Determination Of Direct Red Dye In Food By Solid Phase Extraction-Ultra High Performance Liquid Chromatography

Pigment is used in great quantities in the food, its main purpose is to improve the sensory properties of food, improve the appetite of consumers and it is an integral part of modern food industry. Due to the low price of synthetic pigment and excellent color strength, it is widely used in food in recent years. There are some kinds of artificial synthetic pigments was allowed to be added to food in GB2760-2011,such as erythrosine, citric yellow, bright blue, indigo, amaranth, carmine, temptation red, sunset yellow, new red, azorubin and so on. Most industrial dyes are azo compounds, were confirmed to the human body has a certain degree of teratogenic, carcinogenic, mutagenic hazards. So industrial dye is explicitly prohibited to add into food. However, food manufacturers add industrial dye into food illegally in recent years for the pursuit of greater benefits, food safety incidents have been reported frequently, such as Sudan dyes, rhodamine B, Acid Orange, basic orange, disperse dyes and other incidents have been reported.Direct red dye is a kind of bright red synthetic azo compound, commonly used in industrial dyeing, medicine clinical diagnosis, biological stain and chemical indicator. However, there are evidence that direct red dye is certain carcinogenic to the human body, so it is strictly prohibited in many countries used as colorant in food. Because detection method of Sudan red, rhodamine B, basic orange has been established, food manufacturers may have begun to shift to other types of red dye. Direct red Ⅱ, Congo red’s price is low and widely used, so it is necessary to establish a sensitive, accurate and rapid detection method of direct red dye in food.This paper focuses on the detection of direct red dye in food, solid phase extraction-ultra high performance liquid chromatography (UHPLC) method have used to analysis the direct red dye and the most common synthetic pigment of red, yellow in food, satisfactory results have been achieved.In this paper the main contents: 1. A determination of direct red dye in food by solid phase extraction-ultra high performance liquid chromatography was established. Direct red in oily food was extracted by ammonia:ethanol=30:70(V/V), ultrasonic assisted heating for extraction for3times and combined with HLB extraction column for purification. The mobile phase to volume after drying with nitrogen, filtered by0.22u m PTFE membrane and detected by UPLC. Direct red in wine samples was extracted with acetonitrile/water-sodium chloride tiered system for two times,combined acetonitrile layer and detected by UPLC.Under the condition of acetonitrile-10mmol/mL ammonium acetate as mobile phase and gradient elution, direct red Ⅱ, direct red was separated within4min by Acquity UPLC BEH C18column (50mm x2.1mm,1.7μm). The detection wavelength was498nm and flow rate was0.4mL/min. Column temperature was20℃. Dye’s recovery was over the range of72.1%-96.6%with relative standard deviation2.16%-5.97%(n=6), the detection limit of direct red Ⅱ and congo red was0.041mg/kg and0.029mg/kg, the correlation coefficient of linear equations were0.9999. The method is simple, rapid, accurate, sensitive and suitable for detecting direct red Ⅱ and congo dye in food.2. The established method’s applicability of common red, yellow synthetic pigment was studuied. The results show that five common synthetic pigments (Red2G, amaranth, carmine, sunset yellow, erythrosine) can be separated in this condition within4min. The correlation coefficient of linear equations was over the range0.9993to0.9999, the recovery was86.2%-95.1%.Detection limit of amaranth, carmine, sunset yellow, Red2G, erythrosine was0.026mg/kg、0.025mg/kg、0.019mg/kg、0.020mg/kg、0.038mg/kg. The method is high sensitivity, the peak time is shorter, is a rapid and simple determination of synthetic pigment in food, satisfactory results were obtained.3. The established solid phase extraction-ultra high performance liquid chromatography (UHPLC) analysis method were applied successfully to different food samples from different markets, statistical analysis of direct red and common synthetic pigments in food was acquired. Common synthetic colorants detection rate is13.6%, its all did not exceed national standard, direct red dye in all samples were not detected, it shows that direct red dye may not illegally added temporarily to food in this city.