Analytical Sciences

Development of an Infrared Hollow Waveguide Sampler for the Detection of Organic Compounds in Aqueous Solutions with Limited Sample Volumes

Jyisy YANG*  and Pon-Yen CHEN**

*Department of Chemistry, National Chung-Hsing University, Taichung, Taiwan 402
**Department of Chemistry, Chung-Yuan Christian University, Chung-Li, Taiwan 320

In this study, an infrared (IR) hollow waveguide sampler was developed to detect organic compounds in aqueous samples with sample volumes less than 50 uL. This sampler was prepared by coating a thin hydrophobic film inside the IR hollow waveguide. After injecting a certain amount of aqueous solution, organic compounds could be absorbed into the hydrophobic film by partitions. By removing the residual water in the hollow waveguide sampler with a nitrogen purging gas, the absorbed organic compounds could be sensed using IR radiation. To investigate the applicability of this hollow waveguide sampler in the detection of small amounts of aqueous samples, an analytical working function was developed following an examination of the parameters which influence the analytical signals. Such factors as the volume of the aqueous solution, the sample concentration, the length of the hollow waveguide, and the sensitivity of this method were investigated. Excellent agreement between the analytical and theoretical predicted values was observed. Upon examining the linear relationship between the analyte signals and the concentration, the regression coefficients were generally higher than 0.998 in the examined concentration range of 1 to 100 ppm. Under the condition that the sample volume was 300 uL and based on three-times the spectra noise level, the calculated detection limits for this method were found at around 1 ppm for the examined analytes.

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