Flow Injection Analysis with On-Line Solid Phase Extraction for Spectrophotometric Determination of Ponceau 4R and its Subsidiary Unsulfonated Dye in Sweets and Cosmetic Products L. F. Capita Ân-Vallvey  , M. C. Valencia, and E. Arana Nicola Âs Department of Analytical Chemistry, University of Granada, 18071 Granada, Spain Abstract. An integrated solid-phase spectrophotome- try/¯ow injection analysis FIA) method is proposed for the determination of the synthetic colorant matter Ponceau 4R P4R) in the presence of its unsulfonated derivative 2-hydroxy-1-[naphthalenyl)azo] naphtha- lene N2N). The procedure is based on the measure- ment of P4R at   508, followed by retention and preconcentrationofthelowlevelconcentrationofN2N on a C 18 silica gel minicolumn and subsequent mea- surementoftheabsorbanceofN2Nat   508nmafter its elution. The applicable concentration range, the detection and the relative standard were the following: for P4R, from 0.30 to 20.0mg/L; 0.052mg/L 1.1%; and for N2N, between 0.020 to 3.0mg/L 0.003mg/L and 1.1%. The method was applied to the determina- tion of small amounts of N2N present in P4R in food and cosmetic products. Percentages of recovery be- tween95and105%wereobtainedinallinstances.The method was applied satisfactorily to the determination of the compounds P4R and N2N in samples of sweets and cosmetic products when compared to results offered by a HPLC reference method. Keywords: Ponceau 4R determination; unsulfonated Ponceau 4R determination; ¯ow injection analysis; on-line solid phase extrac- tion; sweets; cosmetic products. The analysis and monitoring of food additives that are permitted by government regulatory agencies is a major concern in many countries, largely because of reports on the toxic and/or carcinogenic effects that the use of these chemicals can cause. Most of the colorants used as additives in the food industry are synthetic products, usually azo-colorants with aromatic rings, containing sulfonic groups to ensure their solubility in aqueous media. The raw dyes used in manufacturing can contain variable amounts of by-products from the synthetic procedures such as other sulfonated derivatives, unsulfonated aromatic amines, the corresponding unsulfonated dyes and chlo- rinated derivatives of the unsulfonated dyes [1]. Many countries and health organizations have pub- lished guidelines to control the use, purity and per- mitted amounts of colorants in foods and also to specify permitted percentages of soluble and insoluble colorant materials. The amounts of impurities in raw dyes are usually limited, such that a maximum of only 0.2% of the total amount of color additive is allowed as ether soluble matter [2]. One of the synthetic sulfonated colorants widely used in the food industry is the 7-hydroxy-8-[4-sulfo- 1-naphthalenyl)azo] 1,3-naphthalenedisulfonic acid trisodium salt, commonly named Ponceau 4R C.I. 16255; E-124). It is the water-soluble colorant de- rived from the unsulfonated colorant 2-hydroxy-1- [naphthalenyl)azo] naphthalene N2N) also named Ponceau 4R Spirit Soluble. The E-124 colorant is found in the colorants which are permitted within the European Community, where their use is authorized in sweets, cakes and cookies, ice creams, syrups, delicatessen drinks and other desserts, with the daily acceptable dose DDA) Mikrochim. Acta 138, 69±76 2002)  To whom correspondence should be addressed