SENSITIVITY ENHANCEMENT IN THE DETERMINATION OF SILICATE BY ION-EXCLUSION CHROMATOGRAPHY USING LUMINOL CHEMILUMINESCENCE DETECTION

An increased chemiluminescence (CL) emission, produced upon mixing an acidified silicate solution with an alkaline luminol solution even in the absence of hydrogen peroxide, provided an effective post-column detection system to enhance sensitivity in the selective determination of silicate by ion-exclusion chromatography. The detection limit of 0.1 ng ml(-1) silicon(IV) obtained under the optimum conditions was much lower than that obtained by using the CL reaction in the presence of hydrogen peroxide. The working range was linear from 1.0 ng ml(-1) to 10 mu g mi(-1). Using the experimental conditions optimized for silicate, a comparative study of the CL behaviour of other anions such as carbonate, phosphate, sulfate and sulfide ions showed that the CL intensity with the silicate ion was the greatest among these anions.