Development of headspace solid-phase microextraction/attenuated total reflection infrared chemical sensing method for the determination of volatile organic compounds in aqueous solutions

Abstract

In this paper, a new method was developed by applying the principle of headspace solid-phase microextraction (HSSPME) to the attenuated total reflection (ATR) infrared (IR) chemical sensing method. This method is highly suitable for the detection of volatile organic compounds (VOCs) in aqueous solutions because it effectively eliminates the problems associated in soaking type of SPME–ATR–IR method. To facilitate the detection of VOCs in headspace, a specially designed sample cell is proposed that permits direct examination of the VOCs in the aqueous solution. Factors that influenced the IR signals in this method such as the effect of agitation, headspace volume, sample volume, and temperature were examined in this work. Results showed that this method was fast and typical time to reach the maximum analytical signals was around 20 min. By applying agitation to the aqueous solution, much stronger analytical signals were observed, especially for lower volatility compounds. The headspace volume influenced the analytical signals strongly, especially for lower volatile compounds. An increase in the sample volume also results in higher analytical signals but these analytical signals are limited to a certain value. By examining five VOCs with different volatility’s, the obtained linear regression coefficients ( R-square) on standard curves in the concentration range of 5–200 ppm were higher than 0.99 and the typical detection limit using this method was around a few hundred ppb. This method can be used repeatedly because the time for regenerating the sensing element can be shorter than 5 min.