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Metrohm IC Metal Contamination

Discussions about IC and related topics

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I was having an issue with my Metrohm IC that I was struggling to resolve and didn't see it mentioned online. I hope someone in my predicament will find this post helpful.

The IC in question is primarily used to analyze anions in drinking water via EPA 300.0. Around 4 months ago, I put a batch of samples on to run over the weekend. MagIC Net spat out an error with the autosampler and halted the batch progression, but the IC remained on, causing the pump to run dry. I began to have chloride peak tailing issues that were indicative of metal contamination. We test very hard drinking water in the southwest United States. It is common for there to be 100-200ppm of chloride present. The chloride tailing was heavily interfering with nitrite resolution. Upon investigation, it appeared the piston arms had corrosion on them that likely got into the flow path.

When corresponding with support, they recommended regenerating the suppressor module and trying a new column and guard, as they might've been contaminated with metal. Unfortunately, both of these actions did not resolve the issue. They brought out a technician who was unsure of what else could be going wrong as well. Over time, I replaced just about every user accessible part on the instrument with no improvement.

However, I flushed the MCS and detector with 0.1M oxalic acid and 10% acetone for approximately an hour. Magically, the tailing completely disappeared! I've attached overlayed check standard chromatograms below. The black line is after cleaning, the red is before.

Lesson learned: Set a minimum pump pressure in your method so it will not continue to run when there is a pressure drop.

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You mean it kept running when it was dry? Dionex automatically shuts down when the pressure drops, but it is still not good for the instrument from what the thermo techs tell me. I had a motor die at 2 years old. New analysts sometimes don't put in the shutdown program properly and sometimes we have an auto-sampler error. I live near the lab so I drop by to make sure it has shut off.
You mean it kept running when it was dry? Dionex automatically shuts down when the pressure drops, but it is still not good for the instrument from what the thermo techs tell me. I had a motor die at 2 years old. New analysts sometimes don't put in the shutdown program properly and sometimes we have an auto-sampler error. I live near the lab so I drop by to make sure it has shut off.
Yes, it kept running till it ran dry. Metrohm's software sets the lower pressure threshold by default as 0 (i.e., there is no threshold), which is not great. The method was already set up when I started in the position, so I completely overlooked that. It ruined the pump seals and created corrosion on the pump pistons that got into the system. It was a headache and a half to deal with, but it's all finally back to normal thankfully.
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