Experimental design approaches to optimize ultrasound-assisted simultaneous-silylation dispersive liquid–liquid microextraction for the rapid determination of parabens in water samples

This work describes a rapid solvent-minimized process to effectively determine four common paraben preservatives (methyl-, ethyl-, propyl- and butyl-paraben) in surface water samples. The method involved the use of a combination of a novel ultrasound-assisted simultaneous-silylation within dispersive liquid-liquid microextraction (UASS-DLLME) with detection by gas chromatography-tandem mass spectrometry (GC-MS/MS). To overcome the challenges related to the different experimental conditions, multivariate experimental design approaches conducted by means of a multilevel categorical design and a Box-Behnken design were utilized to screen and optimize parameters that have significant influences on the efficiency of silylation and extraction. The method was then validated and shown to provide low limits of quantitation (LOQs; 1-5 ng L-1), high precision (3-11%), and satisfactory mean spiked recoveries (accuracy; 79-101%). Upon analyzing samples of surface water obtained from the field, we found that, in total, there was a relatively high concentration of the target parabens ranging from 200 to 1389 ng L-1. The sources of the elevated levels of these parabens may be from the release of untreated municipal wastewater in this region, and also due to the widespread application of parabens in personal care and food products.