METHAMPHETAMINE . . . on Wipes by SPE: METHOD 9109, Issue 1, dated 17 October 2011 - Page 6 of 33
MEASUREMENT: See APPENDIX G for special instructions on measurement. 15. Analyze the calibration standards, quality control samples, blanks, a continuing calibration verification (CCV) standard consisting of one of the initial calibration standards, and samples by GC/MS. a. Set gas chromatograph according to manufacturer’s recommendations and to conditions listed on page 9109-1. b. Set mass spectrometer conditions to manufacturer’s specifications and those given on page 9109-1 for the scan mode or those in Table 6 for the SIM mode. c. Inject sample volume 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 = concentration in sample (in µg/sample determined from the calibration curve). V1 = volume correction factor (needed only when the volume of internal standard spiking V2 solution used for spiking the samples - such as for composite samples requiring larger
desorption solution volumes - is different from that used for spiking the calibration standards). (See Table 7, footnote 4). V1 = volume in µL of internal standard spiking solution used to spike samples. V2 = volume in µL of internal standard spiking solution used to spike the standards.
V3 = dilution factor, if applicable. V4
V3 = 5 mL (volume of desorbate normally taken for extraction in step 8d).
Method rev. 1.1.1
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition
