Absorption, Distribution and Excretion
Urine samples of 18 workers in a small scale unit manufacturing Direct Black 38 were /determined/ by high-pressure liquid chromatography for the presence of benzidine and mono and diacetyl benzidine. Acetylated metabolites were found in all the urine samples, and benzidine was found in all except two. Two workers excreted very high levels of benzidine and its metabolites in their urine. This study highlights the potential risk of bladder cancer in such units of developing countries where manufacture of benzidine based dyes is yet to be regulated.
The time course of dermal absorption of two azo dyes was investigated in rats and rabbits. A benzidine derived dye, CI Direct Black 38 and a related dye CI Direct Black 19 which contained a p-phenylenediamine moiety instead of benzidine, were employed. Specific pathogen free male New Zealand white rabbits and male Fischer 344 rats were shaved on the left dorsum and radiolabeled dye was applied to a 2 centimeter by 2 centimeter area. ... Radioactivity from CI Direct Black 38 treated rats appeared in urine and feces in negligible quantities. Cumulative excretion of radioactivity at 144 hours was 0.05% of the total dermal dose in the urine and 0.16% in the feces. Cumulative excretion of radioactivity from CI Direct Black 38 dosed rabbits was higher at 144 hours: 3.12% of total dermal dose in urine and 5.12 in feces. At 144 hours excretion of radioactivity from CI Direct Black 38 dosed animals of both species was still increasing. ... CI Direct Black 38 is less stable on rabbit skin under experimental conditions than CI Direct Black 19, although differences in skin permeability and microflora may be partially responsible

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Metabolism / Metabolites
SINGLE DOSE (100 MG/KG) OF PURIFIED DIRECT BLACK 38 ADMIN TO HAMSTERS REVEALED BY URINE ASSAY HIGH LEVELS OF BENZIDINE, MONOACETYLBENZIDINE, DIACETYLBENZIDINE, 4-AMINOBIPHENYL, & ALKALINE HYDROLYZABLE CONJUGATES OF BENZIDINE & 4-AMINOBIPHENYL DURING 1ST 8 HR OF EXCRETION
DIRECT BLACK 38 WAS SHOWN TO BE METABOLIZED IN ANIMALS TO HUMAN CARCINOGEN BENZIDINE.
Caution is also indicated by preliminary results from the NIOSH field studies showing that humans working with these same dyes /Direct Black 38, Direct Brown 95, and Direct Blue 6/ also excrete higher than expected levels of benzidine in their urine. Both laboratory and field studies indicate that these benzidine derived dyes can be metabolized to benzidine, which is present in the urine of animals and humans. Based on the data from the short-term study, National Cancer Institute scientists believe that a cancer causing potential exists on exposure to the benzidine derived dyes, most likely through the mechanism of metabolic conversion of the dyes to benzidine in the animal system.
Benzidine and monoacetylbenzidine were found in the urine of rats and mice on the course of 13-week subchronic toxicity studies with Direct Black 38. Analysis of 24-hour urine samples 4 and 12 weeks (rats) and 3 and 11 weeks (mice) later showed a clear-cut relationship between the concentration of dyestuff in the food consumed and the amount of benzidine excreted. Mice biotransformed considerably more dye to benzidine than did rats.
For more Metabolism/Metabolites (Complete) data for C.I. DIRECT BLACK 38 (10 total), please visit the HSDB record page.

Toxicity Data
LCLo (rat) = 180,000 mg/m3/1h

[1]. Beije B. Induction of unscheduled DNA synthesis in liver and micronucleus in bone marrow of rats exposed in vivo to the benzidine-derived azo dye, Direct Black 38. Mutat Res. 1987 Apr;187(4):227-34.

Direct Black 38 (Technical Grade) can cause cancer according to an independent committee of scientific and health experts.
C.i. direct black 38 appears as gray-black microcrystals or black powder. (NTP, 1992)
CI Direct Black 38 is a Benzidine-based azo dye that is metabolized to free Benzidine in vivo. Direct black 38 is primarily used for the dyeing of textiles, leather and paper. Benzidine and its metabolic derivatives have been detected in the urine of workers exposed to Benzidine-based dyes. Exposure to this dye is strongly associated with the occurrence of bladder cancer. (NCI05)

C34H25NA2O7S2

781.7295

781.111

1937-37-7

Direct Black 38 free acid;22244-14-0

5284349

Light brown to black solid powder

1.61g/cm3

109-110°C

1.768

11.918

4

16

7

54

1460

0

XRPLBRIHZGVJIC-UHFFFAOYSA-L

InChI=1S/C34H27N9O7S2.2Na/c35-22-10-15-27(26(36)18-22)41-38-24-11-6-19(7-12-24)20-8-13-25(14-9-20)40-42-32-28(51(45,46)47)16-21-17-29(52(48,49)50)33(34(44)30(21)31(32)37)43-39-23-4-2-1-3-5-23;;/h1-18,44H,35-37H2,(H,45,46,47)(H,48,49,50);;/q;2*+1/p-2

disodium;4-amino-3-[[4-[4-[(2,4-diaminophenyl)diazenyl]phenyl]phenyl]diazenyl]-5-hydroxy-6-phenyldiazenylnaphthalene-2,7-disulfonate

NSC-47756; NSC 47756; C.I. Direct Black 38

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~25 mg/mL (~31.98 mM)
H2O : ~5 mg/mL (~6.40 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (3.20 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (3.20 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: 3.85 mg/mL (4.92 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

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 (Please use freshly prepared in vivo formulations for optimal results.)