An analytical method for determination of total nitrogen and total organic carbon in water

An analytical method for determination of total nitrogen (TN) and total organic carbon (TOC) in water was investigated. Nitrogen compounds and carbon compounds were converted into nitrogen and carbon dioxide, respectively, in a stream of carrier gas (helium) by injecting a sample with a microsyringe into a reaction tube which was packed with alumina coated with palladium (0.3%). After removal of steam, oxygen and hydrogen from the gas stream, nitrogen and carbon dioxide were analyzed with a gas chromatograph, and TN and total carbon (TC) were determined. Inorganic carbon (IC: carbonate or bicarbonate) in water was converted into carbon dioxide by injecting a sample into a reaction tube which was packed with ion exchange resin containing sulfonic group and analyzed with a gas chromatograph after removal of steam. TOC was determined from the difference between TC and IC. The detection limits of TN and TC were about 0.5 mg/l using a sample size of 20μl and that of TN about 0.1 mg/l using a sample size of 80 μl The coefficients of variation were several % in case of concentration above 10 mg/l and about 10% in case of concentration under 10 mg/l. The observation time was about several minutes and analysis was made using peak height of chromatogram. The results of TN by this method were agreed with those by the Kjeldahl method.