Rapid structure identification of nineteen metabolites of ondansetron in human urine using LC/MSn.

Ondansetron, a 5-hydroxytryptamine type 3 (5-HT3 ) receptor antagonist, is regarded as an excellent candidate to treat chemotherapy- and radiotherapy-induced nausea and vomiting. To better understand the metabolic profiles of ondansetron in human urine, the metabolites were analyzed using liquid chromatography/mass spectrometry (LC/MSn ). Urine samples were collected after oral administration of 8 mg ondansetron to healthy volunteers. Then samples were treated by solid-phase extraction and detected with LC/MSn . Besides ondansetron, in human urine, a total of 19 metabolites including 13 new metabolites were detected and identified via comparing the retention time and product ion spectra with those of reference standards isolated and characterized. The results showed that ondansetron was metabolized via hydroxylation, glucuronidation, sulfation and minor N-demethylation in human. LC/MSn was demonstrated to be useful and sensitive in the metabolic study of ondansetron.

On-line focusing of 5-hydroxy-tryptamine type 3 receptor antagonists via the combination of field-enhanced sample injection and dynamic pH junction in capillary electrophoresis with amperometric detection.

In the present work, an on-line dual focusing technique based on field-enhance sample injection (FASI) and dynamic pH junction (DypH) was developed for the analysis of two 5-hydroxy-tryptamine type 3 receptor (5-HT3) antagonists ondansetron (Ond) and tropisetron (Tro) by capillary electrophoresis with amperometric detection (CE-AD) system. By preparing the sample in a lower conductivity (FASI condition) and lower pH value (DypH condition) matrix relative to the background electrolyte (BGE) solution, a simple and effective dual focusing approach, FASI-DypH was achieved. In this stacking mode, a large amount of analytes could be electrokinetically injected into the capillary and stacked at the boundary of the sample and the BGE zone as a result of deprotonation and decrease in the electric field. Effects of separation, detection and FASI-DypH focusing conditions were investigated in detail. Under the optimum conditions, good separation for Ond and Tro was achieved within 8min. In comparison with the conventional CE-AD analysis method, the present dual focusing technique enabled the enhancement factors in terms of peak heights to reach 357-fold and 345-fold for Ond and Tro, respectively. The limits of detection (LODs) (S/N=3) for Ond and Tro were 2nM and 5nM, respectively. The intraday and interday repeatabilities (RSDs) were less than 4.5% and 2.9% for peak height and migration time, respectively. The proposed method was successfully applied for the analysis of Ond and Tro in human urine sample.