On-matrix derivatization for dynamic headspace sampling of nonvolatile surface residues

The goal of this study is to extend sampling by the field and laboratory emission cell (FLEC) dynamic headspace technique to applications that target nonvolatile residues. On-matrix derivatization of residues to render analytes stable and more volatile is explored to achieve this goal. Results show that on-matrix derivatizations of nerve agent hydrolysis products (monoalkyl methylphosphonic acids and methylphosphonic acid [MPA]) with diazomethane were successful on glass and painted wallboard (at the 10-μg level). It also was successful on the more difficult concrete (at the 500-μg level) and carpet (at the 20-μg level), substrates that cannot be successfully sampled using swipe techniques. Analysis of additional chemical warfare (CW)-associated residues can be approached by on-matrix derivatization with trifluoroacetic anhydride (TFAA). For example, amines (used as stabilizers or present as decomposition products of the nerve agent VX) or thiodiglycol (hydrolysis product of sulfur mustard) could be sampled as their TFAA derivatives from glass, painted wallboard, and concrete (at the 40-μg level), as well as carpet (at the 80-μg level) surfaces. Although the amine and thiodiglycol are semi-volatile and could be sampled directly, derivatization improves the recovery and chromatographic behavior of these analytes.