Page:NIOSH Manual of Analytical Methods - 9109.pdf/8

 METHAMPHETAMINE. . . on Wipes by SPE: METHOD 9109, Issue 1, dated 17 October 2011 - Page 8 of 33

Precision and accuracy were determined by analyzing 6 replicates at each of 6 concentration levels (nominally 0.1, 0.3, 1, 3, 10, and 30 μg/sample). Results are presented in Table 8a for cotton gauze and 8b for AlphaWipe®. The best precision and accuracies were dependent upon the use of carefully chosen internal standards, especially with steric hindrance of the amine (e.g., having N-ethyl and N-propyl groups). Long term sample storage stability was determined for periods up to 30 days under refrigeration (<6 °C) and for up to 7 days at room temperature (22-24 °C). Results are given in Table 5. Chlorodifluoroacetic anhydride (CDFAA) and pentafluoro propionic anhydride (PFPA) were evaluated as derivatizing agents for the SPE eluates. These were not effective, probably due to the high level of ammonium chloride residues in the SPE column eluates. They were most effective with the liquid-liquid extraction procedure of NIOSH 9106 [4]. For SPE, the mixed silanization-acylation reagent, MSTFA and MBHFBA [10, 18], proved very effective. The derivatization mixture is transferred directly to amber mini-GC vials and direct-injected without prior heating. Recovery of amphetamines from six different types of surfaces using cotton gauze was evaluated (see Table 10). The practice of serial wiping (wiping the same surface area a second time with a second gauze wipe and combining both wipes as a single sample) was evaluated. Four solvents for wetting the gauze were tested (distilled water, 5% distilled white vinegar, isopropanol, and methanol). Six replicates samples were taken on a latex painted wall. Recoveries and precisions are given in Table 10. The recoveries with 5% distilled white vinegar were better than for distilled water, but not as good as for isopropanol. Methanol is superior to isopropanol. Recoveries with isopropanol are greatly improved with a repeat (serial) wipe (11% improvement compared to only about 6% improvement with methanol). The study and results are reported in the Backup Data Report for NIOSH 9109 [1]. Additional research on surface sample recovery and solvent effectiveness has been reported by Martyny [10, 11]. REFERENCES: [1]	 Reynolds JM, Siso MC, Perkins JB [2004]. Backup Data Report for NIOSH 9109, Methamphetamine and illicit drugs, precursors, and adulterants on wipes by solid phase extraction, Abridged. Unpublished. Prepared under NIOSH Contract 200-2001-0800. [2]	 NIOSH [1995]. NIOSH Technical Report: Guidelines for air sampling and analytical method development and evaluation. By Kennedy ER, Fischbach TJ, Song R, Eller PM, Shulman SA. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 95-117. [3]	 Martyny JW, Arbuckle SL, McCammon CS Jr., Esswein EJ, Erb N [2003]. Chemical exposures associated with clandestine methamphetamine laboratories [http://www.njc.org/pdf/chemical_ exposures.pdf ]. [4]	 NIOSH [2011]. Methamphetamine and illicit drugs, precursors, and adulterants on wipes by liquid-liquid extraction: Method 9106. In: Ashley KA, O’Connor PF, eds. NIOSH manual of analytical methods. 5th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, [www.cdc. gov/niosh/nmam/]. [5]	 NIOSH [2011]. Methamphetamine on wipes by liquid chromatography/mass spectrometry: Method 9111. In: Ashley KA, O’Connor PF, eds. NIOSH manual of analytical methods. 5th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, [www.cdc.gov/niosh/nmam/]. [6]	 Baum RM [1985]. New variety of street drugs poses growing problem. Chemical and Engineering News, 63(63):7-16. [7]	 Buchanan JF, Brown CR [1988]. Designer drugs, a problem in clinical toxicology. Medical Toxicology 3:1-17.

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NIOSH Manual of Analytical Methods (NMAM), Fifth Edition