Where can I find wipe sampling methods in SW-846?
There are two instances where wipe sampling is addressed within SW-846, Method 3572 and Appendix A of Method 8290A. The two methods differ in their approach and applicability, method 8290A has a limited discussion of wipe sampling only in the context of laboratory safety concerns relative to dioxins and furans, the wipe sampling procedure in method 3572 is intended to assess surface contamination both inside and outside of the laboratory. However, EPA does not recommend that the procedures described in either of these methods be extended to other analytes or other situations.
Outside of SW-846, wipe sampling is specified as a means for determining compliance with certain cleanup and decontamination requirements in the TSCA PCB regulations (40 CFR 761). The method for conducting wipe sampling under the TSCA PCB regulations can be found at 40 CFR 761.123 under “standard wipe sample.” When the TSCA PCB regulations require wipe sampling as the method for determining compliance, the unit used is micrograms per 100 cm2.
While wipe sampling has been described in the open literature, one of the biggest problems is that it is very difficult to interpret the results. By its very nature, the analysis of whatever material is used to wipe a surface (often filter paper wet with a solvent) yields the mass of the analyte(s), for example nanograms of dioxin or micrograms of another analyte. However, there is no straightforward way in which to convert that mass into a concentration per unit area, nor any good way in which to compare results from different wipes, except to say that one wipe picked up more material than another. If the surfaces that are wiped have different characteristics, for example a smooth metal surface versus a rough concrete block, there is no way to judge the efficiency of the wiping process itself. Therefore, use caution in interpreting the results of wipe samples.
Other Category: Sampling