改进的离子色谱法测定乳制品中亚硝酸盐和硝酸盐

改进了国家标准方法GB 5009.33-2010《食品安全国家标准 食品中亚硝酸盐和硝酸盐的测定》中离子色谱法用于乳制品中亚硝酸盐(以亚硝酸根计)和硝酸盐(以硝酸根计)的测定方法。乳制品经水提取后,加入3%乙酸溶液沉淀蛋白,离心后上清液用反相固相萃取柱净化,以NaOH为淋洗液,加入乙腈作为有机改进剂分离亚硝酸根和硝酸根,外加水模式抑制,离子色谱分析柱为AS 19,柱温30 ℃,池温35 ℃,检测波长设定为225 nm,进样量200 μL。在上述条件下,亚硝酸盐和硝酸盐的质量浓度分别在0.005～0.50和0.05～1.50 mg/L时与色谱峰面积之间的线性关系良好。在电导检测模式下,亚硝酸盐的检出限为0.2 mg/kg,硝酸盐的检出限为0.04 mg/kg;在紫外检测模式下,两者检出限分别为0.02 mg/kg和0.01 mg/kg。将该方法用于乳制品的检测,加标回收率为84.0%～104.1%。该法简便、快速、准确,适用于乳制品中低含量亚硝酸盐和硝酸盐的检测。

Determination of nitrite and nitrate in dairy products by improved ion chromatography

Nitrite and nitrate are common inorganic salts in the diet and drinking water.It is generally believed that excessive intake of these substances may result in methemoglobinemia or other diseases.However,the traditional detection methods for nitrite and nitrate in dairy products restrain their applications to routine analysis due to the presence of certain limitations.In order to solve this problem,an improved national food safety standard method for the determination of nitrite and nitrate in dairy products has been studied.After water extraction,protein precipitation and centrifugation,the supernatant was cleaned up by a solid phase extraction(SPE) column.The eluent mainly composed of sodium hydroxide with acetonitrile as organic modifier.External water mode was used for suppressor.An AS 19 column was used as the analytical column,and the oven temperature was 30 ℃ while the cell temperature was 35 ℃.The detection wavelength was 225 nm and the injection volume was 200 μL.The results showed that good linearity existed when the concentrations of nitrite and nitrate were between 0.005-0.50 and 0.05-1.50 mg/L respectively.The detection limits of nitrite and nitrate were 0.2 and 0.04 mg/kg respectively when using a conductivity detector;while the values were only 0.02 and 0.01 mg/kg using an ultraviolet(UV) detector.The recoveries were between 84.0% and 104.1% when analyzing dairy products.It is a simple,fast and highly sensitive way for nitrite and nitrate detections.