Abstract: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.
