency testing samples, i.e., samples which are prepared externally to the laboratory doing the analyses* For laboratories analyzing industrial hygiene samples within Dow, the Analytical Proficiency Testing Round Robin (APT) is one source of such samples. Approxi mately once every two years, a different set of samples is sent out to all participating laboratories. The samples cover the spectrum of analytes of interest to Dow industrial hygienists, and the analytes for a given sample set are intended to reflect the compounds which might be expected in a given plant's work environment, at a range of levels from approximately one-tenth to two times the Industrial Hygiene Guide (IHG) or Threshold Limit Value (TLV), assuming an air sample volune of 20 liters. The APT results discussed in this report are for samples containing the four chlorinated methanes: methyl chloride, methylene chloride, chloroform, and carbon tetrachloride. Late in December of 1983, a set of six samples and three blanks was sent out to each participating laboratory for analysis of these four compounds. Three pairs of identical samples, each containing a different level of the four compounds (identified as low, mediun, and high for simplicity in the tabulations), as specified in the protocol^ were prepared on 2-gram activated charcoal tubes. The participating laboratories were Louisiana Division Chlorinated Methanes, Louisiana Division Environmental Control, Texas Division Chlorinated Methan s, Dow Europe Stade, and the H4ES Industrial Hygiene Laboratory, with the study director serving as the "reference laboratory." EXPERIMENTAL The charcoal tubes were prepared by passing known volunes of a gas containing approximately 120, 300, 200, and 200 mg, respectively, of CH3CI, CHjCljt CHCI3, and CCl^ in 7000 g of dry nitrogen, through the charcoal tubes. The tubes were prepared on a twelve-place metal manifold, with each tube having its own pre calibrated rotameter. Since eighteen tubes of each loading level were prepared in two runs (one with partially used manifold), efforts were made to distribute the tubes such that each laboratory received some tubes from more than one run, and also received tubes loaded at different positions on the manifold, should this be a variable as well. Analysis of the cylinder gas was done to estimate the flow time needed to attain the desired loadings for each analyte. The low, medltmi, and high loadings had 7, 12, and 20 liters of the "spiked" nitrogen passed oyer them at a rate of roughly 150 ml/minute. The gas was analyzed by introducing 500 ul samples directly from the cylinder into a gas sampling valve and then into the gas chromatograph (Hewlett-Packard Model 5730A) with a hydrogen flame ionization detector and a Hewlett-Packard 3380A integrator. The theoretical loading, determined by a direct gas analysis, was not used as the "true" value of the analyte in this study because (1) the gas entering the gas chromatograph may not have b en exactly the same as that 105985 CONFIDENTIAL 3 entering the sorbent tubes, (2) the peak shape and location of the CSj solvent peak in the chromatogram made the sorbent tube and gas analysis methods slightly different, and (3) the sampling loop may not have a volume of exactly 500 ml. For these reasons, the true value was estimated by the average of the analyses of the sorbent tubes. For practice, the reference laboratory analyzed a dozen tubes loaded in th manner described and did four measurements of recovery using the phase equilibriun recovery method^. Of the samples actually prepared for the study, five of each type were set aside to be analyzed by the reference laboratory. One was lost in a laboratory accident. Nine other samples, three each at three different levels of concentration, were analyzed to determine recovery as a function of loading, using the phase equilibriun