National Institute for Occupational Safety and Health

“ However, the maximum possible error can be calculated. Since the maximum amount of alcohol that a recommended wipe can hold is about 6 mL when saturated (dripping wet) , there can only be a deviation of plus or minus 3 mL from the 3 mL alcohol added to the calibration standards. Therefore, the maximum error in a result due to differences in the volume of residual alcohol in a cotton gauze sample compared to the standards can only be three times the error for a 1 mL difference in volume. Since the error for ±1 mL is ±3.03%, the maximum error for ±3 mL is three times larger, or ±9.1%. ”

“ The practice of serial wiping (wiping the same surface area a second time with a second gauze wipe and combining both wipes as a single sample) was evaluated. Four solvents for wetting the gauze were tested (distilled water, 5% distilled white vinegar, isopropanol, and methanol) . Six replicate samples were made on a latex painted wall. Recoveries and precisions are given in Table 11a. The recoveries with 5% distilled white vinegar were better than for distilled water, but not as good as for isopropanol. Methanol is superior to isopropanol. ”

“ A template might not always be applicable, as in curved or odd-shaped areas such as around burners on stove tops or a fan blade. In such cases sample an area as close to either 100 cm2 or 1000 cm2 as feasible and provide the measurement to the regulatory agency and to the analytical laboratory for proper reporting. Tape can be used to delineate the sampling area. 4.
It is recommended to provide extra wipe media from the same lot for required media blanks, field equipment blanks, samples, and quality-control samples. 5. ”

“ Gauze in sterile packaging is recommended to minimize the chance for cross-contamination, which can more easily occur with open bulk packaged cotton gauze. 6.
To prevent contamination in the field, another alternative is to 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 (or other analytes) . If the wipes were prepared off-site, then remove pre-wetted gauze wipe from sample container, opening only one sample container at a time. ”

“ Lower LODs are achievable with lower concentration calibration standards and operation of the mass spectrometer in the SIM mode. LODs were calculated on liquid standards using the procedure of Burkart [8] . (4) MDLs are provided as an alternate expression of sensitivity. These MDLs are calculated as the standard deviation of six replicates on spiked media analyzed at the 0.1 μg/sample level (except as noted) times the Student’s t value for 6 replicates (3.365) . (Normally 7 replicates are used.) (5) Cotton gauze samples were spiked at 3 μg/sample per analyte. ”

“ NIOSH has not established health-based or feasibility-based airborne Recommended Exposure Limits (RELs) or surface contamination guidelines for clandestine drug laboratories. State surface contamination limits are provided as an aid to those seeking additional information and does not constitute endorsement by NIOSH. The National Alliance for Model State Drug Laws (NAMSDL) website: http://www.namsdl.org/home.htm periodically summarizes state feasibility-based decontamination limits and proposed state legislative requirements and guidelines [16] . ”

“ METHOD 9106, Issue 1, dated 17 October 2011 - Page 30 of 31
e. The problem of incomplete derivatization can be minimized by the use of an isotopic (e.g. deuterated) analog for each of the target analytes as the internal standard for that compound. This allows quantification in spite of incomplete derivatization. 2.
Dilution Procedure B (dilution of a smaller aliquot of the original desorbate) : If the sample was not completely derivatized or if large dilutions are needed (e.g. greater than about 1:5) , the following procedure can be used. ”

“ If an oil-like residue or film persists, then the sample may have too many contaminants that were not removed at the cleanup step or were introduced subsequent to cleanup. In such a case, return to step 7f and perform the clean-up (step 8) on another 10-mL aliquot of the sample desorbate using methylene chloride as the cleanup solvent instead of hexane. Discard the (lower) organic layer to waste before proceeding to steps 9 through 11. e. Reconstitute the dried residue with 1 mL of the reconstitution solvent. The reconstituted solution normally will become deep blue in color. ”

“ On areas larger than 100 cm2, more than five passes and blots will be needed. c. Repeat or Serial Wiping: If isopropanol is used for wiping, a serial or repeat wipe sample of the same area with a fresh gauze wipe will improve sampling efficiency. (See recoveries for second wipe in Tables 11a and 11b.) For serial wiping, repeat the wiping procedure described above (APPENDIX steps 7a or 7b) with a fresh gauze wipe. Place the second gauze wipe into the same shipping container as the first gauze. The 50-mL polypropylene centrifuge tubes are large enough to contain up to two gauze wipes. ”

“ Aspirate the (upper) organic layer to waste. Exercise care to not remove any of the aqueous layer. 9.
Extraction of analytes into methylene chloride: a. Add 1-2 drops (20-50 μL) of the mixed pH indicator (phenolphthalein + bromothymol blue) solution to each sample. The color of the samples should be yellow, which indicates that the samples are sufficiently acidic for desorption of the analytes from the wipe samples. b. Add 0.5 mL of 10 M sodium hydroxide to each sample. ”

“ 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. Note: Wiping in concentric squares is described by OSHA [21] . It is especially suitable for large (e.g. 1000 cm2) areas. ”

“ 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. ”

“ For methamphetamine, the range is 0.05 to 60 μg/sample (sample = 100 cm2 or 1000 cm2) . This method was developed for the analysis of selected drugs and precursors on surfaces in clandestine drug labs. [1, 2] Sampling methodology was tested using wipes on smooth, non-porous surfaces. The APPENDIX contains sampling information for other types of surfaces. INTERFERENCES: No chromatographic interferences detected. Water, surfactants and polyols inhibit derivatization. ”

“ Not all forms are presented. Parent compounds are not presented that have irregular or overly broad GC peak shapes under the GC conditions used. Spectra for chlorodifluoroacetyl derivatives are given in the Backup Data Report [1] (5) Retention time relative to 4,4’-dibromooctafluorobiphenyl. (6) Retention time relative to the chlorodifluoroacetyl derivative of methamphetamine. (7) I$ = Internal standard. (8) Intentional or unintentional adulterants. For example, phentermine may be added to MDMA and caffeine added to methamphetamine. ”

“ Avoid ring-labeled amphetamine-D5 (CAS 65538-33-2) since the primary (quantification) ion is the same as for amphetamine and GC peaks overlap significantly. Also avoid methamphetamine-D5 (CAS 60124-88-1) since GC peaks significantly overlap and secondary ions for the chlorodifluoroacetyl derivative are not baseline resolved. ”

“ 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.) ”