Modification of the Standard Method for Determination of Sudan Red in Foodstuffs

As described in the standard method(GB/T 19681-2005 HPLC Determination of Sudan Red Dyes in Foodstuffs),the sample is finally dissolved in acetone after pretreatment,and standards of the sudan red dyes are dissolved in n-hexane.It was found that in the HPLC determinations,significant differences of values of retention time tR and peak area were found for sudan red dyes of same concentration but in different solvents(e.g.in n-hexane or in acetone),and that remarkable deviations were obtained in both qualitative and quantitative testings as different solvents were used in dissolving sample and standards.As a modification,it was proposed that the n-hexane solutions of standard sudan red dyes should be converted to acetone solutions before they are used for preparation of standard curves.By this modification,the correlation coefficients obtained were over 0.999 for linearity range of 0.15-4.0 mg·L-1 of either the sudan red dyes,and values of RSD′s obtained were less than 5%,as well as values of recovery larger than 90%.