Gas Diffusion in cFI Format
Flow based gas diffusion techniques are well suited for separation of volatile species form aqueous solutions. The first work on FI –gas diffusion technique was concerned with assay of total inorganic carbon (Baadenhuijsen 1979). Sample, injected into an acid carrier stream released carbon dioxide that diffused across a silicone membrane from a donor (red) to an acceptor (green) stream, thus changing the color of an acidobasic indicator. Since then, hydrophobic Teflon® membranes became widely used, allowing ammonia, sulphur dioxide, chlorine, ozone, hydro cyanide, ethanol, acetic acid, hydrofluoric and hydrochloric acid as well as many other volatile compounds, (Luque de Castro 1998, 2008) to be selectively separated from complex aqueos matrices, and determined either by spectrophotometry or by eletrochemical detection. The drawback of Teflon ® membranes was fouling by surfactants that destroy the air gap barrier. Recently new polypropylene membrane materials, developed for lithium batteries, far more mechanically stable than Teflon® made “plumbers tape”, became available. Also replacing the constant flowrate by programmed flowrate allowed miniaturization of gas diffusion module thus increasing sensitivity and improving LOD of gas diffusion methods.
H. Baadenhuijsen & H.E.H. Seuren-Jacobs, Clin. Chem. 25, 443, (1979)
M. D. Luque de Castro & I. Papaefstathiou, TRAC, 17, 41, (1998)
M.D. Luque de Castro , Membrane Based Separation Techniques, Dialysis, Gas Diffusion and Pervaporation.
Ch 8 in S. D. Kolev, I. McKelvie, Ed. Advances in FIA and Related Techniques. Elsevier , Amsterdam 2008
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