Use of Alternative Liquefied Gases

While CO2 was the first liquefied gas used for enhanced-fluidity liquid chromatography, other gases may also be useful to increase the fluidity of a liquid mixture. CO2 is limited in its applications in that, when it is included in mixtures with water, carbonic acid is produced. Acidic buffer conditions can be generated for the reversed-phase separations but not basic buffers.

For a gas to be useful as a fluidity modifier, the gas must be highly miscible with the organic liquid solvent and have a low viscosity. Fluoroform is an example of a liquified gas that is highly soluble under similar pressure and temperature conditions to CO2. Accordingly, the efficient separation of basic solutes using basic buffered mobile phases is possible when fluoroform is used to decrease the viscosity of the mobile-phase mixture instead of CO2. For example, Figure 11 shows a comparison of the separation of some triazine herbicides and a common metabolite, hydroxyatrazine, using 64:36mol% methanol-10 mmol L"1 phosphate buffer (Figure 11A) with 51 : 29 : 20 mol% methanol-10 mmol L"1 phosphate buffer-CO2 (Figure 11B) and 51:29: 20 mol% methanol-10 mmol L"1 phosphate buffer-fluoroform (Figure 11C) as the mobile phase with the same flow restrictor. The addition of CO2 clearly causes the co-elution of the more polar solutes. When the chromatogram using the methanol-buffer mixture is compared to that containing the same mole ratio methanol-buffer but with the addition of 0.20 mol fraction fluoroform, use of fluoroform is clearly optimal. The linear velocity and the efficiency increased with the addition of fluoroform. At constant linear velocity, the addition of 20 mol% fluoro-form to the methanol-buffer solution increased the efficiency by approximately 30%.

Figure 11 Chromatogram at same restrictor length and pressure drop of 16.3 atm with different mobile-phase conditions (A) 64: 36 mol% methanol-10 mmol L~1 phosphate buffer; (B) 51 : 29 :20 methanol-10 mmol L~1 phosphate buffer-CO2; (C) 51 : 29 : 20 methanol-10 mmol L~1 phosphate buffer-CHF3. Peaks: 1, ammeline; 2, hydroxyatrazine; 3, atrazine; 4, terbut-ryne. (Reproduced with permission from Yuan and Olesik (1998b).)

Figure 11 Chromatogram at same restrictor length and pressure drop of 16.3 atm with different mobile-phase conditions (A) 64: 36 mol% methanol-10 mmol L~1 phosphate buffer; (B) 51 : 29 :20 methanol-10 mmol L~1 phosphate buffer-CO2; (C) 51 : 29 : 20 methanol-10 mmol L~1 phosphate buffer-CHF3. Peaks: 1, ammeline; 2, hydroxyatrazine; 3, atrazine; 4, terbut-ryne. (Reproduced with permission from Yuan and Olesik (1998b).)

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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