Oxygen interference

Volkamer, R., T. Etzkorn, A. Geyer, and U. Platt, Correction of the Oxygen Interference with UV Spectroscopic (DOAS) Measurements of Monocyclic Aromatic Hydrocarbons in the Atmosphere, Atmos. Environ., 32, 3731-3747 (1998). 

Adamic and Bartak [6] used high pressure aqueous size exclusion chromatography with reverse pulse amperometric detection to separate copper(II) complexes of poly(amino carboxylic acids), catechol and fulvic acids. The commercially available size exclusion chromatography columns were tested. Columns were eluted with copper(II) complexes of poly(aminocarboxylic acids), citric acids, catechol and water derived fulvic acid. The eluent contained copper(II) to prevent dissociation of the labile metal complexes. Reverse pulse electrochemical measurements were made to minimise oxygen interferences at the detector. Resolution of a mixture of DTP A, EDTA and NTA copper complexes was approximately the same on one size exclusion chromatography column as on Sephadex... 

Figure 2. Cyclic voltammetry showing oxygen interference on chlorine detection. Bare amperometric sensor in a 0.1 M KC1 solution, 1) N2, 2) N2 +...

Other methods have been developed for the removal of oxygen (particularly from flowing streams).These include the use of electrochemical or chemical (zinc) scrubbers, nitrogen-activated nebulizers, and chemical reduction (by addition of sodium sulfite or ascorbic acid). Alternately, it may be useful to employ voltammetric methods that are less prone to oxygen interference. The background-correction capability of modern (computerized) instruments is also effective for work in the presence of dissolved oxygen. 

Oxidative electrochemical detection has tended to be used more frequently, but this is only because it is more robust and easier to operate. Reductive analyses suffer from problems with oxygen interference and the requirement to use mercury as the electrode material. 

Either a gold or platinum electrode may be used in a PAD, although gold electrodes are more popular. One reason is that dissolved oxygen contributes a cathodic response at a platinum electrode over the entire useful range for anodic detection. Serious oxygen interference at the gold electrode can be avoided by careful selection of detection potential. 

Because luminol detection for the PANs does not suffer from the oxygen interference which affects BCD, separation of NO2 and the PANs can be accomplished in a much shorter analysis time with luminol detection and the same nonpolar column materials. Bigure 19.6 shows three replicate analyses of room air, every 30 sec, with fast gas chromatography and luminol chemiluminescence detection (GC/LCD), a capillary column, and a 5-cm sample loop. The column used in Bigure 19.6 is a 10 m X 0.53 mm i.d. DBl capillary column maintained at room temperature (25°C). A carrier gas mixture of 5% O2 in helium was used at a flow of 60 cm min The arrows in Bigure 19.6 indicate the NO2 peak (first elution) at a RT of approximately 6 sec and... 

Another sensor type [158] utilizes the effect of water vapor on the fluorescence quantum yield of adsorbed fluorophores. Thus, a silica-gel-adsorbed perylene dy when excited with an LED at 490 nm, shows a ca 90 Fo reduction in fluorescence on going from 0 to 100% relative humidity. Although this sensor covers the whole humidity range, the response is not linear, and oxygen interferes to some atent. 

It is important that oxygen gas was extremely scarce in Earths early atmosphere. If it had been more abundant, life as we know it probably could not have evolved. Oxygen interferes with the chemistry that... 

Yamaguchi,T., Kiwa,T.,Tsukada, K. and Yokosawa, K. (2007), Oxygen interference mechanism of platinum-FET hydrogen gas sensor. Sensors and Actuators A, 136(1), 244-8. 

Dissolved oxygen occurs at high concentrations in natural waters ( 3 x 10 " moll ) and interferes with voltammetric measurements. Therefore, oxygen interference is usually removed by deoxygenation of the sample for a period of 3-5 min using an inert gas... 

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