A superhydrophobic silica aerogel with high surface area for needle trap microextraction of chlorobenzenes

The authors have synthesized a superhydrophobic silica aerogel by using a sol-gel technique. The material is shown to be an efficient sorbent for needle trap microextraction of chlorobenzenes. Hydrophobicity affects the performance of the sorbent as shown by altering the ratio between tetraethylorthosilicate (TEOS) and methyltrimethoxysilane when synthesizing the sorbent. The observed contact angle (which is > 150A degrees) underpins the superhydrophobic properties of the aerogel. The microstructure of the sorbent was investigated by BET adsorption, revealing a surface area above 1000 m(2) g(-1). The sorbent was applied to needle trap extraction of chlorobenzenes from aqueous samples, and their subsequent determination by GC/MS. The effects of extraction temperature and extraction time, ionic strength, desorption temperature and time were optimized. The method has a detection limit range of 0.4-1.1 ng mL(-1), and quantification limits from 2.2 to 7.3 ng L-1. The relative standard deviations (at a level of 10 ngL(-1)) are between 4 and 8% (for n = 3). The calibration plots for chlorobenzenes are linear in the 2 to 100 ng L-1 concentration range. The method was successfully applied to the analysis of water samples, and relative recoveries were between 88 and 109%.