A fast, highly efficient, continuous degassing device and its application to oxygen removal in flow-injection analysis with amperometric detection

A new continuous degassing device, based on the permeation of gases dissolved in a liquid through the walls of a narrow-bore polymeric tube, is described. The key innovation, responsible for the superior efficiency in relation to other designs, consists in maintaining a reduced pressure of an inert gas (N2, ca. 1600 Pascal) in the degassing chamber that contains the coiled polymeric tube wandered by the solution. When applied to the continuous removal of oxygen from an electrolyte in flow-injection analysis, FIA, with amperometric detection (flow of 1.0 mlmin, 34 s residence time), a decrease of at least 99.97% in the oxygen reduction current is experienced. Routine determination of 80 samples per hour of heavy metals like cadmium is afforded with a detection limit of about 10 ppb (1.8 × 10−12 mol of Cd(II) for 20-μl injections), by using a sessile drop mercury electrode. FIA with pre-concentration followed by voltammetric stripping extends the detection limit to the sub-ppb level, as illustrated by monitoring lead and cadmium in samples of drinking water.