A simple optical sensor for chromium(VI) based on a cationic ion exchange film coupled with attenuated total reflectance spectroscopy

摘要

A new optical sensor for Cr(VI) in environmental water samples has been developed. The device is based on uptake of Cr(VI) as HCrO_4~(1-) at acidic pH into a quaternized poly(4-vinylpyridine) (QPVP) film followed by direct optical detection using attenuated total reflectance (ATR) spectroscopy in a thin-layer flow cell. Cr(VI) uptake is demonstrated to be reversible such that the film can be regenerated for multiple uses over extended periods of time. The sensor was investigated over a pH range of 3-7 and gave a linear response over a Cr(VI) concentration range of 5 μM to 1 mM at pH 4. Analysis of potential interferences demonstrates that the sensor provides excellent discrimination against cationic species, including Cr(III). We also demonstrate a prototype 'field ready' version of the sensor utilizing a 410-nm light-emitting diode source, fixed angles, and prismless construction that is used in conjunction with a rugged miniature spectrometer.