Flow injection turbidimetric determination of total organic carbon with a gas–liquid transfer microreactor Original Research Article

A procedure for the determination of total organic carbon (TOC) and its fractions in industrial effluent samples is proposed. A flow injection system using a gas–liquid transfer microreactor was developed, and adapted to a turbidimetric spectrophotometer. Samples were decomposed into glass vials in a microwave oven and a fraction of the CO2 was injected into a carrier gas and pumped to a glass microreactor. This device was specially developed to assure a quantitative reaction with a barium hydroxide solution. The resulting suspension was removed from the microreactor and pumped to the flow cell and the transient signal was recorded. With minor modifications, the system allows the determination of different carbon fractions. The advantages of the proposed procedure are simplicity, low volume of samples and reagents, high frequency of determinations and low cost. The dynamic range is 20–800 mg C l−1, and the calculated LOD (n=10, confidence level 99.7%) is 17 mg C l−1. The maximum analytical frequency was 120 determinations per hour. Compared to a reference method for TOC determination, no significant differences (t-test), were observed.