Field desorption mass spectrometry of the B vitamins: pyridoxal, pyridoxamine, their phosphates, and thiamine

Quantitation of berberine chloride in human urine by use of selected ion monitoring in the field desorption mode

A method is described for the microdetermination of berberine chloride in human urine by a field desorption mass spectrometry selected ion monitoring system using a deuterium labelled analogue of berberine chloride as an internal standard. Prior to the quantitation of berberine in human urine, the fundamental problems related to field desorption selected ion monitoring, such as quality of emitters, amounts of sample loading, and the programming rate of the emitter current, were statistically investigated in detail. Berberine chloride can be determined in a concentration of 10 ng ml-1 in human urine by the method described. The analytical results were compared with those from gas chromatography mass spectrometry selected ion monitoring in the chemical ionization mode suggesting that the reliability of field desorption selected ion monitoring may be almost equivalent to that of gas chromatography chemical ionization selected ion monitoring.

Determination of choline and acetylcholine in distinct rat brain regions by stable isotope dilution and field desorption mass spectrometry

The determination of choline and acetylcholine by field desorption mass spectrometry from rat brain tissue samples has been demonstrated. Essential points of the assay are the use of stable isotope labelled internal standards, a simple ion pair extraction procedure, direct analysis of the quaternary ammonium ions without derivatization, and accumulation of the electrically recorded field desorption ion signals with a multi-channel analyser. The analysis of sample amounts in the picogram range gave quantitative data of good precision (0.6--10% standard deviation).