Exploring Novel Strategies for Universal Detection in Chromatography
Abstract
This thesis presents novel strategies for the universal detection of polar analytes in chromatography. This included the further development of a universal detector that is compatible with organic solvents, as well as exploring separation techniques that are compatible with the universal Flame Ionization Detector (FID). For instance, the universal response of the Acoustic Flame Detector (AFD) was comprehensively compared to the FID, where a very close linear correlation (r2 of 0.9103) was found between them. A few minor exceptions were also observed, where the most notable differences occurred for organometallic compounds. Overall, results indicate that the AFD provides a uniform response toward most hydrocarbons that is qualitatively very similar to that of an FID.
Interestingly, a novel response mode for alkali metals was also observed in a Subcritical Water Chromatography operating regime. Optimal hydrogen flame gas flow rates were found near 40 mL/min for hydrocarbon response and 80 mL/min for alkali response. KCl, NaCl, LiCl and ethanol each displayed a linear FID response with respective sensitivities of 7500, 980, 130 and 1 mV/µg of analyte. This was subsequently demonstrated to greatly alter the FID response of organic salts. Accordingly, their presence in analytical samples or mobile phases must therefore be accounted for when using this detector.
Finally, a novel method of separating polar analytes in Supercritical Fluid Chromatography through dynamically controlling analyte retention by tuning the pH of a water stationary phase is presented. The method utilizes a change in mobile phase from N2 to CO2 to effectively reduce stationary phase pH and control the elution of organic acids from the column. This effect is also observed to be reasonably independent of column length and time. For example in the latter case, at 80oC, a hexanoic acid standard analyte can be readily eluted on demand from a 10 m column by switching to CO2 at any point over a run time of about 1 hour. The N2/CO2 switching system is used to analyze organic acids present in a variety of different samples and it is found that they can be eluted on demand with high selectivity over other matrix components.
Description
Keywords
Chemistry--Analytical
Citation
Scott, A. F. (2016). Exploring Novel Strategies for Universal Detection in Chromatography (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26094