HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC MEASUREMENT OF UROCANIC ACID ISOMERS AND THEIR RATIOS IN NATURALLY LIGHT-EXPOSED SKIN AND NATURALLYSHIELDED SKIN

We have developed methods for sampling and extraction of trans-urocani c acid and cis-urocanic acid from human skin, and subsequent high-perf ormance liquid chromatographic measurement of these isomers. Sampling involves applying cellophane adhesive tape to the skin for 10 s. Uroca nic acid isomers were completely extracted by immersing the tape in KO H solution. The HPLC column was a Tosoh ODS 80(TS) (250x4.6 mm LD., 7 mu m average particle size) eluted with 20 mM potassium dihydrogenphos phate containing 1 g/l sodium heptanesulphonate (pH 3.7)-acetonitrile (93:7, v/v) at a flow-rate of 1.0 ml/min. The isomers were detected by UV absorbance at 264 nm. This technique was used to analyze the ratio of trans-urocanic acid/cis-urocanic acid on human skin at various sit es on the body. It was found that the ratio was low in naturally Light -exposed skin and high in naturally shielded skin. (C) 1997 Elsevier S cience B.V.