The evaluation and comparison of ion chromatography, segmented flow analysis and flow injection analysis for the determination on nitrate in natural surface waters

A study to evaluate the comparability of IC, SFA and FIA for the determination of nitrate in natural surface waters has been completed. Assessment of method performance was based on the precision, accuracy, detection limit and analysis rate obtained from analyses of synthetic and natural samples by each technique. Precision (as RSD) and accuracy (as % recovery) for each method are typically 3 and 103% for IC, 1 and 101% for SFA and 1 and 100% for FIA, respectively. The method detection limits (expressed as mg/1 nitrate ion) were 0.007 mg/1 for IC, 0.006 mg/1 for SFA and 0.030 mg/1 for FIA. IC analysis time is 10 samples/h, however chloride and sulfate can be determined along with nitrate in a sample run. SFA and FIA can analyze 30–60 samples/h, but only nitrate can be determined. The colorimetric method responses were significantly larger than IC responses. The bias is apparently related to the sample matrix but has not been traced to any single matrix component. No relationship to dissolved organic carbon (DOC) was observed.