Page:NIOSH Manual of Analytical Methods - 9111.pdf/5

This page needs to be proofread.

METHAMPHETAMINE on Wipes by LC/MS : METHOD 9111, Issue 1, dated 17 October 2011 - Page 5 of 12

standard. Recommended primary (quantification) ions and internal standard ions are given in Table 2. Prepare a calibration graph (relative peak area vs. µg analyte per sample). 15. 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 LC vial may be diluted with the sulfuric acid desorption solution and reanalyzed. CALCULATIONS: 16. Determine the mass in µg/sample of methamphetamine found in the wipe samples and in the media blank from the calibration graph. 17. Calculate final concentration, C, of methamphetamine in µg/sample:

C =c

V1 -b V2

Where: c = concentration in sample (in µg/sample determined from the calibration curve)

V1 = dilution factor, if applicable V2 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. b = concentration in media blank (in µg/sample determined from the calibration curve). 18. Report concentration, C’, in µg per total area wiped (in cm²) as follows:

C’=

C A

Where: C = ug/sample (step 17). A = Total area wiped in cm² per sample. NOTE: For example, if the sample was a composite sample and the area was 400 cm², report results as µg/400 cm2. In general, if the area wiped was greater than or less than 100 cm2, do not convert value to µg/100 cm². To avoid confusion, report separately both µg/sample (C) and the total area wiped in cm2 per sample (A) for both discrete and composite samples. EVALUATION OF METHOD: This method was evaluated for methamphetamine over a range of approximately 0.4 µg/sample to 17.8 µg/sample on cotton gauze. These concentration levels represent approximately 3 through 100 times the limit of quantitation (LOQ) level. Results are reported in the Backup Data Report for 9111s[1]. The limit of detection (LOD) and LOQ were determined by preparing a series of media spiked standards, desorbing in the sulfuric acid desorption solution and analyzing in the SIM mode. The LODs were estimated using the procedure of Burkart [4]. An LOD of less than 0.02 µg/sample for methamphetamine on wipes was achieved in the SIM mode. The LOD was set at 0.05 µg/sample and the LOQ at 0.15 µg/sample for method development purposes. Lower LODs can be achieved in practice by including calibration standards at lower concentration levels and with proper instrument NIOSH Manual of Analytical Methods (NMAM), Fifth Edition

Method rev. 1.1.1

This article is issued from Wikisource. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.