Major sensitivity improvements in ion chromatography determinations involving post-column spectrophotometric reaction detectors through elimination of pump noise using a dual wavelength monitoring procedure

Abstract

A novel dual wavelength procedure is described for the elimination of baseline pump noise in spectrophotometric post-column reaction detection systems in high-performance liquid chromatography. The method is applicable if there is some overlap between the spectrum of the analyte reaction product and the spectrum of the excess reagent. One wavelength is chosen to monitor the analyte reaction product and the other wavelength is set close to the isosbestic point. After simple arithmetic manipulation of the data using commonly available computer software, the pump noise is subtracted from the analyte baseline, allowing much higher sensitivity settings to be used. The two examples shown are taken from the ion chromatography of trace metals using colorimetric post-column reaction detectors, where close to a 20-fold increase in signal to noise ratio was obtained when using the dual wavelength procedure.