In this paper, the use of airborne chemistry (acoustically levitated drops) in combination with Raman spectroscopy is explored. We report herein the first Raman studies of crystallization processes in levitated drops and the first demonstration of surface-enhanced Raman scattering (SERS) detection in this medium. Crystallization studies on the model compounds benzamide and indomethacin resulted in the formation of two crystal modifications for each compound, suggesting that this methodology may be useful for investigation of polymorphs. SERS detection resulted in a signal enhancement of 27 000 for benzoic acid and 11 000 for rhodamine 6-G. The preliminary results presented here clearly indicate that several important applications of the combination between Raman spectroscopy and acoustic drop levitation can be expected in the future.

Abrin is a toxic protein found in the jequirity seed. L-Abrine (N-methyl-tryptophan) is also found in the jequirity seed and can be used as a biomarker for abrin exposure. Analysis of L-abrine was added to an existing method for quantifying ricinine as a marker for ricin exposure in human urine and analytically validated. Accuracy and reproducibility were enhanced by including a newly synthesized (13)C(1)(2)H(3)-L-abrine internal standard. One-milliliter urine samples were processed using solid-phase extraction prior to a 6-min high-performance liquid chromatography separation. Protonated molecular ions were formed via electrospray ionization in a triple-quadrupole mass spectrometer and quantified via multiple reaction monitoring. Method validation included the characterization of two enriched urine pools, which were used as quality control materials. Endogenous levels of L-abrine were quantified in a reference range of 113 random urine samples at 0.72 +/- 0.51 ng/mL. Urinary concentrations of L-abrine were monitored in an intentional rat exposure study for up to 48 h. Comparing the results from the human reference range and the animal exposure study indicates that this method is suitable for quantifying L-abrine within 24 h post-exposure. Quantification of L-abrine beyond 24 h is limited by rapid excretion of the biomarker and the level of the L-abrine dose.

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Separations of naphthalene compounds that differ in position of substitution and type of substituent were accomplished using cyclodextrin distribution capillary electrochromatography. Separation systems composed of running buffers containing mixtures of native neutral and single isomer anionic cyclodextrins (CDs) were employed yielding efficiencies of approximately 200,000 plates/meter. Solute migration rates and relative orders can be readily modified by changing CD types and concentrations. Experiments were performed to determine distribution coefficients between each of the CDs used in these studies and an aqueous running buffer. For this work, naphthalene-CD cavity inclusion is assumed to be the principal mode of interaction. The distribution coefficients for carboxymethyl-beta-cyclodextrin (CM-beta-CD), degree of substitution 1, were 10-70% larger than those for native beta-CD and 75-1800% large than those for gamma-CD. The CM-beta-CD was singly charged and yielded a narrow elution window. Nevertheless, baseline resolution was achieved for several substituted naphthalene compounds using CM-beta-CD in conjunction with beta-CD or gamma-CD. Under certain conditions, the gamma-CD system yielded an elution order that differed from that of the beta-CD system. Heptakis-(2,3-dimethyl-6-sulfato)-beta-CD with its -7 charge produced a much larger elution window. The extensive substitution with sulfonic groups at the truncated bottom of the CD seemed to inhibit inclusion as the distribution coefficients for the naphthalene compounds were generally more than an order of magnitude smaller than those for CM-beta-CD. Moreover, there was evidence that this sulfato-CD interacted with both the capillary wall and neutral beta-CD. This work differs from prior uses of CDs in that relatively complicated mixtures of neutral, achiral compounds are separated using combinations of recently developed single-isomer CDs as running-buffer additives. The single-isomer CDs, as opposed to most highly complex derivatized CD products, facilitate predictions of separation performance for multicomponent samples. In this manner, the ability to use knowledge of distribution coefficients to predict elution characteristics for a ternary CD system is demonstrated.

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Presented in this study is an approach to optimize conditions for capillary electrophoresis separations of multianalyte enantiomeric pairs (D- and L-dansyl (Dns)-amino acids) that involves the rational use of combinations of cyclodextrins (CDs) as enantioselective running buffer additives. Migration data is experimentally obtained for a range of concentrations for native CDs used individually and employed to determine inclusion constants for the Dns-amino acids of interest. An expression for the mobility of the amino acids when multiple (two in this work) CDs are present in the running buffer is used to simulate separations for more complex CD systems. A chromatographic response function involving predicted resolution is generated to gauge the quality of these separations. Simplex methods are then employed for the first time to optimize conditions for the separation of amino acid enantiomers. The validity of this approach is demonstrated for separations of five Dns-amino acid enantiomers using gamma- and beta-CDs at various concentrations. Extending the dual-CD approach to other CDs and increasing the number of CDs beyond two should be possible. To this end, preliminary experiments are performed by using several available single-isomer, derivatized CDs (individually) to determine if they have potential for further studies. Although results with these particular derivatized CDs are not encouraging, we did find that molecular mechanics modeling is useful in interpreting those cases in which low inclusion constants possibly contributed to the ineffectiveness of the CDs.

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The homoleptic tetraarylaurate anion, Au(C6Cl5)4 -, which has never been prepared via traditional chemical methods, has been synthesized by use of an electrochemical technique and crystallized in situ with the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, or ET) electron-donor molecule. This salt, (C10H8S8)Au(C6Cl5)4, crystallizes having the monoclinic space group P21/c, with a = 14.7835(9) Å, b = 20.2270(12) Å, c = 16.7303(10) Å, β = 101.396(1)°, Z = 4. The crystal structure of this (ET)Au(C6Cl5)4 salt contains the Au(C6Cl5)4 - anion in an essentially square-planar coordination with the pentachlorophenyl groups arranged in a propeller-like D 4 symmetry, consistent with the formal oxidation state +3 of the central metal atom. The ET+ cations are completely surrounded by the pentachlorophenyl rings of the anions, thereby precluding the formation of a S···S network with concomitant conducting properties. Analysis of the Raman spectrum of (ET)Au(C6Cl5)4 confirms that the ET molecule in this salt is in the +1 oxidation state. The variable temperature spin susceptibility data obtained from ESR spectroscopy indicate a weak ferromagnetic coupling between the radical ET+ cations. This salt provides the unique opportunity to investigate the properties of a highly isolated ET+ cation in the solid state.