Supercritical fluid chromatography and microbore liquid chromatography for drug analysis

Supercritical fluid and microbore liquid chromatography offer potential applications for drug analysis. In supercritical fluid chromatography (SFC), the mobile phase is a gas (e.g., carbon dioxide) maintained at its supercritical state--that is, above its critical temperature and pressure, above which it cannot be liquefied even with further increases in applied pressure. The SFC mobile phase has low viscosity, approximating that of a gas, and high diffusivity, between those of a gas and a liquid. These properties yield favorable column efficiency, between that of capillary gas chromatography (GC) and liquid chromatography (LC). SFC analysis may be performed by either packed or open tubular capillary columns and with GC and LC detectors. SFC, interfaced with mass spectrometry, may become a viable alternative to GC/MS for drug identification in clinical and forensic toxicology. Advantages of microbore liquid chromatography include enhanced mass sensitivity, reduced solvent consumption, and others. Microbore columns (internal diameters 1 to 2 mm) may be packed with 3-, 5-, or 10-micron particles. Potential applications include micro-sample analysis (5-200 microL) for neonatal and pediatric drug monitoring, and drug confirmation analysis for toxicology.