Chromatography Forum

Hi all,

Our lab recently purchased a refurbished 6530 to go with an Infinity 1290 series LC stack we inherited from the previous inhabitants. Recently, I have been having trouble with maintaining good mass accuracy for certain analytes I am measuring and I believe the problem may lie with the reference spray. Our lab uses two reference ions, purine (121 mz) and HP-0921 (922 m/z). Generally at the start of a run, both reference ions can be found easily. However, as the run progresses, generally only one or none of the ions can ever be found. For example, here is an EIC for purine in the first blank injection of a worklist I had run last evening:



And here is an EIC for that ion at the end of the run:



There is a similar story for the second reference. Here are two EICs from the start and end of the worklist:




Similarly, the mass accuracy for the reference ions can be well over 100 ppm in scans where they are not very abundant. Can anyone offer any advice for maintaining a consistent spray for the reference solution? Currently I have tried plumbing the outlet from the pump into the reference sprayer with the valve open to try to flush any sort of clog. Any advice for solving this or maintaining good mass accuracy in general would be greatly appreciated.

Nick

Hi Nick
I would contact the company who sold you the refurbished system and get them to address the issue.
The agilent reference sprayer in theory is a good concept,
but over complicated.
One test you can try is to swap over the two nebulisers and observe any difference.
When I was a service engineer, many nebulisers got replaced for no other reason that the replacement nebuliser fixed mass accuracy/resolution problems without understanding the reason why.
Matt

Nick,

Are you using the built in delivery system or an external pump? The lab I work in uses isocratic pumps with 100:1 reducers in line to deliver reference solution. That way we can run the pump in its normal range and still have the low flow delivery. That helps with a consistent delivery.
A syringe pump with a large volume syringe may be a way to test or compare the delivery. I’ve never looked at the reference delivery system in the Agilent, but we sometimes check the calibration delivery system (CDS). We do use the built in system for calibration. Well time the drops from the tubing with the CDS active after disconnecting it from the nebulizer (should be ~11 sec for th CDS according to the Agilent engineer we work with pretty regularly). You could time it before and after the runs and see if it changes.
Just some thoughts, good luck!

MM