Department of Analytical Chemistry, University of Valencia, 46100 Burjassot, Valencia, Spain.
Department of Analytical Chemistry, University of Valencia, 46100 Burjassot, Valencia, Spain.
Talanta. 2017 May 1;166:81-86. doi: 10.1016/j.talanta.2017.01.037. Epub 2017 Jan 13.
A new analytical method for the determination of N-nitrosodiethanolamine (NDELA), a very harmful compound not allowed in cosmetic products, is presented. The method is based on a new approach of dispersive liquid-liquid microextraction (DLLME) useful for extraction of highly polar compounds, called reversed-phase DLLME (RP-DLLME), followed by liquid chromatography-ultraviolet/visible (LC-UV/Vis) determination. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the optimized conditions, a mixture of 750µL of acetone (disperser solvent) and 125µL of water (extraction solvent) was rapidly injected into 5mL of toluene sample solution. The extracts were injected into the LC-UV/Vis system using ammonium acetate 0.02M as mobile phase. After chromatographic separation, the eluate passed throughout a photolysis unit in order to convert NDELA to nitrite, and then it was merged with a flow stream of Griess Reagent and passed throughout a post-column reactor at 50°C to derivatize nitrite into an azo-dye, which was finally measured spectrophotometrically at 540nm. The method was successfully validated showing good linearity, an enrichment factor of 31.5±0.9, limits of detection and quantification of 1.1 and 3.6ngmL, respectively, and a good repeatability (RSD <8%). Finally, the proposed analytical method was applied to the determination of NDELA in commercial cosmetic samples of different nature, specifically three lipophilic creams and a hydrophilic shower gel, with good relative recovery values (87 - 117%) thus showing that matrix effects are negligible. These results were compared with those obtained by applying the ISO 10130 official method, which uses the same detection approach. It was concluded that a great improvement in the sensitivity was achieved, whereas the use of organochlorine solvents is avoided and therefore it can be considered as a greener approach.
一种新的分析方法，用于测定 N-亚硝基二乙醇胺（NDELA），这是一种非常有害的化合物，不允许在化妆品中使用。该方法基于一种新的分散液液微萃取（DLLME）方法，用于萃取高极性化合物，称为反相 DLLME（RP-DLLME），然后进行液相色谱-紫外/可见（LC-UV/Vis）测定。研究了 RP-DLLME 过程中的变量，以提供最佳的富集因子。在优化条件下，迅速将 750µL 丙酮（分散溶剂）和 125µL 水（萃取溶剂）混合液注入 5mL 甲苯样品溶液中。萃取物用 0.02M 乙酸铵作为流动相注入 LC-UV/Vis 系统。在色谱分离后，洗脱液通过光解单元将 NDELA 转化为亚硝酸盐，然后与格里斯试剂的流动相合并，通过 50°C 的柱后反应器将亚硝酸盐衍生为偶氮染料，最后在 540nm 处进行分光光度法测量。该方法经过成功验证，具有良好的线性、31.5±0.9 的富集因子、1.1 和 3.6ngmL 的检出限和定量限，以及良好的重复性（RSD<8%）。最后，将所提出的分析方法应用于不同性质的商业化妆品样品中 NDELA 的测定，特别是三种亲脂性乳膏和一种亲水性沐浴露，具有良好的相对回收率（87-117%），表明基质效应可以忽略不计。这些结果与采用相同检测方法的 ISO 10130 官方方法获得的结果进行了比较。结果表明，灵敏度得到了很大提高，同时避免了使用有机氯溶剂，因此可以认为是一种更环保的方法。
