| Part I of this study involved the development of a liquid chromatography column for the size-exclusion analysis of macromolecules over a wide range of molecular weights. By using a mixture of silicas containing 80A diameter pores and 500A diameter pores, a column was constructed which provided for the size-exclusion analysis of polystyrene homopolymers from 517 D to 1.8 {dollar}times{dollar} 10{dollar}sp6{dollar} D. This column was then used to study the retention behavior of the polystyrene homopolymers using two different binary mobile phases. It was found that the behavior of the polymers differed in the two mobile-phase systems. It has previously been observed that a transition from low retention to very high retention occurs over a narrow range of mobile phase compositions. In the present study this was found to be true using a mobile phase consisting of CH{dollar}sb2{dollar}Cl{dollar}sb2{dollar}:MeOH. However, using THF:ACN it was possible to measure retention over a wider range of mobile phase compositions. Thus it was found that not only is the retention process for macromolecules dependent on the nature of the molecules, on the nature of the stationary phase, and on the percentage of "good" and "poor" solvents used in the mobile phase, but it is also dependent on the solvents that make up the mobile phase.; Part II of this study demonstrated the use of capillary electrophoresis (CE) for the analysis of samples of interest to forensic scientists. The use of micelles in CE provides an interactive media for analytes that would not otherwise separate under electrophoretic conditions. The organic constituents of gunshot and explosive materials are largely neutral species. By using micellar CE it was possible to effect the separation of 26 of these constituents in under 10 minutes with efficiencies in excess of 200,000 theoretical plates. Four isomers of dinitrotoluene were resolved to the baseline. Detection limits were found to be around 20 pg for the aromatic constituents and around 100 pg for the aliphatic constituents. The method was applied to the analysis of ammunition shell casings, reloading powders, and plastic explosives, resulting in the identification of the various gunshot and explosive constituents making up each sample. |
