Department of Analytical Chemistry, University of Valencia, Dr Moliner 50, 46100, Burjassot, Valencia, Spain.
Universidade Católica Portuguesa, CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior de Biotecnologia, Rua Diogo Botelho 1327, 4169-005, Porto, Portugal.
Mikrochim Acta. 2023 Mar 10;190(4):126. doi: 10.1007/s00604-023-05702-5.
A microfluidic paper-based device (µPAD) has been combined with metal-organic frameworks (MOFs) for total phenolic compounds (TPC) quantification in fruit samples for the first time. The performance of the µPAD, based upon the vertical flow approach, was enhanced in order to determine the TPC content with high accuracy in fruit samples. The method was based on the traditional Folin-Ciocalteu Index using gallic acid or oenotannin as reference phenolic compounds. This novel design and construction of the device are in agreement with the principles of Green Chemistry avoiding wax technology (lower toxicity). The analytical parameters that affect the colorimetric method (using digital imaging of the colored zone) performance were optimized including design, sample volume, and MOF amount. Then, the analytical features of the developed method were investigated such as dynamic range (1.6-30 mg L), limit of detection (0.5 mg L), and precision (RSD < 9%). Besides, the in-field analysis is achievable with a color stability up to 6 h after the loading process of the sample and storage stability for at least 15 days without performance losses (under vacuum at - 20 °C). Furthermore, the MOF ZIF-8@paper was characterized to study its composition and the successful combination. The feasibility of the proposed method was demonstrated by determining the TPC in 5 fruit samples using oenotannin as reference solute. The accuracy was validated by comparison of the data with the results obtained with the recommended protocol proposed by the International Organisation of Vine and Wine (OIV).
首次将微流控纸基装置（µPAD）与金属有机骨架（MOFs）结合，用于水果样品中总酚类化合物（TPC）的定量分析。该µPAD 基于垂直流动方法，其性能得到了增强，可在水果样品中高精度地测定 TPC 含量。该方法基于传统的福林-希卡尔特指数，使用没食子酸或单宁酸作为参考酚类化合物。该设备的新型设计和构造符合绿色化学原则，避免了蜡技术（毒性更低）。优化了影响比色法（使用彩色区域的数字成像）性能的分析参数，包括设计、样品体积和 MOF 用量。然后，研究了开发方法的分析特性，如动态范围（1.6-30 mg/L）、检出限（0.5 mg/L）和精密度（RSD<9%）。此外，在加载样品和至少 15 天无性能损失（在-20°C 下真空）的情况下，在 6 小时后仍可实现现场分析，且具有颜色稳定性。此外，对 MOF ZIF-8@paper 进行了表征，以研究其组成和成功结合。使用单宁酸作为参考溶质测定 5 种水果样品中的 TPC，验证了所提出方法的可行性。通过与国际葡萄与葡萄酒组织（OIV）推荐方案得到的结果进行比较，验证了数据的准确性。
