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Ion-pair single-drop microextraction (SDME) coupled to gas chromatography–mass spectroscopy (GC–MS) methods for the determination of four degradation products of chemical warfare agents were investigated in water. Acidic analytes were converted into their ion-pair complexes with cation surfactants in aqueous sample and then extracted into the organic single drop containing the derivatising agent. Upon injection, the analytes were derivatised in the GC injection hot port. Parameters, such as type of extraction solvent, ion-pairing (IP) reagent, reagent concentration, salt concentration, stirring speed and pH, were all optimized. This method is reproducible for spiked water sample for four different analytes (RSDs 0.9945). The limit of detection (LOD) is in the range of 0.08–0.01 ng mL−1 (S/N = 5) under GC–MS selected ion monitoring mode. The method was successfully applied to the proficiency test samples from the Organization for Prohibition of Chemical Weapons (OPCW).

The 14N NMR spectrum of hexamethylenetetramine (HMT) is dominated by the very large electric quadrupole coupling constant of 4.412 MHz at room temperature. Nonetheless, by carefully accounting for this interaction one can subtract its first- and second-order effects on the spectrum, leaving the much smaller anisotropic chemical shift interaction. The chemical shielding anisotropy of HMT is −8.3±3.2 ppm, small but different from zero, with an isotropic chemical shift in good agreement with the value in aqueous solution. This study illustrates how even very tiny chemical shift tensors can be extracted from the NMR spectra of quadrupolar nuclei using appropriate techniques. Copyright © 1999 John Wiley & Sons, Ltd.

Lead, strontium and barium nitrates, like the titanates of the same cations, form a continuous set of solid solutions. 207Pb NMR spectra of mixed crystals of lead/strontium nitrate and lead/barium nitrate each show up to 13 lines, arising from lead ions with from zero to twelve Pb2+ nearest-neighbor cations replaced by Sr2+ or Ba2+. In the case of (Pb,Sr)(NO3)2 these shifted lines are further split by the multiplicity of inequivalent nearest-neighbor replacements. The average shift per Sr2+ ion is 21.8 ppm; that for Ba2+ is smaller. Using Monte Carlo/Metropolis calculations, the intensities of the resonances can be fit to statistical models of Pb2+ and Sr2+ ion distributions, and used to probe the microenergetics of solid solution formation. The data can be satisfactorily fit by distributions in which the cations are slightly clustered, with like pairs of nearest neighbors being favored by 120 J/mol over unlike pairs. Interestingly, this finding is inconsistent with the conventional interpretation of powder diffraction results for the mixed crystals, where the dependence of lattice parameter on composition shows a slight positive curvature, generally held to indicate a favorable interaction between unlike ions.

207Pb NMR spectra of mixed crystals of anhydrous lead and strontium nitrate show up to 13 lines, arising from lead ions with 0-12 Pb(2+) nearest-neighbor cations replaced by Sr(2+). The shifted lines are further split by the multiplicity of inequivalent nearest-neighbor replacements. The average shift per Sr(2+) ion is 21.8 ppm. Similar but somewhat smaller effects are seen in [Pb,Ba](NO(3))(2) mixed crystals. The intensities of the resonances can be fit to Monte Carlo models of Pb(2+) and Sr(2+) ion distributions and are consistent with like nearest-neighbor pairs being 120 J/mol lower in energy than unlike pairs.