DETERMINATION OF RETINOL AND RETINOIC ACID IN CAPILLARY BLOOD BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A simplified method for quantitation of retinol in capillary blood by high-performance liquid chromatography (HPLC) is described. Serum (10- 20 mu l) obtained by centrifugation of capillary blood is extracted wi th a solvent mixture of isopropanol-dichloroethane, and the extract is directly injected into a HPLC system to quantitate retinol. The lower limit of quantitation is 0.25 ng retinol, thus permitting quantitatio n of serum or plasma level of 8 mu g or more retinol/L. Although endog enous retinoic acid cannot be analyzed, retinoic acid, following an or al dose, can be extracted along with retinol in presence of acetic aci d and quantitated. The lower limit of quantitation of retinoic acid is 0.5 ng, thus permitting quantitation of 50 ng or more of retinoic aci d/ml serum or plasma. The small sample size required, their simple pre paration, and rapid analysis make this method well suited for clinical studies. The method should be very useful for monitoring retinol leve l in blood of patients suspected of vitamin A deficiency or of retinol and retinoic acid levels in patients undergoing retinoic acid therapy for skin disorders or acute promyelocytic leukemia.