|MadSci Network: Biochemistry|
Your question is a little too general to warrant a simple answer. Different applications require different column parameters. For example, a small-scale microanalytical column for organic substances can be 0.3-0.5 mm in diameter, packed with 0.7-1.2 micron beads, containing (for example) C18 silica, whereas a large-scale preparative HPLC column for large peptides can be 1 cm in diameter, packed with 3-5 micron C4 silica. And that's just the hydrophobic columns - there are various applications that call for a huge variety of substrates (sugars, for instance, are particularly finicky).
So, if it's organic materials - it's likely a Cn series with C18 being one of the most common ones, but for everything else - things vary. Likewise, with LC-MS applications the columns tend to be very thin and pack very small beads - whereas semianalytical, semipreparative, and preparative columns can be as large as 1 meter in diameter (that'd be a factory-scale column, which costs hundreds of thousands of dollars).
Hopefully this helps,
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