Chromatography Forum

I have recently purchased a REZEX ROA H+ column. After attachment of the compatible guard column, backpressure of the system increased ( by ~150 psi) and the retention time got delayed (by ~ 3 mins) from the one mentioned in Certificate of Quality Assurance.

The column is brand new and we have just injected standards.

Is is possible that addition of a guard column affects the back pressure and retention time of a column?

When using a guard column (same material as the column?), you are raising the total coloumn length. This affects all parameters which - among others - depends to the length of a column like pressure, retention time etc.

As long as the increased parameters are reasonable, it should be no problem.

The effects of a guard column depends also to the ratio guard column/column.

A guard column with the length of 1/2 of the column affects the parameters more than a guard column with 1/20 of column length.

Guard column is part of the separation system. Guard should be included when doing validation of the method.
Back pressure is increased, for sure. 3cm more column length are significant.
Please use a direct coupler which should be death volume free. MAde from PEEK is recommended.
If a guard column is used during validation, it must be used when ever this method is running.
Good luck

Gerhard Kratz!

I am using a coupler which was provided by Phenomenex with another column. I don't think it will cause any problem.

Thanks for your response

asm!

The column length is 300mm and the guard column is 1/6th of column length i.e. 50 mm.
Both are made of the same material.

The pressure is 696 psi which is less than the max. 1000 psi.

Thankyou so much for your response

i had a recent problem with a Agilent column with a Phenomenex Guard but for me it was a faulty Guard but phenomenex told me it was the column only when the column was tested at Agilent we found it was the guard

Christopher_j !

What was the problem exactly? Did they replace the guard column?

I thought Phenomenex has solved all problems with their guard columns, mainly the holder?
95% of all column complaints are, at the end of the day, not related to the analytical column.

How can we identify if there is a manufacturing defect with the guard column?

Check the back pressure of 1.) system without any column, 2.) column without guard column, 3.) column with guard column and 4.) guard column without column. Post the values here.

Connect the holder to your system, without guard column and see if back pressure increases significantly.
Test from both sides. If one side gives high back pressure ask Phenomenex to exchange the holder.

Check the back pressure of 1.) system without any column, 2.) column without guard column, 3.) column with guard column and 4.) guard column without column. Post the values here.

Good advice.

My biggest complaint with many guard cartridges is that they apparently are too small for many manufacturers to put identification and/or part number on the cartridges, so when troubleshooting one cannot even verify whether the correct type of guard cartridge had been used. Invest in some printing or stamping equipment, guys !!!

Another complaint is that each supplier wants you to only use their system, so most guard cartridges only fit in that supplier's holders (which typically also don't have a part number stamped on them either).

My biggest complaint with many guard cartridges is that they apparently are too small for many manufacturers to put identification and/or part number on the cartridges, so when troubleshooting one cannot even verify whether the correct type of guard cartridge had been used. Invest in some printing or stamping equipment, guys !!!

Another complaint is that each supplier wants you to only use their system, so most guard cartridges only fit in that supplier's holders (which typically also don't have a part number stamped on them either).

This is SO TRUE! But it is still better to throw away a cartridge you are not sure about (~26 €, phenomenex) and reuse the holder, compared to buying completely one-way cartridges (e.g. ZIC HILIC starting at 160 €)...

Jörg

It is not true . Buy our guards - all information including lot number, serial number etc is visible:
http://www.sielc.com/Products_GuardColu ... mesep.html

Check the back pressure of 1.) system without any column, 2.) column without guard column, 3.) column with guard column and 4.) guard column without column. Post the values here.

1. System without any column- 131 psi
2. Column without guard column- 537 psi
3. Column with guard column- 682 psi
4. Guard column without column- 334 psi