The interfacial properties of multiphase systems are often difficult to quantify. We describe the observation and quantification of immiscible solvent entrapment on a carbonaceous electrode surface using microscopy-coupled electrogenerated chemiluminescence (ECL). As aqueous microdroplets suspended in 1,2-dichloroethane collide with a glassy carbon electrode surface, small volumes of the solvent become entrapped between the electrode and aqueous phase, resulting in an overestimation of the true microdroplet/electrode contact area. To quantify the contribution of solvent entrapment decreasing the microdroplet contact area, we drive an ECL reaction within the microdroplet phase using tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)₃]Cl₂) as the ECL luminophore and sodium oxalate (Na₂C₂O₄) as the co-reactant. Importantly, the hydrophilicity of sodium oxalate ensures that the reaction proceeds in the aqueous phase, permitting a clear contrast between the aqueous and 1,2-dichloroethane present at the electrode interface. With the contrast provided by ECL imaging, we quantify the microdroplet radius, apparent microdroplet contact area (aqueous + entrapped 1,2-dichloroethane), entrapped solvent contact area, and the number of entrapped solvent pockets per droplet. These data permit the extraction of the true microdroplet/electrode contact area for a given droplet, as well as a statistical assessment regarding the probability of solvent entrapment based on microdroplet size.

中文翻译：

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电生化学发光法分析多相系统中的溶剂截留

多相系统的界面特性通常难以量化。我们描述了观察和定量使用显微镜耦合电生化学发光（ECL）的碳质电极表面上不混溶的溶剂截留。当悬浮在1,2-二氯乙烷中的水性微滴与玻璃碳电极表面碰撞时，少量溶剂被截留在电极和水相之间，导致高估了真实的微滴/电极接触面积。为了量化溶剂截留减少微滴接触面积的贡献，我们使用三（联吡啶）钌（II）氯化物（[Ru（bpy）₃ ] Cl ₂）作为ECL发光体和草酸钠驱动微滴相内的ECL反应（Na₂ C ₂ O ₄）作为共反应物。重要的是，草酸钠的亲水性确保了反应在水相中进行，从而使水与电极界面处的1,2-二氯乙烷之间形成鲜明的对比。借助ECL成像提供的对比度，我们可以量化微滴半径，表观微滴接触面积（水+截留的1,2-二氯乙烷），截留的溶剂接触面积以及每滴截留的溶剂囊的数量。这些数据允许提取给定液滴的真实微滴/电极接触面积，并基于微滴大小进行有关溶剂截留概率的统计评估。