Reverse phase liquid chromatography most polar solvent

Most HPLC is based on the use of so-called normal-phase columns (useful for class separations), reverse-phase columns (useful for homolog separations), and polar columns (used in either the normal- or reverse-phase mode). Since reverse-phase HPLC columns are generally easier to work with, almost all authors use high-performance reverse-phase liquid chromatography with octade-cyl chemically bonded silica as the stationary phase and nonaqueous solvents as mobile phases (so-called NARP, or nonaqueous reverse-phase chromatography). 

Reversed phase liquid chromatography was performed on a 150 mm x 3.0 mm Waters Symmetry C-8 column at 30 °C and a flow rate of 1.0 mL/min. The solvent phase was acetonitrile tetrahydrofuran 0.1 % aqueous phosphoric acid (50.4 21.6 28v/v/v). Under these operating conditions, most of the UV absorbance occurred as a peak at 3.83 minutes for all samples. Chromatograms of all samples had some small peaks (presumably the more polar compounds) eluting prior to the major peak. Product C presented a small but significant UV absorbing peak that eluted after the peak at 3.83 minutes. 

Separation of phenols with LC is normally performed with reversed-phase liquid chromatography (RPLC). The mobile phase consists of a mixture of a polar organic solvent (methanol or acetonitrile) and an aqueous buffer, and in most cases different types of hydrophobically modified silica, Cis, or Cs columns are used as analytical columns. 

Alkyl substituents (specifically the octadecyl ODS form) are the most common bonded groups these convert the surface polar hydroxyl groups to a markedly hydrophobic surface upon which chromatography occurs. Elution is carried out with polar solvents such as water and methanol there is a polarity reversal of the stationary and moving phases compared with conventional liquid chromatography on silica, hence the term reverse-phase HPLC. 

The most commonly used separation technique is open column separation using clay followed by silica gel, e.g., ASTM D2007 [52]. Polar components in the mixture are retained on clay, and saturate and aromatic compounds are allowed to flow through the column. The polar components can be recovered later using a polar solvent for analysis or further separations [78]. The mixture of saturates and aromatics is then separated on a silica gel column using proper solvents. High-performance liquid chromatography (HPLC) with both normal phase and reversed phase procedures can also be used for the same purposes [58]. 

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