PROPOSED CLOSED-TUBE REFLUX COLORIMETRIC METHOD FOR THE DETERMINATION OF TOTAL ORGANIC CARBON IN BOTTLED DRINKING WATER

Abstract

The American Public Health Association (APHA) analysis of chemical oxygen demand (COD) by the closed-tube reflux colorimetric method requires the use of Kalium dichromate (K2Cr2O7), silver and mercury sulfates. It involves using large volumes of both reagents and samples. This placed a restriction on analysis reagent, increase cost of COD determination and risk of environmental pollution. The present method used Kalium chromate (K2CrO4) and reduced the amounts of reagent and sample needed for the analysis. The use of kalium chromate was possible because it exists as the dichromate in strong acid mixture, a medium suitable for the digestion. The UV-Vis spectra of the K2Cr2O7 and K2CrO4 in H2SO4 acid medium and a comparison of the proposed method with APHA method proved it. The proposed method eliminates the dependent on kalium dichromate and reduces the amount of the sample by 60%, and digestion mixture (chromate and mercury sulfate) and catalyst (silver sulfate) by 33.33% and 60% respectively. The method was applied for the UV-Vis spectrometry determination of COD in bottled drinking water