Application of direct-injection detector integrated with the multi-pumping flow system to photometric stop-flow...

A novel direct-injection detector (DID) integrated with multi-pumping flow system (MPFS) for the photometric determination of iron is proposed. Paired emitter-detector diodes have been used as a photometric detection system. The sample and reagent were injected using appropriate solenoid pulse micro-pumps directly into the detection chamber where effective mixing occured. The use of proposed stop-flow detector considerably simplified the analytical procedure. The potassium thiocyanate has been chosen as a chromogenic reagent for photometric Fe(III) detection. The total volume of reagent and sample/standard solutions involved in the detection process was adjusted to the volume of the reaction-detection chamber. Calibration graph was found to be linear in the range up to 10mgL(-1). The detection limit (3s(b)/S) was 0.15mgL(-1). The repeatability (R.S.D.), calculated from 10 analyses of sample containing 5mgL(-1) Fe(III), was 1.5% and the sample throughput 180 determinations per hour. The consumption of sample and reagent was 20μL each with the waste generation at the level of 0.24mL. The applicability of the proposed method to the determination of total iron in groundwater samples has been proved. The analytical parameters are compared to those obtained exploiting the MPFS system with typical configuration containing a confluence point and reaction coil.