Determination of Trace Oxygen in Gases

Abstract

4 rapid and accurate method for the determination of oxygen in inert cover gases was required for experiments involving oxygen-sensitive materials. The method developed is spectrophotometric, utilizing the oxygen-pyrogallol complex. The apparatus is constructed in a manner which allows for direct calibration. Blank, or reference solution, values are determined for each analysis. Equilibrium conditions are established with the aid of a 70" C. controlled temperature bath. Beer's law is obeyed for a range of 0 to 800 micrograms of oxygen. The method has been applied to the determination of traces of oxygen in nitrogen, argon, helium, and hydrogen.ECENT projects at this laboratory involving high purity R inert gas "blankets" necessitated analysis of samples for trace oxygen on a routine basis. Various difficulties were encountered in applying the methods proposed in the literature. A variety of colorimetric methods based on oxidation of ferrous iron and subsequent determination of ferric iron color complexes is reported by Mellan (4). Most of these complexes were found t o be somewhat unstable and nonreproducible. The method of Shaw ( 5 ) showed promise, but vas rather involved for routine application, as was that of Hand ( 3 ) . The latter was, however, the most sensitive and consistent of all methods tried. One 10 ASPIRATOR TO SAMPLE SOURCE LJ Figure 1. Apparatus significant lack of all methods was a means of determining a reliable reagent and procedural blank. Blanks could be determined on separate samples, but the variance between blanks was greater than the per cent of oxygen in the sample in question. Most of the methods investigated involved complicated apparatus and subsequent difficulty in applying the method routinely. I O C 8C W 0 z a E 6C z v) 2 0: a t-4 c 8 2c C 0 -ixio-2gms O X Y G E N o-ix 1 0 -3 g m s O X Y G E N -3 X ~o -~g m s OXY GEN --CORNING FILTER #50 5 0 4 5 0 550 6 5 0 75c Figure 2. Transmittancy Curves W A V E L E N G T H ( M k )The method here described was devised with an eye to accurate routine determination of traces of oxygen in gas samples. "Blanks" are determined for each run and represent true reagent and operational values. The method is colorimetric and is based on the oxidation of an alkaline solution of pyrogallic mid.The pyrogallol-oxygen complex undergoes a rearrangement before a ronstant optical density is reached. Willstatter and Heiss ( 7 ) have postulated that the oxidation of pyrogallol progresses through several intermediates. The authors have found

Modeling the Syn Disposition of Nitrogen Donors in Non-Heme Diiron Enzymes. Synthesis, Characterization, and Hydrogen Peroxide Reactivity of Diiron(III) Complexes with the Syn N-Donor Ligand H2BPG2DEV

“…When H 2 O 2 was added to a basic solution of the diiron compounds 6 , 7 , or 8 , O 2 formation was observed, as confirmed by a test with an alkaline pyrogallol solution 63,64. The catalase-like activity of the carbonato complex 8 was investigated in more detail and the O 2 formed in the reactions was quantified.…”

“…A test with an alkaline pyrogallol-solution confirmed the formation of dioxygen 63,64. The intermediate products from reactions with H 2 O 2 , 6a , 7a , and 8a , in solutions of CH 3 CN/H 2 O were monitored by UV-vis spectroscopy.…”

Detection of small quantities of photochemically produced oxygen by reaction with alkaline pyrogallol

“…The photolysis cell was made of cylindrical quartz with two optical windows giving a path length of 5 cm. The total volume of the (1) Copper powder furnace to remove oxygen, (2) and (3) alkaline pyrogallol gas scrubbers, (4) irradiation cell, (5) cold finger, (6) detection cell in spectrometer, (7) silicone oil gas bubbler to stop suck-back, (7a) gas flow meter, (8) blackened support board, (9) lens, (10) filters, (1 1) water cooled filter, (12) xenon-arc lamp, 250 W cell was 150 mL and the contents were stirred by a well dispersed flow of carrier gas. A septum seal at the top of the cell facilitated removal of photolysate for analysis and allowed injection of oxygen-saturated water for calibration purposes.…”

Evaluation of Polymeric Materials I.

“…complexation of oxygen by pyrogallic acid in an alkaline solution (14). The following reagent was used in this study: pyrogallic acid, 4 Gm.…”

“…The quantity of oxygen passing through the films was determined by the Beckman model B spectrophotometer at room temperature. The wavelength of 425 mfi was used as suggested by Williams, et al (14). The presence of oxygen was also noted visually by the change of a nearly colorless solution to varying shades of brown and then to black.…”