INTRODUCTION:

A dye is a colored substance that has an affinity to the substrate to which it is being applied. Dyes are one form of color additives which are used in foods and are soluble in water but not in oil. Dyes are products in various forms such as liquids, powders and granules. Sudan III is a synthetic azoic dye that is widely used in industry because of their colorfastness and low price. They have dangerous properties that’s why sudan dyes have been banned in products for human consumption in the European Union and several other countries. Notwithstanding, these dyes are often illegally used to enhance the appearance of products such as chili, tomato sauces, salami, olive oil, and many other frequently eaten foodstuffs.

In fact, repeated notifications about the detection of these illegal additives in imported foods have been issued by the European Union Rapid Alert System for Food and Feed since 2003. In particular, the discovery of Sudan III in products from India promoted the European Commission to make a decision on emergency measures concerning Sudan III in food products intended for human consumption¹.

The detection limit for the substances at 0.5-1.0 mg/kg^2-3. The analytical techniques frequently employed for the determination of the colors include thin layer chromatography⁴, capillary electrophoresis⁵, HPLC coupled with photodiode array⁶, chemiluminescence⁷, electrochemical with carbon nanotube modified electrodes⁸ and inter-laboratory comparison⁹.

In all instances, most of these methods require a highly qualified operator and high cost instrumentation. Thus, a highly sensitive and low cost method is still needed for the development in the field of analytical chemistry. So, Sudan III dye has been determined by spectrophptometric methods after preconcentation using β-CDP in food samples.

Supramoleculer complexes with β- cyclodextrin has been a very active research field in the past few years^10-11. β- cyclodextrin (β-CD) is a very stable oligosaccharide that is composed of seven glucose units linked with each other by α-(1,4)-glycosidic linkage. It can form supramoleculer complexes with several organic compounds by incorporating them into their hydrophobic cavities. Two or more β-cyclodextrin covalently linked with each other are known as polymers. These β- cyclodextrin polymer have been used for the preconcentration of various analytes^12-15. In the present work, β-cyclodextrin epicholorohydrin polymer (β-CDP) has been used as a solid support for the preconcentration of Sudan III dye.

EXPERIMENTAL:

A Shimadzu UV-1800 spectrophotometer (Shimadzu Ltd., Japan) equipped with the matched 10 mm quartz cells was used to measure absorbance. Digital century pH-meter Cp - 901 with a combined glass electrode was used to carry out pH measurements. A thermostatic shaking water bath (Perfit India Ltd.) was used to carry out all the inclusive procedures.

Reagents:

All chemicals used were of AnalR grade unless otherwise stated. Double distilled water was used throughout the experiment. Brilliant green dye solution was prepared by dissolving 0.248 g in 100 mL of double distilled water to give 0.01 M standard stock solution and further diluted as and when required. β-CDP was synthesized by method given in Literature (1^a). A brief procedure is given here: 40g of β-CD, 10 g of soluble starch and 100 mL of 20% sodium hydroxide were added into a beaker. The mixture was vigorously stirred at 50-60ºC until the reactants dissolved. Total 60 mL of epichlorohydrin was added drop wise into the solution, and β-CDP was formed in 30 min. Filtered with pressure through Buchner funnel and then washed with distilled water 5-6 times, the polymer was dried at 100ºC and then stored at room temperature in the desiccators for further use.

Buffer solution in the pH range of 2.0-3.5 were made by mixing equimolar solutions of hydrochloric acid/Sodium Acetate and buffer solutions in the pH range of 4.0-6.5 were made by mixing equimolar solutions of sodium acetate and acetic acid solutions in the different proportions While those in the pH range of 7.0-11.0 were made by mixing equimolar solutions of ammonia and ammonium chloride. The glass wares were washed with chromic acid and soaked in 5% nitric acid and then cleaned with double distilled water before use and dried in an electric oven.

Procedure:

300 mg of β-CDP and 2.5 mL of buffer solution (pH 4.0) were added to a 100 ml stoppered conical flask at room temperature. The mixture was allowed to stand for 15 min. so that β-CDP should swell sufficiently and an appropriate amount of dye was added and made up to 75 ml with double distilled water. The mixture was shaken in the thermostatic shaking water bath for 75 min. at a rate of 120 r.p.m. agitation speed. 5.0 ml of supernatant solution was transferred into a test tube and the absorbance was measured spectrophotometrically.

Optimization of various parameters:

Effect of Ph:

The formation of inclusion complex of the dye in the polymer depends on the pH of the sample solution which was studied in the range of (1.0-7.0) using different buffer solutions. % uptake (≥ 95) was obtained at pH 4.0. (Fig.3). Therefore, the working pH was chosen as 4.0 for the subsequent studies.

Effect of shaking time:

Shaking time is an important factor in determining the possibility of application of the β-CD polymer for the selective uptake of Sudan III dye. Different shaking time (ranging from 15 to 120 min) were studied for the % uptake of Sudan III dye by β-CD polymer. The results of % uptake of Sudan III dye vs. the shaking time show that the % uptake of (≥95%) was attained within 75 min. (Fig. 4). Therefore, the shaking time of 75 min. was selected for further studies.

Effect of sample volume:

Enriching low concentration of dye from large volume of sample the effect of sample volume is an important factor in determining the possibility of application of polymer for the % uptake of Sudan III dye. For this purpose 15, 30, 45, 60, 75 and 90 mL of sample volumes containing a fixed amount of dye were take and uptake of Sudan III dye was studied (Fig.5). The maximum % uptake (≥95%) of Sudan III dye was found with sample volume of 75 mL. Therefore, 75 mL of sample volume was used for further studies.

Effect of agitation speed:

Shaking speed is an important factor in determining the possibility of application of polymer for the quantitative % uptake of Sudan III dye. The driving force i.e shaking speed could help in mass transfer and facilitate the concentration gradient between the sample solution and the polymer. Different speeds (ranging from 40 to 140 r.p.m) were studied for the % uptake of Sudan III dye by polymer. The results of % uptake of Sudan III vs. agitation speed (Fig.6) shows that the % uptake was maximum (≥95%) at 120 r.p.m. Therefore, the shaking speed of 120 r.p.m. was selected for further studies.

Effect of amount of polymer:

The amount of the β-CD polymer is another important parameter that affects %uptake of dye. A quantitative removal (≥95%) cannot be achieved when the β-CD polymer is less than the optimum amount. In order to optimize the smallest amount of polymer, 100 mg, 200 mg, 300 mg, 400 mg and 500 mg of the polymer were added to the solution containing known amount of dye. The quantitative recoveries were obtained at 300 mg of β-CDP (Fig. 7). Therefore, 300 mg of the β-CDP has been used for further studies.

Applications:

Determination of samples:

The proposed method has been applied for the determination of Sudan III dye in Navratan oil and Curry paste. The results are given in table.

CONCLUSION:

The proposed preconcentration method consist of a simple and low procedure which permits the quantitative recovery of Sudan III dye from food samples. The synthesis of the polymer is easy and the method has a good accuracy, sensitivity and repeatability. The polymer has been used in all the experiments performed for the study. It has a unique stability and reusability. This method is convenient for the determination of Sudan III dye.

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Received on 07.09.2017 Modified on 11.10.2017

Asian J. Research Chem. 2017; 10(6):810-812.

DOI: 10.5958/0974-4150.2017.00135.3