Nitrite determination

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 ... 

Results for the nitrate plus nitrite determinations (Table 12.7) show that there was very little difference in the amounts extracted with either technique. 

There are two approaches to the analysis. In the first, the extractable ammonium-N is determined by a Kjeldahl distillation, and this is subtracted from the value for ammonium plus nitrate (and nitrite) determined by a further separate Kjeldahl distillation preceded by reduction with nascent hydrogen produced by the reaction of Devarda s alloy (45% Al, 50% Cu, 5% Zn) in strongly alkaline solution ... 

The rate at which the aminoguanidine sulfate is added to the solution of sodium nitrite determines the size of the tetrazene crystals. If the aminoguanidine sulfate is added quickly, small crystals are formed, whereas large crystals are formed when the solution is introduced slowly. Dextrin can be added to the reacting solution to obtain a more uniform crystal size. 

An indirect electrochemical method developed for nitrite determination may be of general applicability for PAA determination, as shown in equation 13. A nitrite sample is placed into a cell containing a known amount of 3-sulfanilic acid in dilute HC1 at pH 3. After 5 min the diazonium ion formation is complete an excess of catechol (109) is added and the concentration of the remaining 3-sulfanilic acid is determined at +0.12 V with a GCE vs. standard calomel electrode, by measuring the adduct (110) formed between the aromatic amine and the quinone derived from catechol in the diffusion layer of the electrode. The 3-isomer of sulfanilic acid was chosen among the three isomers, aniline and 4-nitroaniline for its highest sensitivity and its lowest LOD, 0.7 pM, with linearity from 20 to 80 pM. A spectrophotometric assay may be carried out for nitrite by measuring at 516 nm the azo dye derived from catechol and the diazonium ion after 3 h ... 

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... 

Fig. 6-11. Comparison of direct UV detection and suppressed conductometric detection in the nitrite determination at 100-fold chloride excess. - Separator column IonPac AS4A eluent 0.0017 mol/L NaHC03 + 0.0018 mol/L Na2C03 flow rate 2 mL/min detection (A) suppressed conductivity (sensitivity 10 pS/cm), (B) UV detection at 215 nm (sensitivity 0.05 aufs) injection volume 50 pL solute concentrations 100 ppm chloride and 1 ppm nitrite.

The classical Griess method for nitrite determination is very well known. However, some of the more recent methods which are also based upon the formation of azo dyes may be better. A critical review of the nitrite determination methods has been published [58]. 

The method for nitrite determination based on the diazotization-coupling reaction by column preconcentration and on the reduction of nitrate to nitrite using the Cd-Cu reductor column has been proposed for the determination of nitrate and nitrite in water and some fruit samples [6]. On-line monitoring of nitrite in fertilizer process streams, natural and waste water effluents based on the diazotization of nitrite in the sequential injection system with N-(l-naphthyl)etylenediammonium dichloride and the formation of a highly coloured dye has been described [7]. 

Table 2. Characteristics of the UV method for nitrite determination (without dilution)...

Nitrite Nitrogen. The Standard diazotization and coupling procedure with sulfanilic acid and a-naphthylamine was used for nitrite determination (I). It should be emphasized that the presence of even... 

Dianisidine m-Phenylenediamine nitrite determination N-(1-Naphthyl) ethylenediamine dihydrochloride nitrite mfg. 

FIA system for nitrite determination expioiting optosensing detection. iV injection vaive RC reaction coii. 

FIA [137-140] and SIA [141-146] are the most common techniques for nitrite determination and monitoring in different kinds of environmental samples (foodstuffs, fertilizer process streams, natural waters, including seawater, and wastewater effluents) by spectrophotometric methods based on the modified Griess reaction. 

SIA system using an on-line solid-phase extraction and preconcentration method for nitrite determination. Detector spectrophotometer (Xmax = 420 nm) HC holding coil RC reaotion ooil SV seleotion valve. 

W.R. Melchert, C.M.C. Infante, F.R.P. Rocha, Development and critical comparison of greener flow procedures for nitrite determination in natural waters, Microchem. J. 85 (2007) 209-213. 

M. Baeza, J. Bartroli, J. Alonso, Autoadaptative sequential injection system for nitrite determination in wastewaters, Talanta 68 (2005) 245-252. 

The sulphanilamide reagent and the NED are the same as the reagents used to determine nitrite. In multi-channel flow-systems common reservoirs may be used for the corresponding reagents. As in the nitrite determination the sulphanilamide and NED reagents may be combined (1 1) to a mixed reagent and applied as such. The mixed reagent should be stored in the dark and at < 8 °C for a maximum of 5 d. 

For determination of nitrites in clean aqueous solutions such as water, there is no need for extraction it is generally enough to filter the sample before it is injected into the FIA system. In some cases preconcentration of the sample may be necessary for determination of nitrite by FIA or sequential injection analysis (SIA). One such example would be direct nitrite determination in nonpolluted water samples where colorimetry is not sensitive enough to determine NO2 (Miro et al., 2000,2001). Preconcentration processes have been based on anionic exchange resins (Dowex 1-X8) (Wada and Hattori, 1971) or on ion pairs coprecipitated with microcrystalline biphenyl (Puri et al., 1998), or with naphthalene (Wang et al., 1998). Dialysis-FIA systems have been proposed for determination of nitrite in residual waters, and even a solid phase (monofunctional Cjg) which is held inside a glass column for an automatic SIA has been tried (Miro et ah, 2000). 

Most FIA methods include the online reduction step (nitrate to nitrite) prior to the color reaction (Griess or other reaction), following the same procedure as in the case of nitrite determination. The sample is then treated with azo dye reagent and the absorbance due to the sum of nitrite and nitrate is measured nitrate is determined from the difference in absorbance values (Figure 7.3) (Ruiz-Capillas et ah, 2006, 2007). In this way, nitrates and nitrites can be determined in the same system. In fact, FIA systems have been developed for simultaneous determination of nitrates and nitrites, with the saving... 

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