APPLICATION OF CLOUD-POINT EXTRACTION-REVERSED-PHASE HIGH-PERFORMANCELIQUID-CHROMATOGRAPHY - A PRELIMINARY-STUDY OF THE EXTRACTION AND QUANTIFICATION OF VITAMIN-A AND VITAMIN-E IN HUMAN SERUM AND WHOLE-BLOOD

Methods available for quantification of vitamins A and E in serum or b lood requires preconcentration and clean-up by liquid-liquid extractio n, evaporation of the extract, and reconstitution of the extract in a solvent of choice before analysis. This process not only involves the use of toxic organic solvents but also requires a long sample preparat ion time. The lipids and other non-polar coextractants often require a dditional steps for sample clean-up and evaporation, which may cause s ample losses. The use of cloud-point extraction eliminates most of the se sample clean-up problems. We recently demonstrated that cloud-point extraction (CPE) can be used for extraction and quantification of pol ycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dio xins (PCDDs) from human serum. We now demonstrate how CPE can be used with human serum and blood, at volumes as low as 50 mu l, and report a methodology for extracting and quantifying two clinically important v itamins, (A and E) from human serum and blood. Vitamins A and E were e xtracted from human serum and blood by using Genapol X-80 as the cloud -point extractant under salting out conditions. Serum and blood sample s were diluted in organic-free water to get sufficiently large sample volumes for CPE. The surfactant-rich phases were separated by centrifu gation, and the samples were analyzed by HPLC-UV after deleterious coe xtractants were removed by precipitating them with acetonitrile. The r ecoveries of spiked vitamins A and E were found to be 85.6+/-0.4% and 82.6+/-5.2%, respectively. The average concentration of vitamins A and E in a serum pool after correction for recoveries were found to be 43 .4+/-1.8 mu g/dl (1.5 +/- 0.1 mu mol/l) and 564.3 +/- 65.3 mu g/dl (13 .1 +/- 1.5 mu mol/l), respectively. Vitamin A and E concentrations in whole blood were found to be 26.3+/-0.4 mu g/dl (0.92+/-0.01 mu mol/l) and 457.5+/-15.6 mu g/dl (10.6+/-0.4 mu mol/l), respectively. These v alues are comparable with those obtained by the reference method used at the Centers for Disease Control and Prevention. The success of the preliminary study will lead to a comprehensive validation of this meth od for vitamins A and E in serum and blood. (C) 1998 Elsevier Science BN. All rights reserved.