(1) Sounds like you are new to HPLC so take advantage of information you already have on hand, always review the literature and use guide provided with the specific column you have. The supplier will have some generic suggestions regarding cleaning and storage of the column too. Review them.

(2) Next, become familiar with the specific column you plan on using. NP columns are very easy to maintain and use. Just do not overload or foul them with material. Make sure you dissolve all samples in the mobile phase, 100%, before injection (they should dissolve fully). Filter samples too.

(3) Your column selection is rather unusual, as it is not a typical analytical column. The column contains a large (15 - 20 µm particle size) irregular silica particle (125Å), with high surface area and is 3.9 mm X 300 mm in size. Est column volume ~ 2.5 mL. *This column has applications in PREP LC scale up or for TLC to LC initial applications, not conventional HPLC analysis.

NOTES:

• Normal phase columns like this one may take a long time to equilibrate, esp with solvents such as Ethyl acetate (which has a high UV cut-off, ~256nm). After a few runs, try flushing the column with a solvent such as PURE EtOH at a lower flow rate (due to high pressure) to maintain a moderate system pump pressure (>50 bars). Alcohols such as ethanol are commonly used in NP work and do a good job of removing other solvents from the pores of the silica columns quickly. EtOH has a very low UV cut-off (~ 210nm) so by monitoring the lower UV signal you will be able to tell when all the EtOAc has been flushed off the support. Wash the column often using a solution that dissolves all materials injected 100%.
• Ratios of IPA/HEX (with more IPA) can also be used too, though these are usually less effective as a "column wash" solution. I usually wash them with EtOH first, then re-equilibrate them in the analysis mobile phase. *IPA/Hex (or IPA/Heptane) in various ratios should be tried to for method development.

An ethanol wash column can be employed as a guard column before the analytical column to remove impurities and contaminants that might interfere with the HPLC analysis. The choice of using ethanol as the solvent in the guard column depends on the nature of the impurities and the specific requirements of your analysis. Different solvents or combinations of solvents can be used in guard columns to target specific types of impurities or contaminants. Ethanol is a commonly used solvent for this purpose due to its ability to remove a wide range of impurities and its compatibility with many HPLC applications. However, it's important to consider the compatibility of the solvent with both the guard and analytical columns to ensure the success of your analysis.

Thank you Fouad El Mansouri and William Letter for the response. Could you recommend a suitable normal phase column? My samples include polymers(PPO, SBR) and small organic molecules like Toluene.

Once you have specified the EXACT compounds you wish to analyze, contact the local column suppliers and review their application notes for column suggestions. There is no single "universal" column (instead, we have thousands of available columns) so it is well worth the time researching which specific column may be applicable for your sample types. The column supplier might offer a service where they will try and match a column to your sample(s) in their lab (inquire with them directly). If offered, this service may save you money and time (in some cases it may not as they may sell you a column that does not work well, but provides them with a 'sale'). *In all cases, make sure you work with an experienced chromatographer first, to develop HPLC methods that follow good fundamentals.