An analytical method for the determination of traces of formaldehyde in cosmetic products containing formaldehyde-releasing preservatives has been developed. The method is based on reversed-phase dispersive liquid–liquid microextraction (RP-DLLME), that allows the extraction of highly polar compounds, followed by liquid chromatography–ultraviolet/visible (LC–UV/vis) determination with post-column derivatization. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the selected conditions, a mixture of 500 μL of acetonitrile (disperser solvent) and 50 μL of water (extraction solvent) was rapidly injected into 5 mL of toluene sample solution. The extracts were injected into the LC–UV/vis system using phosphate buffer 6 mmol L⁻¹ at pH 2 as mobile phase. After chromatographic separation, the eluate merged with a flow stream of pentane-2,4-dione in ammonium acetate solution as derivatizing reagent and passed throughout a post-column reactor at 85 °C in order to derivatize formaldehyde into 3,5-diacetyl-1,4-dihydrolutidine, according to Hantzsch reaction, which was finally measured spectrophotometrically at 407 nm. The method was successfully validated showing good linearity, an enrichment factor of 86 ± 2, limits of detection and quantification of 0.7 and 2.3 ng mL⁻¹, respectively, and good repeatability (RSD < 9.2%). Finally, the proposed analytical method was applied to the determination of formaldehyde in different commercial cosmetic samples containing formaldehyde-releasing preservatives, such as bronopol, diazolidinyl urea, imidazolidinyl urea, and DMDM hydantoin, with good relative recovery values (91–113%) thus showing that matrix effects were negligible. The good analytical features of the proposed method besides of its simplicity and affordability, make it useful to carry out the quality control of cosmetic products containing formaldehyde-releasing preservatives.

已经开发了一种测定含有释放甲醛的防腐剂的化妆品中痕量甲醛的分析方法。该方法基于反相分散液-液微萃取（RP-DLLME），该方法可萃取高极性化合物，然后进行液相色谱-紫外/可见（LC-UV / vis）测定和柱后衍生化。研究了RP-DLLME过程中涉及的变量，以提供最佳的富集因子。在选定的条件下，将500μL乙腈（分散溶剂）和50μL水（萃取溶剂）的混合物快速注入5 mL甲苯样品溶液中。使用磷酸盐缓冲液6 mmol L ^-1将提取物注入LC-UV / vis系统在pH 2下作为流动相。色谱分离后，洗脱液与戊酸-2,4-二酮在乙酸铵溶液中的流动物流合并为衍生试剂，并在85°C下通过整个柱后反应器，以将甲醛衍生为3,5-二乙酰基-根据Hantzsch反应，最终在407nm处用分光光度法测量了1，4-二氢二甲基吡啶。该方法已成功验证，显示出良好的线性，富集系数为86±2，检出限和定量限分别为0.7和2.3 ng mL ^-1，重复性好（RSD <9.2％）。最后，所提出的分析方法被用于测定含有释放甲醛的防腐剂的各种商业化妆品样品中的甲醛，例如溴硝酚，重氮烷基脲，咪唑烷基脲和DMDM乙内酰脲，具有相对较高的回收率（91–113％）表明基质效应可以忽略不计。所提出的方法的简便，价格低廉的特点使其具有良好的分析特性，使其对含有释放甲醛的防腐剂的化妆品进行质量控制非常有用。