Patent ID: 8857279

Claim:
A method of concentrating an analyte that is in liquid comprising: a) forming a retentate that contains an analyte by passing a liquid that contains an analyte through a stage 1 ultrafilter membrane that the analyte cannot pass through, wherein the stage 1 ultrafilter membrane has a retentate side on which the liquid that contains the analyte is contacted and a permeate side from which a filtrate exits upon passing through the stage 1 ultrafilter membrane; and, b) collecting the retentate by i) displacing filtrate from the permeate side of the stage 1 ultrafilter membrane with a gas to remove liquid and introduce gas into the permeate side prior to collecting retentate, and ii) collecting retentate by flushing the retentate side of the stage 1 ultrafilter membrane with gas and with liquid to produce a retentate solution that comprises the retentate, and iii) collecting the retentate solution.