为了检验牛奶中是否掺杂尿素并将其量化测定,配置含有尿素质量浓度范围为1-20g/L之间40个牛奶样品,以掺杂物尿素浓度为外扰,分别研究了掺杂尿素牛奶的二维相关(近红外-近红外,中红外-中红外,近红外-中红外)光谱特性,在此基础上,分别选择随浓度变化大的4200-4800cm0和1400-1704cm^-1为建模区问,采用偏最小二乘方法建立定量分析模型。研究结果表明:4200-4800cm^-1建模分析效果优于14001704cm^-1建模结果,其交叉验证均方根误差为0.266g/L,对未知样品集预测相关系数达到0.999,预测均方根误差为0.219g/L,这表明所建模型具有较好的预测效果。该方法无需样品处理,成本低,为快速判别牛奶是否掺杂提供了一种新的可能的方法。
For the detection and quantification of urea in milk, pure milk samples and 40 adulterated milk samples added different contents of urea were prepared. Then 2D correlation (NIR-NIR, IR-IR, NIR-IR) spectroscopy under the perturbation of adulteration concentration was calculated and the spectra in the range of 4 200-4 800 cm^-1 and 1 400-1 704 cm^-1 were selected to construct the partial least square (PLS) calibration model, respectively. The PLS calibration model showed 4 200-4 800 cm^-1 was the better range for calibration performance and the root mean square errors of cross validation (RMSECV) of the model was 0.266 g/L. When using this model for predicting the urea contents in prediction set, the root mean square errors of prediction (RMSEP) was 0.219 g/L and the coefficient correlation of actual values and predicted values was 0.999, which means the model has good prediction ability. The method can be used for a correct discrimination on whether the milk is adulterated and provides a new and cost-effective alternative to test the adulteration of milk.