Chrom Tech offers both Positive Pressure and Vacuum manifolds for Solid Phase Extraction and Filtration Membranes, but, we always recommends Positive Pressure Manifolds, here’s why:
A major problem with conventional vacuum manifolds occurs as faster flowing channnels in theSPE plate (or cartridges) run dry, allowing a free flow path for vacuum through the dry ports,thereby slowing the flow in the remaining wells. The result is variation in column processingtimes, thus contributing to irreproducible analyte recoveries.In contrast, our positive pressure manifolds have restricted-flow gas ports. These ports createsuperior flow control such that even if 95 out of 96 wells (47 out of 48 ports) are empty, dry, orwet, the remaining single port will receive normal pressure to allow easy processing.Our positive pressure manifolds are an efficient solution to viscous samples. Vacuum manifoldsoften cannot provide adequate processing power, since the maximum pressure is limited toless than atmospheric pressure (approx. 15 PSI). The positive pressure manifold allows for gaspressures up to the supplied line pressure (typically 60-75 PSI), thus supplying greater motive force for viscous sampleflow. Adjusting the pressure up or down, produces a column flow response that is smooth and immediate.