Multicommutation in flow analysis exploiting a multizone trapping approach: spectrophotometric determination of boron in plants Original Research Article

A flow system based on multicommutation to implement a sequential zone trapping approach to retain multiple sample zone into the analytical path during a previous preset time interval is proposed. This permits an increase of the sample residence time to improve sensitivity of spectrophotometric methods based on a relatively slow reaction. The flow network comprises a set of solenoid valves assembled in order to form three analytical pathways with equal length. With this configuration three sample zones could be sequentially loaded and trapped into the reaction coils to allow the chemical reaction to reach completeness. The flow system was controlled by means of a 486 microcomputer equipped with an electronic interface running software written in Quick BASIC 4.5. Feasibility of the proposed system was ascertained by the spectrophotometric determination of boron in a mineralized plant material using Azomethine-H as chromogenic reagent. The proposed system showed a linear response from 0.25 to 6.00 mg B l−1 and an analytical throughput of 35 determinations per hour. Other favourable features such as a low relative standard deviation of 2.5% (n=9) and a consumption of only 0.5 mg Azomethine-H per determination were also obtained.