On-flow identification of metabolites of paracetamol from human urine using directly coupled CZE–NMR and CEC–NMR spectroscopy

Abstract

Direct NMR spectroscopic detection on-flow to capillary electrophoresis (CE) or capillary electrochromatography (CEC) was applied to the separation of metabolites of paracetamol from an extract of human urine. The detection and characterisation of the major metabolites, the glucuronide and sulfate conjugates of the drug as well as identification of the endogenous material hippurate was achieved. This demonstrates that NMR detection and identification of drug metabolites is possible with nanolitre volumes of analyte.

Quality control of herbal medicines

“…The hyphenated CE instruments, such as CE-DAD, CE-MS and CE-NMR, all appeared in the past decades. The techniques have also quickly been used for the analysis of the samples from herbal medicines [161][162][163][164][165][166][167]. On-line coupling of capillary electrophoresis to mass spectrometry and other spectrometry allows both the efficient separation of CE and the specific and sensitive detection to be achieved.…”

“…However, correction of retention time shift of the fingerprint of herbal medicines should be taken into consideration first, since some types of variation sources are inevitably encountered from one chromatogram to another [7][8][9][10][11][12][13][166][167][168][169][170][171][172][173][174][175][176][177][178][179][180][181][182]. Under this situation, some unacceptable results, one of which is imposed by the retention time shifts, will be produced.…”

Recent progress in capillary electrochromatography

“…These detection schemes offer unique possibilities because of the additional structural information that can be obtained. On-line coupling of NMR with capillary separation techniques offers many possibilities [193] and was recently coupled to CEC [184, 194±197] as well as being used, for example, in metabolite analysis [195,197] and analgesics [194]. The use of CEC-MS is becoming more popular mainly because of solvent compatibility, in addition to the volumetric flow rates that closely match the requirements of electrospray interfaces available.…”

Recent advances in the study of biomolecular interactions by capillary electrophoresis

“…The major drawback is still the low capacity of standard CE systems, equipped with UV detectors to yield specific information about sample components. CE coupled with other detectors, such as CE-MS [132,151], CE-inductively coupled plasma (ICP)-MS [152,153], CE-NMR [154,155], CE-FTIR [156], CERaman [157,158], and CE-X-ray [159] is capable to provide more structural elucidation. At present, however, only the on-line MS technique has a sufficient detection sensitivity for structural identification.…”