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Fabrication of a macro segmented flow analysis (MSFA) system based on reconfiguration of the manifold by adjustment of the sample/reagent ratio, has been found to produce a sensitive method for orthophosphate analysis based on colorimetric detection at 880nm. Optimization of sample tube length, reaction temperature and molybdate concentration in the carrier solutions has been carried out. The larger sample tube internal diameter led to the combined advantages of better sensitivities, wider working range and higher sample throughput over most existing methods. Using the optimized conditions of 50.0cm sample tube length (1.6mm i.d.), 37.0 degrees C reaction temperature and 0.0113M molybdate concentration in the carrier solution, the calibration model for orthophosphate standard solutions was found to be linear (y = 0.04895x + 0.003561; correlation coefficient, r(2)=0.9970) over the working range 0.01-2.00mgl(-1) orthophosphate. The volume of the sample injected was 1.396ml at a flow rate of 6.0mlmin(-1). The sample throughput of this MSFA method was 40 samples per an hour, with a detection limit of 4.0mugl(-1), and %R.S.D.'s below 5%. The MSFA method was successfully applied to analysis of water and wastewater samples.

The nitrate-selective copperised-cadmium (Cu-Cd) reduction reaction coupled directly to the highly sensitive nitrite ion chromatographic detection, produced a more precise method for determination of nitrate than any one of the two conventional methods. A borate buffer solution used in the reduction reaction, in place of the conventional ammonium-EDTA buffer solution, eliminated interferences from co-eluting ions in the subsequent ion chromatographic detection of nitrite. Optimised experimental conditions included using a packed-bed Cu-Cd reductor column length of 12.5 cm, a solution flow rate of 3.0 ml/min, and using 10.0 ml of borate buffer solution for each 20.0 ml of nitrate-containing solution. Precision was high for results obtained within a greatly extended linear dynamic range of 0.006-1.20 mg/l NO3-, with a much lower limit of detection of 0.40 microg/l NO3-. Cu-Cd reductor column efficiency was 98.20+/-6.03%. Validation of the method was undertaken using certified reference materials. The method was successfully applied to analysis of dam water, river water and storm water samples, producing more precise results than either the conventional colorimetric method or the conventional ion chromatographic method.