(SN, Sigma, USA) was selected as a model water-soluble hydrophilic drug with oleic acid (OA, Fluka, Germany) as permeation enhancer.
A method of quantitative determination of sulphanilamide
by reaction with p-dimethylaminocinnamic aldehyde  in acid medium has been suggested.
Equal volumes (100 ul) of supernatant and Griess reagent (1% sulphanilamide
, 0.1% N-1 naphthylethylenediamide dihydrochloride in 5% [H.sub.3]P[O.sub.4]) were incubated on microplates at room temperature for 15 min.
(2,3) Following the sulphanilamide
and thalidomide tragedies of the 1930s and 1960s, respectively, there has been growing global concern about the safety of medicines administered to children.
SRSi was determined by the molybdenum blue method, with ascorbic acid as reductant; nitrogen in the form of nitrite (N[O.sub.2.sup.-]) was determined by sulphanilamide
in an acid solution method and nitrate (N[O.sub.3.sup.-]) was measured as N[O.sub.2.sup.-] after its reduction in Cd-Cu column; SRP was determined using the molybdenum blue method (Strickland & Parsons 1972).
After 30 min, 1.5 ml of the incubated solution was removed and diluted with 1.5 ml of Griess reagent (1% sulphanilamide
, 2% phosphoric acid and 0.1% N-1-naphthylethylenediamine dihydrochloride).
It was prepared fresh by mixing equal volumes of 1% sulphanilamide
and 0.1% naphthylene diamine dihydrochloride in 2.5% orthophosphoric acid.
After this step, 100 [micro]L of Griess reagent was added (0, 1% NEED, 1% sulphanilamide
, 5% [H.sub.3]P[O.sub.4]) (Sigma) and the nitrite concentration was obtained against a NaN[O.sub.3] standard curve.
Post-coital treatment centres were also set up in many locations, but the breakthrough in the management of gonorrhoea came with the discovery of sulphanilamide
, the first anti-gonococcal antibiotic.
and N-(1-naphthyl)-ethylenediamine dihydrochloride were used for the determination of N[O.sup.-.sub.2] (Koroleff, 1982).
Before antibiotics, nearly one of the first things that came out as regards chemicals was Sulphanilamide
which replaced the old tradition of bleeding horses to cure them.
The colorimetric nitrite standard test method and its modifications [1-4] are based on the reaction of nitrite with an aromatic amine (sulphanilamide
, sulphapyridine, sulphathiazole) to form a diazonium salt, and on the following reaction with a coupling reagent (1-naphtol-4-sulphonate, N-1-naphtylethylenediamine) to produce a highly coloured potentially carcinogenic azo dye.