Analysis of lycopene geometrical isomers in biological microsamples by liquid chromatography with coulometric array detection

Methods of analysis for determining low quantities of lycopene cis-trans is omers in biological tissues are needed. Development of two liquid chromatog raphy (LC) methods based on the polymeric C-30 stationary phase equipped wi th coulometric electrochemical array detection (ED) is described. Separatio n of 13 lycopene isomers including prolycopene, (a novel tetra-cis-lycopene found in Tangerine tomatoes) was accomplished with both isocratic and grad ient methods using different proportions of methanol, methyl tert.-butyl et her, water and 1 M ammonium acetate buffer. Carotenoids were detected at po tential settings between 200 and 620 mV. Differences in generated current-v oltage curves aided in tentative identification of trans carotenoid species and select cis isomers of lycopene. These methods were successfully applie d in the analysis of small quantities of plasma, buccal mucosal cells, pros tate and cervical tissues. Limits of detection for trans-lycopene by ED wer e found to be 50 fmol representing a 10- to 100-fold increase over conventi onal UV-Vis absorbance methods. (C) 2001 Elsevier Science B.V. All rights r eserved.