AMINO-ACID PROFILES BY HPLC AFTER FILTER-PAPER SAMPLING - APPROPRIATE TECHNOLOGY FOR MONITORING OF NUTRITIONAL-STATUS

This paper describes a rapid analysis of free amino acid levels in capillary blood samples using a modified HPLC system. Capillary whole blood (25 μl) is dried on a filter paper, extracted and the equivalent of 0.25 μl of the initial blood sample is used for each amino acid analysis. Nineteen free amino acid levels are determined with a reproducibility of better than ± 10% for the entire procedure of sampling, preparation and analysis, with the exception of ornithine (± 19%) and lysine (± 12%). Cystine and proline cannot easily be determined by this method. Alanine, tyrosine, methionine, valine, phenylalanine, isoleucine and leucine concentrations on the filter paper are unaltered after 1, 2 and 21 wk. Storage at room temperature should not be for longer than 2 wk, but storage at +4°C, -18°C and -70°C is acceptable for 21 wk. This new micromethod seems to be a practical and reliable tool. Because of its simplicity and, above all, the need for a minimal amount of capillary blood, it is a valid means for the routine monitoring of amino acid profiles in sick preterm infants on different protein regimens. The sampling and storage methods are also examples of 'appropriate technology' for field studies of nutritional adequacy in population samples derived from infants. This is because centrifugation is not necessary and the fact that the relevant amino acids on the dried filter paper samples display high stability. © 1990.