Page:NIOSH Manual of Analytical Methods - 9111.pdf/11

METHAMPHETAMINE on Wipes by LC/MS : METHOD 9111, Issue 1, dated 17 October 2011 - Page 11 of 12

APPENDIX: SAMPLING NOTE: For further information and data on the effects of surface composition and porosity as well as the use of different solvents on the efficacy of wipe sampling, please see reports by Martyny [6, 7]. 1. Follow specific requirements of surface area to be wiped (usually 100 cm2) and action threshold (or maximum allowable residual level) set by the agency having legal jurisdiction 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. 2. The following steps only summarize the overall sampling procedure and are not intended to be used as a shortcut or wipe sampling procedures that may be specified by the legal jurisdiction or the client. 3. Prepare a rigid template from disposable cardstock or a sheet of Teflon® having either a 10 cm x 10 cm or 1 ft x 1 ft (1000 cm²) square hole cut according to the dimensions required by the regulatory agency. The template must be able to retain its shape during wiping to ensure that the areas wiped were 100 cm² or 1 ft². Single-use disposable cardstock is preferred because it eliminates the possibility for cross-contamination and the necessity to take a blank wipe between samples in step 3. 4. Provide enough wipe media from the same lot to cover all required laboratory media blanks, fieldequipment blanks, samples and sample duplicates, and quality control samples. Use gauze in sterile packaging to minimize the chance for cross-contamination which might more easily occur with open bulk packaged cotton gauze. The gauze wipes needed for the laboratory media blanks and QC samples are to be sent to the laboratory in their unopened sterile packages. 5. 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 crosscontamination and provide laboratory with a blank wipe of the cleaned template between samples to ensure that no cross-contamination has occurred. 6. With freshly gloved hand, take one gauze and wet it with isopropanol or methanol (about 3-4 mL for either the 3” x 3” (7.5 cm x 7.5 cm) 12-ply or the 4” x 4” (10 cm x 10 cm) 8-ply cotton gauze wipes). Alternatively, pre-wet and insert the gauze wipes into the sample containers off-site. This avoids any possibility of the bottle of methanol or isopropanol becoming contaminated on-site with methamphetamine. If the wipes were prepared off-site, then remove pre-wetted gauze wipe from sample container, opening only one sample container at a time. In either case, squeeze out and discard any excess solvent from the gauze wipe. Use fresh latex or nitrile gloves for each separate sample and blank. Do not use vinyl gloves due to the potential for leaching of phthalate plasticizers and contamination of the samples. 7. Wipe Techniques a. Concentric Squares Wiping Technique (particularly suitable for smooth and non-porous surfaces): Fold the pre-wetted gauze in half and then fold in half again. Using firm pressure wipe the area within the template. Start at one of the inside corners of the template and wipe in concentric squares, progressing toward the center. End with a scooping motion. Without allowing the gauze to touch any other surface, reverse the last fold so that the exposed side of the gauze is facing inward and using a fresh surface of the gauze, wipe the same area in the same manner as before. Roll or fold the gauze again and insert into the shipping container. b. Side-to-side Wiping (or Blotting) Technique (particularly suitable for rough, porous, and/or soiled surfaces): Fold the pre-wetted gauze in half and then fold in half again. Using firm pressure wipe or blot the area within the template with at least five overlapping side-to-side horizontal passes (see NOTE) beginning at the top and progressing to the bottom in a “Z” pattern. End with a scooping motion. If blotting, blot at least five times on each horizontal pass (see NOTE). Without allowing the gauze to touch any other surface, reverse the last fold so that the exposed side of NIOSH Manual of Analytical Methods (NMAM), Fifth Edition

Method rev. 1.1.1