Why acetonitrile and methanol are most commonly used solvent for reverse phase HPLC?
These two solvents can mix well with water at any ratio and do not have significant UV absorption within the UV detection range. They are also easy to obtain. 18. What are the differences between acetonitrile and methanol as mobile phase? Acetonitrile has lower UV absorbance at short UV region (200-210 nm) and is better choice if your UV detection is in this region (such as for some small organic acids). Acetonitrile also generate lower back pressure than methanol. This is good when you are trying to use higher flow rate or when your column is partially clogged. On the other hand, methanol is of lower cost. It is also more stable than acetonitrile. When acetonitrile is dry and is exposed to ambient light, some polymers may be produced which may block your HPLC valves or filters. It is a good idea to use amber bottles for acetonitrile. 19. What are the differences between reverse phase HPLC and normal phase HPLC? In the reverse phase LC, the mobile phase is polar and the column packing
