Study On Determination Of Thiocyanate In Milk By IC And HPLC

Adding sodium thiocyanate in the milk can effectively restrain bacterial growth and extend shelf life of milk. But sodium thiocyanate is poisonous. Eating little sodium thiocyanate can damage to the people's health. In December 2008, government announced that sodium thiocyanate couldn't be used in food. But there is no standard method to detect sodium thiocyanate in our country.Chromatographic analysis has been widely used in food safety inspection due to its characteristics of speediness, convenience, good selectivity and high sensitivity. This paper established a new, fast and accurate method to detect sodium thiocyanate in milk by IC and HPLC. This method simplifies the sample processing.Through the research on the sample processing method, chromatographic conditions of IC and HPLC and the limit ,precision, linear range of the measuring method, we get the results:1. Acetone or acetonitrile is used to precipitate the milk protein. Thiocyanate is extracted by liquid-liquid extraction method. Then by ultrasound, centrifuge and filtration, sample solution can be determined directly.2. Conditions of IC: Column: Metrosep A Supp5; Detector: Conductivity detector; Eluent: 7mmoL/L Na2CO3+1mmoL/L NaHCO3+10% Acetone; Flow Speed: 0.7 mL/min; Volume: 20μL.3. Conditions of the HPLC: Column: Zorbax SAX; Column temperature:30℃; Detector: Ultraviolet detector; Mobile phase: 0.02mol/L NaH2PO4 (pH=4.0)+ Acetonitrile (50+50); Flow Speed: 1.2 mL/min; Volume: 10μL.4. The minimum detection limits of two methods of detecting thiocyanate are 0.08mg/L and 0.06mg/L.The relative standard deviations are 0.4% and 1.2%.The add recovery are 88.0%～106.4% and 84.0%～89.1%.The linear ranges are 0.5～10μg/mL and 0.2～20μg/mL. The correlation coefficients are 0.9995 and 0.9998.Through the study, this paper establish scientific, rapid and accurate method to detect thiocyanate in the milk. This study can provide reference for drafting standard test method to detect thiocyanate in the milk.