The Oxygen Selective Detector OFID

The phasing out of lead antiknock compounds in gasoline and their replacement by 'oxygenates' - mainly alcohols and ethers such as methyl tertiary butyl ether (MTBE) - created a need for an oxygen-selective detector, easy to use with capillary columns. The O-FID was first proposed by Schneider in 1982 and is now commercially available. The principle of the detector is that the effluent from the GC column is first passed through a microfurnace made of platinum/rhodium alloy heated to about 1200°C where hydrocarbons are cracked to carbon (which is deposited on the Pt/Rh tubing) and hydrogen. Oxygenated compounds on the other hand form CO which is then passed to a second microreactor with a stream of hydrogen. The microreactor containing nickel deposited on alumina is heated to about 350°C and is small enough to fit into the body of a standard FID. Under these conditions each CO molecule is reduced to a methane molecule so that every oxygen atom in the original effluent peak produces one methane molecule. The whole arrangement sounds complex but it works remarkably well for samples up to 20 |g which is of course satisfactory for capillary columns. The detector is ideally suited for the purpose for which it was designed. Figure 4 shows an O-FID chromato-gram of a gasoline sample containing alcohols, water, ethers and acetone. It should be noted that the detector gives a quite respectable peak from the oxygen in the water.

The disadvantages of the detector are its relatively low concentration sensitivity and linearity compared to other selective detectors and the ordinary FID. The limit of concentration sensitivity is about 0.01%.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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