本文通过对样品提取方式、提取剂、流动相等条件进行改进和优化，建立了一种同步测定食品中L-抗坏血酸、D-抗坏血酸和脱氢抗坏血酸的方法。针对果蔬样品，采用液氮冷冻研磨进行预处理，相比机械匀浆，可以显著提高提取率，减少化学试剂用量，简化前处理操作。为保护L-抗坏血酸不被氧化，在偏磷酸提取液中加入0.019 mol/L硫代硫酸钠作为保护剂，结果表明，实验无需避光操作，提取物可在4 ℃ 24 h内保持性质稳定；采用磷酸二氢钾-癸胺缓冲盐混合溶液作为流动相，可以使不同构型抗坏血酸在较高浓度时依然达到基线分离。抗坏血酸在0.5 mg/L~200 mg/L范围内呈良好线性关系，检出限为0.04 mg/100 g。样品回收率为99.7%~107.3%，相对标准偏差为3.80%。对于准确测定食品中活性抗坏血酸的组分含量、建立标准化操作规程具有重要意义。

A method for the simultaneous determination of L-ascorbic acid, D-ascorbic acid and dehydroascorbic acid in food was established in this paper by optimizing and improving the sample extraction, extraction agent and mobile phase. Compared with mechanical homogenate, the liquid nitrogen freeze-grinding pretreatment could significantly improve the extraction rate, reduce the dosage of chemical reagents and simplify the pretreatment process for fruit and vegetable samples. 0.019 mol/L sodium thiosulfate was added as a protective agent in the metaphosphoric acid to protect L-ascorbic acid from being oxidized. The results showed that the experiment did not be protected from light, and the extract remained stable within 24 h at 4 oC. The baseline separation for different configurations of ascorbic acid in high concentration could be achieved by using potassium dihydrogen potassium–decylamine as the buffer solution. Ascorbic acid showed a good linear relationship in the range of 0.5 mg/L to 200 mg/L and the detection limit was 0.04 mg/100g. The average recoveries were 99.7%~107.3% and the relative standard deviation was 3.80% (n=5). Consequently, it was of great significance to establish a standardized operating procedure for accurately determining the content of active ascorbic acid in food.

山东省泰山产业领军人才工程项目（鲁政办字[2016]190号）；青岛市“人才特区”项目（2016）；山东半岛国家自主创新示范区发展建设资金项目（鲁科字[2017]41号）