By Anonymous on Thursday, November 20, 2003 - 01:58 pm:
What is the correct way to calculate HETP when using a guard column: to add guard column length to the main column length in the formula or not? Does the answer depend on their relative size?
By Chris Pohl on Monday, November 24, 2003 - 12:27 pm:
Frankly, it's a bit strange to perform such a calculation in the first place since the main purpose of the guard is to protect the analytical column not to improve the separation. But, if your going to calculate HETP with guard and analytical column, you should add the column lengths.
By Anonymous on Tuesday, November 25, 2003 - 09:03 am:
Thank you, Chris,
Of course our main purpose is to protect the column. I was wondering, because sometimes the guard cartrige is 3mm long and main is 300mm, and there are methods with guard 10mm long and main 150mm. I thought that HETP is a characteristic of a main column, sinse we assume that separation is not affected, than why add? But in a case with 10mm guard I am not sure what to do.
Thank you.