Establishment Of High Performance Liquid Chromatography And Capillaryelectrophoresis For Detection Of Thiocyanate Sodium In Milk

Thiocyanates exist in many kinds of foods, including milk, and it could be synthesized as a metabolite in the liver of human beings. They have been added into milk to suppress the growth of bacteria and extend the storage life. However, thiocyanates have been considered as a toxic substance which could cause acute poisoning by high intaking, and lead to the deficiency of iodine by low intaking. For the latter, it is reported mainly on that thiocyanates are harmful to the thyroid gland, and especially dangerous to babies.Nowadays, the mainly adoptive analysis methods for detecting thiocyanates include colorimetric spectrophotometry method, ion chromatography-conductivity detector method, and ion chromatography-mass detector method at home and abroad. But after reviewing the domestic reports on detecting thiocyanates, we found that standards of determining the concentration of thiocyanates in milk had not been established. Furtherly, there is neither limits/requirements specified the thiocyanates concentration in milk in the national standard, nor the risk assessments about their threat on human’s health. Based on the information above, a method with high accuracy, sensitivity, simple pretreatment steps and convenient detection steps to determine the concentration of thiocyanate sodium in milk need to be established.Two kinds of methods including HPLC and CE were taken to determine the sodium thiocyanate in raw milk and market Palestinian sterile milk. First, the effect of different mobile phases on the separation of deteced components were studied in HPLC and the composition of the mobile phase were fixed. The system flexibility parameters and calibration curves were determined. The pretreatment process was optimized and the recovery experiments of target samples were also completed. Then the pH, composition and concentration of the mobile pahse were tested in CE analysis. The calibration curves and the pretreatment process were determined. Finally the comparison of HPLC and CE on the same sample treated by standard process was conducted. The methods to determine the concentration of thiocyanate sidium in milk was established separated by HPLC and CE in this paper. First, a method to determinate sodium thiocyanate in milk by RP-HPLC was established. The separation was performed on Agela—ASB(?)C18column (250mm×4.6mm,5μm) with the mobile phase of phosphoric acid solution (0.2%, v/v, A):methanol (B)=95:5. The detection wavelength was218nm. The flow rate was0.8ml/min and the column temperature was30℃±2℃. Good linearity was obtained during the range of5-500mg/L with r>0.9995. The average recoveries was larger than90.0%with RSD<10%. The method was convenient, rapid and reliable for the determination of sodium thiocyanate in milk with the LOD of0.2mg/kg and the determination range of0.5-50mg/kg.A method to determinate sodium thiocyanate in milk by CE was also established. The separation was performed on NaH2PO4-Na2B4O7with TTAB used as the electro-osmotic flow (EOF) modifier to change the direction of EOF. The detection wavelength was218nm. The separate votege was20kV and the separate temperature was30℃. Good linearity was showed within the range of5-500mg/L respectively, r>0.9995. The average recoveries was larger than90.0%respectively, RSD<10%. The method was simple, rapid and reliable for the simultaneous determination of sodium thiocyanate in milk with the LOD of0.05mg/kg and the determination range of0.5～50mg/kg.