IR chemical sensor for detection of chlorinated anilines in aqueous solutions based on ATR waveguides coated with derivatized polystyrene

A method based on the combination of solid phase micro-extraction (SPME) and infrared (IR) attenuated total reflection (ATR) spectrometry was used to determine chlorinated anilines in aqueous solutions. To overcome the limitations of commercially available polymers, polystyrene (PS) was derivatized with alkanes and alcohols of different chain lengths to increase the performance of SPME-IR/ATR in the detection of chlorinated anilines in aqueous solutions. The derivatized PS provides a higher extraction efficiency and rate of diffusion in the determination of aromatic compounds than the polymers commonly used in SPME-IR/ATR methods. The increase in extraction efficiency is mainly caused by the pi-pi interaction between the phenyl rings of PS and the aromatic compounds. The high rate of diffusion of analytes in the SPME phase was due to the lowering of compactness after derivatization. Based on the signal-to-noise ratio in the detected spectra, the detection limits using derivatized PS were around the ppm level for the chloroanilines examined. The effects of salt and pH on the detection of chloroanilines were also examined. The results showed that the IR signals were increased around threefold after the addition of 20% NaCl to the solutions. The effect of pH was small if the pH of the solution was kept higher than 6.