Chromatography Forum

I am a new HPLC user. My Agilent 1100 system was blocked. I listed how to diagnose system block as below. Please add more that I missed and correct any mistake I made.

How to solve frit block problem?
How to do pressure test?

Diagnosis for system block procedure:
1. switch a column to a connecter to check if the pressure can drop. Yes, Column blocked. No, it might not be the column
2. open the connecter to see if there is any liquid coming out (1ml/min). Yes, it is after the column. No, it is before the column
3. Open the black valve. With 1ml/min flow, if the pressure is larger than 5 bar, the frit is blocked (the salt concentration of my mobile phase matters)
4. 6-port valve can be used to diagnose the block location

Add:
1. can be changed to: unscrew column inlet and check if the pressure drop. Yes, column may be blocked.

5. There may be blockage in ALS (needle or needle seat). I'm not sure right now but I suppose that you cannot raise needle (ALS diagnose-Positions -Needle up) without automatic switching to bypass with 1100 series ALS. Then unscrew the needle holder, raise needle manually and check if the pressure drops.
I found several times a piece of septum inside needle or directly in needle seat.

6. sometimes is blocked connection capillary somewhere in system.

7. Another malicious problem is blockage of inlet frits (directly in mob. phase bottle).

How to solve frit block problem?

Did you mean my point 7? I solve this with sonication in HNO3 conc. (must be carefully cleaned with water before and after this)

How to do pressure test?

Agilent offers for their systems Blanking nut (P/N:01080-83202) which you must use for proper blocking. Then you can test individual modules for tightness (pump on purge valve, ALS on Rheodyne output, col. heater on column inlet). Do not test detector and system with installed column.

Regards
Jan

You may want to use "divide and conquer" approach to sort out your problem. Detach your LC inlet from MS or DAD cell, take one compont off the line at one time, and monitor the pressure. If you see significant prsssure drop after removing one compont, e.g. cloumn, at the degree that are not supposed to be. You find the culprit.

Good luck

thank
I found the location.

it is the 3 ul heating part that is blocked. I was running 50 C and I stopped flow without lowering the temperature first. so that part ran dry and some salt condensed and blocked the path right away.

thanks everyone again.