Determination of total organic carbon in water in the form of carbamate by means of a simple denuder/electrolytic conductivity flow cell system

A simple and sensitive technique for measuring both volatile organic carbon (VOC) and total organic carbon (TOC) in water is presented. The VOC fraction is stripped by a stream of oxygen and subjected to high-temperature catalytic combustion after removing the carbon dioxide, obtained from inorganic constituents at pH ? 2, with lithium hydroxide. The residual non-volatile organics (NVOC) are converted into carbon dioxide by injecting an aliquot of the stripped sample directly into the combustion tube. The carbon dioxide derived from the VOC/NVOC is preconcentrated from the gas stream by absorption in a stainless-steel capillary tube coated with a 2 M ethanolic solution of 3-methoxypropylamine. The carbamate formed in the liquid film is then eluted with a stream of the absorbent circulating through a microelectrolytic conductivity detector. The change in specific conductance due to the presence of the carbamate in the effluent stream is linearly related to the amount of VOC/NVOC/TOC up to 4.5 μg of carbon. The limit of detection for VOC is 0.5 μg l^?1 and for NVOC it is 100 μg l^?1. A simple determination takes 5 min. The precision was better than 5% (P=95%) for 0.5–4.5 μg of carbon. The method is also suitable for the determination of total carbon and inorganic carbon in water.