PubMed · 7752946
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H Scheer. 1995. Diode array detection in liquid chromatography.. https://doi.org/10.1016/0076-6879(95)46032-2
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The metabolites from leucine degradation are involved in dry fermented sausage aroma. The catabolism of leucine by a strain of Carnobacterium piscicola was studied directly in the growth medium with 3H-labelled leucine to investigate the effect of five parameters: phase of growth, pH, oxygen, glucose and alpha-ketoisocaproic acid. Resting cells (RC) were also incubated with 3H-labelled leucine. The radioactive metabolites from leucine catabolism were analysed by high performance liquid chromatography (HPLC). At pH 5.4 and 7.2, the main metabolites detected were 3-methyl butanal, 3-methyl butanol and alpha-ketoisocaproic acid. At pH 6.5, the leucine catabolism was maximum and was characterised by a high production of 3-methyl butanoic acid. Leucine catabolism was most important during the exponential phase of growth. The addition of alpha-ketoisocaproic acid at 1%, glucose at levels of 0.5% to 2% and shaking of the growth medium increased leucine catabolism.
The aim of the present study is to establish a highly sensitive method for the determination of uric acid (UA) in human saliva. The monitoring of UA levels in less invasive biological samples such as saliva is suggested for the diagnosis and therapy of gout, hyperuricemia, and the Lesch-Nyhan syndrome, and for detecting such conditions as alcohol dependence, obesity, diabetes, high cholesterol, high blood pressure, kidney disease, and heart disease. Reversed-phase high-performance liquid chromatography with electrochemical detection (HPLC-ED) was employed for the determination of UA obtained by solid-phase extraction from saliva. To quantify UA, we compared the ED efficiencies of an amperometric ED (Ampero-ED) with a single electrode and a coulometric ED (Coulo-ED) with a multiple electrode array. The results showed that the detection limits (S/N=3) were 3 nM for Ampero-ED and 6 nM for Coulo-ED, and the linearity of the calibration curves of 60-6000 nM had correlation coefficients exceeding 0.999. In addition, the total analytical time was 10 min. In the sample preparation of UA in saliva, an Oasis MAX solid-phase cartridge was used. The recoveries of UA spiked at 0.6 and 3 microM in saliva were above 95% with a relative standard deviation (RSD) of less than 15%. Therefore, the present method may be used in the routine and diagnostic determination of UA in human saliva.
High-performance liquid chromatographic assays for the O- and N-demethylated oxidative metabolites of hydrocodone and oxycodone formed in human liver microsomes are described. A solvent-solvent extraction/re-extraction procedure followed by reversed-phase HPLC with UV detection at 210 nm allows for the quantification of hydromorphone, norhydrocodone, oxymorphone and noroxycodone. Calibration curve concentration ranges were 0.63-400 microM (0.18-114 microg/ml) and 1.25-400 microM (0.36-114 microg/ml) for hydromorphone and norhydrocodone, respectively and 0.13-20 microM (0.04-6.03 microg/ml) and 1-200 microM (0.30-60 microg/ml) for oxymorphone and noroxycodone, respectively. Assay performance was determined by intra- and inter-assay precision and inaccuracies for quality control samples and was <15% for all metabolites at each quality control concentration. These methods provide good precision, accuracy and sensitivity for use in in vitro kinetic studies investigating the oxidative metabolism of hydrocodone and oxycodone in human liver microsomes.