Nitrite flow-injection analysis

Flow injection analysis is another technique that has been applied to the determination of nitrate and nitrite in seawater. Anderson [ 126] used flow injection analysis to automate the determination of nitrate and nitrite in seawater. The detection limit of his method was 0.1 imol/l. However, the sampling rate was only 30 per hour which is low for flow injection analysis. Reactions seldom go to completion in a determination by flow injection analysis [127,128] because of the short residence time of the sample in the reaction manifold. Anderson selected a relatively long residence time so that the extent of formation of the azo dye was adequate to give a detection limit of 0.1 pmol/l. This reduced the sampling rate because only one sample is present at a time in the post-injector column in flow injection analysis. Any increase in reaction time causes a corresponding increase in the time needed to analyse one sample. 

Johnson and Petty [129] reduced nitrate to nitrite with copperised cadmium, which was then determined as an azo dye. The method is automated by means of flow injection analysis technique. More than 75 determinations can be made per hour. The detection limit is 0.1 xmol/l, and precision is better than 1% at concentrations greater than 10 xmol/l. 

Flow-injection analysis (FIA) is a technique for automating chemical analyses. The principles of FIA are reviewed here. Methods for applying FIA to the anayses of nitrate, nitrite, phosphate, silicate, and total amino acids in seawater are examined. Analyses of other nutrients, metals, and carbonate system components are also discussed. Various techniques to eliminate the refractive index effect are reviewed. Finally, several examples of the application of FIA to oceanographic problems are presented. 

Some authors [75-77] have proposed using flow-injection analysis for determining nitrite, through the formation of azo dyes. 

M.F. Gine, H. Bergamin-Filho, E.A.G. Zagatto, B.F. Reis, Simultaneous determination of nitrate and nitrite by flow injection analysis, Anal. Chim. Acta 114 (1980) 191. 

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. 

J.-H. B. Hansen, Flow Injection Analysis. Spektrofotometrisk Bestem-melse af Chlorid, Nitrit og Nitrat [in Danish]. Dan. Eng. Acad., Denmark, (1981). (M. Sc. Thesis). 

S. Xu and Z. Fang, Sinultaneous Spectrophotometric Determination of Nitrate and Nitrite in Water and Soil Extracts by Flow Injection Analysis [in Chinese]. Fenxi Huaxue, 11 (1983) 93. 

K. S. Jonson and R. L. Petty, Determination of Nitrate and Nitrite in Seawater by Flow Injection Analysis. Limnol. Oceanogr., 28 (1983) 1260. 

S. Nakashima, M. Yagi, M. Zenki, A. Takahashi, and K. Toei, Spectro-photometric Determination of Nitrite in Natural Waters by Flow Injection Analysis. Anal. Chim. Acta, 155 (1983) 263. 

E. A. Jones, The Determination, by Flow Injection Analysis, of Fluoride, Chloride, Phosphate, Ammonia, Nitrite, and Nitrate. Rep.-MINTEK (S. Africa), M200 (1985) 65. 

A. Trojanek and S. Bruckenstein, Novel Flow-Through Pneumatoamper-ometric Detector for Determination of Nanogram and Subnanogram Amounts of Nitrite by Flow-Injection Analysis. Anal. Chem., 58 (1986) 866. 

M. O Toole, R. Shepherd, K.T. Lau, D. Diamond, Detection of nitrite by flow injection analysis using a novel paired emitter-detector diode (PEDD) as a photometric detector, Proc. SPIE Int. Soc. Opt. Eng. (2007) 6755. 

Daniel, A. et al.. Characterization and reduction of interferences in flow-injection analysis for the in situ determination of nitrate and nitrite in sea water, Analytica Chimica Acta 308, 413,1995. 

The second part describes the application of this automated potentiostat as an electrochemical detector for various electro-inactive anionic species nitrate (NOg ), nitrite (NOg"), sulfate (SO "), chloride (CD, etc. (1,2). The electrochemical detection involves the use of a conducting poly(3-methylthiophene) (P3MT) polymer modified platinum electrode in a flow injection analysis (FIA) mode. 

Figure 6 Typical Signal Response of P3MT Anion Sensor Towards Sodium Nitrite at Concentrations of 5.5 x 10, 1.1 x 10 , 2.2 x 10" , 5.5 x 10" and 1.1 x 10" M in Flow Injection Analysis Mode...

Ameida, F. L., S. G. dos Santos Filho, and M. B. A. Fontes. 2013. FIA-automated system used to electrochemically measure nitrite and interfering chemicals through a 1-2 DAB/Au electrode Gain of sensitivity at upper potentials./. Phys. Conf Ser. 421 1-8. Anderson, L. 1979. Simultaneous spectrophotometric determination of nitrite and nitrate by flow injection analysis. Anal. Chim Acta 110 123-128. 

Brabcova, M., P. Rychlovsky, and I. Nemcova. 2003. Determination of nitrites, nitrates and their mixtures using flow injection analysis with spectrophotometric detection. Anal. Lett. 36 2303-2316. 

Haghighi, B. and A. Tavassoli. 2002. Flow injection analysis of nitrite by gas phase molecular absorption UV spectrophotometry. Talanta 56 137-144. 

ISO. 1996. Water quality—Determination of nitrite nitrogen and nitrate nitrogen and the sum of both by flow analysis (continuous flow analysis and flow injection analysis). Geneva International Organization for Standardization (ISO 13395 1996 (E)). 

Ruiz-Capillas, C., P. Aller-Guiote, and F. Jimenez-Colmenero. 2007. Application of flow injection analysis to determine protein-bound nitrite in meat products. Food Chem. 101 812-816. 

This technique has been established for many years particularly for water, soil and feeding-stuff analysis, where a large number of analyses are required for quality control or monitoring purposes. A number of applications have been published for food additives including aspartame (Fatibello et al., 1999), citric acid (Prodromidis et al., 1997), chloride, nitrite and nitrate (Ferreira et al., 1996), cyclamates (Cabero et al., 1999), sulphites (Huang et al., 1999 AOAC Int, 2000), and carbonate, sulphite and acetate (Shi et al., 1996). Yebra-Biumm (2000) reviewed the determination of artificial sweeteners (saccharin, aspartame and cyclamate) by flow injection. 

A. A. Ensafi and G. B. Dehaghi, Ultra-Trace Analysis of Nitrite in Food Samples by Flow Injection with Spectrophotometric Detection, Fresenius J. Anal. Chem. 1999,363, 131. 

Y.Q. Zhao, Y.Z. He, W.E. Gan, L. Yang, Determination of nitrite by sequential injection analysis of elec-trokinetic flow analysis system, Talanta 56 (2002) 619-625. 

FIGURE 1,6 Example of manifolds developed for flow injection speciation analysis, (a) Manifold of the reversed FIA system for speciation of chromium with pH measurements and spectrophotometric detection, q—peristaltic pumps, V—injection valves, L— reaction coil, M.E.—pH glass electrode. (Adapted from Ruz, J. et al. 1986. J. Autom. Ghent. 8 70-74.) (b) Manifold of branched FIA system for simultaneous biamperomet-ric determination of nitrate and nitrite. (Cd)Cu—reductive column with copperized cadmium, L—mixing coils. (Adapted from Trojanowicz, M., W. Matuszewski, and B. Szostek. 1992. Anal. Chim. Acta 261 391-398.) (c) Example signal recordings obtained in the FIA system shown in (b) 1-6—standard solutions, A-I—natural water samples. Concentration in standard solutions 1—0.075 2—0.050 3—0.025 mM nitrate and 4—7.5 5—5.0 6—2.5 pM nitrite. 

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