本文研究了柱前衍生-高效液相色谱（HPLC）-荧光检测技术测定乳制品中左旋肉碱(L-肉碱)含量的分析方法。经优化后的前处理条件为：提取液采用10%（V/V）甲醇水溶液（经磷酸调节pH至2.7~2.8），经超声提取20 min过滤后调节pH至6.0，取一定滤液加热浓缩近干，用20 mL乙醇溶解。经重复两次高速离心（12000 r/min、5 min）、旋转蒸发浓缩后，残留物用乙醇溶解，以L-丙酰胺-β-萘胺为衍生化试剂于50 ℃恒温衍生5 min后终止反应，于激发波长280 nm、发射波长328 nm下经HPLC分析测定。乳粉检出限为4.0 mg/kg，液体乳检出限0.5 mg/kg、0.2~20.0 mg/L范围内线性关系良好，相关系数0.9990，平均回收率为80~90%，相对标准偏差RSD小于10%。同时，利用该方法对不同配方奶粉及液体乳中L-肉碱进行了含量测定。该方法灵敏度高，准确性好，适用于乳制品中L-肉碱的含量测定。

A method was developed for determination of L-carnitine in milk products by high performance liquid chromatography (HPLC) with fluorescence detection, with a procedure of pre-column derivatization. The sample testing conditions were optimized. And the results were satisfied at the conditions with the methanol volume ration at 10%, pH 2.7~2.8 (adjusted with phosphoric acid), and ultrasonic extraction time of 20 min. The extraction solution was adjusted to pH 6.0, and then evaporated to near dryness. The obtained residue was resolved with 20 mL alcohol followed by a step of centrifugal at 12000 r/min for 5 minutes, and then the obtained upper clear liquid was rotated to near dryness by rotary evaporator. At last, the L-carnitine in the obtained residues was derived with L-Alanine-β-naphthylamide at the optimum conditions with the reaction time of 5 min and temperature of 50 ℃. Then the compound was detected with the excitation wavelength at 280 nm and emission wavelength at 328 nm. And the method parameters were obtained with the limit of quantification of 4.0 mg/kg in milk powder and 0.5 mg/kg in milk. The linear in the range, correlation and the average spiked recoveries were of 0.2~20.0 mg/L, 0.9990, and 80~90%, respectively, with RSD less than 10%. The developed method can be used for determination of L-carnitine in different formulas and milk.

浙江省质量技术监督局定向委托项目（No:20100401）