超高效液相色谱法测定婴幼儿乳粉中的色氨酸

Determination of tryptophan in infant formulas using ultra-high performance liquid chromatography

中文关键词:  超高效液相色谱法  色氨酸  乳粉  碱水解

英文关键词:ultra-high performance liquid chromatography  tryptophan  infant formula  alkali hydrolysis

中文摘要:

      目的 建立婴幼儿乳粉中色氨酸的超高效液相色谱检测方法, 并考察乳粉中色氨酸含量与蛋白质含量的相关性。方法 样品在145℃下碱性水解4 h, 经C18色谱柱(50 mm×4.6 mm, 1.8 μm)分离。以100 mmol/L KH2PO4-NaOH缓冲溶液-甲醇为流动相, 40% 甲醇(v:v)等度洗脱, 流速为0.5 mL/min, 进样量5 μL, 柱温45℃。荧光检测器检测, 激发波长280 nm; 发射波长350 nm。结果 方法在1~1000 μg/L范围内线性关系良好(r=0.999); 定量限为1 μg/L。添加浓度在0.2、0.5、1.5 mg/g时, 色氨酸的回收率介于110.7%~116.3%之间。结论 本方法操作简便, 可应用于市售乳粉样品中色氨酸含量的测定。对市售样品的测定结果表明, 部分婴幼儿乳粉样品的色氨酸含量低于国家限量, 此外, 乳粉中色氨酸含量与蛋白质含量之间并不呈线性相关。

英文摘要:

      Objective To establish an ultra-high performance liquid chromatography (U-HPLC) method for the determination of tryptophan in infant formulas, and then to investigate the relationship between tryptophan concentration and protein concentration in infant formulas. Methods NaOH was used as hydrolytic so-lution. Then sample hydrolysis under an alkaline condition at 145 ℃. The U-HPLC separation was achieved using a C18 column (50 mm×4.6 mm, 1.8 μm) as solid phases and KH2PO4-NaOH buffer solution–methanol (60:40, v:v) as mobile phases. under isocratic elution. The flow rate was 0.5 mL/min and the column oven temperature was 45 ℃. The injection volumn was 5 μL. It was detected on a Fluorescence Detector and quantitatively determined by the peak area at excitation wavelength of 280 nm and emission wavelength of 350 nm. Results The linear concentration ranges of the calibration curve were 1~1000 μg/L for tryptophan (r=0.999), and the limit of quantification of the method was 1 μg/L. The mean recoveries varied from 110.7%~116.3% when spiked negative samples with 0.05, 0.5 and 2.5 mg/g tryptophan. Conclusion The established method is simple and can be suitable for the rapid determination of tryptophan in infant formulas. The determined results demonstrated that the relationship was not linear between tryptophan concentration and protein concentration in infant formulas.