Measuring venous-arterial differences of valine, isoleucine, leucine, alanine and glutamine in skeletal muscles using counter-current electrophoresis with contactless conductivity detection

Abstract

Plasmatic levels of valine, isoleucine, leucine, alanine and glutamine were determined by capillary electrophoresis with contactless conductivity detection. A new kind of covalently coated capillary based on polyacrylamide and (3-acrylamidopropyl) trimethylammonium chloride was employed. The amino acids were separated in the counter-current regime, in which the analytes migrate under counter-current electro-osmotic flow with a value of 5.53 · 10−9 m2 V−1 s−1 in the background electrolyte, 3.2 mol/L AcOH +10% v/v MeOH. The baseline separation of all five amino acids from other plasmatic compounds was achieved in <5 min; the limits of detections are 0.13–0.14 μmol/L for the treated sample and 0.50–0.58 μmol/L for the untreated plasma. The method was used to measure venous-arterial differences of amino acids in hyperinsulinemic patients with cachexia.