Departamento de Química Analítica, Nutrición y Bromatología, Universidad de La Laguna-ULL, La Laguna-Tenerife 38206, Spain.
J Chromatogr A. 2012 Sep 28;1257:9-18. doi: 10.1016/j.chroma.2012.08.026. Epub 2012 Aug 15.
A novel and simple preconcentration step for aqueous micellar solutions of the common cationic surfactant cetyltrimethylammonium bromide (CTAB) has been developed. The procedure is based on the formation of another phase (a micro-droplet), not soluble in water, in which analytes (originally present in the aqueous solution) experience preconcentration. The method resembles to that of classical coacervation, but it does not require high ionic strengths neither acidic pH values. The optimum method implies mixing aqueous micellar solutions of CTAB with lithium bis[(trifluoromethane)sulfonyl]imide (Li-NTf₂) in a 1:1 molar ratio with a 16.5% (v/v) of acetonitrile content, followed by vortex, heating at 65 °C during 2 min, and centrifugation. The obtained microdroplet containing analytes is then subjected to high-performance liquid chromatography (HPLC) with diode-array detection (DAD). The method has been applied to the determination of a group of organic contaminants including alkylphenols, polycyclic aromatic hydrocarbons and parabens, present in aqueous samples (including seawater) or solid samples (such as sediment samples, which are subjected to a previous microwave-assisted extraction). Average preconcentration factors of roughly 14 and 12 are obtained for aqueous and sediment samples, respectively; being the limits of quantification down to 0.5 μg L⁻¹ and 0.02 mg kg⁻¹, respectively.
一种新颖而简单的浓缩步骤，用于常见阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）的水胶束溶液。该程序基于形成另一种不溶于水的相（微滴），其中分析物（最初存在于水溶液中）经历浓缩。该方法类似于经典凝聚，但不需要高离子强度或酸性 pH 值。最佳方法涉及将 CTAB 的水胶束溶液与双（三氟甲烷磺酰基）亚胺锂（Li-NTf₂）以 1：1 的摩尔比混合，并含有 16.5%（v/v）的乙腈含量，然后涡旋、在 65°C 下加热 2 分钟，然后离心。然后将含有分析物的所得微滴用高效液相色谱（HPLC）与二极管阵列检测（DAD）进行分析。该方法已应用于测定包括烷基酚、多环芳烃和对羟基苯甲酸酯在内的一组有机污染物，这些污染物存在于水样（包括海水）或固体样品中（如沉积物样品，这些样品需要进行微波辅助提取）。对于水样和沉积物样品，平均浓缩因子分别约为 14 和 12；定量下限分别低至 0.5 μg L⁻¹和 0.02 mg kg⁻¹。
