Study On Rapid Electrochemical Determination Of Contraband Food Pigment Addictives

A sensitive and convenient method was developed for the electrochemicaldetermination of Sudan I by using an expanded graphite paste electrode（EGPE）. Due to the multiporous structure and large specific surface area ofthe EG, the EGPE showed high electrocatalytic activity toward the oxidationof Sudan I. Under optimal experimental conditions, the EGPE exhibited awide linear response to Sudan I ranging from5×10-9to7.0×10^-6M with a lowdetection limit down to0.9nM （S/N=3）, which is remarkably lower thanthose reported previously using other modified electrodes. The assay resultsof Sudan I in ketchup and chilli sauce samples obtained by the proposedmethod were in a good agreement with the reference values detected byHPLC. The proposed method provided a useful tool for the assay of Sudan Iin food samples.A sensitive and convenient electrochemical method was developed for thesimultaneous determination of the isomers of Ponceau4R and Amaranth byexpanded graphite paste electrode （EGPE）. Compared with flake graphitepaste electrode and carbon paste electrode, the EGPE showed higherelectrocatalytic activity toward the oxidations of Ponceau4R and Amaranth.Under optimal experimental conditions, the EGPE exhibited wide linearresponses to Ponceau4R and Amaranth ranging from6.0×10^-8to4.0×10^-6Mand8.0×10^-8to4.0×10^-6M, respectively, and the detection limits for Ponceau4R and Amaranth were2and36nM at a signal-to-noise ratio of3,respectively. The designed electrode showed good accuracy, precision andreproducibility. The proposed method was successfully applied in thedetection of Ponceau4R and Amaranth in grape wine samples.An ionic liquid （IL）1-Butyl-3-methylimidazolium hexafluorophosphate（[BMIM]PF6） modified expanded graphite paste electrode （EGPE） wasfabricated and used for the simultaneous determination of Sunset yellow （SY）and Tartrazine （Tz）. Due to excellent conductivity and fast electron transfer ofthe [BMIM]PF6, the IL modified expanded graphite paste electrode （IL-EFPE）showed a strong enhancement effect on the oxidations of SY and Tz, and the current signals were greatly increased. This novel IL-EFPE exhibited veryattractive properties such as high sensitivity and selectivity, high stability andlow background current. Under optimal experimental conditions, the peakcurrents of square-wave stripping voltammetry （SWSV） response increasedlinearly with concentrations of SY and Tz over the ranges of1.0×10^-8-5.0×10^-6M and5.0×10^-8-5.0×10^-6M with the detection limits of5.4×10-10and1.35×10^-9M, respectively, which are remarkably lower thanthose reported previously using other modified electrodes.