Experimental Methods and Instrumentation

The instrumentation required to do enhanced-fluidity liquid chromatography is very similar to a standard HPLC with two exceptions. Firstly, the components of the mobile phase (liquefied gas and associated liquid) are mixed under pressurized conditions. Therefore two pumps are required to make the mixtures. Either syringe pumps or reciprocating pumps may be used. Pumps that are commonly used for SFC are optimum for pumping the liquefied gases. Secondly, the outlet of the column must be pressurized to maintain single-phase conditions for the mobilephase mixture at least until after the solutes are detected. Therefore a flow restrictor similar to those used in SFC is used in enhanced-fluidity LC. However, the problems which are often experienced in SFC with restrictor plugging do not occur in enhanced-fluidity LC because phase changes are not occurring in the restrictors and the solvent strength of the enhanced-fluidity liquids is greater than that of commonly used supercritical solvents. Finally, phase diagram information can be used to determine what the minimum operating pressure at the end of the column should be, to ensure that the mobile phase is operating under single-phase conditions. This information for the mixtures described herein is readily available in the literature.

Figure 4 Variation of Kamlet-Taft n* as a function of mixture composition for methanol-CO2 mixtures at 25°C and 170 atm. (Reproduced with permission from Cui and Olesik (1991).)

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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