Benzidine-based Dyes

Benzidine-based dyes Benzidine hydrochloride Benzidines Benzidine Yellows AAMX Benzil [134-81-6]... 

Other mechanisms Dibutyl phthalate Benzidine-based dyes Vinylcyclohexene... 

EH34 Benzidine based dyes health and safety precautions. 

Benzidine-based dyes Benzo Azurine G Benzo(a)fluoranthene Benzo(b)fluoranthene Benzo(j)fluoranthene Benzo(k)fluoranthene Benzo(g,h,i)perylene Benzopurpurine 4B Benzo(a)pyrene Benzo(c) pyrene Benzo(e) pyrene Benzosulphonazole Benzothiazole Benzoyl peroxide Benzyl chloride Beryllium... 

Kalme SD, Parshetti GK, Jadhav SU, Govindwar SP (2007) Biodegradation of benzidine based dye Direct Blue-6 by Pseudomonas desmolyticum NCIM 2112. Bioresour Technol 98 1405-1410... 

One of the major uses of 1,2-diphenylhydrazine is as a starting material in the production of benzidine however, it is no longer produced in the United States. 1,2-Diphenylhydrazine rearranges to benzidine upon treatment with strong acid benzidine is used by the dye industry for the production of benzidine-based dyes including many of the Direct dyes (e.g.. Direct Red 28, Direct Black 4, Direct Blue 2) (Ferber 1978 Lurie 1964). Fabricolor, the last producer of benzidine based dyes, discontinued production in 1988 (Personal communication, Alvarez 1989). 

The available database limits analysis of exposures in two ways. First, very little information is available concerning the manufacturing processes used in the production of phenylbutazone and sulfinpyrazone, the two drugs that use 1,2-diphenylhydrazine as a starting material. A better understanding of these processes would allow the estimation of worker exposure potentials. Second, dye manufacturers in the United States no longer produce benzidine based dyes (the last manufacturer stopped production in 1988) and the number of workers potentially exposed to... 

In metabolism studies of azo dyes and pigments in the hamster, in vivo cleavage of the benzidine-based dye, Direet Black 38, to benzidine was shown by analysis of the urine. However, studies of the 3,3 -diehlorobenzidine-based pigment. Pigment Yellow 12, showed no evidenee for in vivo cleavage to release 3,3 -diehlorobenzidine (Nony et al. 1980). 

NIOSH, in 1980, concluded that dming the use of benzidine-based dyes, the greatest potential for exposme would be expected to be by dermal absorption or inhalation by personnel who routinely handle dry powders (NIOSH 1980). However, EPA (1980b) has generalized that dermal absorption in the workplace is probably a minor route of 3,3 -dichlorobenzidine exposure, although dermatitis has occurred in workers in plants where 3,3 -dichlorobenzidine and 3,3 -dichlorobenzidine-based pigments were manufactured. It may be that health risks with regard to 3,3 -dichlorobenzidine exposme depend on the specific operations of the individual plant and the extent of personal protective practices of the individual operator. 

Direct Black 38 (see also Benzidine-based dyes) Direct Blue 6 (see also Benzidine-based dyes) Direct Brown 95 (see also Benzidine-based dyes) Disperse Blue 1 Disperse Yellow 3... 

Development of an Analytical Method for Benzidine-Based Dyes... 

The only published method available for the determination of personal exposure to benzidine-based dyes utilized the analysis of urine for benzidine and benzidine metabolites (JO, J 1 ). This method does not allow for quantitation of a daily exposure, since benzidine and its metabolites have been found in the urine of hamsters fed a benzidine-based dye up to 168 hours after a single dosing (J 2). A method for the determination of personal exposure to azo dyes and diazonium salts has been developed (J 3), but it is not specific enough to determine an exposure to a benzidine-based dye. 

In the development of a sampling and analytical method for benzidine-based dyes, the most important feature was the verification of the benzidine moiety in the dye molecule. 

Specificity for a particular dye was not reasonable due to the large number of benzidine-based dyes and the possibility of dye substitution. The method should provide quantitative collection and recovery at the microgram level and be free... 

