Determination of Nitrite and Nitrate

Nitrite ion has been shown to be toxic in the human body and animals, since diazotization of amines present in the body can lead to carcinogenic N-nitroso compounds. Furthermore, nitrite oxidizes hemoglobin to methemoglobin which is incapable of binding oxygen. In contrast, nitrate itself is not toxic but is easily reduced to nitrite by microorganisms. 

Enzymatic assay of nitrite and nitrate is based on the following reactions catalyzed by nitrate reductase (EC 1.9.6.1) and nitrite reductase (EC 1.6.6.4)  

Nitrate is reduced to ammonia via intermediate nitrite with the participation of reduced methylviologen as electron donor. 

Kiang et al. (1978) developed an enzyme reactor incorporating the immobilized reductases. The eluate from the reactor was mixed with NaOH to expel the liberated NH3 gas which was subsequently detected 

Direct coupling of the enzymes with the ammonia electrode is not possible, since the sensitivity of the electrode is too low at the optimum pH of the reductases (7.4-7.8). 

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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]...

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

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. 

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. 

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. 

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. 

Butt, S.B, Riaz, M., and Iqbal, M.Z. Simultaneous determination of nitrite and nitrate by normal phase ion-pair liquid chromatography. Talanta 2001, 55, 789-797. 

High performance 3-pm particles gained popularity in the early 1990s. For example, a fast (<50 s) IPC determination of nitrite and nitrate on a short 3.0 cm x 0.46 cm... 

Direct UV detection gained great significance in the determination of nitrite and nitrate [18,19] as well as bromide and iodide in the presence of high chloride concentrations. The optimal measuring wavelength for the determination of those anions is listed in Table 6-4. Fig. 6-11 illustrates the superiority of direct UV detection over conductometric detection with a nitrite determination in the presence of a 100-fold chloride excess. Determinations of this kind may be performed in all saline samples such as body... 

Crystallise orthaniUc acis from aqueous solution, containing 20mL of cone HCl per L, then crystalUse it from distilled water, and dry it in a vacuum desiccator over Sicapent (m 315°). When an aqueous solution is chilled below 13.5°, the hydrated form of the acid is obtained. It is used for the determination of nitrite and nitrate. The S-benzylisothiuronium salt has m 137° (from H2O). [Wertheim Org Synth Coll Vol II471 1943, Beilstein 14 H 681, 14 I 714, 14 II 429, 14 III 1896, 14 IV 2638.]... 

R. Burakham, M. Oshima, K. Grudpan, S. Motomizu, Simple flow-injection system for the simultaneous determination of nitrite and nitrate in water samples, Talanta 64 (2004) 1259. 

T. Perez-Ruiz, C. Martinez-Lozano, V. Tomas, Kinetic spectrofluorometric determination of nitrite and nitrate at the nanograms per milliliter level by manual and flow-injection methods, Anal. Chim. Acta 265 (1992) 103. 

Ensafi, A. A., Rezaei, B. and Nouroozi, S. (2004) Simultaneous spectrophotometric determination of nitrite and nitrate by flow injection analysis. Anal Sci, 20 (12), 1749-1753. 

L. Andersson, Simultaneous Spectrophotometric Determination of Nitrite and Nitrate by Flow Injection Analysis. AnaL Chim. Acta, 110 (1979) 123. 

Oztekin, N., Nutku, M. S., and Erim, F. B., Simultaneous determination of nitrite and nitrate in meat products and vegetables by capillary electrophoresis. Food Chem., 76,103, 2002. 

K. Fukushi, Y. Nakayama and J.-l. Tsujimoto, Highly sensitive capillary zone electrophoresis with artificial seawater as the background electrolyte and transient isotachophoresis as the on-line concentration procedure for simultaneous determination of nitrite and nitrate in seawater, J. Chromatogr. A, 1005, 197-205, 2003. 

The determination of nitrite and nitrate in meat and sausage products is an important problem, because their tolerated concentrations are strictly limited. Sample preparation includes homogenization of the sample, its extraction with a 5% borax buffer in a hot water bath, and subsequent Carrez precipitation with 15% potassium hexacyanoferrate(II) and 30% zinc sulfate solution. 

The determination of nitrite and nitrate is usually performed simultaneously by using a bicarbonate/carbonate or hydroxide eluent and suppressed conductivity detection, alone or coupled with UV/Vis detection in the case of complex matrices. 

Figure 10.247 Determination of nitrite and nitrate in an instant baby food sample. Chromatographic conditions see Figure 10.233 injection volume 25 pL sample instant milk ...

Nitrogen speciation has been facilitated with the introduction of SIA, which allows multi-parametric determinations with simpler instrumental setups and reduced reagents consumption [165-169]. SIA systems using the Griess reaction have been exploited for determination of nitrite and nitrate in natural waters, wastewaters, vegetables, dairy products, and soils with incorporation of the solid-phase reactor either on one port of the selection valve or in the holding cod. 

Experimental MPFS setup proposed for the determination of nitrite and nitrate. Detector spectrophotometer (Xmax = 540 nm) MP solenoid micropump RC reaction coil V solenoid valve. 

A. Kazemzadeh, A.A. Ensafi, Sequential flow injection spectrophotometric determination of nitrite and nitrate in various samples. Anal. Chim. Acta 442 (2001) 319-326. 

C. Pons, J.L.M. Santos, J.L.F.C. Lima, R. Forteza, V. Cerda, Multi-pumping flow system for the determination of nitrite and nitrate in water samples, Microchim. Acta 161 (2008) 73-79. 

Using an identical analytical setup for the determinations of nitrite and nitrate (identical cuvette lengths and reagents), the calibration factor (see Section 10.2.4) for nitrate should be 0.48 times that of nitrite. A 50 % reduction of the absorbance/nitrate ratio is caused by the 1 + 1 sample/buffer dilution in the nitrate determination. The addition of 2mL of reagents (2 1 mL) to a 25 mL nitrate sample as opposed to 2mL of reagents to a 50 mL nitrite sample causes another 2 % loss in the absorbance/nitrate ratio. 

Most seawaters, however, contain more nitrate than nitrite (about ten times as much). The determination of nitrite and nitrate with one analytical manifold, therefore, might require different spectrophotometer adjustments. 

Fig. 9-168. Determination of nitrite and nitrate in an instant baby food sample. - Chromatographic conditions see Fig. 9-155 injection volume 25 pL sample instant milk solute concentrations 40pg/L nitrite (1) and 0.6 mg/L nitrate (2), corresponding to 0.8 pg/g nitrite and 12 pg/g nitrate of the solid compound.

Narayana B, Sunil K (2009) A spectrophotometric method for the determination of nitrite and nitrate. Eurasian J Anal Chem 4(2) 204-214. ISSN 1306-3057 Neyens E, Baeyens J (2003) A review of classic Fenton s peroxidation as an advemced oxidation technique. J Hazard Mater 98(l-3) 33-50. Pll 80304-3894(02)00282-0 Nohynek GJ, Antignac E, Re T, Toutain H (2010) Safety assessment of persontd care products/ cosmetics and their ingredients. Toxicol Appl Pharmacol 243 239-259. doi 10.1016/j. taap.2009.12.001... 

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