ASTM D5441 Standard Test Method for Analysis of Methyl Tert-Butyl Ether (MTBE) by Gas Chromatography
4. Summary of Test Method
4.1 A representative aliquot of the MTBE product sample is introduced into a gas chromatograph equipped with a methyl silicone bonded phase fused silica open tubular column. Helium carrier gas transports the vaporized aliquot through the column where the components are separated by the chromatographic process. Components are sensed by a flame ionization detector as they elute from the column.
4.2 The detector signal is processed by an electronic data acquisition system or integrating computer. Each eluting component is identified by comparing its retention time to those established by analyzing standards under identical conditions.
4.3 The concentration of each component in mass percent is determined by normalization of the peak areas after each peak area has been corrected by a detector response multiplication factor. The detector response factors are determined by analyzing prepared standards with concentrations similar to those encountered in the sample.
5. Significance and Use
5.1 The presence of impurities in MTBE product can have a deleterious effect upon the value of MTBE as a gasoline additive. Oxygenate and olefin contents are of primary concern. This test method provides a knowledge of the composition of MTBE product. This is useful in the evaluation of process operations control, in the valuation of the product, and for regulatory purposes.
5.2 Open tubular column gas chromatography with a flame ionization detector, used by the test method, is a technique that is sensitive to the contaminants commonly found in MTBE, and a technique that is widely used.
6. Interferences
6.1 Cyclopentane and 2,3-dimethylbutane have been observed to co-elute with MTBE. However, these are not commonly found impurities in MTBE.
