根据肉桂醛、苯甲醛和苯甲酸的紫外吸收光谱特征及肉桂醛和苯甲醛在228 nm和256 nm波长处有两个等吸收点,提出了测定三组分的紫外分光光度法.选择228 nm,256 nm及311 nm 3个波长作为测定波长,建立了联立方程组,求得了组分浓度与吸光度之间的关系:C肉桂醛=(A311 nm-0.008 4)/0.042 4;C苯甲醛=(A256 nm-0.000 5)/0.062 2-C肉桂醛;C苯甲酸=(A228 nm+0.005 7)/0.061 1-C肉桂醛-C苯甲醛.相应的线性范围依次在18.03,13.08,9.233 mg·L-1以内.对方法的重现性作了试验,上述3种化合物的相对标准偏差(n=6)均小于1%.用标准加入法进行回收试验,测得其平均回收率在99.1%~100.5%之间.

UV Spectrophotometry was applied to determination of cinnamaldehyde (CIN),benzaldehyde (BEN) and benzoic acid (BA) in their mixtures.Based on their UV-absorption spectra and by using the iso-absorption point,measurements of absorbance were made at the wavelengths of 228,256,311 nm,and linear relationships between values of absorbance and concentration of the 3 compounds were found as follows:Ccin.=(A311 nm-0.008 4)/0.042 4,Cben.=[(A256 nm-0.000 5)/0.062 2]-Ccin.,CBA=[(A228 nm+0.005 7)/0.061 1]-Ccin.-CBA,corresponding to ranges of linearity within 18.03 mg·L-1 for cinnamaldehyde,within 13.08 mg·L-1 for benzaldehyde and within 9.233 mg·L-1 for benzoic acid.Reproducibility of the determination of 3 compounds in a mixture for 6 replicates within a period of 9 h,values of RSD′s found were all less than 1%.Results of tests for recovery obtained for the 3 compounds were in the range of 99.1%-100.5%.