Multicommutation in flow analysis. Part 6. Binary sampling for wide concentration range turbidimetric determination of sulphate in plant digests Original Research Article

An automatic continuous flow procedure for turbidimetric determination of sulphate in acidic digests of plant materials, employing a flow network based on multicommutation and binary sampling is described. The method is based on the precipitation of sulphate anions with barium ions followed by photometric monitoring of the resulting suspension. A single pumping channel was used, handling both samples and reagents by means of computer-controlled three-way solenoid valves. In order to extend the determination concentration range up to 500 mg l−1 SO2−4 without any modification in the structure of the flow network two analytical curves are generated. The first curve comprized the concentration range from 10–150 mg l−1 SO2−4 and the second one, that from 100–500 mg l−1 SO2−4. Results presented good agreement at the 95% confidence level with those obtained by the usual FIA system. Other relevant features such as a throughput of 100 determinations per hour, a relative standard deviation of 2% (n=11) and a reagent consumption of 7 mg BaCl2.2H2O plus 1.5 mg EDTA per determination were also achieved.