NOVEL METHOD OF NITRATE-NITROGEN DETERMINATION IN SOILS BY ION CHROMATOGRAPHY

The standard determination of nitrate-N in soil samples requires extraction into potassium chloride solution, nitrate to nitrite reduction with a cadmium column, and a colorimetric analytical finish with sulfanilamide. The reduction and colorimetry steps are difficult and time consuming and are prone to contamination and matrix interferences. Instrumental ion chromatography (IC) is a less complicated and more rapid procedure for nitrate determination in aqueous samples. However, the high concentration of chloride (2M) necessary for extraction has precluded the use of IC due to column and detector saturation. Recently, the development of a silver pretreatment cartridge (Dionex OnGuard® II Ag) has provided means of removing chloride ion prior to IC determination of nitrogen-nitrate. We have found that more than 96.0% of the chloride can be removed from solution by the silver cartridges. Calibration standards were assayed and nitrate was recovered with no loss in the silver cartridges (p<0.001). Nitrate-N was determined by both the colorimetric and IC methods in samples collected from White House Farm in Luray, Virginia in the Shenandoah Valley for method comparison.

Additional Abstract Information

Student(s): Allison E Wickham

Department: Chemistry and Biochemistry

Faculty Advisor: Dr. Daniel M. Downey

Type: Oral

Year: 2012