An exploiting of cost-effective direct current conductivity detector in gas diffusion flow injection system.

In this work, a homemade direct current (DC) conductivity detector as an alternative cost-effective detection device has been fabricated and investigated to use in flow analysis system. Under the selected appropriate conditions of flow system, the electrolysis of a carrier stream at the conductivity detector was negligible and provides well-defined signal. The cost-effective DC conductivity detector was demonstrated to couple with gas diffusion flow injection system for determination of dissolved inorganic carbon (DIC) in water. The method is based on the conversion of DIC (dissolved CO, HCO and CO) presented in the injected sample to carbon dioxide in an acidic donor stream and then CO gas diffuses through a hydrophobic porous membrane to an acceptor stream. As a result, the change of conductivity signal was observed corresponding to DIC concentration. A linear calibration range of DIC in 1.0-10mmolL, with limit of detection of 70µmolL, repeatability of <3% RSD and 15 injections h sample throughput can be obtained. This method was applied for DIC determination in natural water.