New system problems

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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Hello, I have recently acquired a Waters 2695 with a 2487 UV/Vis detector. The system was bought from an auction and upon receipt I realized it was not taken care of the best.

I have rebuilt the flow cell and changed the lamp on the detector. For the separations unit itself I have changed the inlet filter, inlet check valves and the syringe.

After all of this I was able to get signal with retention times and back pressure and %RSD comparable to my other Waters 2695 with a 2996 PDA detector. However, the signal is not as strong as the system with the 2996.

The main problem is seen when comparing the same sample set between the two systems. In some samples with the new system there is no signal and on the system with the 2996 there is signal with the same samples. Also, on the new system the sample order doesn't match what is expected (The standard that is supposed to be twice the signal of the previous point is inverted. i.e. expected= 5 then 10, actual=10 then 5). The system pressure and inline degasser pressure is constant with isocratic runs with the new system when these erroneous results are seen. The same column was used for the runs on both systems.

Any suggestions would be very helpful as to the reason behind this reproducibility issue.

Thank you
Hi:

the first thing I would do is pm the entire alliance. you did not do the injector assy.

Also what is the sample and reference energy at 230 nm. it just has to be ~ 11 to boot, but the range of at least 50-100 is best.
If energy is low, you need m1 and m2 adjusted or replaced
The sample energy was ~3 and the reference energy was ~28. Now I'm thinking there is something wrong with the optics. How do I adjust the M1 and M2?
These #'s indicate a severe issue with the optics, as in needing to be replaced or aligned. Replacement is easy, which will cause need to realign. Realign is not easy. Im surprised it even boots up !.

Where are you located onsite service may be available
I am in St.Louis MO. Where could I find the parts that I need? Or will a service engineer needed?

Thank you
What you have observed is very common on very old detectors like the one you purchased at auction. The optics get coated from normal use and must be replaced. We do not recommend replacement at all. As noted, the parts are hard to find and you need to have the right equipment to perform the alignment after installation. It is usually less expensive to replace the detector with another (younger) model or different system. *These system are cheap for a reason. Most have old coated optics inside. Sometimes you get lucky and find one that was hardly used, but most of the 2690/95 (2790/95) had many years of abuse before they were put away wet.
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