Keto acids, detection identification

When male F-344 rats were injected with NNN-2 -14c, 75-95% of the dose was excreted in the 48 hr urine. In one experiment, the urine was collected in vessels containing DNP reagent. However, the DNPs of 4-hydroxy-l-(3-pyridyl)-l-butanone and 4-hy-droxy-4-C3-pyridy1)butanal were not detected. Since this was likely due to further oxidation in vivo, methods were developed for isolation of their probable oxidation products. This resulted in identification of the lactone, 5- C3-pyridyl)—tetrahydrofuran-2-one (1-2%), the keto acid, 4-(3-pyridyl).-4-oxobutyric acid (1-2%) and the hydroxy acid, 4-(3-pyridyl)-4-hydroxybutyric acid (26-40%) as urinary metabolites. These metabolites resulted. 

The chemistry and analysis of sialic acids have been reviewed. Picomole quantities of sialic acids have been measured by the fluorescence produced by the periodate-oxidized acid in the thiobarbituric acid reaction. " Contamination of the sialic acids with 2-deoxy-D-eryt/iro-pentose (derived from cellular material) could be detected by a downfield shift of the excitation maximum. Fluorescent derivatives are also produced when free sialic acids react with pyridoxamine, a procedure that compares favourably with the thiobarbituric acid reaction for determining sialic acids. Keto-acids e.g. pyruvic acid) interfere with the determination, but 2-deoxy-D-arabmo-hexose and 2-deoxy-D-c/-ytliro-pentose do not. A nonfading chromophore is produced when DMSO is used instead of n-butanol in the thiobarbituric acid ssay for sialic acids. A new histochemical method for the visualization and identification of unmodified or 0-acylated sialic acids has been reported. ... 

Derivatized acids include monocarboxylic, dicarboxylic, and keto- and hydroxyacids. These are usually measured under standard GC conditions (Table 13.4) where split, splitless, or on-column injections are used in combination with standard capillary columns. The type of injection employed depends largely on the concentrations to be measured and the solution matrix. Flame ionization detectors (FID) are used as nonspecific detectors,whereas ECDs are utilized to measure halogenated derivatives, thus improving detection limits.In both cases retention times are used for compound identification. Several applications employ mass spectrometric (MS) detection," especially where identification of new constituents or by-products is required, thus giving additional compound information through mass spectra. 

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