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Solid-phase microextraction (SPME) is a fast, solvent-free alternative to conventional sample preparation techniques. This technique involves exposing a fused silica fiber that has been coated with a stationary phase to an aqueous solution or its headspace to selectively extract compounds from their matrix. The fiber is then removed, and the analytes are thermally desorbed in the injector of a gas chromatograph. By sampling from the headspace above sample matrices, SPME can be used to extract target analytes from very complex matrices. In this study, SPME in the headspace is used in developing a method for the dye 1-methylaminoanthraquinone (MAAQ) and two lachrymators: orthochlorobenzalmalononitrile (CS) (tear gas) and 2-chloroacetophenone (CN) (tear gas). The focus is to develop a robust method to minimize sample preparation and to reduce matrix interferences encountered by other extraction techniques. In developing the method, several fibers are studied for their affinity for the compounds of interest. Although this method is developed for qualitative analysis, the extraction time and temperature profile are thoroughly investigated to provide the optimal conditions. The use of a salt solution is evaluated to increase the partitioning of MAAQ into the headspace. Using this method, qualitative extraction is achieved for the analysis of CN, CS, and MAAQ from its matrices. CN and CS are extracted in less than 5 min, though MAAQ needed more than 15 min to achieve a reasonable response. If more sensitivity is required, the use of a salt solution increases the response of MAAQ by 90-fold.

Temperature dependencies of the electrical resistivity, ρ, and the thermoelectric power, α, are reported for Re6 MxTe15 (M = Ga, In, Ag; x = 0, 1, 2) between 90–380 K. Theoretical discussion of the results is presented. The materials, synthesized by filling large voids in the Re6Te15 cluster system, may have potential thermoelectric applications around and below room temperatures. The samples are prepared by reacting 99.99% pure elemental powders in evacuated and sealed quartz ampoules at 1070 K for 170 hours. The resistivity data indicate semiconducting behavior for all samples. Possible hopping conduction is present at lower temperatures. The energy gap is observed at higher temperatures in all the samples.Positive values of α in Re6(Ga,In)x Te15 (x = 0, 1, 2) indicate p-type semiconducting behavior in the studied temperature range. For these samples α increases initially with temperature, then levels off to a nearly constant value. The positions of the sharp peaks in a, observed at lower temperatures for x = 1, 2 only, depend on the Ga (In) concentration. High values of a (∼ 300 μV/K) are measured at room temperatures. In Re6AgTe15 α has small positive values (∼ 20–40 μV/K) between 185 K and 270 K. Outside this range α is negative. It reaches local maxima of -340 μV/K at 105 K and -350 μV/K at 370 K. In Re6Ag2Te15 α changes from positive to negative values above 295 K. A maximum positive value of +350 μV/K is reached at 250 K and maximum negative of -250 μV/K at 330 K. The power factor, α2/ρ, increases with temperature for all studied samples. Theoretical fits to α(T) for all samples are discussed. Also discussed is the effect of filling the voids in the rhenium-telluride system on the figure of merit.