recovery method. The reference laboratory performed the final sample analyses using a HewlettPackard (H-P) Model 5730A gas chromatograph with an H-P Model 7672A autosampler, the entire system being coupled to a H-P laboratory computer system. Calibra tion of the gas chromatograph was done using standards of the four compounds in carbon disulfide at two different levels, bracketing the expected responses for the samples to be analyzed. A duplicate of the higher standard was also pre pared to verify the accuracy of that standard^. RESULTS Table 1 is a compilation of all the data submitted. Table 2 shows the results submitted as percent of actual. The "actual" mass loading was calculated as the grand mean of all results submitted, after outliers had been eliminated using the Dixon criteria**'. The results submitted include thirty results from the fiv participating laboratories plus 12-H results from the reference laboratory. The grand mean, with outliers removed, was used because it Is the feeling of the author that the results of a large number of analyses done by proficient analysts gives a better indication of the "true" value than the results of a single analyst. This approach was used in the NIOSH/PAT program for many years, and a grand mean of "reference laboratories" is still used by NIOSH/PAT to determine true values. Table 3 shows the accuracy for each laboratory by deter mining the mean value and the standard deviation of the percent of actual reported, for each contaminant. Mean values that are significantly different from one hundred percent indicate problems with getting accurate values, while large standard deviations indicate a wide variation in the percent of actual values calculated for each level, for a given contaminant. Figure 1 shows the overall accuracy of each participating laboratory, for ach contaminant. Each of the four points is an average of the six values of percent of actual found for each contaminant. RESTRICTED: for use within The Dow Chemical Company only. 00 105986 CONFIDENTIAL 4 Figure 2 shows the precision of the reported values. Each of the numbers was normalized by using the following equation: N (Normalized) = ^ x 100 where R1 = the individual value reported for a compound at a given level, (T a the mean of the two values reported for a compound at a given level. This normalization was done so that all of the precision values could be displayed on the same figure using one set of control limits. Without the normalization, each laboratory would have required a different figure with different control limits shown, because the mean values reported for a given contaminant varied widely from laboratory to laboratory. Figure 3 shows the mean recovery reported by laboratory and by contaminant, with the relative precision of the calculated average percent recovery shown as the error bar. This is calculated from the formula tS RPn -- -------x 100 RnV"" Where t = student's t value for the number of measurements made S * standard deviation of the measurements for a given laboratory, lTn * average percent recovery reported n = number of measurements made The accuracy goal for this and subsequent Analytical Proficiency Testing Round Robins will be the larger of the following: a) 90% to 110% of actual value for compounds whose relative precision of a single determination at the 95% confidence level is 24.5% or less or b) (100 - X)% to (100 + X)% of the actual value for compounds whose rela tive precision of a single determination at the 95% confidence level is greater than 24.5%, where RP, X = --5 yr and RPs = relative precision for a single determination at the 95% confid nee level, as reported in the Industrial Hygiene Methods Manual, n = the number of measurements reported by the laboratory The precision goal for this and subsequent studies will be that, for each laboratory, the