Oral: High Efficiency Ion Chromatography Electrodialytic Suppressors using 3D Printed Monolithic Channels

Electrodialytic membrane suppressors are used in ion chromatography to neutralize an eluent acid or base thereby lowering the background conductance and enhancing analyte detection. The suppressor design must balance maintaining the chromatographic efficiency with the maximal eluent concentration that can be used. To minimize dispersive broadening, we have used high resolution stereolithographic 3D printing (<25 micron resolution) to generate monolithic porous flow channels inserted between the ion exchange membranes. The monolith is comprised of a 3D gyrohelic structure (“gyroid”) which is a triply periodic (repeats in all 3 axes), continuous, smooth surface. This geometry has been thoroughly investigated in high efficiency heat exchanger applications; notably heat transfer efficiency is often analogous to mass transfer in suppressors and chromatography. This new design overcomes several shortcomings in previous suppressor designs including improved pressure tolerance, robustness, and dispersion. The channel monolith is surrounded by and bonded to a smooth solid perimeter which serves as a hard sealing surface. This prevents collapse of the packed bed due to the pliable membranes distending under high pressure or rupture of the soft seals of other designs. The presently fabricated channels exceed commercial state of the art devices with dispersion volumes < 400 µL2 for use with 4 mm columns. On average, plate heights were 1.51 mm, compared to 1.61-1.74 mm observed on the commercial 4 mm suppressors. Following printing, the device remains in an uncured state which permitted facile polymer grafting of ionic monomers to improve the overall ionic conduction of the device. Suppressed chromatographic separations of 9 mM Na2CO3 had conductance noise of < 0.03 µS/cm and were comparable with the commercial devices. The device also showed ~50% lower pressure drop than devices of comparable efficiency consistent with monolithic stationary phases.