| Recent research in Gas Chromatography (GC) has focused in the areas of high-speed separations, micro-fabrication and methods development for the analysis of mixtures containing large numbers of components. Methods for high-speed separations often involve the use of shorter columns, high carrier gas velocities, micro-bore columns and fast temperature-programming. While these methods do reduce analysis times, their applications are limited. Common test mixtures for GC analysis may contain up to several hundred components and with shorter columns, the peak capacity is limited and therefore the resolving power is decreased. The development of methods for the more efficient use of the available peak capacity is therefore of great interest.; The development of selectivity enhancement techniques using pneumatic and thermal methods on a series-coupled dual-column ensemble is discussed. By controlling the carrier gas flow or temperature on each of the two columns, peaks can be separated at the ensemble outlet that would otherwise co-elute. Methods presented include pressure-pulse modulation, stop-flow operation, at-column heating and zone heating.; A spreadsheet-based model was used to study experimental parameters and to design experimental methods. This model uses a series of equations to calculate carrier gas velocity, temperature, carrier gas viscosity, retention factors and time as a function of solute position over the length of the column. The model results in a band-trajectory plot that shows the path each solute takes from injection to elution.; Comprehensive two-dimensional GC (GC x GC) is an emerging technique that offers both an increased peak capacity and detectability. Using this method, sample components are separated in two orthogonal dimensions, resulting in a chromatogram in which peaks are displayed across a two-dimensional plane. Samples studied using this technique include tholin, a synthetic analogue to the atmospheric haze particles that surround Titan, soils, minerals and meteorites. A pyrolysis inlet system was used so that samples that would not otherwise be suitable for GC analysis could be studied, and TOF-MS detection was used for peak identification. These samples were chosen for their complex nature and for their similarity to the mixtures that may be observed by the 2009 Mars Science Laboratory (MSL) mission. |
