A simple automated injection technique for the high-pressure liquid chromatographic determination of plasma retinol

We describe a rapid automated method for determination of retinol in 100 microliters plasma. A lipid extract of plasma is analysed by reverse phase high pressure liquid chromatography using methanol-water as eluent. Automation of injection is achieved by adaptation of a Technicon AutoAnalyzer Sampler 2 coupled with a Micromedic dilution system and a pneumatically actuated loop injector. Twenty patients' specimens can be analysed in 4 hours, including extraction time, standards, and quality controls, with one extract injected every 4 minutes.