Diazotization spectrophotometry

Spectrophotometry, Griess method (reduction to nitrite and diazotation) Spectrophotometry [displacement of SCN in Hg(SCN)T, determination of colored Fe(SCN) complex]... 

Lab method using glass-fibre/Tenax tube sampling and high performance liquid chromatography Field method using acid hydrolysis, diazotization, coupling and spectrophotometry... 

A method frequently used to determine aromatic amines in water-soluble dyes involves their extraction with chloroform, followed by diazotization of amines and coupling of diazonium salts with a reagent R-salt (disodium-3-hydroxy-naphthalene-2,7-disulfonate) or pyrazolone T (4,5-dihydro-5-oxo-l-(4-sulfophenyl-)l/7-pyrazole-3-carboxylic acid). The separated products are detected by UV-VIS spectrophotometry or fluorescence (210-212). 

No satisfactory method for the quantitative determination of bile pigments in urine has yet been evolved (W9). Direct spectrophotometry is impossible on account of the presence of yellow pigments other than bile pigments. Diazotization procedures necessitate the application of correction factors, which are not entirely adequate. Some purification can be effected by absorption of the bile pigments onto barium sulfate but their subsequent elution is by no means quantitative. 

Diazotization with p-nitroaniline, paper chromatography, UV absorption spectrophotometry Methylation, paper chromatography, UV absorption spectrophotometry Formation of 2,4-dinitrobenzoates Formation of phenylazobenzene sulfonic acid derivatives Methylation, gas chromatography Gas chromatography, internal standard addition... 

Chemical pretreatments may be required due to lack of selectivity and/or sensitivity of direct spectrophotometry. The chemistry of spectrophotometric determinations in pharmaceutical analysis is by now well documented common procedures are redox reactions metal ion chelation reactions for the determination of organic compound or metal ion components charge transfer complex formation reactions ion pairing and diazotization. 

VV Kuznetsov, S.V. Zemyatova, Flow-injection spectrophotometry of nitrites based on the diazotization reactions of azine dyes, J. Anal. Chem. 62 (2007) 637-644. 

The standard method for the determination of nitrite in seawater is based on the reaction of nitrite with an aromatic amine leading to the formation of a diazonium compound which couples with a second aromatic amine. The product is an azo dye which is quantified by spectrophotometry. Early methods were modifications of the Griess-Ilosvay procedure where the nitrite diazotized with sulphamic acid. The diazonium salt then coupled with 1-naphthylamine. The method described below is generally accepted for seawater analysis and is based on the method proposed by Shinn (1941) and adapted for seawater by Bendschnei-der and Robinson (1952). This method is very sensitive and is unaffected by the presence of other constituents normally occurring in seawater. Sulphanilamide hydrochloride is used as the amino compound, which after diazotization is coupled with N-(l-naphthyl)-ethylene-diamine dihydrochloride. 

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