Abstract：
A fast and straightforward reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) using a deep eutectic solvent (DES) procedure to determine free tryptophan in vegetable oils was developed. The influence of eight variables affecting the RP-DLLME efficiency has been studied by a multivariate approach. A Plackett-Burman design for screening the most influential variables followed by a central composite response surface methodology led to an optimum RP-DLLME setup for a 1 g oil sample: 9 mL hexane as the diluting solvent, vortex extraction with 0.45 mL of DES (choline chloride-urea) at 40 °C, without addition of salt, and centrifugation at 6000 rpm for 4.0 min. The reconstituted extract was directly injected into a high-performance liquid chromatography (HPLC) system working in the diode array mode. At the studied concentration levels, the obtained method detection limits (MDL) was 11 mg/kg, linearity in matrix-matched standards was R2 ≥ 0.997, relative standard deviations (RSD) was 7.8%, and average recovery was 93%. The combined use of the recently developed DES -based RP-DLLME and HPLC provides an innovative, efficient, cost-effective, and more sustainable method for the extraction and quantification of free tryptophan in oily food matrices. The method was employed to analyze cold-pressed oils from nine vegetables (Brazil nut, almond, cashew, hazelnut, peanut, pumpkin, sesame, sunflower, and walnut) for the first time. The results showed that free tryptophan was present in the range of 11-38 mg/100 g. This article is important for its contributions to the field of food analysis, and for its development of a new and efficient method for the determination of free tryptophan in complex matrices, which has the potential to be applied to other analytes and sample types.
摘要：
开发了一种使用低共熔溶剂（DES）程序确定植物油中游离色氨酸的快速，直接的反相分散液液微萃取（RP-DLLME）。已经通过多变量方法研究了影响RP-DLLME效率的八个变量的影响。Plackett-Burman设计用于筛选最有影响力的变量，然后是中央复合响应面方法，导致1g油样品的最佳RP-DLLME设置：9mL己烷作为稀释溶剂，在40°C下用0.45mLDES（氯化胆碱-尿素）进行涡旋萃取，不添加盐，并以6000rpm离心4.0分钟。将重建的提取物直接注射到以二极管阵列模式工作的高效液相色谱（HPLC）系统中。在研究的浓度水平下，方法检出限(MDL)为11mg/kg,矩阵匹配标准的线性为R2≥0.997，相对标准偏差（RSD）为7.8％，平均回收率为93%。结合使用最近开发的基于DES的RP-DLLME和HPLC提供了一种创新，高效,成本效益高,和更可持续的方法，用于提取和定量油性食品基质中的游离色氨酸。该方法用于分析9种蔬菜（巴西坚果，杏仁,腰果,榛子,花生,南瓜,芝麻,向日葵,和核桃）第一次。结果表明，游离色氨酸在11-38mg/100g范围内存在。本文对食品分析领域的贡献具有重要意义。并开发了一种测定复杂基质中游离色氨酸的新方法，它有可能应用于其他分析物和样品类型。
