Single Microdroplet/Water Extraction and in situ Microanalysis by Microcapillary Injection and Differential Pulse Voltammetry

Abstract

A redox species was extracted from water (50 × 10 -6 dm 3 ) into a single micro-oil-droplet (30 × 10 -12 dm 3 ) in contact with a microelectrode using microcapillary injection and manipulation techniques. Further, an in situ microanalysis of the solute in a single oil droplet was demonstrated by differential pulse voltammetry. The redox species of 10 -16 mol concentrated in the droplet could be quantitatively analyzed independently of the distribution coefficient of the solute between the oil and water phases. The potential of this technique was considered in terms of the preconcentration and separation as well as a microanalysis and an ultratrace analysis.

A mechanistic study on ion pair extraction using single microdroplet injection and microelectrochemical techniques

“…Electrochemical measurements of single microdroplets were performed by microcapillary injection/manipulation and microelectrochemical methods. 29,32,33 Water-saturated TBP and TBP-saturated water containing FcTMABr (0.5-1.5 mM, 1 M ¼ 1 mol dm À3 ), NaPF 6 (0.5-1.5 mM) and NaCl (0-0.1 M) were used as the oil and water phases, respectively. A gold wire (diameter of 25 mm) insulated in a glass capillary (tip diameter of $100 mm) was used as a working electrode.…”

Laser-Induced Liquid-to-Droplet Extraction of Chlorophenol: Photothermal Phase Separation of Aqueous Triethylamine Solutions

“…On the other hand, spectroscopic and electrochemical studies on microdroplets in solution have been reported. [10][11][12][13][14][15][16][17] As an example, we introduced a laser trapping-microanalysis technique to study chemical characteristics of individual oil droplets in solution. 10 It is worth noting that such experiments are the indispensable basis for studying size-dependent chemical/physical processes in or across single microdroplet/solution interfaces.…”

“…By a strict definition, however, such an experimental mode is not a "single-particle measurement" but is a "particle-resolved mode", since a sample solution involves a large number of droplets. As another approach to droplet measurements, a single droplet can be hung in a solution at the end of a glass tube, 13 while the droplet is connected with the inner solution in the glass tube. In both cases, chemical/physical responses of a single droplet by an external stimulus cannot be followed in a quantitative manner owing to disturbance by untrapped droplets or the solution connected with the droplet.…”

“…A droplet injection method has been also reported. 12,13 However, simultaneous manipulation of an injected droplet in solution (i.e., levitation) is in general very difficult. In such a case, therefore, a nonspherical droplet attached on the bottom of a sample cell or the surface of an electrode has been studied.…”