SummaryAlumina-coated porous layer open tubular (PLOT) columns are widely used for analyses of light hydrocarbons (Ci to C6). There is, however, a need for improved selectivity for complex analyses such as the determination of impurities in high purity petrochemical products. Some commercial alumina PLOT columns do not have sufficient selectivity for such analyses. The selectivity of four commercial alumina PLOT columns is evaluated for analyses of propylene and ethylene, and differences in column selectivity discussed. Requirements of column selectivity and retention are presented for several applications including the analysis of refinery gas, transformer oil gas, and fuel gas.
An approach is described for optimizing chromatographic conditions for dual‐column analysis of U.S. EPA Method 608 pesticides. Sample throughput for environmental analysis of pesticides can be increased by performing the screening and confirmation analyses at the same time. This requires simultaneous injection, separation, and detection in a GC with dual inlets, columns, and detectors. Resolution maps for flow rate and temperature relationships of poorly resolved peak pairs for 5%‐phenyl methyl silicone and 7%‐cyanopropyl 7%‐phenyl methyl silicone capillary columns are presented. Resolution of target pesticides on the 5%‐phenyl methyl silicone column was much more sensitive to changes in flow and temperature‐ramp rates than was the 7%‐cyanopropyl 7%‐phenyl methyl silicone column. Optimal conditions resulted in a run time of approximately 20 min.
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