Determination of retinol, antioxidant vitamins and homocysteine in skin puncture blood

For determination of the vitamin status via mass screening, simple and rapi d methods are required. Additionally, blood samples should be obtained usin g simple and low invasive:sampling techniques;:To fulfill this existing met hods have been modified to analyze retinol, tocopherols, beta-carotene, vit amin C and homocysteine in 20 mu l plasma. Blood samples were obtained via skin punctures. HPLC measurements were carried out with isocratic separatio n and precolumn derivatization. Intra and interday variation coefficients w ere below 8% and regression coefficients better than 0.99 for all measureme nts. The difference between-venous and capillary samples were < 5%. In conc lusion, the methods employed proved satisfactory for-the: determination of important nutritional parameters in blood samples obtained via skin punctur es. These methods are-therefore well suited for mass screening, especially under field conditions in developing countries.