Pentafluorobenzyloxime Derivatives Research Articles

The measurement and mass spectral identification of indole-3-pyruvate from tomato shoots

Endogenous indole-3-pyruvate has been identified by full-scan combined gas chromatography-mass spectrometry and measured using gas chromatography with an electron capture detector. High specific-activity [5- 3H]indole-3-pyruvate was synthesized from [5- 3H] tryptophan and used as an internal standard. In order to allow purification of the labile indole-3-pyruvate it was stabilised by the formation in the crude extract of its pentafluorobenzyl oxime derivative. This derivative also allowed sensitive detection and measurement of indole-3-pyruvate in the picogram range using a gas chromatograph with an electron capture detector. Endogenous levels were found to be between 8–10 ng/g f.wt. of tomato shoots which is comparable to that of the indole-3-acetic acid pool size,11 ng/g f.wt., in this tissue.

Occurrence of 4-hydroxyalkenals in rat tissues determined as pentafluorobenzyl oxime derivatives by gas chromatography-mass spectrometry

Malondialdehyde measurements have been the major tool for studying relationships between lipid peroxidation and tissue pathology. Recently, we presented a novel gas chromatography-mass spectrometry method for direct detection of phospholipid peroxides with picogram sensitivity based on transesterification of phospholipids or triglycerides to form pentafluorobenzyl esters. Under some circumstances the reactive primary oxidation products break down. Therefore, we developed a convenient, high sensitivity method to detect more stable secondary lipid oxidation products, the 4-hydroxyalkenals. The method accomplishes a facile extraction of 4-hydroxynonenal from tissues by forming pentafluorobenzyl oxime derivatives to displace aldehydes from Schiff base linkages. 4-hydroxynonenal was found in heart, liver, adrenal, and testis from rats and was detected to the 10-100 pg level by the current method.

Fast atom bombardment mass spectrometry of steriod sulphates: Qualitative and quantitative analyses

Negative ion mass spectra obtained by fast atom bombardment of glycerol solutions of steroid sulphates include the steroid sulphate anion as the single prominent feature. High sensitivity is achieved, with full spectra obtained for samples of less than 15 ng. Differentiation of the isomeric steroids, dehydroepiandrosterone sulphate and testosterone sulphate, is made by comparison of the products of fragmentation of metastable ions. Analyses of biological extracts suffer from poorly-understood matrix effects which may cause partial or complete suppression of the signal attributable to steroid sulphates. Use of an immunoadsorption extraction technique, however, has permitted the detection and approximate quantification (using a (2H2) analogue as internal standard) of dehydroepiandrosterone sulphate in blood plasma. Interference from glycerol background is avoided by preparation of the pentafluorobenzyloxime derivatives.

Structure determination of carbohydrates and glycosphingolipids by fast atom bombardment mass spectrometry

We have used fast atom bombardment mass spectrometry to aid the structural analysis of blood group glycosphingolipids, carbohydrates excreted by gangliosidosis patients, glucans from fast growing Rhizobium species and a variety of plant cell wall oligosaccharides. Samples have been examined in their native form or as acetyl, permethyl, methoxime or pentafluorobenzyloxime derivatives. Negative FAB spectra of permethylated carbohydrates have been obtained for the first time by salt dosing. High sensitivity for permethylated samples has been achieved in the positive mode by ammonium cationisation. Spectra up to m/z 6620 are reported for permethylated glucans.