Analytical devices made of inherently porous material can provide platforms for sensor applications in point-of-care medical diagnostics and environmental monitoring. However, separation and concentration of analytes on such devices has received limited attention. Neither have porous coatings, with their potential high surface area for chromatographic separation, in such devices been studied in detail. This study investigates inkjet printed polyelectrolyte patterns on such a coating as a possible method for concentration and separation of cationic and anionic compounds through surface charge interaction. Both anionic (sodium polyacrylate) and cationic (poly(diallyldimethylammonium chloride)) polyelectrolytes were printed on a custom designed porous pigment coating, having fine internal particle pore structure to ensure high surface contact with analytical samples. Printed polyelectrolyte patterns were poorly visible under visible or ultraviolet light. In a proof of principle test, a controllable degree of separation of three anionic dyes (amaranth, tartrazine and uranine) from aqueous solution passing through a printed cationic polyelectrolyte region was observed. Separation of the two tested cationic dyes (crystal violet and methylene blue) on printed anionic polyelectrolyte regions could not be evaluated effectively with the set-up, since the dyes were too strongly arrested by the anionic micro-fibrillated cellulose binder in the pigment coating. The weakly cationic/zwitterionic dye rhodamine B was shown to remain free to pass in solution through either cationic or anionic printed polyelectrolyte regions. The principles illustrated can provide a basis for enhancing detection on certain analytical device designs.
- Polyelectrolyte, Inkjet printing, Functional printing, Functional pigment coating, Absorption-fluidics