牛乳与乳粉中亚硝酸盐和硝酸盐的固相萃取离子色谱测定法

目的建立离子色谱同时测定牛乳与乳粉中亚硝酸盐和硝酸盐含量的方法。方法采用甲醇-乙腈对样品进行萃取并离心,上清液经C18小柱净化后,利用IonPac AS 11—HC柱分离和电导检测器测定,外标法定量。结果亚硝酸盐:线性范围0.02～0.20 mg/L,相关系数0.999 5,样品加标回收率90.0%～104.8%,RSD 3.5%,检出限为牛乳0.002 mg/kg,乳粉0.006 mg/kg;硝酸盐:线性范围0.20～2.0 mg/L,相关系数0.999 4,样品加标回收率90.0～105.8%,RSD 2.3%,检出限为牛乳0.006 mg/kg,乳粉0.03 mg/kg。结论该方法简便,快速,适合牛乳与乳粉中亚硝酸盐和硝酸盐含量的测定。

Determination of nitrite and nitrate in milk and milk powder by ion chromatography with solid phase extraction

Objective] To establish a method for simultaneous determination of nitrite and nitrate in milk and milk powder by ion chromatography with solid phase extraction.Methods] Methanol-acetonitrile was used for extraction and centrifugation of the sample.Supernatant fluid was purified with C18 cartridge.The separation was carried out on IonPac AS 11—HC column.External standard method was used.Results] Nitrite：the linear range was 0.02-0.20mg/L,correlation coefficient r = 0.999 5,the recoveries were 90.0-104.8%;RSD was 3.5%,the detection limit was 0.002 mg/kg（milk） and 0.006 mg/kg（milk powder）.Nitrate：the linear range was 0.20-2.0mg/L,correlation coefficient r=0.999 4,the recoveries were 90.0-105.8%;RSD was 2.3%,the detection limit was 0.006 mg/kg（milk） and 0.03 mg/kg（milk powder）.Conclusion]This method is simple,fast,and suitable for the determination of nitrite and nitrate in milk and milk powder.