Chromatographic system for simultaneous determination of levodopa, biogenic amines, and methylxanthines in food has been developed. Chromatographic column and precolumn with octadecylsilane phase and simultaneously fluorescence and DAD detectors have been used. Gradient elution with acetate buffer (pH=4.66) with acetonitrile has been applied. Examination included levodopa, norepinephrine, dopam...

A new analytical method has been developed and is proposed for the rapid determination of eighteen common amino acids, including tryptophan, in plasma and dried blood spots, by liquid chromatography coupled with ionspray tandem mass spectrometry. Potentially the method can include other amino acids and can be used for the diagnosis of metabolic disease. The use of the ionspray tandem mass spect...

Statistical experimental design was used to optimize the chromatographic separations of two pharmaceutical compounds from their respective potential impurities. A fractional factorial design was utilized to study the effects of pH, organic solvent in mobile phases A&B, and flow rate on the resolution of Rabeprazole and Rabeprazole Sulfone, which had closely eluting peaks. A desirability functio...

Liquid chromatography with amperometric detection remains the most widely used method for acetylcholine quantification in microdialysis samples. Separation of acetylcholine from choline and other matrix components on a microbore chromatographic column (1 mm internal diameter), conversion of acetylcholine in an immobilized enzyme reactor and detection of the produced hydrogen peroxide on a horse...

An internally standardized method for the determination of 3-methylhistidine in human urine is presented. This methylated amino acid and the chemically analogous internal standard 3-ethylhistidine were isolated from human urine specimens using small columns of cation-exchange resin. Quantification was accomplished by high-performance liquid chromatography using post-column derivatization with o...

Different chromatographic and electrophoretic techniques commonly used in the instrumental inspection of herbal medicines (HM) are first comprehensively reviewed. Chemical fingerprints obtained by chromatographic and electrophoretic techniques, especially by hyphenated chromatographies, are strongly recommended for the purpose of quality control of herbal medicines, since they might represent a...

A rapid overview of the Three Phase Partitioning (TPP) system as an efficient non-chromatographic tool is given. This elegant non-chromatographic tool is able to purify numerous proteins and especially proteases in a one step protocol. TPP is able to do not only purify proteins, but also concentrate them into one of the phases and enhance their proteolytic activity. The application of TPP for t...

Complete development of a gas chromatographic method often involves a significant amount of effort. Once a method is completed, retention time locking (RTL) can be used to implement the method and to obtain the same retention times on multiple systems. This application note describes how to use method translation combined with RTL to implement precise time-scaled versions of a method on multipl...

Complete development of a gas chromatographic method often involves a significant amount of effort. Once a method is completed, retention time locking (RTL) can be used to implement the method and to obtain the same retention times on multiple systems. This application note describes how to use method translation combined with RTL to implement precise time-scaled versions of a method on multipl...

A sensitive electron-capture gas-liquid-chromatographic method for the determination of sub-nanogram quantities of prostaglandin F(2alpha) was developed. The method is based on the sub-microgram scale conversion of the prostaglandin into the electron-capturing pentafluorobenzyl ester, and analysis of the latter as the tris-trimethylsilyl ether. The lower limit of detection was 12.5pg of the est...