Zinc/Chromium (II) reduction for nitrate determination in agricultural materials by colorimetry or ion‐selective electrode

To phase analytical pathways within this laboratory, recent approaches to nitrate analysis have been studied; of particular interest were the U V spectrophotometric approach (Heanes 1982, 1986) and zinc/chromium (II) reduction procedure (Pruden et al 1985). By combining and modifying various aspects of the aforementioned procedures with an adaption of an indophenol blue colorimetric procedure (Mitchell 1972) it was possible to measure nitrate‐nitrogen 0.10‐8.00 g kg⁻¹ DM routinely on a range of agricultural materials (at present hays, straws, grasses, calabrese, potato leaves, cereals, soils and perlites) on a sophisticated high‐volume‐throughput microprocessor‐controlled auto‐sampler/spectrophotometric system.