7.2.2.3. Supercritical Fluid Chromatography:
Supercritical fluid means a gas or liquid at conditions above its critical point. A supercritical fluid has both the gaseous character of being able to penetrate anything, and the liquid aspect of being able to dissolve materials. Supercritical fluid chromatography (SFC) has been one of the greatest breakthroughs in analytical chemistry in recent times [129].The use of carbon dioxide in the form of a supercritical fluid offers a substitute to organic solvent as with super critical water chromatography. Using of pressurized carbon dioxide in the supercritical or subcritical state as a chromatographic eluent exhibits the advantage of possessing solvent properties similar to petrochemical-derived hydrocarbons,
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[145]
9. Determination of clonazepam and its related substances in pharmaceutical formulations The use of tetrahydrofuran and methanol as a part of mobile phase and extraction procedure. HPLC with a mobile phase composed of 2% sodium dodecyl sulfate, 0.05 M sodium acetate buffer pH 3.5 and isopropanol in ratio (25:55:20). The use of an environmentally benign mobile phase without hazardous, toxic solvents, simple extraction procedures, relatively lower retention time, no internal standard required, rapid, accurate and precise. [146]
10. Determination of cephalexin in pharmaceutical dosage forms and human urine The usage of hazardous organic solvent. Using a micellar mobile phase composed of 0.1M sodium dodecyl sulphate and 10 % isopropanol. Fast, eco-friendly as avoids usage of toxic solvents and reagents. [147]
11. Quantification of ertapenem sodium Use of highly-aqueous mobile phases which can lead to a decrease in the lifetime of the chromatographic column. RP-HPLC method with a mobile phase consisting of purified water and ethanol (80:20 v/v) with 0.1% formic acid. Simple, economic and eco-friendly.