光程对黄酒金属元素近红外透射光谱分析精度的影响

Influence of Optical Path Length on NIR Analysis Results for Trace Metal Determination in Chinese Rice Wine

应用近红外透射光谱分析技术开展了不同光程对黄酒中金属元素(钾、钙、镁、锌和铁)分析结果影响的研究。实验采用傅里叶变换近红外光谱仪(800～2500nm)及不同光程(1,2,5,10mm),石英比色皿以空气为参比进行了光谱采集,并采用偏最小二乘法进行了数据分析。金属含量采用原子吸收光谱分析法测定。分析结果表明,5mm光程的分析结果最优,对于钾、钙、镁、锌和铁的相关系数(r2)分别为0·93,0·85,0·93,0·72,0·66,交互验证误差(RMSECV)分别为26·5,35·6,4·63,0·26,0·64mg·L-1;而10mm光程的光谱分析结果最差,其r2分别为0·61,0·65,0·63,0·09,0·25。通过实验说明,光程对近红外透射光谱分析的影响,不是光程越长或越短越好,需要通过测试及对比分析确定。

The prediction performance of near infrared （NIR） spectra with different optical path-length for trace metal （potassium, calcium, magnesium, zincum, and iron） determination was investigated. NIR transmission spectra of Chinese rice wine were collected in rectangular quartz cuvette with different optical path lengths （1, 2, 5 and 10 mm） using Fourier transform near infrared （FT-NIR） spectrometer in the wavelength range of 800-2 500 um with air as the reference. The reference data for potassium, calcium, magnesium, zincum, and iron were determined by atomic absorption spectroscopy （AAS）. Calibration models were developed by partial least squares （PLS） regression. The PLS models of NIR spectra group with 5 mm path length gave the best calibration result. The determination coefficients （r^2 ） for potassium, calcium, magnesium, zincum, and iron were 0.93, 0.85, 0. 93, 0. 72, and 0. 66, respectively, and the root mean square error of cross validation （RMSECV） for the five elements were 26. 5, 35.6, 4. 63, 0. 26, and 0.64 mg ·L^-1 , respectively, whereas the models established by NIR spectra group of 10 mm path length was the worst. And the r^2 values for potassium, calcium, magnesium, zincum, and iron were 0. 61, 0. 65, 0. 63, 0. 09, and 0. 25, respectively. The results indicated that the optical path length has an influence on the NIR analysis resuits for trace metal determination in Chinese rice wine, and that the appropriate path length for the NIR analysis should be determined by comparison analysis.