High resolution gas chromatography of tobacco smoke: The contributions of kurt grob

The contributions made by Kurt Grob to tobacco science are reviewed with emphasis on the application of high resolution gas chromatography to tobacco smoke analysis. Highlighted are his pioneering achievements in the preparation and use of glass capillary columns, GC-MS, and splitless injection.     

Validation and application of a method for the determination of nicotine and five major metabolites in smokers' urine by solid-phase extraction and liquid chromatography-tandem mass spectrometry

An SPE-LC-MS/MS method was developed, validated and applied to the determination of nicotine and five major metabolites in human urine: cotinine, trans-3'-hydroxycotinine, nicotine-N-glucuronide, cotinine-N-glucuronide and trans-3'-hydroxycotinine-O-glucuronide. A 500 microL urine sample was pH-adjusted with phosphate buffer (1.5 mL) containing nicotine-methyl-d3, cotinine-methyl-d3 and trans-3'-hydroxycotinine-methyl-d3 internal standards. For the unconjugated metabolites, an aliquot (800 microL) of the buffered solution was applied to a 30 mg Oasis HLB-SPE column, rinsed with 2% NH4OH/H2O (3.0 mL) and H2O (3.0 mL) and eluted with methanol (500 microL). The eluate was analyzed isocratically (100% methanol) by LC-MS/MS on a diol column (50 x 2.1 mm). For the total metabolites, a beta-glucuronidase/buffer preparation (100 microL) was added to the remaining buffered solution and incubated at 37 degrees C (20 h). An aliquot (800 microL) of the enzymatically treated buffered solution was extracted and analyzed in the same manner. The conjugated metabolites were determined indirectly by subtraction. The quantitation range of the method (ng/mL) was 14-10,320 for nicotine, 15-9800 for cotinine and 32-19,220 for trans-3'-hydroxycotinine. The validated method was used to observe diurnal variations from a smoker's spot urine samples, elimination half-lives from a smoker's 24 h urine samples and metabolite distribution profiles in the spot and 24 h urine samples.     

Preparation of α,ω-ditriazinylperfluoroalkane derivatives

The synthesis of 2-oxa and 2-thiaperfluoroglutaric acids and their corresponding ethyl esters, amides, nitriles, acid chlorides, and also 2-thiaperfluoroglutaric anhydride are described. These compounds were prepared as precursors to α,ω-ditriazinylperfluoroalkane derivatives containing a heteroatom in the perfluoroalkylene chain. The ditrazinylpropanes were prepared most satisfactorily from the diacid chlorides rather than the dinitriles.     

Structural diversity in the first metal complexes of 2,5-dicarboxamidopyrroles and 2,5-dicarbothioamidopyrroles

Metal complexes of 2,5-dicarboxamidopyrroles and 2,5-dicarbothioamidopyrroles have been structurally characterised for the first time, complementing the significant amount of work that has been reported for the analogous pyridine ligands. N,N'-Bis(3,5-dinitrophenyl)-3,4-diphenyl-1H-pyrrole-2,5-dicarboxamide forms octahedral bis(tridentate) complexes with cobalt(iii) and nickel(ii), where the ligands are bound to the metal centres through deprotonated pyrrole and amide N atoms. N,N'-Dibutyl-3,4-diphenyl-1H-pyrrole-2,5-dicarboxthioamide and N,N'-diphenyl-3,4-diphenyl-1H-pyrrole-2,5-dicarboxthioamide also form bis(tridentate) cobalt complexes but are only deprotonated at the pyrrole N atom, the remainder of the coordination sphere comprising the thioamide S atoms. The dibutyl derivative was isolated as a Co(ii) complex, whereas the diphenyl system deposited a Co(iii) complex. In contrast, N,N'-dibutyl-3,4-dichloro-1H-pyrrole-2,5-dicarboxamide was found to act as a bidentate ligand, in an octahedral cobalt(ii) complex comprising of two bidentate pyrrole ligands, and two aqua ligands. Synthesis of N,N-bis(pyridin-2-ylmethyl)-3,4-diphenyl-1H-pyrrole-2,5-carboxamide gave a pyrrole ligand with increased denticity. Reaction with cobalt(ii) chloride resulted in the isolation of a dinuclear helicate complex. The ligand was found to have undergone addition of a methoxy group to one of the linking methylene carbons, presumably as a result of the oxidative addition of solvent methanol.     

Functional data classification: a wavelet approach

In recent years, several methods have been proposed to deal with functional data classification problems (e.g., one-dimensional curves or two- or three-dimensional images). One popular general approach is based on the kernel-based method, proposed by Ferraty and Vieu (Comput Stat Data Anal 44:161–173, 2003). The performance of this general method depends heavily on the choice of the semi-metric. Motivated by Fan and Lin (J Am Stat Assoc 93:1007–1021, 1998) and our image data, we propose a new semi-metric, based on wavelet thresholding for classifying functional data. This wavelet-thresholding semi-metric is able to adapt to the smoothness of the data and provides for particularly good classification when data features are localized and/or sparse. We conduct simulation studies to compare our proposed method with several functional classification methods and study the relative performance of the methods for classifying positron emission tomography images.     

Acoustically enriching, large-depth aquatic sampler

In marine biology, it is useful to collect water samples when exploring the distribution and diversity of microbial communities in underwater environments. In order to provide, e.g., a miniaturized submersible explorer with the capability of collecting microorganisms, a compact sample enrichment system has been developed. The sampler is 30 mm long, 15 mm wide, and just a few millimetres thick. Integrated in a multilayer steel, polyimide and glass construction is a microfluidic channel with piezoelectric transducers, where microorganism and particle samples are collected and enriched, using acoustic radiation forces for gentle and labelless trapping. High-pressure, latchable valves, using paraffin as the actuation material, at each end of the microfluidic channel keep the collected sample pristine. A funnel structure raised above the surface of the device directs water into the microfluidic channel as the vehicle propels itself or when there is a flow across its hull. The valves proved leak proof to a pressure of 2.1 MPa for 19 hours and momentary pressures of 12.5 MPa, corresponding to an ocean depth of more than 1200 metres. By reactivating the latching mechanism, small leakages through the valves could be remedied, which could thus increase the leak-less operational time. Fluorescent particles, 1.9 μm in diameter, were successfully trapped in the microfluidic channel at flow rates up to 15 μl min(-1), corresponding to an 18.5 cm s(-1) external flow rate of the sampler. In addition, liquid-suspended GFP-marked yeast cells were successfully trapped.     

On the third- and fourth-order constants of incompressible isotropic elasticity

Consider the constitutive law for an isotropic elastic solid with the strain-energy function expanded up to the fourth order in the strain and the stress up to the third order in the strain. The stress-strain relation can then be inverted to give the strain in terms of the stress with a view to considering the incompressible limit. For this purpose, use of the logarithmic strain tensor is of particular value. It enables the limiting values of all nine fourth-order elastic constants in the incompressible limit to be evaluated precisely and rigorously. In particular, it is explained why the three constants of fourth-order incompressible elasticity μ, ā, and D are of the same order of magnitude. Several examples of application of the results follow, including determination of the acoustoelastic coefficients in incompressible solids and the limiting values of the coefficients of nonlinearity for elastic wave propagation.