A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. A hybrid echo canceller includes a limited tap length FIR filter to cancel short-term echo, while an interpolated filter is used to cancel the long-tail echo. The lower gate electrode layer and the cap gate layer are patterned to form a gate electrode structure. Then first and second bag sections, which may be on a first and second side respectively of a web of folded bag material, or on a first web and second web of bag material respectively, are dispensed with the combined web of valve material positioned in between, and brought together to form a combined web of valve bag material.