O-phosphoamino acid analysis of phosphorylated proteins by gas chromatography with flame photometric detection

Microemulsion electrokinetic chromatographic analysis of some polar compounds

This study presents the optimization of a microemulsion electrokinetic chromatographic (MEEKC) electrolyte solution by using UV detection and with the method, simultaneous separations of chemically, biochemically and pharmaceutically related anionic and cationic compounds. Representatives of the compound groups were from isoflavonoids, benzodiazepines, metanephrines, diuretics and peptide hormones. The MEEKC separations under basic conditions were first optimized using a two-component isoflavonoid mixture as the sample and an electrolyte containing 10 mM tetraborate as the main buffer (pH 9.5). The stable microemulsion phase was adjusted with various amounts of octane, 1-butanol and sodium dodecyl sulfate (SDS). An only acidified electrolyte solution used in the study was made of phosphoric acid (pH 1.8) containing octane, SDS and ethyl acetate. The analyses with isoflavonoids showed that electrophoretic mobilities of the investigated compounds were highly related to the concentrations of SDS and 1-butanol with linear and parabolic correlation, respectively. However, addition of octane gave linear correlation only at low concentrations. In most cases four to six structurally related compounds and even 13 diuretics with various polar properties were separated from each other in basic microemulsion medium. The acidified MEEKC electrolyte gave good resolution for anionic metanephrines.

Analysis of free and bound O-phosphoamino acids in urine by gas chromatography with flame photometric detection

A selective and sensitive method has been developed for the analysis of free and bound forms of O-phosphoamino acids, such as O-phosphoserine, O-phosphothreonine and O-phosphotyrosine, in urine samples by gas chromatography (GC). For free O-phosphoamino acid analysis, the urine sample was extracted with trichloroacetic acid and run through an ion exchange column. For total (free plus bound) O-phosphoamino acid analysis, the urine sample was hydrolysed in acid and base in order to release the O-phosphoamino acid from peptides or proteins. O-Phosphoamino acids in these prepared samples were converted into their N-isobutoxycarbonyl trimethyl ester derivatives and then measured by GC with flame photometric detection (FPD-GC). The calibration curve was linear in the range of 10-500 ng for each O-phosphoamino acid, and the detection limits were 30-80 pg as injection amounts. O-Phosphoamino acids in the urine samples could be selectively determined by the FPD-GC method without any influence from coexisting substances. The recoveries of O-phosphoamino acids added to urines and urine hydrolysates were 90-98% and relative standard deviations were 1.5-8.0%. By using this method, we investigated an age dependence of O-phosphoamino acid excretion in normal subjects.

Identification of O-phosphoamino acids in urine hydrolysate by gas chromatography-mass spectrometry

The occurrence of O-phosphoserine (P-Ser), O-phosphothreonine (P-Thr) and O-phosphotyrosine (P-Tyr) in the hydrolysate of human urine was demonstrated. Urine samples were separated into non-adsorbed and adsorbed fractions by DEAE-cellulose column chromatography. After acid and base hydrolyses of these fractions, the O-phosphoamino acids in the hydrolysates were converted into their N-isobutoxycarbonyl methyl ester derivatives and identified by gas chromatography-mass spectrometry. By gas chromatography with flame photometric detection, the urinary contents of P-Ser, P-Thr and P-Tyr were estimated to be 945 +/- 3, 109 +/- 3 and 2.9 +/- 0.2 ng/ml, respectively.