GAS-CHROMATOGRAPHIC DETERMINATION OF FREE AMINO-ACIDS IN CHEESE

The paper presents the gas chromatographic determination of amino acids in the form of isobutyl-heptafluorobutyryl derivatives (iso-BuOH-HFB). Optimum peak separation was obtained using a capillary OV 1701 column, fused silica, 25 m long, Analytical reproducibility has been evaluated for the whole procedure for both amino acid standards (ionic exchange chromatographic purification, derivatization, HRGC analysis) and for free amino acids in cheese samples. For the last sample also the phase of extraction of amino acids from the matrix was considered. Results showed a high accuracy of final HRGC analysis for several iso-BuOH-HFB amino acids and a fairly good repeatability for the whole procedure, with methionine and glycine giving higher errors. The most critical steps for repeatability are the free amino acid extraction from the cheese matrix and the amino ac d purification on the ionic exchange resin.