Comparative column chromatographic estimations of phenylalanine in plasma, whole blood, native and paper‐dried capillary blood of healthy children and adults, and patients with hyperphenylalaninaemia

Abstract
The concentration of phenylalanine in plasma, whole venous and capillary blood, and paper-dried blood of 75 probands (25 healthy adults, 27 healthy children, and 23 patients with hyperphenylalaninaemia) were measured by use of a sensitive short column chromatography method. The comparison of the values in each group of probands by several statistic methods showed an excellent correlation of the phenylalanine concentration in paper-dried whole blood to those measured in venous plasma. Evaluation of the analytical method revealed a high sensitivity and accuracy by use of a sample volume of 50 µl. We would therefore suggest that the estimation of phenylalanine for the diagnosis and therapy control in hyperphenylalanine is as accurate in paper-dried blood as in venous plasma and would simplify sampling for the patients as well as enhance the diagnosis and therapy control in hyperphenylalaninaemia.