Patent ID: 7759125

Claim:
A method of determining chemical oxygen demand of a water sample under non exhaustive degradation conditions, comprising the steps of a) applying a constant potential bias to a thin layer photoelectrochemical cell, having a photoactive nanoparticulate semiconductive working electrode and a counter electrode, and containing a supporting electrolyte solution; b) illuminating the working electrode with a light source and recording the background photocurrent produced at the working electrode from the supporting electrolyte solution; c) adding a 5 μl to 200 μl of water sample, to be analysed, to the photoelectrochemical cell; d) illuminating the working electrode with a light source and recording the total photocurrent produced with the sample; e) deducting the back ground photocurrent from the total photocurrent produced with the sample to obtain the net photocurrent due to the oxidation of organic material in the sample f) determining the chemical oxygen demand of the water sample according to the following sequence of computations i lsample =nFAk[COD] sample =K[COD] sample i lstandard =nFAk {[COD] sample +[COD] standard }=K {[COD] sample +[COD] standard} Where K=nFAk is a constant for given experimental conditions n=number of electrons transferred during the photoelectrochemical degradation, F=Faraday constant, A=active electrode area, k=mass-transfer coefficient; and [ C ⁢ ⁢ O ⁢ ⁢ D ] sample = i lsample i lstandard - i lsample × [ C ⁢ ⁢ O ⁢ ⁢ D ] standard .