フローインジェクション分析法による土壌抽出液の硝酸態窒素の定量法

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A flow injection analysis based on the cadmium reduction-diazo coupling colorimetric method was applied to the determination for a wide range of amounts of NO_3-N in potassium chloride soil extracts. Positive effect of potassium chloride in sample solution on the absorbance was removed by addition of potassium chloride at 0.1 M level to a carrier solution. Decreasing of the reduction rate of nitrate to nitrite with cadmium was overcome by addition of HCl at 0.15 mM level to the carrier solution. A sample solution (30μl) was injected into a reagent (1 mM EDTA + 0.1 M KCl + 0.15 mM HCl) which acted as the carrier stream (0.75 ml/min) and passed through a copperized cadmium column (4mm ×5 cm ; particle size, 0.5-2mm) to convert nitrate to nitrite quantitatively. Then, the carrier solution was merged into the stream of a color developing reagent (0.92% p-amino-acetophenone + 0.055% m-phenylendiamine + 24 mM HCl) from the other channel. The mixture passed through a reaction coil (0.5 mm ×120 cm) in a thermostated air bath at 50 ℃ to develop the diazo coupling reaction. The absorbance area at 456 nm was measured using spectrophotometer and integrating recorder. Sampling rate was about 50 samples/h. The calibration was linear over the range 0.1- 10.0 ppm NO_3-N. The precisions were 0.4 and 0.6 CV% for 0.4 and 4.0 ppm of NO_3-N, respectively. The measured values of NO_3-N in potassium chloride soil extracts by this method agreed with the values of BREMNER's distillation-titration method (FIA value : Y=1.00 X-0.18, r= 0.998). For the determination of NO_3-N in soil extracts, it was concluded that this flow injection analysis is more useful than manual methods.
社団法人日本土壌肥料学会の論文
1991-04-05

フローインジェクション分析法による土壌抽出液の硝酸態窒素の定量法

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