Liquid-chromatographic assay for retinol (vitamin A) and retinol analogs in therapeutic trials.

A "high-performance" liquid-chromatographic separation of retinoids (retinol, isotretinoin, all-trans retinoic acid, retinal, etretinate, and retinyl acetate) in serum is described. The separation was used in developing a quantitative assay for retinol (vitamin A) and two therapeutic analogs, isotretinoin (13-cis-retinoic acid) and etretinate (Ro 10-9359). The procedure requires 1 mL of serum. Overall analytical recovery for retinol, isotretinoin, and etretinate from serum was 100% (SD 7%). The between-day coefficient of variation for specimens with concentrations ranging from 0.70 to 0.95 mg/L was less than 4%. Normal reference intervals for serum retinol in men and women are 0.61 to 1.33 and 0.44 to 1.19 mg/L, respectively.