Page:NIOSH Manual of Analytical Methods - 9111.pdf/3
METHAMPHETAMINE on Wipes by LC/MS : METHOD 9111, Issue 1, dated 17 October 2011 - Page 3 of 12
SAMPLING: See APPENDIX for special instructions on sampling. 1. Using a new pair of gloves, remove a gauze wipe from its protective package. Moisten the wipe with approximately 3 to 4 mL of methanol (or isopropanol). NOTE 1: Apply no more solvent than that needed to moisten approximately the central 80% of the area of the gauze wipe. Excess solvent may cause sample loss due to dripping from the wipe. NOTE 2: Do not use vinyl gloves due to the potential for leaching of phthalate plasticizers and contamination of the samples. 2. Place the template over the area to be sampled (may tape in place along outside edge of template). Wipe the surface to be sampled with firm pressure, using vertical S-strokes. Fold the exposed side of the pad in and wipe the area with horizontal S-strokes. Fold the pad once more and wipe the area again with vertical S-strokes. 3. Fold the pad, exposed side in, and place in shipping container and seal with cap. NOTE: Keep samples refrigerated (<6 ºC). While methamphetamine and several related amines are stable on the recommended wipe media for at least 7 days at room temperature, refrigeration is recommended as soon as possible. 4. Clean the template before use for the next sample or use a new disposable template. 5. Label each sample clearly with a unique sample identifier. 6. Prepare a minimum of two field blanks with one field blank for every ten samples. NOTE: In addition, include at least 3 media blanks for the analytical laboratory to use for their purposes. The wipes used for the media blanks should be from the same lot as the field samples. SAMPLE PREPARATION: 7. Desorption from media: a. Remove cap from shipping container. Sample media should fit loosely in the container. If not, rearrange media carefully with rinsed forceps or transfer to a larger container. If the sample media are transferred to a larger container, do not discard the original container. Samples may consist of more than one wipe. If this is the case, internal standard and desorption solution volumes may be adjusted accordingly. b. Spike exactly 50 µL of internal standard spiking solution onto each wipe sample. c. Add 30 mL desorption solution (0.1 M sulfuric acid). If the samples were transferred to a larger container, the original shipping container must be rinsed with the desorption solution first, shaken, and the rinsate decanted into the larger container. d. Cap securely and mix contents by inverting the tubes end over end on a rotary mixer at 10-30 rpm for at least one hour. NOTE 1: The desorption solution must percolate freely through the gauze wipes. NOTE 2: If there is reason to believe that the samples may be alkaline enough to overcome the acidity of the desorption solution (e.g. wipes of unpainted concrete or stucco surfaces), then the pH must be adjusted to about ≤ 4. See APPENDIX for instructions. e. Filter an aliquot of the sample through a 0.45 µm pore size Ion Chromatography Acrodisc® for analysis. 8. Transfer the filtered sample into a vial and cap. 9. Analyze samples, standards, blanks, and Quality Control samples (QCs) by LC-MS. (See MEASUREMENT, steps 13-15.)
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition
Method rev. 1.1.1