Indophenol blue method

Berg and Addullah [47] have described a spectrophotometric autoanalyser method based on phenol, sodium hypochlorite, and sodium nitroprusside for the determination of ammonia in sea and estuarine water (i.e., the indophenol blue method). 

The Adamski [13] procedure is semiautomated. It gives an accuracy of 8.1% and a precision of 8.2% for seawater samples spiked with 3-35 p,g/l organic nitrogen. This procedure is based on the indophenol blue method and was employed using a Technicon AutoAnalyzer II system with the appropriate accessories. Various workers have described automated procedures for determination of low levels of organic nitrogen in seawater [15,16]. 

Colorimetry. A variety of colorimetric techniques have been used to measure ions such as NH4, SO4-, and NO7 in ambient particles. For example, nitrate can be measured by reduction to nitrite using hydrazine in the presence of a copper catalyst, followed by its conversion to a colored azo dye, which can be measured by its absorbance at 524 nm (Mullin and Riley, 1955). Sulfate has been determined using an exchange reaction between sulfate and a barium-nitrosulfo-nazo(III) chelate in aqueous acetonitrile the chelate has an absorbance peak at 642 nm and hence the decrease in this peak can be followed as a measure of the amount of sulfate present that has exchanged with the chelate (Hoffer et al., 1979). Similarly, NH4 can be measured by the indophenol blue method (Weather-burn, 1967). 

Keay and Menage [24] carried out an automated determination of nitrate and ammonia in 2 M potassium chloride extracts of soils. The sample is reacted in an autoanalyser with a 0.25% suspension of magnesium oxide the ammonia liberated from ammonium ion is absorbed in 0.1 M hydrochloric acid and determined spectrophotometrically at 625 nm by the indophenol blue method. The sum of ammonium and nitrate is determined similarly but with the addition of 4.5% titanous sulfate solution before distillation, thereby reducing nitrate but not nitrite to ammonia. The nitrate content of the soil can then be obtained by difference. 

The phenol-hypochlorite (Indophenol-blue) method was used for ammonia analysis (Solorzano, 1969). Appropriate sample sizes were fixed with phenol within 24 hours of collection (Degobbis, 1973) and stored at all times at 4 C. Analyses were made within 2 weeks of collection. The reagent dilutions given by Presley (1971) were used, but the quantity added was doubled. All reaction and color development was done in polyethylene scintillation vials. Color development was allowed for 6-8 hr to obtain a straight-line standardization curve blanks (always <0.010 absorbance with respect to distilled water, 1-cm cell) were insignificant compared to sample absorbances and precision better than 3%. Standards were diluted immediately before use. 

Ammonia mg/litre NH d Absorption spectrophotometry, Nessler s method, or indophenol blue method. 

Note Other determinations could be used for nitrogen compounds in fertilizer, such as ion chromatography, spectrophotometric (dye approach), gas diffusion, potentiometric, and indophenol blue methods. These methods have not been approved as official methods by credible organizations such as AOAC International and AFPC. Potentiometric... 

J.F. van Staden, R.E. Taljaard, Determination of ammonia in water and industrial effluent streams with the indophenol blue method using sequential injection analysis. Anal. Chim. Acta 344 (1997) 281 289. 

Sagi (1966) introduced the indophenol blue method with a nitropnisside catalyst for the direct measurement of ammonia in seawater. 

Organic Nitrogen in Polymers. Kjeldahl Digestion - Spectrometric Indophenol Blue Method... 

Standard nitrogen solution (for calibration of the indophenol blue method). 

METHOD 85 - DETERMINATION OF BETWEEN 0.002% AND 75% ORGANIC NITROGEN IN POLYMERS. KJELDAHL DIGESTION - SPECTROMETRIC INDOPHENOL BLUE METHOD. 

Novozamsky, I., R. van Eck, J.Ch. van Schouwenburg and I. Walinga. 1974. Total nitrogen determination in plant material by means of the indophenol blue method. 

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