Rapid Determination of Nitrates and Nitrites

Extraction of NOx and Determination of Nitrate by Acid Reduction in Water, Soil, Excreta, Feed, Vegetables and Plant Materials

“…Overall per cent accuracy has been 2.8 ± 0.5 (n=20), and precision as estimated from values of coefficient of variation as 3.0 ± 0.5 for four sets of experiments. Per cent recovery with different extraction procedures have ranged from 85 to 112 (Green et al, 1982;Guevara et al, 1998;Lewis, 1951;Nelson et al, 1954). Reagent blanks did not show any background coloration indicating the reagents were free of any detectable nitrite/nitrate.…”

“…Water blank and standard nitrate solutions, 1 and 3 ppm as N, were subjected to identical treatments. The extracts from selected samples including soil, carrot, morning-glory, and feed were simultaneously assayed for nitrate by modified (Mir, 2007) metal reduction technique (Nelson et al, 1954).The modifications included: a) substituting sulfanilic acid with a more stable aromatic amine, sulfanilamide, b) substituting 1-naphthylamine with a widely employed safer coupling agent NEDA, c) separately adding coupling agent to avoid adsorption of the azo-dye by the filter paper, and d) using optimized mass of zinc in the reduction powder to curtail furthering of reduction process by the metal (Mir, 2007). Urea-treated sample extracts were each added 9 mL of acetic acid solution, and a scoopful, ca.…”

“…Methods based on the principle of Griess reaction are widely employed for their determinations as these are simple, specific and sensitive enough for routine use. However, for determination of nitrate, these methods require prior reduction of nitrate to nitrite which is accomplished by cadmium (APHA, 1998;AOAC, 2000;Cortas and Wakid, 1990;Green et al, 1982;Schneider and Yeary, 1973), vanadium (Miranda et al, 2001), zinc (Nelson et al, 1954;Diven et al, 1962;Mir, 2007), hydrazine (Oms et al, 1995), or specific nitrate reductases (Guevara et al, 1998). Of late, an inexpensive, rapid acid reduction method has been optimized for determination of nitrate (Mir, 2008).…”

“…Perusal of literature reveals use of different extractants for extracting NO x from different samples. These include water (Bhargava and Raghupathi, 1993), 0.1M HCl (Krishna and Ranijhan, 1980;Nelson et al, 1954), CdCl 2 + BaCl 2 (AOAC, 2000), Somogyi reagent (Cortas and Wakid, 1990), CuSO 4 + Ca (OH) 2 + MgCO 3 (Gupta, 2004), methanol/diethyl ether (Guevara et al, 1998), calcium chloride + charcoal (Chiroma et al, 2007) or Carez reagent (ISO, 1984). A need to develop a uniform protocol for extracting NO x from different samples was mooted on the considerations of ensuring stability of the anions particularly of nitrite, removal of potential interfering agents, minimize losses and obtain colorless transparent extracts.…”

Nutritional status of soil and plant species in several clearings in coniferous woods compared to that in two related habitats

“…The total concentration of the mineral elements was determined after destruction of a soil sample with aqua regia and subsequent dilution with water: K and Na by flame emission photometry; Ca, Mg, Fe and Mn by atomic absorption spectrophotometry; PO4-P colorimetrically following Chen et al (1956). The concentration of available NO3-N was determined by means of a modified method following Nelson et al (1954) and Woolley et al (1960), both in the actual situation and after 4 weeks incubation of fresh soil in a closed plastic bag at 28 °C, The concentration of available PO4-P was determined as described above after shaking a soil sample for I h with calcium lactate (1976) or water (1977). The amount of exchangeable cations was measured as described above after shaking a soil sample for 1 h with ammonium acetate (or water in the case of Fe).…”