Droplet size control with methanol-repellent surface in a sampling device for continuous annular electrochromatography.
The eluent droplet size defines the number of sampling compartments in a continuously operated annular electrochromatograph and therefore influences separation efficiency. In this work, an assembly of two capillaries, a feeding capillary on the top and a receiving capillary placed under it, has been investigated to control droplet size. The receiving capillary prevents the liquid droplet formation beyond a critical size, which reduces the volume of sampling compartment as compared with the case of the electrolyte flow driven solely by gravity. With a receiving capillary, the electrolyte droplet size was reduced from 1.5 to 0.46 mm. Further decrease of droplet size was not possible due to a so-called droplet jump upwards effect which has been observed on a hydrophilic glass surface with water. A typical electrolyte used in CAEC has high methanol content. In an attempt to improve the methanol-repellent properties of the glass surface, two approaches have been implemented: (i) self-assembled chemisorbed monolayers of an alkylsiloxane and (ii) fabrication of a nano-pin film. The methanol-repellent surface of the feeding capillary suppressed the droplet jump upwards effect. The surface remained methanol repellent in different solutions with lower polarity than that of water.
Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Micro Flow Chemistry & Process Technology, Eindhoven, The Netherlands.
Qi
Q
Wang
Evgeny V
EV
Rebrov
Volker
V
Hessel
D053801:Capillary Electrochromatography / Q000295:instrumentation; D000432:Methanol / Q000737:chemistry*; D012833:Siloxanes / Q000138:chemical synthesis / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D012833:Siloxanes; D014867:Water; D000432:Methanol