Binary mixtures of model systems consisting of the antibiotic ampicillin with either Escherichia coli or Staphylococcus aureus were subjected to pyrolysis mass spectrometry (PyMS). To deconvolute the pyrolysis mass spectra, so as to obtain quantitative information on the concentration of ampicillin in the mixtures, partial least squares regression (PLS), principal components regression (PCR), and fully interconnected feedforward artificial neural networks (ANNs) were studied. In the latter case, the weights were modified using the standard backpropagation algorithm, and the nodes used a sigmoidal squashing function. It was found that each of the methods could be used to provide calibration models which gave excellent predictions for the concentrations of ampicillin in samples on which they had not been trained. Furthermore, ANNs trained to predict the amount of ampicillin in E. coli were able to generalise so as to predict the concentration of ampicillin in a S. aureus background, illustrating the robustness of ANNs to rather substantial variations in the biological background. The PyMS of the complex mixture of ampicillin in bacteria could not be expressed simply in terms of additive combinations of the spectra describing the pure components of the mixtures and their relative concentrations. Intermolecular reactions took place in the pyrolysate, leading to a lack of superposition of the spectral components and to a dependence of the normalized mass spectrum on sample size. Samples from fermentations of a single organism in a complex production medium were also analyzed quantitatively for a drug of commercial interest. The drug could also be quantified in a variety of mutant-producing strains cultivated in the same medium. The combination of PyMS and ANNs constitutes a novel, rapid, and convenient method for exploitation in strain improvement screening programs. 0 1994John Wiley & Sons, Inc.

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The application of Li‐metal‐anodes (LMA) can significantly improve the energy density of state‐of‐the‐art lithium ion batteries. Lots of new electrolyte systems have been developed to form a stable solid electrolyte interphase (SEI) films, thereby achieving long‐term cycle stability of LMA. Unfortunately, the common problem faced by these electrolytes is poor oxidation stability, which rarely supports the cycling of high‐voltage Li‐metal batteries (LMBs). In this work, a new single‐component solvent dimethoxy(methyl)(3,3,3‐trifluoropropyl) silane is proposed. The electrolyte composed of this solvent and 3 m LiFSI salt successfully supports the long‐term cycle stability of limited‐Li (50 µm)||high loading LiCoO2 (≈20 mg cm−2) cell at 4.6 V. Experiments and theoretical research results show that the outstanding performance of the electrolyte in high‐voltage LMBs is mainly attributed to its unique solvation structures and its great ability to build a highly stable and robust interphase on the surface of LMA and high‐voltage cathodes. Interestingly, this proposed electrolyte system builds a stable SEI film rich in LiF and Li3N on the surface of LMA by improving the two‐electron reduction activity of FSI− without adding LiNO3, the well‐known additive used for LMBs. The design idea of the proposed electrolyte can guide the development of high‐voltage LMBs.

We describe an evaluation of a transportable quadrupole mass spectrometer and the modifications required for the direct measurement of trace levels of organic solvents in breath. The instrument has been used in human volunteer breath studies and has potential as a non-invasive measure of industrial solvent uptake.

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