Hyphenated techniques in anticancer drug monitoring. I. Capillary gas chromatography-mass spectrometry.

Most anticancer agents are relatively unstable substances and are subjected to intensive metabolism in vivo and radiation during sample pretreatment. Hyphenated techniques including a separation technique and, most frequently, mass spectrometry are therefore chosen to obtain insight into the in vivo behavior of anticancer agents. Once established, simpler assays can be derived from those based on hyphenation, which are less expensive. Capillary gas chromatography (cGC)-mass spectrometry (MS) is amongst the most frequently applied hyphenated analytical technologies in anticancer drug monitoring. Here a selection has been made of: (i) cGC-MS applied to the analysis of agents frequently used in clinical oncology (e.g. tamoxifen, oxazaphosphorines); (ii) cGC-MS applied to the development of new agents (Swainsonine and Brefeldin); (iii) cGC-MS applied to the analysis of agents for which comparisons with other frequently applied hyphenation technologies are possible (see Part I of this series). cGC-MS played a key role in the elucidation of the in vivo behavior of the oxazaphosphorine cyclophosphamide, historically the most frequently applied anticancer agent. cGC-MS appeared to be of special interest in the analysis of cyclophosphoramide and congeners in human erythrocytes by coupling of the hyphenated technique with a measurement of sediment technique. This resulted in the quantitative and qualitative analysis of oxaphosphorine-related mustard gas moieties in human erthrocytes for the first time.

Hyphenated techniques in anticancer drug monitoring. II. Liquid chromatography-mass spectrometry and capillary electrophoresis-mass spectrometry.

High-performance liquid chromatography has become the separation technique of choice for the monitoring of generally thermolabile anticancer agents. With the introduction of electrospray mass spectrometry, the coupling of liquid chromatogaphy and mass spectrometry has opened the way to widely and routinely applied anticancer drug monitoring. Real-time metabolism versus degradation can now be distinguished, since derivatization is no longer obligatory. This is important for the monitoring of the anabolic and catabolic pathways of the same agent, such as 5-fluorouracil. Detection limits almost equal to those obtained with capillary gas chromatography-mass spectrometry are realistic with the latest generation of mass spectrometers, enabling quantitative analysis of various anticancer agents and their metabolites down to the low ng/ml level. Furthermore, sample clean-up and chromatography can be downscaled markedly using the latest column technologies, such as the generally applied 10 cm x 2.8 mm I.D. RP 18 columns. The coupling of capillary electrophoresis to mass spectrometry is today far from a routine application in anticancer drug monitoring. Nevertheless, interesting applications have been reported and are selected for the present review.