METHAMPHETAMINE . . .on Wipes by Liquid-Liquid Extraction: METHOD 9106, Issue 1, dated 17 October 2011 - Page 6 of 31
d. Spike a known volume of analyte spiking solution into each calibration standard by spiking directly onto the media or into solution. Use the spiking volumes suggested in Table 7 to cover the desired range. e. Process each of these through steps 7 through 11 (same as the field samples.) f. Analyze these along with the field samples. (See MEASUREMENT, steps 15-17.) 14. Prepare matrix-spiked (QC) and matrix-spiked duplicate (QD) quality control samples [7]. a. Cotton gauze from the same lot used for taking samples in the field should be provided to the analytical laboratory to prepare these matrix-spiked quality control samples. b. The quality control samples (QC and QD) must be prepared independently at concentrations within the analytical range. (See Table 7 for applicable concentration ranges.) c. One quality control media blank (QB) must be included with each QC and QD pair. i. Transfer clean gauze wipes to new shipping containers. ii. Add 3 mL of isopropanol (or methanol if methanol was used in wiping) to each gauze wipe. iii. Spike QC and QD with a known amount of analyte as suggested in Table 7. d. Process each of these through steps 7 through 11 (same as the field samples). e. Analyze these along with the field samples. (See MEASUREMENT, steps 15-17.) MEASUREMENT: See APPENDIX G for special instructions on measurement. 15. Analyze the calibration standards, quality control samples, blanks, and samples by GC/MS. a. Set gas chromatograph according to manufacturer’s recommendations and to conditions listed on page 9106-1. b. Set mass spectrometer conditions to manufacturer’s specifications and those given on page 9106-1 for the scan mode or those in Table 6 for the SIM mode. c. Inject sample aliquot with autosampler or manually. NOTE: After the derivatives are prepared and just before analyzing any samples or standards, inject the highest concentrated standard several times in order to prime or deactivate the GC column and injection port. This will help minimize any drift in the instrument’s response to target analytes relative to their internal standards. d. After analysis, the vials should be recapped promptly and refrigerated if further analysis is anticipated. 16. Using extracted ion current profiles for the primary (quantification) ions specific to each analyte, measure GC peak areas of analyte(s) and internal standard(s) and compute relative peak areas by dividing the peak area of the analyte by the area of the appropriate internal standard. Recommended primary (quantification) ions and internal standards are given in Tables 6, 8, and 9. Prepare calibration graph (relative peak area vs. μg analyte per sample). 17. Samples from initial investigations of clandestine laboratories are likely to include highly contaminated samples. If sample results exceed the upper range of the calibration curve, the sample in the GC vial may be diluted and reanalyzed or a smaller aliquot of the initial acid desorbate diluted, re-extracted, derivatized, and analyzed. Refer to APPENDIX H for instructions and limitations on making dilutions. CALCULATIONS: 18. Determine the mass (in μg/sample) of respective analyte found in the wipe samples, and in the media blank from the calibration graph. 19. Calculate final concentration, C, of analyte in μg/sample:
= C c
V V1 V3 −b 5 V2 V4 V2
Where: c = concentration in sample (in μg/sample determined from the calibration curve). Method rev. 1.1.1
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition
