[Determination of ultraviolet filters in environmental aqueous samples by dispersive liquid-liquid microextraction with online derivatization-gas chromatography-mass spectrometry].

A method of dispersive liquid-liquid microextraction (DLLME) combined with online derivatization-gas chromatography-mass spectrometry (GC-MS) was developed for the determination of benzophenone-type ultraviolet (UV) filers (BPs) in environmental aqueous samples. It is found that the online derivatization was superior to the off-line derivatization with its simplicity, high reaction efficiency and less consumption of potential poisonous reagents. The influential factors for online derivatization, including the temperature of the injection port, the splitless time, the proportion of derivatization reagent and sample solution, were initially optimized. In addition, the influential factors for DLLME, including the type of the extractant and dispersing solvent, the proportion of the extractant and the dispersing solvent, the volume of sample solution, the pH and the salt concentration of the sample solution were individually optimized in detail. Under the optimized derivatization and DLLME conditions, the limits of detection for the six BPs, benzophenone, 2,4-dihydroxybenzophenone, oxybenzone, 4- hydroxybenzophenone, octabenzone and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, ranged from 0.011 to 0.15 µg/L. The intra-day and inter-day relative standard deviations varied from 0.7% to 16.6%. The method was applied to the analysis of lake and river water with good recoveries. It is cost effective, reliable, easy to operate, environment-friendly and promising in the real applications.