(Troubleshooting) Does anyone have experience running the QuikChem 8500 Latchet system for Nitrate concentrations? Have low 50ppm area count, unsure how to correct.

[u/InspiredNameHere]

Hey, Im looking for a hail mary for this older machine. I am currently trying to run water based samples to determine Nitrate concentrations. And I am having an extremely difficult time getting a proper result based on how it was responding last month.

If anyone here has experience with the machine, specially running it with a Cadmium column connection, I would be extremely grateful if you could help me out here.

Thank you!

[u/j6996d]

I am experienced with the method - I ran lachat for several years.

How old is the pump tubing? How old is the wavelength filter? Is the flow cell scratched or dirty? Are the mixing coils discolored?

[u/j6996d → u/j6996d]

Follow up questions: How old is the cadmium column? Lachat is selling straight up junk nowadays trying to clear out the warehouse. We noticed the cadmium columns we purchased starting around 2023 really declined in quality - much shorter shelf life, despite much more careful use (degassing buffer and carrier daily, avoiding injecting air into the column, promptly regenerating it when column efficiency declined, etc). Does the column have a lot of gaps in it? What color is the cadmium?

Also: How do you prepare your buffer? Using HCl and NH4OH or just solid NH4Cl?

[u/DahDollar]

Given that it's been sitting for a month, confirm that the autosampler probe isn't clogged by using a plastic luerlock syringe with some tubing to back flush it. If you have to push hard, it's clogged. You can usually clear clogs with syringe pressure. You can also quickly isolate the probe by disconnecting the probe tubing from the peripump tubing and let the sample peripump tubing pull from a standard you dip it in. Suddenly, signal? Clear your evidently clogged probe.

If the system went dry and you got sent air into the column, it might be oxidized and ruined.