A planar high field asymmetric waveform ion mobility spectrometer (PFAIMS) with a micro-machined drift tube was characterized as a detector for capillary gas chromatography. The performance of the PFAIMS was compared directly to that of a flame ionization detector (FID) for the separation of a ketone mixture from butanone to decanone. Effluent from the column was continuously sampled by the detector and mobility scans could be obtained throughout the chromatographic analysis providing chemical inforrmation in mobility scans orthogonal to retention time. Limits of detection were approximately I ng for measurement of positive ions and were comparable or slightly better than those for the FID. Direct comparison of calibration curves for the FAIMS and the FID was possible over four orders of magnitude with a semi-log plot. The concentration dependence of the PFAIMS mobility scans showed the dependence between ion intensity and ion clustering, evident in other mobility spectrometers and atmospheric pressure ionization technologies. Ions were identified using mass spectrometry as the protonated monomer and the proton bound dimer of the ketones. Residence time for column effluent in the PFAIMS was calculated as approximately 1 ms and a 36% increase in extra-column broadening versus the FID occurred with the PFAIMS.

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Improvements in the stability and performance of a capillary microwave-induced plasma-mass spectrometer (MIP-MS) were achieved by optimizing power transfer to the cavity using a tunable coaxial MIP. The MIP, operating at atmospheric pressure, was sustained with 30 mL/min He and 60 W of power. Measurement precision and sensitivity for the standard waveguide and coaxial systems were determined using 16 organochlorine pesticide solutions separated by gas chromatography (GC). The linear dynamic range obtained with the tunable MIP-MS extended over 3 orders of magnitude, a 10 time improvement with respect to the standard MIP. Detection limits were between 3 and 19 pg of Cl mol(-1) s(-1), 7 times lower than the detection limits obtained with the nontunable MIP-MS. Analysis of pesticides containing sulfur atoms was also possible, further demonstrating multielement MIP-MS detection. Excellent accuracy (10% recovery) and precision (5% RSD) were found for the detection of the pesticides in a petroleum-contaminated reference soil. By placing the GC column at the plasma expansion stage, molecular fragmentation of a mixture of volatile organic compounds was also demonstrated. With the MS operated in the selected ion monitoring mode, measurement sensitivity was approximately 500 pg/s per compound.

A micromachined surface stress sensor based on a thin suspended crystalline silicon circular plate measures differential surface stress changes associated with vapor phase chemisorption of an alkanethiol self-assembled monolayer. The isolated face of the suspended silicon plate serves as the sensing surface treated with a receptor layer sensitive to a target molecule, in this case Au(111). Chemisorption of an alkanethiol on the gold coated silicon surfaces results in plate bending. Plate displacements, measured with a phase scanning interferometer, indicate a differential surface stress change Δσs=−0.72±0.02Nm−1 for 1-dodecanethiol.

<p>Coffee prepared via gravity-drip filtration is an alternative to obtain varied sensorial profiles and determine the acidity, bitterness, and body thereof. In the present study, the retention of certain bioactive components was determined, as was the antioxidant activity and cup profiles for coffee beverages prepared by way of seven different gravity-drip filtration methods. The methods which registered the greatest bioactive metabolite retention were the Vietnamese, Clever, and RS 16 methods. The greatest hydroxycinnamic acid content was obtained with the Clever, Yama, Vietnamese, and V60 methods, in descending order. Antioxidant capacity was proportional to the retention of bioactive components, by way of ABTS and ORAC techniques, in the beverages prepared. The V60 and V60 Kalita methods retained the lowest amounts these compounds and their activity. The most predominant hydroxycinnamic acid in the seven evaluated preparations was chlorogenic acid. In accordance with consumer preferences, which seek functional food, it is recommended that coffee be consumed using the Clever or Vietnamese preparation methods, which present fuller body and enhanced bitter notes. In their absence, the RS 16 method is suggested, which presents a sensorial profile identical to that of the U.G.Q. pattern, with less intensity of bitterness.</p>

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The micromachined Planar High Field Asymmetric Waveform Ion Mobility Spectrometer (PFAIMS) is a novel detector for chemical and biological sensing applications. This detector fills an unmet market need, providing spectrometer capabilities and extremely high sensitivity, at a cost comparable to stand-alone sensors. The PFAIMS is quantitative, and has detection limits down to the parts-per-trillion. The performance of the PFAIMS in a number of applications ranging from industrial to biomedical, where it is used as both a stand alone sensor, and as a gas chromatographic detector are demonstrated. These applications include the detection of xylene isomers and non-invasive medical diagnosis through breath analysis.