relative precision of the calculated average per cent of actual values reported (RPn) be no larger than RPS^ yp' DO 105987 confidential N 5 RPS and n have the same definitions as in the equation given above. RPn is calculated using the following equation: __ ts RPn - Z--_ * 100 where S is the standard deviation calculated for a given laboratory's set of measurements t is the student's t-value for the nunber of measurements, nt at the 95% -- confidence level and Rn = average percent of actual reported for the measurements made. Any laboratory submitting data points which were determined to be outliers by the Oixon criteria (Laboratories A and E) should review its analytical methods to ascertain possible sources of error. Possible sources of error includ the following: 1. Incorrect preparation of standards. Action: check calculations used to determine how to prepare standards; prepare two independent standards at the same or similar concentrations; loss of methyl chloride in preparing or handling standard would lead to a larger response factor and high results. 2. Erroneous calculations. Action: recheck all calculations. 3. Loss of compounds during desorption. Action: cool carbon disulfide to dry ice temperature before adding charcoal from tubes. A-. Loss of methyl chloride during storage, prior to analysis. Action: in the future, refrigerate prior to analysis. 5. Adsorption of compounds (especially CCl^) on charcoal after desorption. Action: if the desorbed sample is not analyzed shortly after preparation, remove the sample from the charcoal since CCl^ in particular, appears to irre versibly adsorb on the charcoal after standing'for an extended period. The study director will be in contact with each of the Dow Chemical U.S.A. industrial hygiene managers where laboratory problems were experienced to discuss corrective actions. -j. Because of the mixed performance on this APT, It is likely that it will be repeated earlier than its next scheduled date of December 1985, in order to assist laboratories in improving their analytical proficiency for these four compounds. RESTRICTED: for um within Th Dow Oemicai Company only. qq iq5988 CONFIDENTIAL vV * . / 6 REFERENCES 1. Poettcker, G., Program for conducting Industrial Hygiene Analytical Proficiency Round Robins, HEH2.12-39-1, 1983-84, August 1983. 2. Melcher, R. G., Industrial Hygiene (Reference) Procedure 106, "Desorption Efficiency and Recovery," Dow Chemical U.S.A., Midland, Michigan. 3. Coyne, l. B., Industrial Hygiene (Reference) Procedure 102, "Standard Preparation," Dow Chemical U.S.A., Midland, Michigan. 4. Dixon, W. 3., Processing Data for Outliers, Biometrics, 9:89, 1953. RESTRICTED: for u*a within The Dow Chemical Company only. DO 105989 CONFIDENTIAL J V 7 , > - ,1 V f:'> f' '* y Table 1. ANALYTICAL PROFICIENCY TESTING : RESULTS (MG/TUBE) Lab Level Actual Found Actual CH3C1 CH3CI CH2C12 Found CH2C12 Actual Found Actual Found CHCI3 CHCI3 CCI4 CC4 A HIGH A HIGH A MED A MED A LOW A LOW B HIGH B HIGH B MED B MED B LOW B LOW C HIGH C HIGH C MED C MED C LOW C LOW D HIGH D HIGH D MED D MED D LOW D LOW E HIGH E HIGH E MED E MED E LOW E LOW F HIGH F HIGH F HIGH F HIGH F HIGH F MED F MED F MED F MED F LOW F LOW F LOW F LOW F LOW Outliers 0.30 0.30 0.18 0.18 0.11 0.11 0.18 0.22 0.12 0.12 0.07 0.07 1.25 1.25 0.76 0.76 0.40 0.40 1.33 1.40 0.94 0.77 0.42 0.31 0.78 0.78 0.47 0.47 0.26 0.26 1.00 1.20 0.69* 0.69* 0.44* 0.38* 0.74 0.74 0.45 0.45 0.24 0.24 0.82 1.03 0.62 0.62 0.41 0.48* 0.30 0.30 0.18 0.18 0.11 0.11 0.21 0.25 0.16 0.16 0.08 0.09 1.25 1.25 0.76 0.76 0.40 0.40 1.09 1.02 0.66 0.69 0.38 0.38 0.78 0.78 0.47 0.47 0.26 0,26 0.53 0.50 0.33 0.34 0.18 0.18 0.74 0.74 0.45 0.45 0.24 0.24 0.60 0.57 0.38 0.40 0.20 0.21 0.30 0.30 0.18 0.18 0.11 0.11 0.29 0.38 0.26 0.18 0,15 0.13 1.25 1.25 0.76 0.76 0.40 0.40 1.06 1.29 0.77 0.70 0.42 0.42 0.78 0.78 0.47 0.47 0.26 0.26 