▎ 摘　　要

NOVELTY - An electrochemical sensor preparing method involves preparing nano-iron oxide-graphene composite material by taking aqueous solution comprising graphene in beaker, and adding aqueous ammonia and stirring to obtain mixed solution. The pH of the mixed solution is adjusted, stopping ammonia water, adding graphene oxide solution and solution of ferrous ions. The mixed solution is allowed to stand, centrifuged, washed and dried, followed by preparing electrode tube and nano-iron oxide-graphene carbon paste electrode. The electrode is polished and placed in solution of nitric acid. USE - Method for preparing electrochemical sensor that is utilized in detection of Sudan red content in food and chili products such as chili powder and chili sauce (all claimed). ADVANTAGE - The method enables preparing electrochemical sensor with increased reliability, rapid detection effect, reduced detection cost of food Sudan red content, and increased sensitivity in a simple and eco-friendly manner. DETAILED DESCRIPTION - An electrochemical sensor preparing method involves preparing nano-iron oxide-graphene composite material by taking 50-80 ml aqueous solution comprising 1.9-2.1 mg/ml graphene in 100 ml beaker, and adding 30% aqueous ammonia and stirring at a stirring speed of 40-60 rpm to obtain mixed solution. The pH of the mixed solution is adjusted to 11 by using pH meter, stopping ammonia water, adding graphene oxide solution and 49.5-50.5 mg/ml solution of ferrous ions at a stirred speed of 40-60 rpm for 1.5-2.5 hours. The mixed solution is allowed to stand for 20-28 hours, and centrifuged at speed of 8000 rpm for 25-35 minutes. The centrifuged solution is washed for 10-20 minutes. The solution is dried at 50-60 degrees C till moisture content of less than 1% to prepare nano-iron oxide-graphene composite material, followed by preparing electrode tube by taking short tube with diameter of 2-5 mm and length of 3-5 cm, using sand paper to polish the ends of short tubes till both ends of the tube is smoothened, to obtain the electrode tube, preparing nano-iron oxide-graphene carbon paste electrode by mixing 8 mg composite material with 60-65 mg graphite powder and 21-23 mg paraffin oil to obtain an electrode material. The electrode material is added to 2/3 of the electrode tube, and compacted under pressure of 0.75-0.85 MPa, followed by filling copper in the tube to obtain nano iron oxide-graphene electrode. The electrode is polished by using mirror-smooth paper and placed in solution of nitric acid having pH of 3 for 11-13 hours to obtain a finished product. An INDEPENDENT CLAIM is also included for a method for detecting Sudan red content in food.