The analysis method was evaluated with four different benzidine-based dye formulations (Figure 1). The results of a repeatability study utilizing spiked samples are shown in Table III. Spiking levels were arbitrarily chosen but do reflect the lower limit of the method. 

Table III Recovery of Benzidine from Benzidine-Based [ Dye Filter...

Evaluation of the Stability of Filter Samples Containing Benzidine-Based Dyes Stored Up to Twenty-Eight Days... 

Since the method did not differentiate between benzidine-based dyes, one LAQL was necessary for the method. By utilizing the 30—jjg level as the LAQL, reduction and analysis in the working... 

Since the method does not distinguish between various benzidine-based dyes and analytically pure dyes are not easily available, recovery correction factors cannot be used. This will cause the results to be equal to or below the true level of dye exposure. 

This method has been used to analyze both symmetrical (C.I. Direct Red 28 and C.I. Direct Blue 6) and unsymmetrical (C.I. Direct Black 38 and C.I. Direct Brown 95) benzidine-based dyes. Based on this work, the application of the method to other benzidine-based dyes should be straightforward. When field samples are submitted for benzidine-based dye analysis, bulk samples of the dyes present in the sample also should be submitted. With these bulk samples, the analyst should be able to determine if this method is applicable to the various dyes submitted and if any interferences are present. The method presently has not been tested on field samples. An existing sampling method (J 3) for azo dyes and diazonium salts should be directly applicable to this method with a change from a cellulose ester to a Teflon filter. This change is necessary to insure quantitative recovery of the sample from the filter. 

In summary, a method for the identification and quantification of benzidine-based dye containing samples has been developed. This method could be expanded to include samples taken from media other than air with minor modification, for instance, in assaying benzidine-based dye formulations at the microgram level. 

A method for the determination of personal exposure to benzidine-based dyes has been developed. This procedure involved the reduction of benzidine-based dye filter samples to free benzidine with neutral buffered sodium hydrosulfite solution. The benzidine-containing reduction solution was then analyzed by high performance liquid chromatography. The reduction was found to be quantitative by visible-spectrum analysis. This reduction and analysis method was evaluated with four benzidine-based dyes over the range from 12 to 300 micrograms per sample. Precision for the reduction and analysis of the four dyes falls within % coefficient of variation. This method can differentiate between benzidine-and benzidine congener-based dyes. Results are reported in terms of free benzidine. 

Since workers can be exposed to these compounds during their manufacture and use, it is important to have reliable analytical methods for determining the degree of exposure through body fluid analysis. Additionally, since these compounds can be present at significant levels in commercial products (derived from them) it is desirable to monitor their level in such products (e.g. dyestuffs) as well. Furthermore, many of the commercial products can be metabolized to the original chemical (e.g. benzidine based dyes can be metabolized to benzidine) making it desirable to monitor the body fluids of workers exposed to the commercial products. 

Two experiments were conducted to study the utility of HPLC in determining aromatic amines in commercial dyes. In the first experiment a benzidine based dye, Direct Blue 6, and a commercial hair dye formulation containing Direct Blue 6 were analyzed for benzidine. In the second experiment a DCB based pigment (diarylide yellow) was analyzed for residual DCB. 

Determination of Benzidine in Hair Dyes. Experiments were conducted to determine whether or not benzidine could be detected in benzidine based dyes and/or hair dye products containing benzidine based dyes. The benzidine based dye Direct Blue 6 was obtained commercially as were two shades of a particular hair dye product. One shade, "Lucky Copper , contained Direct Blue 6 whereas another shade, Silver Lining", did not contain any benzidine based dyes. 

Figure 6. Chromatogram for extract of commercial hair dye formulation not containing benzidine-based dyes...

Azo dyes made from 47, and also their cleavage products from azo reduction, are appreciably less genotoxic than the corresponding benzidine-based dyes. An example is the mutagenic (and carcinogenic) benzidine-based dye Direct Violet 43 (48) and its corresponding isosteric analog (49), in which the benzidine moiety is replaced with 47. Other examples are available [84]. 

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