Cai Longfei, Ouyang Zhuang, Song Jiahong, Yang Liye
School of Chemistry and Environmental Engineering, Hanshan Normal University, Chaozhou, Guangdong 521041, China.
Chaozhou Central Hospital, Chaozhou, Guangdong 521000, China.
ACS Omega. 2020 Jul 22;5(30):18935-18940. doi: 10.1021/acsomega.0c02143. eCollection 2020 Aug 4.
We described an indicator-free argentometric titration strategy using a microfluidic paper-based analytical device. This strategy was based on the formation of insoluble silver salts by reactions occurring between analytes and titrant (Ag) on a paper channel. After the insoluble silver salts were formed and precipitated on the channel, the paper substrate modified with the surplus titrant on the channel turned reddish-brown by exposure of the devices to a simple and cheap UV light source for 5 min, generating a colored band on the channel. Distance-based detection of chloride was achieved by measuring the length of the colored band with a detection limit of 1.7 mg L Cl. This method was used to detect chlorides in tap water, with an analytical result (10.1 ± 1.2 mg L) agreeing well with that obtained by a classical conventional precipitation titration (9.8 mg L), which was based on the measurement of the consumed volume of titrant. This paper-based precipitation titration method is free of skilled personnel and has advantages of low reagent/sample consumption, disposability, portability, and simple operation over the conventional precipitation titration. More importantly, being free of any indicator, this method may be used to detect more species than the conventional precipitation titrations, which are limited by the indicator, for example, CO and SO , which could form insoluble silver salts in aqueous liquids. Additionally, comparing with most of those paper-based titrimetry reported previously, this presented precipitation titration is free of any indicator or ion selective electrode to detect the end point of titration.
我们描述了一种使用基于微流控纸基的分析装置的无指示剂银量滴定策略。该策略基于分析物与纸通道上的滴定剂（Ag）之间发生反应形成不溶性银盐。在通道上形成不溶性银盐并沉淀后，通过将装置暴露于简单且廉价的紫外光源5分钟，通道上用过量滴定剂修饰的纸基质变为红棕色，在通道上产生一个色带。通过测量色带的长度实现基于距离的氯离子检测，检测限为1.7 mg/L Cl。该方法用于检测自来水中的氯离子，分析结果（10.1±1.2 mg/L）与通过经典的常规沉淀滴定法（9.8 mg/L）获得的结果非常吻合，后者基于滴定剂消耗体积的测量。这种基于纸的沉淀滴定法无需专业人员，与传统沉淀滴定法相比，具有试剂/样品消耗低、可一次性使用、便携且操作简单的优点。更重要的是，由于无需任何指示剂，该方法可用于检测的物质种类比受指示剂限制的传统沉淀滴定法更多，例如CO 和SO ，它们可在水性液体中形成不溶性银盐。此外，与之前报道的大多数基于纸的滴定法相比，这种沉淀滴定法无需任何指示剂或离子选择性电极来检测滴定终点。
