Factors Optimization And Interference Control Of Determination Of Selenium In Food By HG-AFS

Selenium is an essential trace element for the human body,and has a very close relationship with human health.2/3 of the regions in China belongs to the lack of selenium area,in one of these areas Keshan disease with local characteristics had occurred,the mortality rate of up to 98%.With the deepening of the study of selenium,selenium for the prevention and treatment of cancer has also made some progress,then people began to promote replenish selenium scientifically.Food is a good source of selenium,but if too much intake also can lead to disease,the suitable intake range of selenium is narrow,therefore the determination and monitoring of selenium mass fraction in food is of great significance.Hydride generation-atomic fluorescence spectrometry(HG-AFS)is used as the main detection method,the optimization of the instrument conditions,hydride generation conditions,effective control of interference and pretreatment of samples were carried out on AFS-9760 atomic fluorescence spectrometer(Beijing Haiguang instrument company).That was aimed at establishing a more simple,more operational detection technology for providing technical basis for the Enshi area selenium resources development and utilization.The main findings are as follows:(1)The optimum conditions for the determination of selenium were measured by atomic fluorescence spectrophotometer with the ratio of 10?g / L selenium standard solution fluorescence intensity to the blank solution fluorescence intensity.The results show that the optimal instrument conditions are: lamp current 80 mA,carrier gas flow300 mL / min,negative high pressure 300V;(2)The fluorescence intensity of 10?g / L selenium standard solution was used as the index to study the hydride generation conditions.The fluorescence intensity and the regression model of 10?g / L selenium standard solution were established by Design Expert8.0 analysis.Y=-2347.282+455.965A+223.510B+239.161C+3.110AB+5.626 AC-22.065A2-19.549B2-23.200C2,where A is the concentration of potassium borohydride;B is the concentration of charged hydrochloric acid;and C is the concentration of hydrochloric acid in the medium.The optimum reaction conditionswere as follows: the concentration of potassium borohydride was 12g/L,the concentration of mesoporous hydrochloric acid and the concentration of hydrochloric acid were 7%.(3)Interfering elements in the detection of selenium by atomic fluorescence spectrometry were eliminated.The results showed: when adding 1.2mL of 100g/L of sulfamic acid solution,the fluorescence signal of 20?g/L selenium standard solution inhibited by nitrosene ion can be completely restored.In addition,the coexisting element Cu2+on the determination of selenium is a negative interference,Pb2+on the determination of selenium is a positive interference.In this Experiment,potassium ferricyanide as a masking agent could eliminate the effect,when adding 1m L 10%potassium ferricyanide solution,10000 times Cu2+and Pb2+would not affect the determination of selenium in food by HG-AFS.(4)The processing conditions of microwave digestion and general wet digestion were optimized.Microwave digestion conditions of 0.1?0.5g?1g samples respectively were: 5mL 40% nitric acid at 200? for 15 min,5mL nitric acid at 180? for 15 min and 10 mL nitric acid at 160 ? for 20 min.After microwave digestion,the reaction was carried out on the rinse agent,the corresponding conditions were: 2mL hydrochloric acid 160? heating 15 min,3mL hydrochloric acid 160? heating 30min(1g sample and 0.5g consistent).0.1g samples were digested by ordinary wet digestion,and the condition was that 4m L nitric acid and 1mL perchloric acid were added to digest at160? to 1-2mL,then adding 4mL 50% hydrochloric acid for reduction.(5)Food samples treated with optimized microwave digestion were measured respectively by HG-AFS,fluorescence method and o-phenylenediamine method.The results showed that the optimized microwave digestion method were compared with national standard,except for cowpea,The difference in the mass fraction of selenium in the sample measured by the same detection method was less than 10%,so the optimized microwave digestion method is also applicable to the fluorescence method and o-phenylenediamine method.In addition,when the selenium mass fraction in the samples is more than 2?g/g,The difference in selenium mass fraction in food samples measured respectively by HG-AFS,fluorescence method and o-phenylenediaminemethod was basically less than 10%.