Synthetic colorants reverse-phase chromatography

Based on the fact that aromatic sulfonic and carboxylic acids were successfully separated by reversed-phase chromatography in the presence of organic electrolytes, Chaytor and Heal (158) developed a method for the separation of 15 synthetic colors using a mobile phase containing o-phosphoric acid (Table 7). The presence of the electrolyte provided lower variation in response and retention over a period of time. Furthermore, eluted peaks were sharper than those seen in ion-pair chromatography. 

The synthetic colorants Quinoline Yellow and Sunset Yellow are determined individually or simultaneously with other food additives by several methods, mainly spectrophotometry and chromatography. At present, the most used technique for synthetic colorants determination is liquid chromatography. The most popular reported HPLC modes applied for synthetic colorants analysis are reversed-phase chromatography (RPC), ion pair chromatography (IPC), and ion chromatography (IC). In recent years, electrochemical techniques have attracted wide attention due to their characteristics such as low operational cost, rapid and sensitive detection, selectivity, and reproducibility. 

Reverse-phase and ion-pair chromatography have been widely used for the separation and quantification of synthetic colorants. Because of the large number of dyes that may be present in food, it is preferable to use at least two quite different HPLC systems to ensure the identification of such compounds (168). 

Minioti, K. S., C. F. Sakellariou, and N. S. Thomaidis. 2007. Determination of 13 synthetic food colorants in water-soluble foods by reversed-phase high-performance liquid chromatography coupled with diode-array detector. Anal. Chim. Acta 583(1) 103-110. 

Zatar, N. A. 2007. Simultaneous determination of seven synthetic water-soluble food colorants by ion-pair reversed-phase high-performance liquid chromatography. J. Food Technol. 5(3) 220-224. 

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