Chemiluminometric branched chain amino acids determination with immobilized enzymes by flow-injection analysis Original Research Article

A tri-enzyme sensor was developed for the flow-injection determination of branched chain amino acids (L-valine, L-leucine and L-isoleucine). Leucine dehydrogenase, NADH oxidase and peroxidase were coimmobilized covalently on tresylate-hydrophilic vinyl polymer beads and packed into transparent PTFE tube (20 cm×1.0 i.d.), which was used as flow cell. The calibration graph was linear for 30 nM–5 μM; the detection limit (signal-to-noise=3) was 10 nM. The sampling rate was 25 h−1 without carryover. The sensor was stable for two weeks. The sensor system was applied to the determination of branched chain amino acid in plasma.