METHAMPHETAMINE . . . on Wipes by SPE: METHOD 9109, Issue 1, dated 17 October 2011 - Page 5 of 33
been capped tightly enough). Such samples need to be reprocessed beginning at step 8 since the derivatives are not stable in the presence of moisture. If the vials are securely capped, the solutions will be stable for several days at room temperature and at least a week refrigerated. Protect vials from light (amber vials recommended.) 11. Analyze samples, standards, blanks, and QCs by GC-MS. (See MEASUREMENT, steps 15-17 and p. 9109-1.) CALIBRATION AND QUALITY CONTROL: 12. Determine retention times for the derivatives of the analytes of interest using the column and chromatographic conditions specified on page 9109-1. Table 11 gives typical retention times for various drugs, precursors, and adulterants. Figure 1 shows a typical chromatogram. 13. Calibrate daily with at least six calibration standards and a blank selected from Table 7 to cover the analytical range. a. Prepare the analyte spiking solution as follows: Add known amounts of individual drug stock solutions to a volumetric flask and dilute to volume with methanol. A recommended final concentration for this solution is approximately 200 μg each per mL. b. Prepare calibration standards and media blanks in clean shipping containers (e.g., 50-mL polypropylene centrifuge tubes or equivalent). NOTE: Liquid standards (standards without added blank wipe media) may be prepared in lieu of media standards if cotton gauze was used for the samples. c. Add 3 mL methanol (or isopropanol if isopropanol was used with the samples in the field) to each calibration standard and media blank. NOTE: If two gauze wipes were routinely used for every sample, increase methanol (or isopropanol) to 4 mL. See Table 7, footnote 2. 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 the desorption, solid phase extraction (SPE), drying, and derivatization steps (steps 7 through 11) along with the field samples. f. Analyze these along with the field samples. (See MEASUREMENT, steps 15-17.) 14. Prepare matrix-spiked and matrix-spiked duplicate (QC and QD) quality control samples.[8] 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. d. Spike QC and QD with a known amount of target analyte as suggested in Table 7. i. Transfer clean wipes to new shipping containers. ii. Add 3 mL of methanol (or isopropanol if isopropanol was used in wiping) to each wipe. iii. Spike QC and QD with a known amount of analyte as suggested in Table 7. NOTE: If two gauze wipes were used for the majority of samples in an analytical set, use two clean gauze wipes for each QB, QC, and QD, and increase isopropanol (or methanol) to 4 mL. See Table 7, footnote 2. e. Process quality control samples through the desorption, SPE, drying, and derivatization steps (steps 7 through 11) along with the calibration standards, blanks, and field samples. f. Analyze these along with the calibration standards, blanks, and field samples. (See MEASUREMENT, steps 15-17.)
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition
Method rev. 1.1.1
