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Determination of combined benzidine in FD & C yellow no. 5 (tartrazine), using a highly sensitive analytical method
M J Prival1, M D Peiperl, S J Bell
1Genetic Toxicology Branch (HFS-236), Food and Drug Administration, Washington, DC 20204.
Summary
Combined benzidine was detected in FD & C Yellow No. 5 (tartrazine) food dye. A new method quantified benzidine down to 5 ng/g, finding it in 25 of 53 analyzed samples.
Area of Science:
- Food Chemistry
- Analytical Chemistry
- Toxicology
Background:
- FD & C Yellow No. 5 (tartrazine) is a widely used food colorant.
- Concerns exist regarding potential contaminants in synthetic food dyes.
- Benzidine is a known human carcinogen.
Purpose of the Study:
- To develop and validate a method for detecting combined benzidine in FD & C Yellow No. 5.
- To quantify the levels of releasable benzidine in commercial samples of FD & C Yellow No. 5.
- To assess the prevalence of benzidine contamination in FD & C Yellow No. 5.
Main Methods:
- A novel method involving dithionite reduction of the dye matrix to release free benzidine.
- Extraction, diazotization, and coupling with pyrazolone T.
- Quantitation of the resulting benzidine-pyrazolone T disazo dye (BZPT) using High-Performance Liquid Chromatography (HPLC) with UV-Vis detection at 500 nm.
- Confirmation of BZPT identity using HPLC with a photodiode array detector.
Main Results:
- The developed method achieved a limit of quantitation of 5 ng/g for benzidine in FD & C Yellow No. 5.
- Combined benzidine was detected in 25 out of 53 analyzed samples (47%), with levels ranging from 7 to 83 ng/g.
- A significant proportion (23 out of 25) of the contaminated samples originated from a single manufacturer.
- Spectral analysis confirmed the identity of the BZPT in representative samples.
Conclusions:
- The study successfully developed and applied a sensitive method for detecting combined benzidine in FD & C Yellow No. 5.
- A notable percentage of commercial FD & C Yellow No. 5 samples contained releasable benzidine, indicating potential safety concerns.
- The findings highlight the importance of rigorous quality control in the production of food colorants to minimize contamination with hazardous substances like benzidine.