Analytical Methods A simple and portable multi-colour light emitting diode based photocolourimeter for the analysis of mixtures of five common food dyes Mohammad-Hossein Sorouraddin a,⇑ , Ali Rostami b , Masoud Saadati a a Analytical Chemistry Department, Faculty of Chemistry, University of Tabriz, Tabriz, Iran b School of Engineering-Emerging Technologies, University of Tabriz, Tabriz, Iran article info Article history: Received 9 January 2010 Received in revised form 16 October 2010 Accepted 30 December 2010 Available online 8 January 2011 Keywords: Food dyes Double-beam photometer Light emitting diode Simultaneous determination Absorbance ratio abstract A simple and cheap spectrophotometric method for the simultaneous determination of Tartrazine, Quin- oline Yellow, Sunset Yellow, Carmoisine and Brilliant Blue in commercial food products with the aid of a portable double beam photocolourimeter are described. The method is based on the difference of the absorptivity ratios at maximum absorbances of two compounds or three compounds. The proposed device uses red–green–blue light-emitting diode as light source and light dependent resistor as detector. A programmable microcontroller sequentially turns the emitters on, receives the signals followed by cal- culating the absorbance and displaying it on a liquid–crystal display. The photometer is capable of per- forming absorbance measurements in a single wavelength as well as in three wavelengths sequentially, allows its application in simultaneous analysis of binary and ternary mixtures based on the differences of absorbance ratios in two and/or three wavelengths. The method was validated against a standard HPLC method and the results obtained were in a good agreement with those of HPLC method. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The use of synthetic additives in general and colours in partic- ular in commercial food products has recently increased consider- ably. The criteria for the quality of food products are, apart from microbiological aspects, generally based on the colour, flavour, tex- ture and nutritive value. However, one of the most important sen- sory qualities of a food product is the colour and the synthetic dyes monitoring. Tartrazine, Quinoline Yellow, Sunset Yellow, Carmoi- sine and Brilliant Blue are the five food additive dyes that may be present in common food products as individually or together to restore a wide range of colours including yellow, orange, red, green, blue, purple, brown, etc. The numerous works published during the last years demonstrate the importance of this problem and the need for developing fast, accurate and selective techniques for synthetic dyes analyses. The most common analytical techniques that frequently used for the determination of colours are: chromatographic methods (Kucharska & Grabka, 2010), high performance liquid chromatog- raphy (Alves, Brum, Andrade, & Netto, 2008; Garcia-Falcon & Si- mal-Gandara, 2005; Minioti, Sakellariou, & Thomaidis, 2007), differential pulse polarography (Chanlon, Joly-Pottuz, Chatelut, Vittori, & Cretier, 2005; Combeau, Chatelut, & Vittori, 2002), photoacoustic spectroscopy (Coelho et al., 2010), voltametric methods (Lin, Li, & Wu, 2008; Mo et al., 2010), capillary electropho- resis (Mejia, Ding, Mora, & Garcia, 2007; Berzas, Cabanillas, & Sal- cedo, 1999; Del Giovine & Bocca, 2003), solid-phase extraction method (Al-Degs, El-Sheikh, Al-Ghouti, Hemmateenejad, & Walker, 2008), and various combinations of these techniques (Breithaupt, 2004; Chailapakul et al., 2008; Murty, Chary, Prabhakar, Raju, & Vairamani, 2009). Most of these methods require a highly qualified operator and high cost instrumentation. Dyes are highly absorbing species in the visible region, hence methods based on this property is most useful for quantitative analyses of food dyes. However, severe absorption spectra overlap- ping is common in mixture sample analyses by means of these methods, therefore, the direct absorption measurement is not of- ten suitable for determining the dye mixtures without a need for a treatment step. Several spectrophotometric methods have been used for the determination of mixtures of food dyes with overlap- ping spectra without preliminary separation. Democratic phase coherent data-scatter (McMillan et al., 2004), Vierordt’s method (Altınoz & Toptan, 2002), hybrid linear analysis (Al-Degs, 2009), multivariate classification techniques (Di Anibal, Odena Ruisán- chez, & Callao, 2009), derivative spectrophotometry (Altınoz & Toptan, 2003; Berzas, Flores, Cabanillas, Llerena, & Salcedo, 1998), multivariate curve resolution-alternating least squares (Lla- mas, Garrido, Di Nezio, & Band, 2009), and different chemometrics methods (Berzas, Flores, Llerena, & Farinas, 1999; Ni, Wang, & Ko- kot, 2009) are the most reliable methods. Although the develop- ment of these methods is significant advances in multi- 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.12.124 ⇑ Corresponding author. Tel.: +98 411 3393082; fax: +98 411 3340191. E-mail address: soruraddin@tabrizu.ac.ir (M.-H. Sorouraddin). Food Chemistry 127 (2011) 308–313 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem