Analysis of polar organic micropollutants in water with ion chromatography-electrospray mass spectrometry

The coupling of ion chromatography (IC) with electrospray mass spectrometry (ES-MS) opens new ways for the determination of polar organic micropollutants in water samples. The technique of conductivity suppression has been found to reduce the background signal in the range of about two orders of magnitude leading to a significant increase in sensitivity. In addition, the formation of salt adducts has been avoided. The usefulness of this method was proven on several polar and environmentally relevant micropollutants such as the herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA), the chelating agent ethylenediamine tetraacetate (EDTA) and diacetonketogulonic acid (DAG). This present study has shown that IC-ES-MS is a simple, sensitive and quick method for the determination of these polar organic traces in water samples after separation on an anion-exchange column without any derivatization. In this work, several possibilities of applications of IC-ES-MS (with varying conditions) are presented. Analysis of glyphosate, AMPA, DAG and EDTA in ground and surface water has been achieved by IC-ES-MS without additional sample preparation at a concentration level of 1 microgram/l.

Identification of glucoside and carboxyl-linked glucuronide conjugates of mycophenolic acid in plasma of transplant recipients treated with mycophenolate mofetil

1. Mycophenolic acid (MPA), is primarily metabolized in the liver to 7-O-MPA-beta-glucuronide (MPAG). Using RP-h.p.l.c. we observed three further MPA metabolites, M-1, M-2, M-3, in plasma of transplant recipients on MMF therapy. To obtain information on the structure and source of these metabolites: (A) h.p.l.c. fractions containing either metabolite or MPA were collected and analysed by tandem mass spectrometry; (B) the metabolism of MPA was studied in human liver microsomes in the presence of UDP-glucuronic acid, UDP-glucose or NADPH; (C) hydrolysis of metabolites was investigated using beta-glucosidase, beta-glucuronidase or NaOH; (D) cross-reactivity of each metabolite was tested in an immunoassay for MPA (EMIT). 2. Mass spectrometry of M-1, M-2, MPA and MPAG in the negative ion mode revealed molecular ions of m/z 481, m/z 495, m/z 319 and m/z 495 respectively. 3. Incubation of microsomes with MPA and UDP-glucose produced M-1, with MPA and UDP-glucuronic acid MPAG and M-2 were formed, while with MPA and NADPH, M-3 was observed. 4. Beta-Glucosidase hydrolysed M-1 completely. Beta-Glucuronidase treatment led to a complete disappearance of MPAG whereas the amount of M-2 was reduced by approximately 30%. Only M-2 was labile to alkaline treatment. 5. M-2 and MPA but not M-1 and MPAG cross-reacted in the EMIT assay. 6. These results suggest that: (i) M-1 is the 7-OH glucose conjugate of MPA; (ii) M-2 is the acyl glucuronide conjugate of MPA; (iii) M-3 is derived from the hepatic CYP450 system.