DETERMINATION OF COMBINED BENZIDINE IN FD-AND-C YELLOW NO-5 (TARTRAZINE), USING A HIGHLY SENSITIVE ANALYTICAL METHOD

53 samples of FD & C Yellow No. 5 (tartrazine; Colour Index No. 19140) were examined for combined benzidine. These samples, which represent separate lots from 12 dye distributors, were submitted to the US FDA f or certification between 28 February 1990 and 27 June 1991. A method w as developed to reduce the dye matrix with dithionite so that combined benzidine present in the form of azo or disazo dyes would be converte d to free benzidine. Reduction was followed by extraction, diazotizati on and coupling with pyrazolone T, and the total benzidine present was quantitated as benzidine-pyrazolone T disazo dye (BZPT) by HPLC with detection at 500 nm. The limit of quantitation for benzidine in FD & C Yellow No. 5 by this method is 5 ng/g. 25 samples of FD & C Yellow No . 5 were found to contain 7-83 ng/g of combined benzidine that was rel eased by dithionite reduction. 23 of these samples were from the same manufacturer. The identity of the BZPT from two FD & C Yellow No. 5 sa mples was confirmed by spectral analysis using HPLC with a photodiode array detector.