1 材料与方法
1.1 化学试剂与标准品
1.2 仪器与设备
1.3 样品采集与制备
1.4 腐胺测定
表1 流动相梯度洗脱程序Table 1 Gradient elution procedure of mobile phases |
| 时间 Time/min | 流速 Flow velocity/(mL/min) | 流动相A Mobile phase A/% | 流动相B Mobile phase B/% | 曲线 Curve |
|---|---|---|---|---|
| 0 | 0.350 | 30.0 | 70.0 | 0 |
| 1.0 | 0.350 | 30.0 | 70.0 | 0 |
| 2.5 | 0.350 | 60.0 | 40.0 | 0 |
| 6.5 | 0.350 | 60.0 | 40.0 | 0 |
| 7.0 | 0.350 | 30.0 | 70.0 | 0 |
| 8.0 | 0.350 | 30.0 | 70.0 | 0 |
表2 腐胺质谱采集参数Table 2 Mass spectrum acquisition parameters of PUT |
| 化合物 Compounds | 保留时间 Retention time/min | 母离子质荷比 m/z of precursor ion | 子离子质荷比 m/z of product ion | 去簇电压 DP/V | 碰撞能量 CE/V |
|---|---|---|---|---|---|
腐胺PUT | 3.83 | 89.1 | 72.1* | 30 | 14 |
| 30.0 | 30 | 22 | |||
1,7-二氨基庚烷(内标) DIA (IS) | 3.11 | 131.1 | 114.0* | 15 | 14 |
| 66.0 | 15 | 10 |
*:定量离子 quantitative ion。 |
1.5 中红外光谱测定
1.6 光谱建模
1.7 统计分析
2 结果与分析
2.1 生乳腐胺含量测定结果
2.2 生乳中红外光谱特征
2.3 中红外光谱预测模型建立
表3 不同中红外光谱预处理方法建立PLSR模型的预测结果Table 3 Prediction results of PLSR models established using different mid-infrared spectral preprocessing methods |
| 预处理方法 Preprocessing methods | 指标Indicators | ||||
|---|---|---|---|---|---|
| 测试集Test set | 验证集Validation set | ||||
| 决定系数 R2 | 均方根误差 RMSE | 决定系数 R2 | 均方根误差 RMSE | ||
| 未处理(原始光谱) Untreated (original spectrum) | 0.896 0 | 0.271 6 | 0.659 2 | 0.497 5 | |
| SG平滑SG smoothing | 0.872 6 | 0.307 0 | 0.545 5 | 0.590 4 | |
| 标准正态变量变换SNV | 0.975 7 | 0.134 4 | 0.787 4 | 0.39 90 | |
| 一阶导数First-order derivative | 0.902 2 | 0.258 3 | 0.737 7 | 0.426 8 | |
| 二阶导数Second-order derivative | 0.817 3 | 0.352 8 | 0.613 9 | 0.514 8 | |
| SG平滑+一阶导数 SG smoothing+first-order derivative | 0.800 9 | 0.375 0 | 0.621 0 | 0.521 3 | |
| SG平滑+二阶导数 SG smoothing+second-order derivative | 0.995 9 | 0.054 2 | 0.811 2 | 0.368 4 | |
2.4 模型验证
图4 生乳中腐胺实测值(lg)与预测值(lg)的线性关系Fig.4 Linear relationship between measured value (lg) and predicted value (lg) of PUT in raw milk |
图5 生乳中腐胺实测值与预测值的线性关系Fig.5 Linear relationship between measured value and predicted values of PUT in raw milk |
