应用亚硝酸钠-硝酸铝-氢氧化钠体系分光光度法测定核桃花青皮中总黄酮含量时受到共存的胡桃醌和焦性没食子酸的明显干扰,经试验,提出了消除此干扰的校正方法。从乙醇提取液中移取两份等量试液(2.0 mL),分别置于25 mL容量瓶中,其中一份按方法加显色混合液,以试剂空白为参比,在波长508 nm处先后于15,25 min测其吸光度A1及A2;另一份中加乙醇(1+1)溶液13 mL及40 g·L-1氢氧化钠溶液10.0 mL,摇匀,测其吸光度A0。根据所推导的公式计算总黄酮的吸光度,代入回归方程计算其含量。按改进的方法分析3份样品,测定值的相对标准偏差(n=6)在0.76%~1.3%之间。加标回收试验的回收率在89.0%~105%之间。

Significant interferences of co-existing juglone and galic acid were observed in the determination of total flavonoids in green husk of walnuts by spectrophotometry using the NaNO2-Al(NO3)3-NaOH system. To eliminate the interference, systematic tests were performed and a modification was given as follows: Two aliqucts (2.0 mL each) were taken from ethanol extract, and place separately into two 25 mL volumetric flosks. In one of the flasks, definite amount of mixed color reaction solution was added and the absorbances of A1 and A2 were measured at 15, 25 min respectively vs. reagent blank at the wavelength of 508 nm. In the other flask, 13 mL of C2H5OH(1+1) mixture and 10.0 mL of 40 g·L-1 NaOH solution were added, and its absorbance A0 was measured at 508 nm also. The absorbance of total flavonoids was calculated by the derived formula, and it content was further calculated by the regression equation. The modified method was used in the analysis of 3 samples, giving values of RSD′s (n=6) and recovery in the ranges of 0.76%-1.3% and 89.0%-105% respectively.