Page:NIOSH Manual of Analytical Methods - 9106.pdf/24

 METHAMPHETAMINE. . .on Wipes by Liquid-Liquid Extraction: METHOD 9106, Issue 1, dated 17 October 2011 - Page 24 of 31

APPENDIX A. REAGENTS and SOLUTIONS: 1.	For derivatization, pentafluoropropionic anhydride (PFPA) may be substituted for chlorodifluoroacetic anhydride (CDFAA). Spectra, retention times, suggested quantification ions, and precision and accuracy data for PFPA derivatives are given in the Backup Data Report [1]. Spectra for CDFAA derivatives are also given in the Backup Data Report [1]. NOTE:	 100 μL of pentafluoropropionic anhydride (PFPA) may be substituted for chlorodifluoroacetic anhydride, but the samples must be heated to 90 °C for 20-30 minutes in step 11c. 2.	The instrumental internal standard, 4,4’-dibromooctafluorobiphenyl is optional. It is useful for monitoring instrument tuning and autosampler performance. 3.	Primary amines form Schiff bases and enamines with ketones and aldehydes. These may in turn form derivatives with the acylating reagents. The use of acetone must be avoided strictly prior to the analytes being derivatized. Glassware and equipment rinsed with acetone must be thoroughly dried. Toluene should be avoided for making up standard solutions because it usually contains benzaldehyde, an oxidation product of toluene. Condensation products have been observed between primary amines and benzaldehyde. The only solvents recommended for the preparation of stock solutions and dilutions thereof are methanol (preferably) and isopropanol. 4.	The reconstitution solvent should not contain methanol or other alcohol since the derivatized alcohol groups in ephedrine type compounds are hydrolyzed over time. Toluene containing 10 percent acetone is recommended. B. EQUIPMENT: 1.	Wipe media: Besides cotton gauze, 4”×4” (10 cm x 10 cm) 4-ply MIRASORB® (Johnson and Johnson), and 4”×4” (10 cm x 10 cm) AlphaWipe® (TX® 1004, Texwipe Corp.) were acceptable wipe media and can be used in the absence of cotton gauze. MIRASORB®, a non-woven cotton/polyester blend, is discontinued but counterparts exist that claim to be of identical construction and fiber composition. AlphaWipe® is a hydrophilic, highly adsorbent, tightly knitted continuous filament polyester wipe. Precision and accuracy data for MIRASORB® and AlphaWipe® are given in the Backup Data Report [1]. 2.	Shipping containers: The 50-mL polypropylene centrifuge tubes with caps are preferred for one or two gauze wipes and are not as breakable as glass 40-mL VOA vials. The 40-mL VOA vials are acceptable for single gauze wipes. Larger containers (glass with a PTFE lined cap) should be used for combining more than two gauze wipes into a single sample. The size of the container for two or more wipes should be approximately 25 mL per gauze wipe (e.g. a minimum size of 100-mL for up to four gauze wipe samples). There needs to be enough extra headspace in the shipping container to allow the desorption solution to cover the gauze wipes and to percolate freely through the wipe sample(s) during mixing. 3.	Each regulatory agency having legal jurisdiction over the contaminated site may require different but specific off-site preparation and on-site sampling procedures. It is important to consult local regulatory agencies or departments of health having legal jurisdiction over contaminated sites to determine specific sampling, quality control, analyses, and reporting requirements. C. SAMPLING: 1.	Follow specific requirements of surface area to be wiped (usually 100 cm2 or 1000 cm2) and action threshold (or maximum allowable residual level) set by the state or specified by the client. Uptake rates depend upon the wipe sampling method used, so the specific wipe technique used must be specified, and any deviations from the required wipe sampling requirements noted. NOTE:	 To ensure that samples have not been tampered with, the use of custody seals and a chain-ofcustody form is strongly recommended. 2.	Prepare a rigid template from disposable cardstock or a sheet of PTFE having either a 10 cm × 10 cm or 32 cm × 32 cm square-cut hole. The template must be able to retain its shape during wiping to ensure that the areas wiped were either 100 cm2 or 1000 cm2. Secure the template(s) to the area(s) to be wiped (e.g. with tape along outside edge of template). If a single-use disposable template is not used, clean the template between samples to avoid cross-contamination, and provide the Method rev. 1.1.1

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition