Impurities of aromatic amines in the azo dye and pigment, Direct Black 38 and Pigment Yellow 12, and in vitro stability of the dye were determined. These factors can affect the results of studies designed to ascertain whether the two compounds are metabolized to potential carcinogens in hamsters. Procedures for removing impurities from the two compounds are also presented. Electron-capture gas chromatography of the heptafluorobutyryl derivatives of the impurities and degradation products was used to satisfy all the analytical requirements of the experiments. Major impurities found in Direct Black 28 were benzidine, 4-aminobiphenyl and 2,4-diaminoazobenzene; whereas, only 3,3'-dichlorobenzidine was found in Pigment Yellow 12. Stability studies of the purified dye conducted in water and in urine from hamsters and humans indicated that the dye would not degrade under the conditions used for collecting and assaying samples from a metabolism experiment. However, within 48 hours at 25 and 37.5 degrees C, the dye did degrade to known carcinogens in both hamster and human urine. Such degradation not only points out the need for proper storage of samples from metabolism studies but suggests that industrial effluents containing the dye should be properly treated before release into the environment.

3,3'-Dichlorobenzidine↗

PubMedDate not supplied

Metabolism studies of an azo dye and pigment in the hamster based on analysis of the urine for potentially carcinogenic aromatic amine metabolites.

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Animals↗

PubMedDate not supplied

Benzidine-congener-based azo dyes: assays for purity and residues in feces from dosed rats.

Analytical methods were required to determine purities of benzidine-congener-based azo dyes and residues of the intact dyes in feces from rats before valid metabolism studies of such compounds could be conducted. A procedure is described for purity assays based on reduction of the dyes with stannous chloride followed by gas chromatography of the released free amine. Sixteen different samples of commercial dyes based on three benzidine congeners were assayed; purities ranged from 26.4 to 83.4%. Several dyes were also shown to be partially purified by cold water washes. A method to determine two intact dyes in feces from dosed rats, which consisted of extraction with dimethylformamide: water, clean-up by a rapid procedure using an octadecylsilane column, and quantification by ion-pair high-pressure liquid chromatography (HPLC) is reported. minimum detectable levels of both dyes in feces are 0.2 ppm. Excretion profiles based on parallel HPLC and radioassays of feces from rats dosed with 14C-labeled Direct Blue 15 and Direct Red 2 are presented. Based on radioassays, about 74% of each dose was excreted via the feces; however, HPLC assays showed that only about 11% of each dose was present as intact dye in the excrement.

Animals↗

PubMedDate not supplied

Metabolism and distribution of two 14C-benzidine-congener-based dyes in rats as determined by GC, HPLC, and radioassays.

Absorption, metabolism and tissue distribution studies were conducted in the rat with 14C-biphenyl ring-labeled Direct Blue 15, a 3,3'-dimethoxybenzidine (DiMxBzd) based azo dye; Direct Red 2, based on 3,3'-dimethylbenzidine (DiMeBzd) and corresponding benzidine congener amines. Single oral doses of the 14C-labeled dyes (12 mg/kg, 62 microCi/kg) and molar equivalent doses of the respective amines were administered and urine and fecal samples collected at intervals up to 192 hours. Urine specimens were analyzed for 14C content and further characterized by EC/GC for free amines, acetylated metabolites, and conjugates. Feces were assayed for 14C content and for unchanged dosed dyes or amines by HPLC. A comparison of the metabolism of Direct Blue 15 with its base DiMxBzd, indicated that the base was more extensively metabolized and that most of the 14C in various extracts was identified as known metabolites. The metabolism of Direct Red 2 compared with its base, DiMeBzd, indicated that the base was more extensively metabolized, yet only a small percentage of the 14C in extracts was identified as known metabolites. Most of the 14C present in the urine could not be extracted with benzene nor chloroform, indicating high polarity. Distribution studies conducted with both dyes showed that liver, kidney, and lung accumulated and retained higher levels of 14C than other tissues (at 72 hrs). Peak levels of 14C, which occurred 8-12 hours after dosing, were significantly higher with Direct Red 2 than Direct Blue 15. Tissue distribution data (72 hr) for rats dosed with the free amines compared with the dyes showed a generally lower but similar distribution pattern.

Absorption↗

PubMedDate not supplied

Determination of tibric acid and clofibrate in animal feed, wastewater and hunan urine.

Analytical chemical procedures are described to determine residues of the drugs clofibrate and tibric acid in animal feed, wastewater, and human urine. Clofibrate was extracted from animal feed and human urine with hexane, whereas residues from wastewater were collected on a Sep-PakTM then eluted with methanol for analysis. Clofibrate residues from the feed, wastewater, and urine were analyzed by high-pressure liquid chromatography (HPLC) with minimum detectable levels (MDL) of about 40, 0.5 and 1.0 ppb, respectively. Tibric acid was extracted from animal feed with 90% methanol and 10% 0.1 N NaOH, whereas wastewater and human urine were acidified with 12 N HCl and then extracted with benzene. The MDL for tibric acid in feed by electron capture/gas chromatography (EC/GC) and HPLC were about 40 ppb and 2.0 ppm, respectively. Residues from these extracts that contained more than 5 ppm of tibric acid were analyzed by HPLC, whereas GC was required for levels below 5 ppm. The GC procedures, which required that tibric acid be derivatized (methylated) prior to analysis, had MDL of 0.1 and 1.0 ppb for wastewater and human urine, respectively. Data are also presented concerning partition values, stability of the compounds in animal feed, and recoveries of the compounds from the three substrates.

Animal Feed↗