Infrared (IR) optical sensors provide fast and nondestructive methods for the detection of organic compounds in aqueous solutions. Among the existing IR methods, attenuated total reflection (ATR) combined with the solid-phase micro-extraction (SPME) principle is the most frequently used method in the detection of organic compounds in aqueous solutions. In an effort to simplify this method for aqueous solution analysis, the SPME/transmission absorption infrared (TA-IR) method was developed in this work, and its performance was compared with that of the ATR-IR method. Results indicated that the SPME/TA-IR method provided better linearity (0 to 200 ppm concentration range) and sensitivity than the SPME/ATR-IR method in detection of chloroanilines. The lower linearity in the SPME/ATR-IR method was most likely caused by the change in the refractive index of the SPME phase after the absorption of different amounts of analytes. Because of the high-energy throughput in the SPME/TA-IR method, which largely reduced the noise level in the spectra, this method can provide slightly lower detection limits than the SPME/ATR-IR method. Another advantage of this new method is that the influence on IR signals by the SPME phase thickness phase can be partially compensated.

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