Fouling is resolvable for at minimum multi-day operation if not multi-week operation using size-selective membranes that pass the analyte but not large foulants such as albumin (Figure ). However, this precludes quantification of proteins that have similar size to large protein foulants since they will also be excluded by protective membranes. Fouling is also potentially resolvable using antifouling chemistry at the fluidfacing terminus of monolayer molecules, albeit less proven in practice for multi-day operation.