Liquid chromatographic determination of cyclosporin A in serum with use of a solid-phase extraction. Comparison between high-performance liquid chromatography and radioimmunoassay levels in clinical investigations.

A simple reliable liquid chromatographic method for assay of cyclosporin A in serum or urine is described. Samples were cleaned up on a solid-phase extraction system (cyanopropyl column). The system involved a reversed-phase C18 Ultrasphere column maintained at 72 degrees C and an acetonitrile linear gradient (65 to 95%) in 0.14% triethylammonium phosphate. Liquid chromatographic analysis of radioimmunoassay standards shows that some samples contain a contaminant peak. Comparison of cyclosporin A levels obtained by radioimmunoassay and high-performance liquid chromatography in clinical investigations show that the former values are generally, but not always, higher than the latter, and that cyclosporin A is very differently metabolized depending on the patient, disease and treatment.

Application of pulse polarography with anodic stripping voltammetry to biological and toxicological analyses for lead and cadmium.

The development of polarographic techniques within the last thirty years has made possible exceptional increases in sensitivity ; thus the order of concentration studied has passed from 10-3 g ion/1. to 10-10 g ion/1. Pulse polarography with anodic stripping voltammetry is, therefore, particularly suitable for the determination of a large number of the so-called " biologically essential " and " highly toxic " metals, more often than not present in extremely low concentrations in biological samples which may be of limited volume (blood, for example). Our principal concern has been to describe and apply a method for the determination of lead and cadmium, sufficiently sensitive, precise, practical and rapid for everyday use by biologists and toxicologists. A fortiori this method is applicable in hydrology to the determination of traces of these metals in water.