Development of novel methodologies for using ICP-MS in bioanalysis and drug metabolism.

Inductively coupled plasma mass spectrometry (ICP-MS) has been widely used for environmental and trace analysis since its introduction in the early 1980s. This thesis describes an exploration of the potential of HPLC-ICP-MS within the pharmaceutical industry. Determination of platinum in the anticancer drug ZD0473 was performed in comparison with conventional HPLC-MSMS, investigating limit of detection, linearity and reproducibility on spiked samples. Both methods were capable of providing accurate and precise results with samples from rats dosed intravenously 0.5 mg/kg and orally at 6 mg/kg, but the HPLC-ICP-MS Pt method had extended linear range and superior sensitivity, providing a limit of quantification of 0.1 ng/mL compared to 5 ng/mL by HPLC-MSMS. Impurity and metabolite profiles for ZD0473, using platinum as a marker with HPLC-ICP-MS, were compared to profiles from 14C-labelled compound with radioactivity detection, showing that the compound was converted to 2-picoline.Since the number of compounds containing platinum found in the pharmaceutical industry is limited ICP-MS was then evaluated for other elements.The detection of carbon was investigated, since this is present in all organic molecules, and a limit of detection of 0.47 mumol of carbon was achieved for sulphanilamide using superheated water as the mobile phase. Isotopically enriched solvents (12C-methanol 99.95 atom %) were used as organic modifier to aid chromatography. Detection limits of 86 mumol for 13C-triple-labelled caffeine and 79 mumol 13C-double-labelled phenacetin.Halogen (Br, I and Cl) detection was investigated. Metabolite profiling and excretion balance studies were carried out using these elements after dosing suitable model compounds (substituted anilines and benzoic acids) to rats. Limits of detection for Br and I were measured down to 0.1 mM. Profiling for 2-, 3-, 4-bromobenzoic acids showed glycine and glucuronide metabolites, in different proportions dependant on the position of the Br. This was also seen for the 2-, 3-, 4-iodobenzoic acids.Sulphur and phosphorous containing drugs were analysed using the reaction cell of the ICP-MS to chemically enhance the signal by reacting the element with oxygen (e.g. to give SO[+]), moving the detection away from a region of isobaric interference. Metabolite profiling of omeprazole was performed, with limits of detection of 800 pg of sulphur on column (an improvement of 100 fold in sensitivity from detection without oxygen). Similar studies with phosphorus containing drugs also showed a significant increase in sensitivity following reaction with oxygen compared to conventional analysis by ICP-MS.The studies undertaken here demonstrate the significant potential of HPLC-ICP-MS as a contributor to the analysis of drugs and metabolites in the pharmaceutical industry.