0.74 0.85 0.49 0.46 0.27 0.28 0.74 0.74 0.45 0.45 0.24 0.24 0.56 0.86 0.50 0.46 0.27 0.27 0.30 0.30 0.18 0.18 0.11 0.11 0.36 0.33 0.21 0.23 0.13 0.12 1.25 1.25 0.76 0.76 0.40 0.40 1.29 1.25 0.74 0.75 0.43 0.41 0.78 0.78 0.47 0.47 0.26 0.26 0.90 0.84 0.51 0.51 0.29 0.29 0.74 0.74 0.45 0.45 0.24 0.24 0.92 0.84 0.55 0.53 0.29 0.30 0.30 0.30 0.18 0.18 0.11 0.11 0.29 0.28 0.20 0.16 0.14 0.12 1.25 1.25 0.76 0.76 0.40 0.40 1.46 1.30 1.37* 0.94 0.87* 1.17* 0.78 0.78 0.47 0.47 0.26 0.26 0.34 0.74 0.50 0.50 ; 0.29 -> 0.28 0.74 0.74 0.45 0.45 0.24 0.24 0.73 0.73 0.45 0.48 0.28 0.25 0.30 0.30 0.30 0.30 0.30 0.18 0.18 0.18 0.18 0.11 0.11 0.11 0.11 0.11 0.33 0.36 0.32 0.35 0.35 0.22 0.19 0.20 0.08* 0.11 0.11 0.14 0.11 0.13 1.25 1.25 1.25 1.25 1.25 0.76 0.76 0.76 0.76 0.40 0.40 0.40 0.40 0.40 1.20 1.21 1.21 1.30 1.34 -- 0.69 0.75 0.72 0.43 0.42 -- 0.43 0.45 0.78 0.78 0.78 0.78 0.78 0.47 0.47 0.47 0.47 0.26 0.26 0.26 0.26 0.26 0.77 0.76 0.80 0.86 0.87 0.46 0.42 0.47 0.47 0.27 0.26 0.26 0.27 0.27 RESTRICTED: for u within Tha Dow Qiamical Company only. 0.74 0.74 0.74 0.74 0.74 0.45 0.45 0.45 0.45 0.24 0.24 0.24 0.24 0.24 0.82 0.72 0.68 0.55 0.75 0.44 0.38 0.29 0.23 0.15 0.17 0.24 0.13 0.23 DO 105990 CONFIDENTIAL ; 8 Table 2. ANALYTICAL PROFICIENCY TESTINGt RESULTS (PERCENTAGE OF ACTUAL) Lab Level CH3C1 CH2C12 CHCI3 CC14 A HIGH A HIGH A MED A MED A LOW A LOW B HIGH B HIGH B MED B MED B LOW 8 LOW C HIGH C HIGH C MED C MED C LOW C LOW D HIGH D HIGH D MED D MED D LOW 0 LOW E HIGH E HIGH E MED E MED E LOW E LOW F- HIGH F HIGH F HIGH F HIGH F HIGH F MED F MED F MED F MED F LOW F LOW F LOW F LOW F LOW 60 106 73 112 67 124 67 101 64 105 64 77 70 87 84 82 89 87 87 90 74 94 85 95 98 85 127 103 142 101 100 91 138 105 115 106 121 103 109 100 114 97 126 99 115 107 105 102 96 117 94 104 111 180 87 124 128 217 110 292 111 96 119 97 107 97 116 104 118 107 121 108 91 111 99 46 94 103 108 104 104 125 102 108 118 112 128 154 147 147 169 146 67 64 70 72 69 70 94 109 104 97 105 107 115 108 109 109 112 112 44 95 106 107 112 107 99 97 102 110 112 98 90 100 101 105 100 100 102 104 111 139 138 138 171 200 81 77 84 89 83 85 75 116 111 102 113 111 124 114 122 118 121 125 98 98 100 106 118 105 110 97 91 74 102 97 84 64 51 61 73 101 53 96 RESTRICTED: for u*e within The Dow Chemical Company only. DO 105^91 CONFIDENTIAL;'. 9 Table 3. ANALYTICAL PROFICIENCY TESTING: RESULTS (PERCENTAGE OF ACTUAL) Laboratory CH3C1 CH2C12 CHCI3 CC4 Mean Std Mean Std Mean Std Mean Std A 66 4 104 16 149 13 150 31 B 82 8 89 5 69 3 83 4 C 120 19 99 9 103 6 105 15 D 115 8 101 4 111 3 121 4 E 104 15 172 73 95 26 104 8 F 108 19 101 7 101 5 82 20 RESTRICTED: for um within The Dow Chemical Company only. DO 105992 CONFIDENTIAL 10 RESTRICTED: for use within Tht Dow Chemical Company only. DO 105993 CONFIDENTIAL Figi 2 GRAPHIC DISPLAY OF PRECISION % 0 MEAN 180 170 (IsCHjCl; 2=CH2C12; 3=CHC13; 4=CC14) 160 150 140 4 130 120 2 1 34 1 110 1 1 4 2 1 2* 4 1 2*3 4+ 1 2+ 1* 2 3 1* 3 4* 2*3 3 4* 100 2 3* 2 3+4 3* 1* 2*3* 4* 1* 2 3 2*3 4 1 4 2 3+ 4 4+ 2 3 4 2 3 1 4 90 1 1 3 31 2 1 80 1 24 70 4 60 4* 3 34 3* 4 4 4 4i 1 4+ 1 12 3 4 1* 2+ 1 2*3* 4 1* 3# 1* 2 3# 1+ 2+ 2*3 4* 4 24 2 4* 2 50 40 l 1 B CD E LAB wo points hree points RESTRICTED: for u* within Th Dow Chtmical Company only. # lx points --F DO 105994 , confidential:- * DOW CHEMICAL U.S.A August 6, 1984 MIDLAND, MICHIGAN 48640 3. Lay Plaquemine, Louisiana cc: C. E. Halphen, Industrial Hygiene Manager, Louisiana Division CHLORINATED METHANES APT: HEH2.12-39-3(11) The results of the chlorinated methanes analytical proficiency testing (APT) are enclosed. The Plaquemine Environmental Control laboratory is identified as letter D in the report. R. Hf. A. Hahne Industrial Hygiene Laboratory 1803 Building ipik 517/636-9065 wi ewh . enclosure 4 i?, AN OPERATING UNIT OF THE DOW CHEMICAL COMPANY FOR USE WITHIN DOW ONLY 00 105996 CONFIDENTIAL,,;.: *`