The spectral characteristics (absorption band intensity and position) of structurally similar natural cinnamic acids absorbed on an aluminum oxide surface were found to depend on the surface concentration and aqueous solution pH. The conditional molar absorption coeffi cients [g/(mol∙cm)] of adsorbed cinnamic \( \left({\upvarepsilon}_{274 nm}^S=1766\right), \) coumaric \( \left({\upvarepsilon}_{286 nm}^S=2056\right), \) ferulic \( \left({\upvarepsilon}_{290 nm}^S=1139\right), \) and caffeic acids \( \left(\left({\upvarepsilon}_{350 nm}^S=1163\right.\right) \) were determined. The optical densities of the adsorbed cinnamic acids were found to correlate with their concentrations in the initial solutions being analyzed. Owing to this, highly disperse aluminum oxide could be recommended as a solid-phase reagent for evaluation of cinnamic, coumaric, ferulic, and caffeic acids in plant-derived products using spectrophotometric or visual test methods. The possibility of selective determination of caffeic acid was also shown.

发现吸收在氧化铝表面上的结构相似的天然肉桂酸的光谱特性（吸收带强度和位置）取决于表面浓度和水溶液的 pH 值。吸附肉桂的条件摩尔吸收系数 [g/(mol∙cm)] \( \left({\upvarepsilon}_{274 nm}^S=1766\right), \)香豆素\( \left({\ upvarepsilon}_{286 nm}^S=2056\right), \)阿魏酸 \( \left({\upvarepsilon}_{290 nm}^S=1139\right), \)和咖啡酸\( \left( \left({\upvarepsilon}_{350 nm}^S=1163\right.\right) \)被确定。发现吸附的肉桂酸的光密度与其在被分析的初始溶液中的浓度相关。因此，可以推荐高度分散的氧化铝作为固相试剂，用于使用分光光度法或目视测试方法评估植物衍生产品中的肉桂酸、香豆酸、阿魏酸和咖啡酸。还显示了选择性测定咖啡酸的可能性。