In-line sample concentration by evaporation through porous hollow fibers and micromachined membranes embedded in microfluidic devices.
Two types of microfluidic systems, a porous hollow fiber and a thin supported membrane with an array of micromachined holes, are investigated for concentrating mass-limited analyte samples. Water evaporation is driven by the partial pressure difference across the hydrophobic membrane, induced by dry sweeping gas on the permeate side. An analytical model permitting clarification of the contribution of design and process parameters on acquisition of concentrated solution and prediction of achievable concentration factors is presented. Concentrating an exemplary solution utilizing the two systems has been studied at different experimental conditions to validate the model. The results show that the hollow fiber gives controllable concentration factors of more than 10. For the micromachined membrane concentrator concentration factors of 6-8 were achieved, at much lower flow rates than predicted by the model. Because of the asymptotic dependence of concentration factor on flow rate, accurate control of the liquid feed is extremely critical in the flow rate range where high concentration factors are obtained, and the smallest variations in liquid flow rate may easily lead to supersaturation and deposition of solutes in the pores. This changes membrane porosity in an unpredictable way and limits the maximum attainable concentration factor.
Mesoscale Chemical Systems Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
Hainan
H
Zhang
Mesoscale Chemical Systems Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
Roald M
RM
Tiggelaar
Mesoscale Chemical Systems Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
Stefan
S
Schlautmann
Mesoscale Chemical Systems Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
Jacob
J
Bart
Mesoscale Chemical Systems Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
Han
H
Gardeniers
D004867:Equipment Design; D008567:Membranes, Artificial; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D016062:Porosity
D008567:Membranes, Artificial
Microfluidics; Micromachined membrane; Sample concentration