为建立测定甜叶菊废渣中总黄酮含量的方法, 通过比较直接法、 AlCl3法和NaNO2-Al(NO3)3-NaOH法三种显色方法的紫外可见光谱, 确定甜叶菊废渣中总黄酮含量测定的最佳方法为NaNO2-Al(NO3)3-NaOH法。 分析了测定波长, 显色剂用量和反应时间、 温度、 pH等因素对测定的影响, 并从浓度与吸光度的线性关系, 稳定性及加标回收率等方面对该法进行了系统研究, 结果表明: 在波长500 nm处, 以芦丁为标准品, 在2～24 μg·mL-1范围内呈良好的线性关系, 线性相关系数R2=0.999 5。 样品加标回收率在96％～104.3％之间, 相对标准偏差(RSD)为3.75%。 NaNO2和Al(NO3)3的用量都为1.0 mL, 反应时间都为6 min, NaOH的用量为15.0 mL, 反应时间为15 min。 整个显色过程温度为40 ℃, pH为5, 进一步优化了NaNO2-Al(NO3)3-NaOH法测定甜叶菊废渣中总黄酮含量的工艺条件。 该方法简便快速, 重现性好, 准确度高, 可用于实际检测工作。

A spectrophotometric method for the determination of flavonoids content in Waste Residue of Stevia Rebaudiana was established by comparing the UV-Vis spectra with three spectrophotometric methods: Direct, AlCl3 and NaNO2-Al(NO3)3-NaOH method. The effects of spectrophotometric reaction were studied by analyzing the wavelength, the dosage of color development reagent, reaction time, temperature and pH. The further research was studied by analyzing linearity between the absorbance and the concentration, the stability of this color system, the recovery rate and so on. The results showed that NaNO2-Al(NO3)3-NaOH method was best. The wavelength was 500 nm. The standard sample was rutin. There was a good linear relationship in the ranges of 2～24 μg·mL-1, correlation coefficient R2=0.999 5. The recovery of the additional sample was 96.0%～104.3%. The relative standard deviation(RSD) is respectively 3.75%. The dosages of NaNO2 and Al(NO3)3 both were 1.0 mL, both of their reaction time was 6 min. The dosage of NaOH was 15.0 mL and the reaction time was 15 min. The temperature in the whole process of the reaction must be maintained at 40 ℃ and pH is 5. The spectrophotometric condition was further improved on the determination of flavonoids content. This method, which is simple, rapid and accuracy, can be used in practical application.