为研究食用靛蓝的降解过程,使用紫外-可见吸收光谱法建立食用靛蓝的光降解率模型。食用靛蓝吸收光谱中611 nm处的吸光度随光照时间增加而递减,光照8 h后,611 nm处的吸光度接近于0。基于不同浓度食用靛蓝的吸收光谱,通过指数拟合分别建立了食用靛蓝在611 nm处的吸光度-质量浓度预测模型和500~700 nm范围内吸收峰面积-质量浓度预测模型。结果表明:吸收峰面积-质量浓度预测模型的效果更好;将完全降解后的食用靛蓝溶液作为干扰物,与新配制的食用靛蓝溶液混合来验证吸收峰面积-质量浓度预测模型的适用性,模型的平均相对误差为2.7%。将不同光照时间后的食用靛蓝在500~700 nm范围内的吸收峰面积代入该模型中,可获得食用靛蓝的含量,进而可推算出不同光照时间后食用靛蓝的降解率,得到食用靛蓝降解率与光照时间之间的指数关系。所建立的降解率模型的测量精度高,可方便地检测食用靛蓝的降解率。

In order to study the degradation of indigo carmine, we establish the indigo carmine photo degration rate model by the UV-vis absorption spectroscopy. The absorbance at 611 nm of the absorption spectra of indigo carmine solution declines with the increase of illumination time and up to 0 after 8 hours. Based on the absorption spectra of the indigo carmine solutions with different mass concentrations, we established an absorbance-mass concentration prediction model at 611 nm and a peak area-mass concentration prediction model within 500-700 nm by exponential fitting. The results show that the peak area-mass concentration prediction model is more accurate than the former. Taking the completely degraded indigo carmine as interferent, we mixed it with the newly-prepared indigo carmine solutions to verify the peak area-mass concentration prediction model, and the model''s average relative deviation is 2.7%. Combining the absorption spectra area of the indigo carmine solutions (within 500-700 nm) at different illumination durations with the peak area-mass concentration prediction model, we obtain the content of indigo carmine and degradation rate, and obtain an exponential function between the degradation ratio of indigo carmine and the illumination time. The degradation rate model established in this paper has high measurement accuracy, and it can easily test the degradation rate of indigo carmine.