Just for posterity - here is what we went through. I was not impressed with
HP's handling of this situation and clearly they need to have a technical
bullitin sent to their field engineers to deal with what appears to be a
common problem - but what is perhaps the result of a multi-component
failure. As we all know these are the worst scenarios - as the field
engineers like to 'fix' one problem at a time and see what the result is -
which certainly fits their budget but now our timelines.
We started with lamp replacement - no effect.
We spent days monitoring detector baseline - with and without the pumps in
line(we had one quat and one binary system) - to convince HP we had a 'real
problem' I was told this was never observed before - clearly in our case the
noise was associated with the detector. There seemed to be two types of
noise - one with a long period of of about 2 minutes and one with a short
period on the order of 20 seconds or so. We thought that they may have been
some feedback problem comming from a power supply source - maybe the
refrigerated autosampler - but could never clearly assign that.
We were able to demonstrate that the noise levels exceeded the factory specs
- and strongly persuaded HP to swap out the optical bench on the worst
detector - this was after they had rebuilt the optical cell - without a
major improvement.
On the second system - they spent time working rebuliding the optical cell -
and then replacing the filter wheel assembly on the optical bench - that
eventually fixed the problem on the second system.
Clearly - HP is still in a "discovery mode" as to the cause of these
problems - it is unfortunate that even under service contract you will have
to spend a considerable amount of your own time trouble shooting this one.
On an aside - along the way we had them replace pump seals and work on the
high pressure pump components in general - which can be associated with the
higher frequency noise problems. If your problems is for some reason pump
related - or just compounded by another probem associated with the pumps -
look carefully at the pump setting for stroke length and rate - these can
compound or elimate problems dependingon how you are set up.
Oh, and welcome to the club!
Good luck & feel free to give me a call.
Paul Maffuid
Executive Director, Pharmaceutical Development
Cabrillo Laboratories
619-547-7834
-----Original Message-----
From: chris halkides [mailto:halkidesc@UNCWIL.EDU]
Sent: Thursday, February 25, 1999 1:36 PM
To: Recipients of ABRF List
Subject: HP-1100 diode array HPLC
Hello Everyone,
We have an 1100 series hewlett-packard with a diode array detector.
We sometimes see slow (period of about 5 min) oscillations in the output.
The pattern is more complex than a simple sine wave. The amplitude is
about 2 milliabsorbance units both at 220 nm and at 280 nm. It is hard to
predict when the oscillations will appear or disappear. HP thinks it could
be the lamp and has suggested turning the flow to zero and seeing what
happens, but they don't have any further suggestions.
Does anyone have any ideas about what is going on, or useful ways
to proceed?
Chris Halkides
Christopher Halkides
Dept. of Chemistry, UNCW
601 S. College Road
Wilmington, NC 28403-3297
(910) 962-7427