Determination of nitrites

Analytical and Laboratory Operations. Sulfamic acid has been recommended as a reference standard in acidimetry (55). It can be purified by recrystaUization to give a stable product that is 99.95 wt % pure. The reaction with nitrite as used in the sulfamic acid analytical method has also been adapted for determination of nitrites with the acid as the reagent. This reaction is used commercially in other systems for removal of nitrous acid impurities, eg, in sulfuric and hydrochloric acid purification operations. 

Discussion. General procedures for the determination of nitrites are usually based upon some form of diazotisation reaction, often involving carcinogenic materials such as the naphthylamines. In the following method these compounds are avoided. 

The determination of primary amines on the macro scale is most conveniently carried out by titration in non-aqueous solution (Section 10.41), but for small quantities of amines spectroscopic methods of determination are very valuable. In some cases the procedure is applicable to aromatic amines only, and the diazotisation method described for determination of nitrite (Section 17.38) can be adapted as a method for the determination of aromatic primary amines. On the other hand, the naphthaquinone method can be applied to both aliphatic and aromatic primary amines. 

CTFA Final Report on Midwest Research Institute Program for Development of Analytical Methods for NDEIA Using HPLC-TEA, Determination of Nitrites , Determination of NDEIA by a non-TEA Method. July 10, 1980. Cosmetic, Toiletry and Fragrance Association, Inc., 1110 Vermont Avenue, N.W., Washington, D.C. 20005 ... 

Spencer and Brewer [144] have reviewed methods for the determination of nitrite in seawater. Workers at WRc, UK [ 145] have described an automated procedure for the determination of oxidised nitrogen and nitrite in estuarine waters. The procedure determines nitrite by reaction with N-1 naphthyl-ethylene diamine hydrochloride under acidic conditions to form an azo dye which is measured spectrophotometrically. The reliability and precision of the procedure were tested and found to be satisfactory for routine analyses, provided that standards are prepared using water of an appropriate salinity. Samples taken at the mouth of an estuary require standards prepared in synthetic seawater, while samples taken at the tidal limit of the estuary require standards prepared using deionised water. At sampling points between these two extremes there will be an error of up to 10% unless the salinity of the standards is adjusted accordingly. In a modification of the method, nitrate is reduced to nitrite in a micro cadmium/copper reduction column and total nitrite estimated. The nitrate content is then obtained by difference. 

Matsunaga et al. [146] have also described a similar procedure for the determination of nitrite in seawater. To 500 ml of sample is added 10 ml of sulfanilamide (1% solution) in 2M hydrochloric acid and 5 ml aqueous N-l-naphthylethylene-diamine hydrochloride (0.1%). After 10 min, 5 ml of aqueous dodecylbenzenesulfonate (0.5%) is added and the mixture extracted for 2 min with 50 ml of carbon tetrachloride. Then 75 ml of acetone and 10 ml of 0.1 M hydrochloric acid are added to the separated organic layer and the azo dye... 

Gianguzza and Orecchio [147] have carried out comparative trials of various methods for estimating nitrites in seawaters. These workers compared a method using sulfanilic acid/a-naphthylamine complexes with a method using sulfanilamide/N( 1-naphthyl) ethylenediamine complexes for the determination of nitrites in saline waters. The second method has the greater sensitivity and lower detection limits. The former method is subject to interference from chlorides, and this interference can be completely eliminated by the coupling diazotisation procedure of the latter method. 

Mass spectrometry has been applied to the determination of nitrite and nitrate in seawater. This method produced results that were free from interference by other forms of nitrogen [150]. 

In this development of a flow injection method for the determination of nitrate andnitrite, Anderson [168] chose the Shinn [155] method to reduce nitrate and nitrite because of its high sensitivity and relative freedom from interferences. Anderson [168] used flow injection in the photometric determination of nitrite and nitrate with sulfanilamide and N-( 1-naphthyl) ethylenediamine as reagents, as discussed next. The detection limit is 0.05 xm for nitrite and 0.1 xm for nitrate at a total sample volume of 200 iL. Up to 30 samples can be analysed per hour with relative precision of about 1%. 

Figure 2.4. Flow diagram for the colorimetric determination of nitrite and nitrate. The internal diameter of the Tygon tubing was 0.64 mm for the 0.23 ml/min flow rates and 1.30 mm for the 1.00 ml/min flow rates all other tubing was 0.7 mm id. The reagents were (A) carrier stream, (B) sulfanilamide solution, and (C) N(1-naphthyl) ethylene diamine solution. S denotes the point of injection and W waste. From [168]...

Another approach to the organic nitrogen problem is to use persulfate wet oxidation to convert the nitrogen to nitrate or nitrite, in place of the reduction to ammonia [13,14,24,25]. Results are fully comparable with those from the micro Kjeldahl digestion but the technique is far simpler. The precision should also be higher, since the final step in the measurement, the colorimetric determination of nitrite, is much more precise than any of the ammonia methods. 

