The recent goal of sustainability in analytical chemistry has boosted the development of eco-designed analytical tools to deliver fast and cost-effective analysis with low economic and environmental impact. Due to the recent focus in sustainability, we report the use of low-cost filter paper as a sustainable material to print silver electrodes and to load reagents for a reagent-free electrochemical detection of chloride in biological samples, namely serum and sweat. The electrochemical detection of chloride ions was carried out by exploiting the reaction of the analyte (i.e. chloride) with the silver working electrode. During the oxidation wave in cyclic voltammetry the silver ions are produced, thus they react with chloride ions to form AgCl, while in the reduction wave, the following reaction occurs: AgCl + e^- -->Ag + Cl^-. These reactions at the electrode surface resulted in anodic/cathodic peaks directly proportional to the chloride ions in solution. Chloride ions were detected with the addition of only 10 μL of the sample on the paper-based electrochemical cell, obtaining linearity up to 200 mM with a detection limit equal to 1 mM and relative standard deviation lower than 10%. The accuracy of the sensor was evaluated in serum and sweat samples, with percentage recoveries between 93 ± 10 and 108 ± 8%. Moreover, the results achieved with the paper-based device were positively compared with those obtained by using the gold standard method (Ion Selective Electrode) adopted in routine clinical analyses.

分析化学可持续性的最新目标促进了生态设计分析工具的开发，以提供快速且具有成本效益的分析，而对经济和环境的影响较小。由于最近对可持续性的关注，我们报告了使用低成本滤纸作为可持续材料来印刷银电极和加载试剂，以进行无试剂的电化学方法检测生物样品中的氯化物，即血清和汗液。通过利用分析物（即氯离子）与银工作电极的反应进行氯离子的电化学检测。在银离子产生在循环伏安法的氧化波，因此它们与氯离子反应，生成氯化银，而在还原波，发生以下反应：氯化银+ E ^-- >的Ag +氯^-。电极表面的这些反应导致阳极/阴极峰与溶液中的氯离子成正比。在纸质电化学电池上仅添加10μL样品即可检测出氯离子，获得高达200 mM的线性，检测限等于1 mM，相对标准偏差低于10％。在血清和汗液样品中评估传感器的准确性，回收率百分比在93±10和108±8％之间。此外，将纸基设备获得的结果与常规临床分析中采用的金标准方法（离子选择电极）获得的结果进行了正面比较。