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 ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 4 of 9

convenient than using the traditional mixed acid hot plate approach. The elimination of perchloric acid in the sample digestion procedure helps to improve the safety of the method. [7] Summary data are presented in Table 3 for levels 3X LOQ (lower level in Table 3) and 300X LOQ (higher level in Table 3) and for the ranges of loadings given in Table 4. Samples were subjected to microwave digestion using a CEM MDS-2100 device according to the conditions specified in the “sample preparation” section above (see Note of step #5). The values in Tables 3 and 4 were determined using several different ICP-AES instruments which were operated according to manufacturer’s instructions. The precision and recovery data, instrumental detection limits, sensitivity, and analytical wavelengths are listed in Table 3 and Table 4. All of the precision data were evaluated for homogeneity for all six concentration levels tested using the Bartlett’s test and the results are listed in the method backup data report [8] and summarized in Tables 3 and 4. A statistical analysis found that the data were poolable and all elements had calculated method precision accuracies of less than 25%. This overall precision (ŜrT ) and accuracy as given in Table 4 is an upper limit predictor of precision. Accuracy data (Table 4) demonstrate the utility of the method for all of the elements listed. A discussion of metals and metalloid analysis by ICP-AES is presented in an international voluntary consensus standard [3] and the microwave digestion procedure has been evaluated against other digestion procedures through an interlaboratory trial [10]. REFERENCES [1]	 ACGIH [2013]. TLVs and BEIs based on the documentation of the Threshold Limit Values for chemical substances and physical agents and Biological Exposure Indices. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists. [www.acgih.org]. [Data accessed April 2014.] [2]	 Institut fur Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung [2013]. GESTIS database on hazardous substances (German Social Accident Insurance). Sankt Augustin, FRG: [http://www. dguv.de/ifa/Gefahrstoffdatenbanken/GESTIS-Stoffdatenbank/index-2.jsp]. [Data accessed April 2014.] [3]	 ASTM [2010]. ASTM D7035-10, Standard test method for the determination of metals and metalloids in airborne particulate matter by inductively coupled plasma atomic emission spectrometry. West Conshohocken, PA: ASTM International [www.astm.org]. [4]	 NIOSH [1994] NIOSH Manual of analytical methods (NMAM). 4th ed. Schlecht PC, O’Connor PF, eds. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113 [www.cdc.gov/niosh/nmam/]. [5]	 ASTM International [2011]. ASTM D1193-77, Standard specification for reagent water. West Conshohocken, PA: ASTM International [www.astm.org]. [6]	 NIOSH [2005]. NIOSH Pocket guide to chemical hazards. Barsan ME, ed. Cincinnati, OH: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2005-149. [7]	 Furr AK, ed. [1995]. CRC Handbook of laboratory safety, 4th ed. Boca Raton, FL: CRC Press. [8]	 Stone LC, Perkins JB, Rogers DM [2003]. Elements by ICP using microwave digestion, NMAM 7302, Issue 1, Backup data report. Cincinnati OH: Datachem Laboratory developed under contract CDC200-2001-08000. Unpublished. [9]	 Lide DR, ed. [1994] Handbook of chemistry and physics. 74th ed. Baca Raton, FL.: CRC Press. [10]	 Butler OT, Howe AM [1999]. Development of an international standard for the determination of metals and metalloids in workplace air using ICP-AES: Evaluation of sample dissolution procedures through an interlaboratory trial. J. Environ. Monit. 1: 23-32.

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition