Geoff C Gerhardt

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The conformational properties of proteins can be probed with hydrogen/deuterium exchange mass spectrometry (HXMS). In order to maintain the deuterium label during LC/MS analyses, chromatographic separation must be done rapidly (usually in under 8-10 min) and at 0 degrees C. Traditional RP-HPLC with approximately 3-mum particles has shown generally poor(More)
A liquid chromatographic method for determining residues of ionophores in bovine, porcine, and avian tissues is described. Tissues were extracted with iso-octane-ethyl acetate and the extracts purified on silica solid-phase extraction columns. Monensin, narasin and salinomycin were detected by UV absorbance following post-column derivatization with(More)
A method for the simultaneous determination of tylosin and tilmicosin residues in animal tissues is reported. Solid-phase extraction columns are used to isolate the drugs from tissue extracts. Determination is accomplished by reversed-phase liquid chromatography with UV detection at 287 nm. Mean recoveries from spiked tissues were 79.9% (coefficient of(More)
The separation and quantitative performance parameters for tetracycline, chlortetracycline and oxytetracycline antibiotics were investigated by capillary zone electrophoresis coupled with fast cyclic voltammetric detection. Optimization of pH and complexation with a boric acid-sodium tetraborate buffer provided good resolution of all compounds. Detection by(More)
Potentiometric end-capillary detection in capillary electrophoresis has the advantage of relatively easy miniaturisation without having to compromise the concentration sensitivity. Potentiometric end-capillary detection using a copper electrode is also attractive because of the sensitive detection of many inorganic and organic UV-transparent ions and the(More)
A method developed for the determination of the aminoglycoside antibiotics streptomycin and dihydrostreptomycin in tissues was applied to the analysis of fluid milk. Samples are extracted with 3.6% perchloric acid, and then injected onto a trace enrichment column, from which they are eluted onto a reversed-phase analytical column. The analytes are detected(More)
A gas chromatography (GC) column is fabricated within a low-temperature cofired ceramic (LTCC) tile, and its analytical properties are characterized. By using a dual-spiral design, a 100 μm wide square channel up to 15 m in length is produced within an 11 cm × 5.5 cm LTCC tile. The channel is dynamically coated with an OV-101 stationary phase that is(More)
A method for the determination of streptomycin and dihydrostreptomycin in pork and bovine muscle and kidney was developed. Dilute perchloric acid solution is used to precipitate proteins and extract the analytes from the tissue. The extract is loaded onto a cation-exchange, solid-phase extraction column, and the drugs are eluted with pH 8 phosphate buffer.(More)
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