高效液相色谱法测定芝麻 和芝麻酱中草酸的含量Determination of oxalic acid in sesame seed and sesame paste by high performance liquid chromatography

旨在为芝麻及其制品中草酸检测方法的开发提供参考，建立了一种高效液相色谱法测定芝麻和芝麻酱中草酸含量的方法。对草酸提取条件和液相色谱条件进行了优化，进行了方法学验证，并测定了实际样品中草酸含量。结果表明：优化的草酸提取条件为采用80 ℃水浴加热提取，提取液为1.0 mol/L盐酸溶液，料液比1∶ 10，提取2次，每次提取时间10 min；优化的液相色谱条件为Agilent Zorbax SB-Aq色谱柱（4.6 mm×250 mm,5 μm），流动相为0.1%磷酸溶液，流速0.5 mL/min；在最优色谱条件下，草酸在10~2 000 μg/mL质量浓度范围内具有良好的线性关系（r2≥0.999 0），方法的检出限和定量限分别为0.083 mg/g和0.250 mg/g(以脱脂样品质量计)，日内和日间精密度（相对偏差标准）均小于1%，脱脂芝麻样品中草酸加标回收率为 94.4%~107.5%，脱脂芝麻酱样品中草酸加标回收率为90.9%~99.7%；芝麻中草酸含量范围为12.12~24.15 mg/g，芝麻酱中草酸含量范围为17.59~25.35 mg/g。综上，所建立的方法精密度良好、准确度高，可应用于芝麻及芝麻酱中草酸含量的检测。Aiming to provide reference for the development of oxalic acid detection methods in sesame seed and sesame products, a high performance liquid chromatography method was established to determine the content of oxalic acid in sesame seed and sesame paste. The extraction conditions for oxalic acid and liquid chromatography conditions were optimized, and the methodology was validated. The oxalic acid content in actual samples was also determined. The results showed that the optimal oxalic acid extraction conditions were as follows: extraction by heating in an 80 ℃ water bath, 1.0 mol/L hydrochloric acid solution as extraction solution, material to liquid ratio 1∶ 10, extraction times twice, and each extraction time 10 min.The optimized liquid chromatography conditions were an Agilent Zorbax SB-Aq column (4.6 mm× 250 mm, 5 μm), with a mobile phase of 0.1% phosphoric acid solution and a flow rate of 0.5 mL/min. Under the optimal chromatography conditions, oxalic acid exhibited a good linear relationship (r2≥0.999 0) within the mass concentration range of 10-2 000 μg/mL. The detection limit and quantification limit of the method were 0.083 mg/g and 0.250 mg/g(based on the mass of defatted sample), respectively. The relative standard deviation of both intra-and inter-day precision were less than 1%. The spiked recovery rates in defatted sesame seed and sesame paste samples were 94.4%-107.5%, and 90.9%-99.7%, respectively. The oxalic acid content in sesame seed was 12.12-24.15 mg/g, and the oxalic acid content in sesame paste was 17.59-25.35 mg/g. In conclusion, the established method has good precision and high accuracy, and can be applied to the detection of oxalic acid content in sesame seed and sesame paste.