摘要
目的推导重氮化偶合法测定食品中亚硝酸钠假阴性结果的原因,并探讨其机理。方法配制不同浓度的亚硝酸钠标准溶液,按照国家标准方法进行测定。根据不同浓度点出现的颜色变化,结合基础化学理论,分析该现象的原因。结果当样品中的亚硝酸钠含量在1.5 mg/kg~12 mg/kg时,检测结果在标准曲线线性范围内,能得出准确的实验结果;当样品中亚硝酸钠含量大于12 mg/kg时,超出标准曲线线性范围,需要减小取样量或者加大溶液稀释倍数,重新测定;当样品中亚硝酸钠含量超过950 mg/kg时,溶液中亚硝酸钠过量,出现假阴性结果。结论在酸性条件下,亚硝酸钠与盐酸反应形成亚硝酸,亚硝酸不稳定,生成亚硝酰正离子,其优先与盐酸萘乙二胺反应生成重氮化合物,但该化合物不稳定,迅速发生傅克烷基化反应,而干扰对氨基苯磺酸重氮盐与盐酸萘乙二胺的偶合反应,不能形成紫红色的偶氮化合物,导致假阴性结果的出现。
Objective To deduce the reason of false negative results and analyze its mechanism of sodium nitrite in foods by diazotization coupling method.Methods The sodium nitrite solution of different concentrations were prepared and determined according to the national standard methods.On the basis of the color changes at different concentrations,and combined with the basic chemical theory,the reason of this phenomenon was analyzed.Results When the contents of sodium nitrite in the samples were during 1.5 mg/kg-12 mg/kg,the detected results were within the range of the standard curve,so it could get the accurate results.When the contents of sodium nitrate in the samples were higher than 12 mg/kg,the detected results surpassed the range of the standard curve,so it couldn’t get the accurate results and the sample amount should be reduced or the sample solution should be diluted.When the contents of sodium nitrite in the sample exceeded 950 mg/kg,the false negative results appeared.Conclusion Under acidic conditions,sodium nitrite reacts with hydrochloric acid to generate nitrous acid which is unstable,then nitrosyl cation is foemed.Nitrosyl cation preferentially reacts with naphthylethylenediamine hydrochloride to generate diazo compound.However,this compound is unstable and undergoes Friedel-Crafts alkylation reaction quickly,which interferes with the coupling reaction between diazonium sulfanilic acid salt and naphthylethylenediamine hydrochloride,so the purplish red azo compound can not be formed,leading to the false negative results.
作者
陈平
CHEN Ping(Changshu Municipal Center for Disease Control and Prevention,Changshu,Jiangsu 215500,China)
出处
《中国卫生检验杂志》
CAS
2022年第21期2583-2585,共3页
Chinese Journal of Health Laboratory Technology
关键词
亚硝酸钠
食品
假阴性结果
重氮化偶合反应
傅克烷基化
Sodium nitrite
Food
False negative results
Diazotization coupling reaction
Friedel-Crafts alkylation reaction
