利用非线性化学指纹图谱法检测奶粉中掺杂的尿素含量

采用"硫酸-丙二酸-溴酸钠-溴化钠-硫酸铈铵"为振荡体系,利用非线性化学指纹图谱法测定奶粉中掺杂的尿素。先向奶粉中掺入不同量的尿素,配成掺杂尿素的奶粉标样,每份奶粉标样的总量为1.00 g。通过非线性化学指纹图谱法对奶粉标样进行测定,运用最小二乘法,拟合出诱导时间相对于奶粉中掺杂尿素含量之间的一元线性关系,可求出奶粉中掺杂的尿素含量。实验表明该方法可以达到以下指标:当奶粉中掺杂的尿素含量在0~40.00 mg/g范围内时,尿素含量与诱导时间线性关系良好,相关系数R2为0.996 6和0.999 5,回收率为95.48%~104.06%,相对标准偏差不大于1.82%,奶粉1#检出限为3.3×10~(-4) mg/g,奶粉2#检出限为4.5×10~(-4) mg/g,奶粉3#检出限为1.1×10~(-4) mg/g。方法准确度高,操作简单,是一种切实可行的测定奶粉中掺杂尿素的方法,也可作为复杂样本中其他成分定量分析借鉴的方法。

Determination of Urea Content in Adulterated Milk Powder by Nonlinear Chemical Fingerprint Method

The urea content in adulterated milk powder was rapidly determined by nonlinear chemical fingerprint method using a reaction system consisting of sulfuric acid, malonic acid, ceric ammonium sulfate, sodium bromate and sodium bromide. Firstly, urea was added at different levels to milk powder to obtain adulterated milk powder standard samples each weighing 1.00 g. The nonlinear chemical fingerprint was recorded for each milk powder standard sample, and a linear relationship between the induction time and the urea content was established. Then, the urea content in milk powder was calculated by the least square method. The results showed that urea contents within the range of 0–40.00 mg/g in milk powder and induction time values displayed a good linear relationship with correlation coefficients equal to 0.996 6 and 0.999 5. The recoveries were 95.48%–104.06%, the relative standard deviations (RSDs) were not greater than 1.82%, and the detection limits (LODs) for milk powder samples 1#, 2# and 3# were 3.3 × 10-4, 4.5 × 10-4 and 1.1 × 10-4 mg/g, respectively. The method developed has the advantages of good accuracy and simple operation. It is a practical and feasible method for determining the urea content in milk powder.