glyphosate analysis

[kerrieb]

Hi

Does anyone test glyphosate using anion exchange conductivity detection, I'm having problems with this.

I'm using a waters anion HC column with a Alltech 320 detector. With borate/gluconate buffer 2ml/min isocratic 4.6 X 150mm col.

The HPLC system is working fine for other UV based tests but there is no column temperature control. It has been passivated and most of the fittings are peek. I'm having problems with drifting baselines and poor reproducibility (5-10%) within runs. I can't use the analyses.

My chromatography looks OK correct retention time nice peak shape.

I suspect that the detector may be the problem. I haven't had any previous expereince with this type of detector with most of my previous HPLC work being UV based or MS. No one else I know has used it before much either.

Any suggestions would be welcome before I send it out to be checked. I usually do most of my own troubleshooting and maintenance but this one has me stumped.

Changing the method is not an option as it has been validated and besides the cost of buying in an ELSD detector (my prefered option) isn't viable at the moment.

Regards

Kerrie

[Markus Laeubli, Metrohm]

I know that some of our application labs did glyphsate successfully with IC.
I will check and come back to you.

[jimmyv]

I bought a ion chromatography 25 years ago from Wescan. It was a non suppress type. I also used Wescans anion column. Alltech I believe took over that line of products. My recollection of the instrument is that the detector is temperature sensitive. Mine was incased in a column compartment and you have to play with a pot to plot baseline flat. It did not bother me a lot since my chromatogram was plotted by a paper chart recorder and I drew my baseline and measured peak height. As the instrument got older the readout numbers fluctuated. I later learned that by spraying contact cleaner on the switches I was able to resurrect the instrument ( after 15 years use). Yours is probably a newer model that mine and a modular conductivity detector.

[Markus Laeubli, Metrohm]

Here comes an application for glyphosate from Brasil.

Column: Metrosep A Supp 5 – 150
Eluent: 1.7 mmol/L bicarbonate / 1.8 mmol/L carbonate
Flow: 0.8 mL/min
Suppressed conductivity (Metrohm Suppresor Module).

[oscarBAL]

Hi Kerrie;
I do not know if your problem is due the column temperature or the detector (may be both).
I wonder regards the lacks of reproducibility if could improved using Internal STD? This do not resolve the problem with the instrument (if is something wrong with it) but colud give you a clue.