Nitrite was converted into nitrous acid in the acidic medium; subsequent diazotization
of sulphanilic acid and formation of diazonium salt are shown in Scheme 2.
4-Aminobenzoic acid can be easily converted to 4-carboxyphenyl diazonium salts by the diazotization
reaction in acid aqueous solution at 0[degrees]C (Figure 2).
After 15 min, the absorbance of the chromophore formed during the diazotization
of the nitrite with sulfanilamide and the subsequent coupling with naphthyl ethylenediamine dihydrochloride was measured at 546 nm .
The reaction is followed by a colorimetric detection of nitrite as a product of the Griess reaction, based on the diazotization
reaction in which acidified N[O.sup.-.sub.2] produces a nitrosating agent, which reacts with sulfanilic acid to yield the diazonium ion.
Fortnightly, water samples were taken from all tanks to perform the analyses of free CO2 (sodium carbonate titration), dissolved oxygen (Winkler's method), nitrite (diazotization
method) and reactive phosphorus (molybdenum blue method), following the guidelines presented by APHA (1999).
The nitrite (N[O.sub.2.sup.-] - mg [L.sup.-1]) was obtained by the Diazotization
The Griess reagent is based on the two-step diazotization
reaction in which acidified nitrite produces a nitrosating agent, which reacts with sulphanilic acid to produce the diazonium ion.
After incubation, 0.5 mL of the reaction mixture mixed with 1 mL of sulfanilic acid reagent (0.33% in 20% glacial acetic acid) and allowed to stand for 5 min for completing diazotization
. Then, 1 mL of naphthyl ethylenediamine dihydrochloride was added, mixed and allowed to stand for 30 min at 25[degrees]C.
The azo dyes are synthesized by diazotization
of aromatic amines and coupling reagent, which include one or more azo groups (-N=N-) attached to one or more aromatic moieties (Karci et al.
of various aromatic amines 1(a-j) was carried out by the method reported in literature .
The largest class of dyestuffs is that of the azo colours, which are made by diazotization
. These isomers, which are crystalline solids of low volatility, act as skin sensitizers and cause contact dermatitis, which appears to be the greatest hazard arising from their use in industry .
Fischhach  determined sulpha-drugs in aqueous solution by diazotization
with sodium nitrite in presence of acid, using p-dimethylaminobenzaldehyde as internal indicator.