Bruce E. Richter

Green chemistry seeks to reduce the environmental impact of chemical products and processes through waste reduction and the use of safer solvents and substances. Chromatographic separation in particular generates significant amounts of harmful organic solvents, acids, bases, and salts, as waste by-products. CO₂-modified solvents have been reported as promising routes to the development of greener analytical methodologies, but normally with stationary phases that are inert to the chemical effects of the CO₂ modifier. We now report the impact of pH and dissolved CO₂ mobile phase concentration on separations that utilize primary, secondary and tertiary amine functionalized silica particles. Ibuprofen, naproxen and ketoprofen, chosen as examples of pharmaceutical analytes containing carboxylic acid groups, have now been separated with CO₂-modified (carbonated) water. Chromatographic retention, selectivity and zeta potential are utilized to demonstrate a dynamic ion exchange mechanism involving both protonation and deprotonation of stationary phase and analyte functional groups. Primary and secondary amine functionalized columns retain the test carboxylic acid compounds more strongly (t_R ≥ 15 min), suggesting that they are beneficial for separations requiring higher retention. The use of CO₂-modified mobile phases has the potential to significantly reduce both solvent and permanent acid use in some chromatographic separations.

CO₂modified mobile phases are used to adjust the retention factor of compounds on (primary, secondary and tertiary amine) functionalized columns.

This paper describes a new in-cell method for pursuing accelerated solvent extraction (ASE) prior to lipid analysis from food samples. It is difficult to pursue direct ASE with acid- or base-hydrolyzed samples due to the corrosive nature of the reagents and material limitations. In this study ion exchange based materials were used to remove acid or base reagents in-cell without compromising the recovery of lipids. The performance data are presented here for the new methods for lipid extraction for a variety of food samples and compared to the Mojonnier method. NIST Standard Reference Materials (SRM-1546 and SRM-1849) were used to validate the ASE methods. Excellent fat recoveries were obtained for the ASE methods. The new methods presented here enhance the utility of ASE and eliminate labor intensive protocols.

The performance of a supercritical fluid chromatograph (SFC) for the analysis of petroleum fractions, specifically diesel and jet fuels, is reported. The SFC instrument passes the requirements of ASTM Method 5186-96 for accuracy, linearity, and repeatability following the proper adjustment of detector gas flows and detector temperature. Up to a sixfold improvement in the precision (measured as relative standard deviation) is seen when the pressure transducer is temperature-controlled independent of the laboratory air temperature.

Accelerated solvent extraction (ASE) is suitable for the extraction of PAHs from solid samples, as a sample preparation technique for subsequent analytical techniques. Due to the elevated temperatures and pressures used for ASE considerable time and solvent savings are achieved. The time required is less than 15 min. per sample, and solvent usage is reduced significantly (15 mL per 10 g sample) compared to conventional solvent extraction techniques like Soxhlet extraction. Equivalency of the extraction results are shown by the cornparision of ASE to conventional extraction techniques. ASE has already been accepted by the U.S. EPA, and meets the requirement of SW-846 method 3545.