Wetters JH, Uglum KL. Direct spectrophotometric simultaneous determination of nitrite and nitrate in the ultraviolet. Anal. Chem. 1970 42 335-340. 

Experiment 37 Solid-Liquid Extraction Determination of Nitrite in Hot Dogs... 

Guan, R, Wu, H., and Luo, Yi. (1996). Sensitive and selective method for direct determination of nitrite and nitrate by high-performance capillary electrophoresis. /. Chromatogr. A 719, 427-433. 

Principally the same, but chemically simpler, sequence was used to prepare arylnitro anion-radicals from arylamines, in high yields. For instance, aqueous sodium nitrite solution was added to a mixture of ascorbic acid and sodium 3,5-dibromo-4-aminobenzenesulfonate in water. After addition of aqueous sodium hydroxide solution, the cation-radical of sodium 3,5-dibromo-4-nitro-benzenesulfonate was formed in the solution. The latter was completely characterized by its ESR spectrum. Double functions of the nitrite and ascorbic acid in the reaction should be underlined. Nitrite takes part in diazotization of the starting amine and trapping of the phenyl a-radical formed after one-electron reduction of the intermediary diazo compound. Ascorbic acid produces acidity to the reaction solution (needed for diazotization) and plays the role of a reductant when the medium becomes alkaline. The method described was proposed for ESR analytical determination of nitrite ions in water solutions (Lagercrantz 1998). 

Nielsen, M. Revsbech, N.P. Larsen, L.H. Lynggaard-Jensen, A. On-line determination of nitrite in wastewater treatment by use of a biosensor. Water Sci. Technol. 2002, 45, 69-76. 

Follett, M.J. and Ratcliff, P.W. (1963) Determination of nitrite and nitrate in meat products. Journal of the Science of Food and Agriculture 14, 138-144. 

Ohta, T. (1986). Fluorometric determination of nitrite with 4-hydroxycoumarin. Anal. Chem. 58, 3132-3135. 

I. Sarudi and I. Nagy, A Gas Chromatographic Method for the Determination of Nitrite in Natural Waters, Talanta 1995,42, 1099. 

Garcia Gutierrez [19] has described an azo coupling spectrophotometric method for the determination of nitrite and nitrate in soils. Nitrite is determined spectrophotometrically at 550 nm after treatment with sulfuric acid and N-1 -naphlhylclhylcnediamine to form an azo dye. In another portion of the sample, nitrate is reduced to nitrite by passing a pH 9.6 buffered solution through a cadmium reductor and proceeding as above. Soils were boiled with water and calcium carbonate, treated with freshly precipitated aluminium hydroxide and active carbon, and filtered prior to analysis by the above procedure. 

International Standard Organization. 1984. Water quality. Determination of nitrite. Molecular absorption spectrometric method. ISO 6777. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

The work of Mosko [116] is important in that he is one of the few workers who have given serious consideration to the determination of nitrite in water. His paper is concerned with the determination of chloride, sulphate, nitrate, nitrite, orthophosphate, fluoride and bromide in industrial effluents, waste water and cooling water. Two types of analytical columns were evaluated (standard anion and fast run series). Chromatographic conditions, sample pretreatment and the results of interference, sensitivity, linearity, precision, comparative and recovery studies are described. The standard column provided separation capabilities which permitted the determination of all seven anions. The fast run column could not be used for samples containing nitrite or bromide owing to resolution problems. 

Alawi [315] has described a simple and specific high performance liquid chromatographic method for the determination of nitrite and nitrate in non saline water based on the nitration of an excess of phenol by nitrate or oxidised nitrite ions the... 

Alawi [319] has discussed an indirect method for the determination of nitrite and nitrate in surface, ground and rain water by reaction with excess phenol (nitrite ions first being oxidised to nitrate) and extraction of the o-nitrophenol produced, followed by separation on a reversed phase high performance liquid chromatography column with amperometric detection in the reduction mode. Recoveries were 82% for nitrate and 77% for nitrite in the concentration range 10-lOOOpg L 1. The method is claimed to be free of interferences from other ions. 

Alawi [319] has discussed the determination of nitrite and nitrate in rain. 

Kim and Kim [6] have described an extremely sensitive determination of nitrite in drinking water (tap water and underground water) and environmental samples (rain, lake water, and soil) by ion exclusion chromatography with electrochemical detection. Potential interferences in the determination of nitrite by the standard spectrophotometric method or by the ion exchange chromatographic method with either conductivity or ultraviolet detection were eliminated. The detection limit was 0.1 pg L 1 without preconcentration. 

Funazo et al. [791] have given details of a procedure for the determination of nitrite in river water by gas chromatography after reaction with /w-nitroanilinc and hypophosphorous acid to convert nitrite to nitrobenzene. 

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