Nitrate flow-injection analysis

Simultaneous determination of both cations and anions in acid rain has been achieved using a portable conductimetric ion-exclusion cation-exchange chromatographic analyzer.14 This system utilized the poly(meth-ylmethacrylate)-based weak acid cation exchange resin TSK-Gel OA-PAK-A, (Tosoh , Tokyo, Japan) with an eluent of tartaric acid-methanol-water. All of the desired species, 3 anions and 5 cations, were separated in less than 30 minutes detection limits were on the order of 10 ppb. Simultaneous determination of nitrate, phosphate, and ammonium ions in wastewater has been reported utilizing isocratic IEC followed by sequential flow injection analysis.9 The ammonium cations were detected by colorimetry, while the anions were measured by conductivity. These determinations could be done with a single injection and the run time was under 9 minutes. 

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. 

Some coupled systems allow measurement of the main N and P forms (nitrate, ammonia and orthophosphates) [22,27,29], among which is a system based on membrane technology in combination with semi-micro continuous-flow analysis (pCFA) with classical colorimetry. With the same principle (classical colorimetry), another system [30] proposes the measurement of phosphate, iron and sulphate by flow-injection analysis (FIA). These systems are derived from laboratory procedures, as in a recent work [31] where capillary electrophoresis (CE) was used for the separation of inorganic and organic ions from waters in a pulp and paper process. Chloride, thiosulphate, sulphate, oxalate,... 

AgN03 = silver nitrate CICN = cyanogen chloride CN" = cyanide ion CNATC = cyanides not amenable to chlorination (Rosentreter and Skogerboe 1992) AAS = atomic absorption spectroscopy EPA = Environmental Protection Agency FIA = flow injection analysis GC/ECD = gas chromatograph/electron capture detector HCN = hydrogen cyanide NaOH = sodium hydroxide NIOSH = National Institute for Occupational Safety and Health... 

Analytical Methods. Temperature, pH, and oxygen were measured in situ by using a combined sensor (Ztillig). Ammonium was determined by flow injection analysis (27), and nitrate and silicate by spectrophotometric methods (Auto-Analyzer) (28). Sulfide was determined by using a H2S-specific electrode (29). 

Tecator Ltd. [16] have described a flow injection analysis method for the determination of 0.2 -1.4 mg/1 (as NH3N) of ammonia nitrogen in soil samples extractable by 2 M potassium chloride. The soil suspension in 2 M potassium chloride is centrifuged and filtered and introduced into the flow injection system for the analysis of ammonia (and nitrate) one parameter at a time. Ammonia is determined by the gas diffusion principle, in which a PTFE membrane is mounted in the gas diffusion cell. 

Van Staden [4,5] employed flow injection analysis coupled with a coated tubular solid-state bromide-selective electrode for the determination of bromide in soils. Soil-extracted samples are injected into 10 mol/1 potassium nitrate carrier solution containing 1000 mg/1 chloride as an ionic strength adjustment buffer. The sample buffer zone formed is transported through the bromide selective electrode onto the reference electrode. The method is applicable in the range 10-50 000 mg/1 bromide. The coefficient of variation of this method is better than 1.6%. 

Techniques used to determine nitrates in soils include titration [17], spectrophotometry [18-26,29-31], flow injection analysis [20,21], ion selective electrodes [27,28], and ion chromatography [28,31-44],... 

Tecator Ltd. (1983) Determination of Nitrate and Ammonia in Soil Samples, Extractable with 2 M Potassium Chloride Application Note AN65/83 (1983) and Determination of Nitrate in Soil Samples, Extractable with 2 M Potassium Chloride using, Flow Injection Analysis, Application Note AN65-31/83, Tecator Ltd., Hoganes, Sweden. 

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. 

ISO/TR 11905-2). Another method oxidizes nitrogen forms into nitrates which can be then estimated (NF EN ISO 11905-1). Lastly, an ISO/CD 29441 method, under development, uses UV digestion, followed by flow injection analysis (FIA), continuous flow analysis (CFA) with spectrophotometric detection, and allows automation of the method. 

Several methods can be used for the determination of chloride in water [2], The argentometric and mercuric nitrate methods are based on the titration of chlorine in the presence of an indicator. Experimental procedures are easy, but many substances may interfere with the results. There are also other methods such as potentiometry, capillary electrophoresis and other automated methods (ferricyanide method or flow injection analysis). 

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. 

J. Ruzicka, E.H. Hansen, E.A.G. Zagatto, Flow injection analysis. Part VII. Use of ion-selective electrodes for rapid analysis of soil extracts and blood serum. Determination of potassium, sodium and nitrate, Anal. Chim. Acta 88 (1977) 1. 

P.H. Petsul, G.M. Greenway, S.J. Haswell, The development of an on-chip micro-flow injection analysis of nitrate with a cadmium reductor, Anal. Chim. Acta 428 (2001) 155. 

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. 

Recently, Karmarkar reported an impressive dual IC-flow injection analysis (FIA) method for the sequential determination of anionic (nitrate and phosphate) and cationic (ammonium) nutrients in wastewater samples. The dual system was based upon the use of an anion exchange column (Lachat QS-A5) and two detectors, one suppressed conductivity detector using a Lachat Instruments QE-Al small suppressor cartridge, which is regenerated between samples, and a second visible absorbance detector. Upon injection of the sample the conductivity detector was switched off line and the nonretained ammonium was passed through the analytical column and detected by the visible absorbance detector, following an on hne colorimetric reaction. The conductivity detector was then immediately switched on hne to detect the retained nutrient anions. The method reported detection limits for phosphate of 0.006 mg/1 phosphate. 

E. H. Hansen, A. K. Ghose, and J. RfliiCka, Flow Injection Analysis of Environmental Samples for Nitrate Using an Ion-Selective Electrode. Analyst, 102 (1977) 705. 

J. Slanina, F. Bakker, A. G. M. Bruijn-Hes, and J. J. Mols, Fast Determination of Nitrate in Small Samples of Rain and Surface Waters by Means of UV Spectrophotometry and Flow Injection Analysis. Fresenius Z. Anal. Chem., 189 (1978) 38. 

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). 

E. B. Schalscha, T. Schirado, and I. Vergara, Flow Injection Analysis of Nitrate in Soil Extracts—Evaluation of a Nitrate-Selective Flow Electrode Method. J. Soil Sci. Soc. Amer., 45 (1981) 446. 

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. 

M. F. Gin6, B. F. Reis, E. A. G. Zagatto, F. J. Krug, and A. O. Jacintho, A Simple Procedure for Standard Additions in Flow Injection Analysis. Spectrophotometric Determination of Nitrate in Plant Extracts. Anal. Chim. Acta, 155 (1983) 131. 

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

E. Schwerdtfeger, Automated Nitrate Assay in Plant Material Following the FIA (Flow Injection Analysis) Principle [in German]. Landwirtsch. Forsch.y Kongressband 1984 (1985) 99. 

S.S.M. Hassan, H.E.M. Sayom, S.S. Al-Mehrezi, A novel planar miniaturized potentiometric sensor for flow injection analysis of nitrates in wastewaters, fertilizers and pharmaceuticals. Anal. Chim. Acta 581 (2007) 13-18. 

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