Synchronous Fluorimetric Determination of Free Amino Acids in Honey

Based on the yellowish-green fluorescence given by N-substituted 2,6-dimethyl-3,5-diacetyl-1,4-dihydropyridine which was produced by the reaction of amino acid with acetylacetone and formaldehyde in acetate buffer medium,a fluorimetric method for determination of free amino acids in honey was proposed.Synchronous fluorescence signals (F) of amino acids were measured at the maximum excitation λex wavelength and with the optimum wavelength difference Δλ.Values of Δλ,λex and F were found to have slight differences for different amino acids,and ranges of linearity were also different.Taking alanine as example,when determined under the optimum conditions of λex 387 nm,Δλ 85 nm and scanning rate of 1 000 nm·min-1,the linear regression equation y=49.03 x+148.11 (r=0.999 2) and linearity range 1.0-10.0 mg·L-1 were obtained.In the determination of total amino acid in honey samples by the proposed method,average value of recovery of 99.3% was obtained.