The outbreak of "melamine" in 2008 has made food safety in milk and dairy products the focus of attention. In addition to melamine, milk and dairy products iodide and thiocyanate also need to focus on. Iodine is the first trace of essential elements found in humans, the human body's mental development and physical development has a very important role in inadequate intake or excessive intake can cause goiter disease, the body generally through dairy products, iodine Salt and seafood to obtain iodine. Milk naturally contains a certain thiocyanate, with a certain anti-corrosion effect. Some illegal dairy farmers use this excessive addition of thiocyanate, a great threat to human health. In 2008, the Ministry of Health announced that "the list of food additives that may be illegally added in food and the list of easy-to-eat food additives (first installment)" list clearly stipulates that thiocyanates in milk and dairy products are illegal additions, but There is no national standard testing method. Iodide and thiocyanate have ionic properties and can be detected using ion chromatography. Import instrument manufacturers generally use KOH gradient leaching, the instrument is expensive, iodide and thiocyanate retention time is greater than 40min. In addition, there are ways to add organic solvent to the mobile phase of the method to keep the thiocyanate retention time ahead, but the organic solvent volatile, toxic to the human body. The use of domestic ion chromatography and amperometric detection, the two substances can be eluted in 5 minutes and detection, sensitivity and imported equipment quite obvious advantages.
Pretreatment program: accurately remove 10ml of a brand of liquid milk in 100ml polypropylene beaker, add 10ml 3% acetic acid and 5ml water mixture, ultrasonic extraction 20min. The liquid was centrifuged at 4000 r / min for 30 min. The supernatant was analyzed by solid phase extraction and 0.22 mm needle filtration.