How can you select mobile phase?

Answer 1

Choose a buffer that is well within 1+/- pH unit of its pKa to ensure the best use. Details of buffer preparations can be found within the internet.

Ensure the pH of your mobile phase is at a point at which it will hinder ionisation of the compound under analysis, i.e. very low pH for an acidic compound (low pKa) and high pH for a basic compound (high pKa/low pKb) to prevent ionisation. In this form more reproduce able analysis can be governed.

Answer 2

The pH for the individual component to be analysed, will depend on the chemical affinity of the component towards the stationary phase. The same will be different at different pH. Hence e.g. at pH 4.0 the system suitability is passing or the desired results are obtained then the pH for that analysis decided is to be 4.0

Answer 3

With increase in pH i.e. making solvents basic - you will get increase RT for most compounds and reduced peak tailing.

With decrease in pH i.e. making solvents acidid - you will get decrease RT for most compounds.

However this WONT be true for all columns. You cannot use random column at pH 1.5 - this will damage your column and same applies to working at high pHs - i.e. working at pH 13 - will damage most columns.

Always check the pH capacity in HPLC before choosing mobile phase pHs

Source: I am analytical scientist.

Answer 4

i have plant park immersed in methanol How i can select mobile phase

Answer 5

based on which criteria s mobile phase is selected