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    柱前衍生-高效液相色谱法测定化妆品中16种氨基酸的含量

    Determination of 16 Amino Acids in Cosmetics by High Performance Liquid Chromatography with Pre-Column Derivatization

    • 摘要: 提出了2,4-二硝基氟苯(DNFB)柱前衍生-高效液相色谱法测定化妆品中甘氨酸、亮氨酸、组氨酸、缬氨酸、甲硫氨酸、脯氨酸、半胱氨酸、苏氨酸、谷氨酸、赖氨酸、酪氨酸、精氨酸、异亮氨酸、色氨酸、苯丙氨酸、丙氨酸等16种氨基酸含量的方法。取化妆品样品5 g置于50 mL离心管中,加入5 mL水,超声10 min,加热煮沸15 min,冷却后加入15 mL 35 g·L−1磺基水杨酸溶液,以转速10 500 r·min−1离心20 min。取全部上清液,用35 g·L−1磺基水杨酸溶液定容至25 mL。取1 mL样品溶液,加入0.5 mol·L−1碳酸氢钠溶液(pH 9.0)1 mL和1%(体积分数)DNFB衍生溶液1 mL,混匀,于60 ℃加热10 min,冷却后用0.01 mol·L−1磷酸二氢钾溶液(pH 7.0)定容至5 mL,所得溶液中16种氨基酸经X Bridge C18色谱柱分离,以不同体积比的含1%(体积分数)N,N-二甲基甲酰胺的0.05 mol·L−1乙酸钠缓冲液(pH 6.5)-体积比1∶1的乙腈-水混合溶液为流动相进行梯度洗脱,在360 nm处检测。结果表明:16种氨基酸标准曲线的线性范围均为0.004~40.0 mg·L−1,检出限(3S/N)为0.1~0.2 mg·kg−1;对空白样品进行3个浓度水平的加标回收试验,回收率为89.0%~105%,测定值的相对标准偏差(n=7)均不大于10%。方法用于11种市售化妆品分析,检出的氨基酸成分多为组氨酸、甘氨酸、甲硫氨酸、谷氨酸。

       

      Abstract: A method for the determination of 16 amino acids including glycine, leucine, histidine, valine, methionine, proline, cysteine, threonine, glutamic acid, lysine, tyrosine, arginine, isoleucine, tryptophan, phenylalanine, and alanine in cosmetics by high performance liquid chromatography with 2,4-dinitrofluorobenzene (DNFB) pre-column derivatization was proposed. 5 g of cosmetic sample was taken into a 50 mL-centrifuge tube, and 5 mL of water was added. The mixture was sonicated for 10 min and boiled for 15 min. After cooling, 15 mL of 35 g·L−1 sulfosalicylic acid solution was added and the mixture was centrifuged at a rotational speed of 10 500 r·min−1 for 20 min. All of the supernatant was taken and its volume was made up to 25 mL with 35 g·L−1 sulfosalicylic acid solution. 1 mL of sample solution was taken, and 1 mL of 0.5 mol·L−1 sodium bicarbonate solution (pH 9.0) and 1 mL of 1% (volume fraction) DNFB derivative solution were added. The mixture was heated at 60 ℃ for 10 min and cooled. Its volume was made up to 5 mL with 0.01 mol·L−1 potassium dihydrogen phosphate solution (pH 7.0). 16 amino acids in the obtained solution were separated on a X Bridge C18 chromatographic column, and gradient elution was performed using a mobile phase consisting of 0.05 mol·L−1 sodium acetate buffer solution (pH 6.5) containing 1% (volume fraction) DMF and a mixture of acetonitrile-water at a volume ratio of 1∶1 at different volume ratios. The detection was performed at 360 nm. As shown by the results, the linear ranges of the standard curves of 16 amino acids were 0.004—40.0 mg·L−1, with detection limits (3S/N) in the range of 0.1-0.2 mg·kg−1. Test for recovery was made on blank sample by standard addition method at 3 concentration levels, giving results in the range of 89.0%-105%, with RSDs (n=7) of the determined values not more than 10%. This method was applied to the analysis of 11 commercially available cosmetics, and it was shown that the detected amino acid components were mostly histidine, glycine, methionine, and glutamic acid.

       

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