Could the use of DEET cause problems with analyses?

TestAmerica receives many questions via its Ask the Experts program, and periodically they are questions that could benefit a large number of our clients. This is a question asked to one of our Experts and we would like to share the question and response.

Ask the Expert Question:

We will be sampling for (among other things) low level VOCs, SVOCs and Pesticides in a grassy area infested with ticks. The sampling plan is to apply tick repellent (probably DEET) to their legs, feet and clothing. The client is concerned that the tick repellent could cause a problem with the analyses, particularly the low level pesticide analysis.

While DEET is not a target, the concern is that it might be picked up during the analysis and cause interference. Have you ever run into this sort of thing before?

We advised the client to apply the repellent and let it dry before they begin sampling, and take care to keep the samples and sampling equipment away from the DEET treated surfaces. Any idea if this is something the client should be concerned about? 

Expert Response:

Although TestAmerica does not specifically analyze for DEET, the compound does fall within the chromatographic range that is analyzed for in the Semi Volatile Organic Compound (SVOC).  Since DEET is not a component in the standards mix, if it is present in a sample, it can be seen as a Tentatively Identified Compound (TIC) in the SVOC analytical run. 

While it is possible for DEET to also appear in an analytical run for Pesticides, we have never specifically experienced DEET interfering with a Pesticides analysis.  This most likely is due to the standards mix for the Pesticides analysis containing each of the target analytes within the EPA Method, which does not include DEET.

With proper application of the repellant as you have directed and the use of appropriate sampling procedures (gloves, care against cross contamination, etc) I would not expect it to be a problem.  I would suggest pre treatment of clothing etc away from the sampling location and supplies if at all possible.  Transfer from hands to equipment may warrant particular attention.