Nice question Mr. Santhosh, agree to the continuous back pressure with the proportion of the particle sizes. We are known an analyt interaction with stationary phase based on the style of column packing. In monolith column part of particle size is doest mean to implement an efficiency of column. However, the porosity of monolith column might be suspect to increase surface area for large molecular reactivity. hence the large space availability reduce the back pressure and diffusion of analyte through the channel in monolith also reduce the same effect. It also might be seems to the logic behind less a void space availablity of particle interaction in silica based column considered to be minimum, as you state of back pressure assumption is correct. If you just read Kelvin eqn. for wet theta angle in capillary condensation reactions of porosity you may get more information regarding your assumption. I may not familiar with technical experience of your column works. Little theory based I give some suggestion, but you only to be realized what the fact behind this. Thank you.

This is answer to the person (VIT institute), who had a doubt about the choice of solvent for extraction of phenol by hplc method. The choice of mobile phase, suppose to be a aqueous solvent increase the retention of time, due to intra molecular interaction of your analyt (phenol) on the column. For this reason, to increase the hydrophobic nature of column can be done with less polar solvent than water by organic solvents methanol/ acetonitrile. Therefore, the choice of solvents depends on the choosing of column interaction with an analyt sample. If you run the HPLC with different solvent usage may get more experience to understanding the knowledge in choice of solvent.

For the question about monolithic column vs. silica based column:

Because there are usually large pores (micrometer range) in the monolithic column, the backpressure is evidently lower than silica based column. Also, due to large pores, the monolithic column is not easy to clog, so the backpressure is reasonably stable when you do continuous analysis. However, the separation capacity of monolithic column usually is not as high as silica based column because of not uniform particle size.

Thank you, Hariharan and Liangliang for your answers, As of present we got good results using monolithic columns with LLE and protein Precipitation as suggested by Sun separation capacity of silica based column is good but in our case we are getting comparable results on silica and monolithic. So I guess it is always a good idea to use monolithic columns (when separation and Resolution are unaffected) in LLE and Protein Precipitation!!!!!!

I my knowledge monolithic columns are available from Merck, do you people know any other vendor and different chemistry available??