Examining the quenching effects of modifiers in packed column supercritical fluid chromatography with flame photometric detection

The quenching effects of organic modifiers are examined in packed-column supercritical fluid chromatography (pSFC) with flame photometric detection (FPD). Previous FPD experiments with capillary-column SFC demonstrate that relatively large percentages of added organic modifiers (i.e. 20%) do not quench emissions severely. However due to the larger column flows used, quenching is found to have a much greater effect in pSFC. It was observed that very low amounts (near 0.5%) of modifier added to supercritical carbon dioxide completely quenched the chemiluminescent emissions of sulfur and phosphorus test analytes. This was consistently observed or several commonly used modifiers added to the mobile phase at varying concentrations. Results show that, as the carbon content of the modifier increases, the quenching effect also increases. Further findings suggest that a modifier with a higher oxidation state produces less quenching. Results indicate that the FPD is not a practically suitable detection method for pSFC applications requiring typical modified mobile phases.