O Dianisidine

Direct Blue 218 had reported sales of 623 t valued at 4.4 million ia 1987. It is produced from Direct Blue 15 (76) by metallizing and elimination of methyl groups from the methoxide to form the copper complex. Direct Blue 15 (76) is prepared by coupling o-dianisidine [119-90-4] to two moles of H-acid (4-amiQO-5-hydroxy-2,7-naphthalenedisulfonic acid) under alkaline pH conditions. Other important direct blues iaclude Direct Blue 80 (74), (9-dianisidine coupled to two moles of R-acid (3-hydroxy-2,7-naphthalenedisulfonic acid [148-75-4]) followed by metallizing to form a bis copper complex, and Direct Blue 22 (77), an asymmetrical disazo dye, prepared by coupling o-dianisidine to Chicago acid [82-47-3] and 2-naphthol. Direct Blue 75 (78) is an example of a trisazo dye represented as metanilic acid — 1,6-Q.eve s acid — 1,6-Q.eve s acid — (alb) Ai-phenyl J-acid. 

GB and other G-agents react with perhydryl ions at pH 9—10 to form a perphosphonate ion, CH2P(0)(0C2H2)00 , which has a sufficiendy high redox potential to oxidize iadole or o-dianisidine to produce colored products. This reaction is thus useful as a method of detection, and less than 1 p.g of GB can be detected ia this manner (15). 

Although manufacture of benzidine itself has virtually ceased in Europe and the United States, similar rearrangement processes are operated for 3,3 -dichlotobenzidine [91-94-1J, o-dianisidine (3,3 -dimethoxybenzidine), and benzidine-2,2 -disulfonic acid. 

Coke (coal tar), high temperature pitch Coke (coal tar), mixed coal-high temperature pitch Coke (coal tar), low temperature, high temperature pitch Diaminotoluene o-Dianisidine Salts of o-dianisidine o-Dianisidine-based azodyes Diarsenic trioxide Diazomethane Dibenz(a,/i)anthracene 1,2-Dibromo-3-chloropropane... 

Warning The substances benzidine and o-dianisidine, which are classified as carcinogenic, react in a similar manner to o-tolidine, which is also suspected of causing cancer. 

Fig ure 3. Starch gel electrophoresis of hemoglobins. Tris-EDTA-boric acid buffer, pH 9.0. O-Dianisidine stain. 

Electrophoretic separation of methemalbumin HpHb, and Hb after addition of excess amounts of Hb, staining with benzidine (L4) or o-dianisidine (J2), and finally scanning of the spots are other possibilities available for routine work. At low Hp concentration these methods do not give exact values since HBG is not taken into account, but the results are accurate enough for routine clinical work. Hommes (H10) eluates the HpHb spots and estimates the peroxidase activity. In this method HbBC is not taken into account. 

Smithies vertical starch gel electrophoresis (S7) separates the plasma proteins more distinctly than any other method. If the Hp concentration is normal, the Hp type can generally be recognized directly after the staining for proteins, but sensitive and more specific staining for heme groups, e.g., benzidine, o-dianisidine (04), and malachite green (N5) are preferable. This technique consumes more hydrolyzed starch than the simpler original horizontal electrophoresis technique (S5). 

Another family of technically important diazo components for pigment formation includes a series of aromatic diamino compounds, primarily 3,3 -dichlorobenzidine, and to a lesser extent 3,3 -dimethoxybenzidine (o-dianisidine), 3,3 -dimethylbenzidine (tolidine) and 2,2, 5,5 -tetrachlorobenzidine ... 

Structurally based on 3,3 -dimethoxybenzidine (o-dianisidine) as a diazo component, P.O.16 is also known as Dianisidine Orange. At present, the pigment only enjoys some importance in Europe, the USA and in Japan. 

Phenols (p-cresol, guaiacol, pyrogallol, catechol) and aromatic amines (aniline, p-tolidine, o-phenyldiamine, o-dianisidine) are typical substrates for peroxidases [90 -109]. These compounds are oxidized by hydrogen peroxide or hydroperoxides under peroxidase catalysis to generate radicals, which after diffusion from the active center of the enzyme react with further aromatic substrates to form dimeric, oligomeric or polymeric products. 

NIOSH. 1980. Health hazard alert benzidine-, o-tolidine-, and o-dianisidine-based dyes. U.S. Department of Health and Human Services. National Institute for Occupational Safety and Health. 

DHHS (NIOSH) Publication No. 81-116, Health Hazard Alert—Benzidine-, o-Toluidine-, and o-Dianisidine-Based Dyes, NIOSH Alert, Washington, DC, 1980. 

F. Blue 2B 250% (C.I. Direct Blue 6, C.I. No. 22610), Direct Brown BRL 200% (C.I. Direct Brown 95, C.I. No. 30145) Fabricolor Inc. Evans Blue (C.I. Direct Blue 53, C.I. No. 23860), Benzo Azurine G (C.I. Direct Blue 8, C.I. No. 24140) Pfaltz and Bauer Inc. Benzidine was obtained from Sigma Chemical Co., o-tolidine from Fisher Scientific Corp. and 3,3 -dimethoxybenzidine (o-dianisidine) from Eastman Kodak Company. Aniline, -aminophenol, -phenylenediamine and -nitroaniline used in the interference study were obtained from Chem Service Inc. 

This system resolved the aniline peak (retention time (rt) = 2.67 min) from the benzidine peak (rt = 2.27 min) as can be seen in Figure 2. Other potential interferences were selected for study by looking at the expected fragments from the reduction of various dyes. Reduced dye samples were spiked with aniline (rt = 2.67 min), -aminophenol (rt = 1.97 min), -phenylenediamine (rt = 1.93 min) and -nitroaniline (rt = 3 16 min). None of these materials interfered with the detection of the benzidine peak. To determine if other types of dyes might interfere with the analysis, two sets of filters were spiked at low and high levels separately with C.I. Direct Red 28 (13 7 yg and 137 yg), C.I. Direct Blue 53 formulation (o-tolidine-based) (21.2 yg and 212 yg) and C.I. Direct Blue 8 formulation (o-dianisidine-based)(23.3 yg and 233 yg). 

Figure 3. Chromatogram of a 10- injection of reduction products of a mixture of C.l. Direct Red 28 (28.8 fig), C.l. Direct Blue 53 (28.6 fig) and C.l. Direct Blue 8 (34.4 fig) showing resolution of benzidine (retention time = 2.33 min), o-dianisidine (retention time = 4.02 min), and o-tolidine (retention time = 4.27 min). Chromatographic conditions as in Figure 2.

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