Determination of Nitrate in Soil Extracts by Dual-wavelength Ultraviolet Spectrophotometry1
- Richard J. Norman,
- Jeffrey C. Edberg and
- Joseph W. Stucki2
A rapid method is described for determining nitrate concentration in a soil extract solution based on its UV absorbance at 210 nm. The interference of nonnitrate species is accounted for by subtracting an empirically-determined multiple of the absorbance of the extract solution at 270 nm from its absorbance at 210 nm. The value of the multiplication factor, R, is calculated from the 210: 270 nm absorbance ratio of the extract solution after it has been treated with Raney-Nickel catalyst to remove nitrate. The method was tested using 10 Illinois soils. The composite value of R for these soils was 3.05 ± 0.22. This value, as well as each individual value of R for the respective soils, was used to calculate the nitrate concentration. The results were then compared to one another and to results obtained by the steam distillation method. Correlation among these various methods was very high, giving values of r2 of 0.9987 and 0.999. Large errors occurred when no correction for nonnitrate species was made.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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