Department of Analytical Chemistry and ‡Department of Organic Chemistry, Faculty of Chemistry, Complutense University of Madrid , Ciudad Universitaria s/n, 28040 Madrid, Spain.
Anal Chem. 2016 Apr 5;88(7):3959-66. doi: 10.1021/acs.analchem.6b00167. Epub 2016 Mar 22.
We have developed disposable color-changing polymeric films for quantification of furfural-a freshness indicator-in beer using a smartphone-based reader. The films are prepared by radical polymerization of 4-vinylaniline, as a furfural-sensitive indicator monomer, 2-hydroxymethyl methacrylate as a comonomer, and ethylene dimethyl methacrylate (EDMA) as a cross-linker. The sensing mechanism is based on the Stenhouse reaction in which aniline and furfural react in acidic media with the generation of a deep red cyanine derivative, absorbing at 537 nm, which is visible to the naked eye. The colorimetric response has been monitored using either a portable fiber-optic spectrophotometer or the built-in camera of a smartphone. Under the optimized conditions, a linear response to furfural in beer was obtained in the 39 to 500 μg L(-1) range, with a detection limit of 12 μg L(-1), thus improving the performance of other well-established colorimetric or chromatographic methods. The novel films are highly selective to furfural, and no cross-reactivity has been observed from other volatile compounds generated during beer aging. A smartphone application (app), developed for Android platforms, measures the RGB color coordinates of the sensing membranes after exposure to the analyte. Following data processing, the signals are converted into concentration values by preloaded calibration curves. The method has been applied to determination of furfural in pale lager beers with different storage times at room temperature. A linear correlation (r > 0.995) between the storage time and the furfural concentration in the samples has been confirmed; our results have been validated by HPLC with diode-array detection.
我们开发了一种用于使用智能手机读取器定量检测啤酒中糠醛（一种新鲜度指标）的一次性变色聚合物薄膜。该薄膜通过 4-乙烯基苯胺（糠醛敏感指示剂单体）、2-羟甲基甲基丙烯酸酯（共聚单体）和乙二醇二甲基丙烯酸酯（EDMA）（交联剂）的自由基聚合制备。该传感机制基于 Stenhouse 反应，其中苯胺和糠醛在酸性介质中反应，生成深红色的花菁衍生物，在 537nm 处吸收，肉眼可见。比色响应使用便携式光纤分光光度计或智能手机的内置摄像头进行监测。在优化条件下，在 39 至 500μg/L-1 范围内，对啤酒中的糠醛得到线性响应，检测限为 12μg/L-1，从而提高了其他成熟的比色或色谱方法的性能。新型薄膜对糠醛具有高度选择性，并且在啤酒老化过程中产生的其他挥发性化合物没有观察到交叉反应。为 Android 平台开发了一个智能手机应用程序（app），用于测量暴露于分析物后的传感膜的 RGB 颜色坐标。在数据处理后，信号通过预加载的校准曲线转换为浓度值。该方法已应用于不同储存时间的淡拉格啤酒中糠醛的测定室温下。已确认样品的储存时间与糠醛浓度之间存在线性相关性（r>0.995）；我们的结果通过二极管阵列检测的 HPLC 进行了验证。
