在乙酸盐缓冲介质中,氨基酸与乙酰丙酮及甲醛反应生成发出黄绿色荧光的化合物N-取代-2,6-二甲基-3,5-二乙酰基-1,4-二氢吡啶,基于此反应提出了测定蜂蜜中游离氨基酸的方法.在氨基酸的最大激发波长λex并在选定的最佳波长差Δλ的条件下测定相应氨基酸的同步荧光信号.试验发现:对不同的氨基酸,其λex,Δλ和所生成的荧光化合物的相对荧光强度以及线性范围均稍有差异.以丙氨酸为例,在λex为387 nm,Δλ为85 nm及扫描速率为1 000 nm·min-1的条件下进行测定,所得线性回归方程为y=49.03 x+148.11(r=0.999 2),线性范围为1.0~10.0 mg·L-1.应用此方法测定了蜂蜜样品中游离氨基酸的总量,在此基础上进行回收试验,测得回收率的平均值为99.3%.

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.