Page:NIOSH Manual of Analytical Methods - 8007.pdf/4

TOLUENE in Blood: METHOD 8007, Issue 1, dated 5 March 2013 - Page 4 of 5

CALCULATIONS: 18. Determine the concentration (µg/mL) of the toluene in each sample of blood using the calibration curve obtained in step 11c. EVALUATION OF METHOD: This method was evaluated over the range specified on page 8007-1. These ranges, 0.0208 to 5.76 µg/mL, represent from 1 times the LOQ to 300 times the LOQ. Six replicates were analyzed at each level. The average recoveries at the various levels ranged from 97% to 106% for toluene. The LOD and LOQ were determined by preparing a series of duplicate standards. Each series was made up and analyzed on a different day. The resulting data was then fitted to a quadratic curve. The LOD and LOQ were estimated according to Burkart’s Method. [9] A long-term storage study was carried out at the 10 x LOQ level. Citrated whole blood samples that were spiked with toluene were stored at 24 °C and 4 °C for 1, 4, and 7 days and for 7,10, 21, and 30 days (respectively,) and then analyzed. Average recoveries were 96% at room temperature and 99% at 4 °C. Room temperature storage is not advised because if the sample clots before it is analyzed, the results will be compromised. LIMITATION OF METHOD: Concerning the use of isobutanol as an internal standard: While the boiling points of toluene and isobutanol are similar, their Henry’s Law constants and thus their partitioning coefficients are quite different. This could lead to biases if there are differences in polarity in the samples or between the samples and the standards. This is one reason the calibration standards in this method are prepared using blood and not just solvent. An alternative approach could entail the use of an internal standard that partitions similarly to toluene, such as fully-deuterated toluene (toluene-d8). This would cause an increase in the cost of the method per sample (and would need to be validated by the end user), but is mentioned here as an option. REFERENCES: [1] ACGIH [2012]. 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. p. 110. [2] Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area [2011]. List of MAK and BAT values 2011; maximum concentrations and biological tolerance values at the workplace. Report no. 47. Weinheim, DFG: Deutsche Forschunggemeinschaft, Wiley-VCH Verlag GmbH & Co., p 218. [3] Stone LC, Perkins JB [2003]. Backup data report for toluene in blood. DataChem Laboratories, Inc. under NIOSH contract CDC-200-2001-08000 (unpublished.) [4] NIOSH [1994]. Methyl ethyl ketone, ethanol and toluene in blood: Method 8002. In Eller PM, Cassinelli ME, eds. NIOSH Manual of Analytical Methods, 4th ed. 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. [5] Blount BC, Kobelski RJ, McElprang DO, Ashley DL, Morrow JC, Chambers DM, and Cardinali FL [2006]. Quantification of 31 volatile organic compounds in whole blood using solid-phase microextractions and gas chromatography-mass spectrometry. J Chrom B 832(2): 292-301. [6] CDC [2007]. 2007 Guidelines for isolation precautions: preventing transmission of infectious agents in healthcaree settings. [1]. Date accessed: April, 2013. [7] OSHA [2012]. Bloodborne pathogens and needlestick prevention. [www.osha.gov/SLTC/ bloodbornepathogens/index.html]. Date accessed: September, 2012. NIOSH Manual of Analytical Methods (NMAM), Fifth Edition