Matthew S. Klee

Evaluation of column performance in constant pressure and constant flow capillary gas chromatography

It has been demonstrated that there is no significant difference between the maximum peak capacity and analysis time at the same peak capacity in constant pressure (isobaric) and constant flow (isorheic) modes of temperature programmed GC. In view of that, the choice between the two pneumatic modes should be based on considerations other than the speed-separation performance of the column.

Superior ECD Performance through Design and Application

A new ECD, the HP 6890 Series Micro-ECD, was designed to address inherent deficiencies in classical electron capture detectors (ECD), especially with respect to sensitivity, linearity, dynamic range, and ruggedness. Several novel technologies were incorporated in the totally new design and were refined through practical testing and user feedback. Validation of the micro-ECD performance was accomplished through side-by-side testing of the Micro-ECD with previous ECDs following US EPA Contract Laboratory Program methods for pesticides and PCBs. In addition, extensive interviews were conducted with early users of the Micro-ECD who also had experience with other designs running a variety of ECD methods. The design and resulting performance improvements are described.

Supercritical fluid chromatography of paclitaxel

The analysis of paclitaxel and related compounds was investigated using supercritical fluid chromatography (SFC). The separation of paclitaxel and five related taxanes was compared on two SFC instruments. The typical analysis time was 20 min on system I and 4 min on system II. Based on this, SFC system II was selected for further studies and a separation of paclitaxel from fifteen of its impurities or degradation products was achieved in about 35 min.

Achiral and chiral analysis of camazepam and metabolites by packed-column supercritical fluid chromatography.

Supercritical fluid chromatography, using carbon dioxide as the mobile phase and ethanol as a modifier, has been applied to the analysis of products formed in rat liver microsomal metabolism of racemic camazepam, a hypnotic/anxiolytic drug in clinical use. An achiral (amino) column and a chiral (Chiralcel OD-H) column were used. The results suggest that achiral and chiral packed-column supercritical fluid chromatography gives a shorter analysis time and higher selectivity and efficiency than achiral and chiral stationary-phase high-performance liquid chromatography in the analysis of camazepam and its derivatives.