Glucuronic acid conjugates analysis

In this example, local analysis of results shows that the glucuronic acid conjugation capacity depends on three factors ... 

In recent years, several techniques have been developed for mass spectrometry, whereby samples are ionized and analysed from a condensed phase, without prior volatilization. These desorption techniques have permitted the extension of mass spectrometric analyses to sulfate and glutathione conjugates, as well as to underivatized and labile glucuronic acid conjugates. Primary among these techniques are field desorption 6, plasma desorption (7), laser desorption (8), fast atom bombardment (or secondary ion mass spectrometry with a liquid sample matrix) ( ) and thermospray ionization ( O). The latter can also serve to couple high pressure liquid chromatography and mass spectrometry for analysis of involatile and thermally labile samples. 

Despite outstanding FD measurements in laboratories at Mainz and a few other places, analysis of glucuronic acid conjugates by FAB is generally more reliable than FD analyses. However, FAB is also not completely reliable. We have worked with some glucuronic acid conjugates which provided neither an anion or cation spectrum from a variety of FAB matrices. In one of these cases the analysis has been obtained successfully by thermospray. 

In the second half of this chapter we discuss in more detail the high potential of fast atom bombardment, demonstrating applications to analysis of some new glucuronic acid conjugates recently synthesized in our laboratory. 

The major analyte in human blood serum was the parent compound, and only small concentrations of ochratoxin A metabolites and/or conjugates could be measured. In contrast, analysis of urine samples indicated that only about 50% of the radioactivity in the urine was parent ochratoxin A, suggesting the presence of ochratoxin A metabolites (particularly ochratoxin alpha) and/or ochratoxin A-glucuronic acid conjugates (Studer-Rohr et al., 2000). 

Figure 5 The 600 MHz H NMR spectra of (A) a sample of human urine collected after the oral ingestion of 200 mg flurbiprofen, (B) the 30.5 min retention time species corresponding to the /3-D-glucuronic acid conjugate of 4 -hydroxyflurbiprofen. Reprinted from (A) Spraul ef a/(1993). Coupling of HPLC with and H NMR spectroscopy to investigate the human urinary extraction of flurbiprofen metabolites. Journal of Pharmaceutical and Biomedical Analysis, 11 (10), 1009-1015 (B) Lindon et al (1996) Direct coupling of chromatographic separations to NMR spectroscopy. Progress In NMR Spectroscopy, 29, 1-49, with kind permission from Elsevier Science-NL, Sara Burgerhartstraat 25,1055 KV Amsterdam, The Netherlands.

Chakir, S. Leroy, R Nicolas, A. Ziegler, J. M. Labory, R. High-performance liquid chromatographic analysis of glucuronic acid conjugates after derivatization with 4-bromomethyl-7-methoxycoumarin. J. Chromatogr. 1987,395, 553-561. 

Methods for analysis of individual phthalates in saliva, blood, urine, and/or feces involve separation of metabolites by HPLC combined with GC/MS (Niino et al. 2001 Sjoberg et al. 1985c) or GC/FID (Albro et al. 19 84). Analysis for metabolites differs from analys is for DEHP mainly in sample preparation procedures (Albro et al. 1984 Sjoberg and Bondesson 1985). Metabolites from urine and/or feces are often treated with -glucuronidase to remove conjugated glucuronic acid moieties. When GC methods... 

In those cases where a suitable antibody for radioimmunoassay is not available, a full multi-component screening procedure is necessary, and also needs to be undertaken as a confirmatory test in cases where the nature of the anabolic steroid is not known. The full analysis involves the separation of the glucuronic acid and sulphate conjugate fractions and their separate hydrolysis followed by GC-MS of their silyl or methoxime-silyl derivatives. It should be noted that the sulphatase in Helix pomatia will not hydrolyse the sulphate conjugates of the 1713-hydroxy steroids, which require mild acid hydrolysis. 

Glucuronic Acid, Sulfate Ester, and Glutathione Xenobiotic Conjugates Analysis by Mass Spectrometry... 

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