Cryofocusing capillary microextraction of volatiles (Cryo-CMV) as a novel headspace extraction device for the analysis of volatile organic compounds and smokeless powders

Abstract A novel field sampling device for fast, sensitive, dynamic headspace sampling of volatile organic compounds (VOCs) and smokeless powders from air is described. The capillary microextraction of volatiles (CMV) is an inexpensive, preconcentration technique that results in fast sampling times (as low as 2 min) with high efficiency and sensitivity. Analysis of the CMV with GC–MS is achieved with a thermal desorption probe to introduce the CMV directly into the injection port of a GC. A cryofocusing device consisting of a Peltier-cooled module that operates down to −10 °C was employed to improve the extraction efficiency of the CMV for sampling both VOCs and smokeless powders. The method performance using the CMV for the analysis of 17 VOC’s, including the BTEX compounds (Benzene, Toluene, Ethylbenzene, and Xylenes) is demonstrated using the criteria established by the Environmental Protection Agency (EPA) for sorbent tube sampling of toxic organic compounds in ambient air (EPA TO-17). Experimental results with known standards yield absolute mass detection limits ranging from 2.0 to 4.6 ng for the target compounds, in a 2 L air sample. A 35–100% improvement in the analytical performance was achieved by sampling at −10 °C, in comparison to 20 °C, for most compounds. Using cryofocusing conditions, precision of 8–53 %RSD was achieved for headspace extraction for the majority of the compounds with recoveries of as much as 37% and low breakthrough. Furthermore, the headspace calibration curves show a linearity of 0.951 or better for the target compounds, suggesting the quantitation capabilities of the CMV device. The CMV method performance was further demonstrated for the detection of markers above the headspace of smokeless powder. Experimental results with known standards, yield method detection limits of 2.0 ng and 1.3 ng for nitroglycerine (NG) and diphenylamine (DPA), respectively, in a 2 L air sampling volume followed by simultaneous SIM mode GC–MS analysis. Using cryofocusing conditions for the headspace extraction of Hodgdon smokeless powder, a 29–38% improvement in the analytical performance of NG was achieved with 18 %RSD precision, by sampling at 2.5 °C to −10 °C, in comparison to room temperature at 20 °C.