Here we have a customer with a Pinnacle PCX and they are observing some discoloration in the piston wash solution. Under normal circumstances, the solution has no color and now the solution is yellowish and the piston wash volume continues to increase.

What could be causing this problem with the customers piston wash solution?

Submit your answers to rsmith@pickeringlabs.com by December 31, 2025!

Announcing the winners of our previous quiz, Chromatography Quiz #46 – Peaking at the wrong time

Pickering Laboratories would like to congratulate the winners for our previous newsletter’s Chromatography Quiz #46: Tom Schneider from SCWA, Josiah Hakala from Minnesota Department of Health, and Narjes Ghafoori from Los Angeles County Public Health Laboratory. 

Our winners will shortly be receiving: a $100 gift card from Amazon.com! 

Congratulations to our quiz winners!  Thank you all for your submissions!

 

 

Chromatography Quiz #46 Solution:

For reference, here is what we observed and also what a good chromatogram looks like:

Troubleshooting Chromatogram:

Reference Chromatogram:

For this problem, we take a look at the chemical reaction taking place:

In the first stage, glyphosate is oxidized by hypochlorite to glycine. In the second stage, glycine reacts with o-phthalaldehyde and Thiofluor™ (a mercaptan) at pH 9–10 to produce a highly fluorescent isoindole. AMPA does not need the initial oxidation to react with OPA.

We observed only AMPA and are suspicious of the reagent 1 preparation or possible a physical problem with Pump 1. If there is a problem with the oxidizing reagent, there will be no Glyphosate signal. AMPA does not require oxidation to react with OPA.