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 sueerior efficiency in relation to other designs, consists in maintaining a reduced pressure of an inert gas (N-2, 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 ml/min, 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 x 10(-12) mol of Cd(II) for 20-mu l 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.