Gas chromatography and detection of microquantities of gibberellins and indoleacetic acid as their fluorinated derivatives

Progress and development of analytical methods for gibberellins

Gibberellins, as a group of phytohormones, exhibit a wide variety of bio-functions within plant growth and development, which have been used to increase crop yields. Many analytical procedures, therefore, have been developed for the determination of the types and levels of endogenous and exogenous gibberellins. As plant tissues contain gibberellins in trace amounts (usually at the level of nanogram per gram fresh weight or even lower), the sample pre-treatment steps (extraction, pre-concentration, and purification) for gibberellins are reviewed in details. The primary focus of this comprehensive review is on the various analytical methods designed to meet the requirements for gibberellins analyses in complex matrices with particular emphasis on high-throughput analytical methods, such as gas chromatography, liquid chromatography, and capillary electrophoresis, mostly combined with mass spectrometry. The advantages and drawbacks of the each described analytical method are discussed. The overall aim of this review is to provide a comprehensive and critical view on the different analytical methods nowadays employed to analyze gibberellins in complex sample matrices and their foreseeable trends.

NMR characterization of functional groups: 9--isomer ratios of available chloromethylstyrene mixtures

From the assignments of the 1H and 13C 11.7 tesla NMR spectra of available mixtures of m- and p-chloromethylstyrene, the proportion of the meta and para compounds are easily determined. For these materials from two common commercial sources, proportions of 72 and 28% and 68 and 32% were found. These concentrations are substantially different from the often assumed 60 and 40% for the meta and para compounds, respectively. The influence of this difference on the desired properties of copolymers made from such mixtures is discussed. An alternative quantitative procedure for determining the chloromethyl group isomer ratios is also described which employs silver trifluoroacetate in acetone displacement of chloride and 19F NMR examination of the resulting ester mixture with a 2.3 tesla spectrometer.

Gas chromatographic determination of phentolamine (Regitine) in human plasma and urine

A method for the determination of unconjugated phentolamine at concentrations down to 5 ng/ml in human plasma, and of free and total (free plus conjugated) phentolamine down to 25 ng/ml in urine is described. After addition of 2-[N-(p-chlorophenyl)-N-(m-hydroxyphenyl)-aminomethyl]-2-imidazoline as internal standard, both compounds are extracted into benzene-ethyl acetate (1:1, v/v) at pH 10, transferred into an acidic aqueous solution and back-extracted at pH 10 into benzene-ethyl acetate. They are then derivatized with N-heptafluorobutyrylimidazole. The derivatives are determined by gas chromatography using a 63Ni electron-capture detector. In urine, total (free plus conjugated) phentolamine is determined after enzymatic hydrolysis. The technique was applied for the study of the plasma concentrations and urinary elimination after oral administration to man.

Electron-capture gas chromatographic assay for metoclopramide in plasma

An original electron-capture gas chromatographic assay has been developed for the quantiation of metoclopramide in human plasma. The method involves derivatization with heptafluorobutyryl imidazole after alkaline extraction, acid backwash, and a further alkaline extraction. Plasma levels of metoclopramide as low as 5 micrograms/l can be measured using 1 ml of plasma, and no interference from related substances or commonly prescribed drugs has been found. The percentage recovery of drug from plasma ranges from 88% to virtually 100%, and the between-run variation in the assay is 4.3%. The assay has been used for the study of metoclopramide pharmacokinetics in man following intravenous single-dose administration. The resultant plasma concentration vs. time curve was biexponential, with a terminal half-life of 5.0 h, and a distribution half-time of 0.3 h.

Formation of indolyl-3-acetylaspartic acid in rats

Indolyl-3-acetylaspartic acid (IAAsp) was detected in the urine of rats given indolyl-3-acetic acid (IAA) i.p. It was ascertained that the conversion of IAA into IAAsp could be carried out not only in plants but also in animals.