ECD cleaning

[Margaret Coe]

I have a severely contaminated ECD which I have thermally cleaned several times. It doesn't fully come clean, and we now have reduced peak size as a result; ~ 1/10th.

I am trying to find other cleaning suggestions, or commercial places where I could possibly send it to be cleaned. I am in New Zealand, which might make things interesting for shipping, but you never know.

We have tried 2 new ECDs, but they have even less sensitivity than this old, dirty one, so we'd like to revive it, if possible. The new ones did meet their manufacturer's specifications, by the way, but one of our peaks of interst is barely discernable using them.

[Peter Apps]

Hi Margaret

If three detectors all give reduced response I would be looking somewhere else in the system for the cause of the problem - starting with the inlet.

Peter

[Ron]

The inlet is a possibility if all three detectors were tried on the same main body, but if they are on different instruments I would look at carrier gas and makeup gas.

[Margaret Coe]

Thanks for the ideas.

We have had the Varian expert here, who could find nothing wrong with our system or set-up. The thing is, the new detectors are not as sensitive as our old one, by about a factor of 20. And, our old one is now about 10x less sensitve than it was, before it got contaminated. We can barely see one of our peaks of interest on the new detectors. We can see it fairly well on our old one, but, of course, I'd like to get back some of the sensitivity we had.

The old one was subjected to severe contamination. We didn't figure out what was happening until the damage was done, to make a long story short. I didn't know about this forum then.

So, I'm looking for someplace to send it to get it cleaned, or some cleaning method other than thermal. Any suggestions?

[AICMM]

Ms. Coe,

You'll ship to the US if you need to then?

Varian guy was okay with the fact that the old one is much more sensitive than the new one???? That seems a really odd marketing tool...

Best regards.

[Peter Apps]

Hi Margaret

I anticipate that cleaning the old ECD, if it is possible at all, will involve so much bureaucratic and legal hassle that you need to eliminate every other possible cause of the problem before you go down that road. Bear in mind also that if the contamination is really severe, cleaning may not restore the old performance.

Depending where you are in the world local service engineers are often not experts on analytical GC - they can do basic troubleshooting using on -board diagnostics, but anything out of the ordinary that was not covered by the factory training is beyond them. I am not talking about the Varian people in Southern Africa now, just so it's clear. It is very odd that the Varian rep is happy with new detectors being less sensitive than the old one - do the new detectors pass their performance checks ? If they do it implies that the old detector is ten times better than its design specs, which is also unexpected.

Can you give us some details of what you are analysing and how, and what the old detector is contaminated with (if you know), we might be able to find a way to restore the old detector, get the new ones working better, or fix something else in the system.

Peter

[Ron]

There are places that can re-foil an ECD, there are not many and I don't know where there is one in your part of the world. Shipping an ECD internationally is not easy, if Varian or a third party offers this service you are better off having them do this and let them go through the legal hassles.

I know that some companies make two different ECD detectors, a regular high sensitivity detector, and a second detector that has a lower output radioactive source that has lower sensitivity but is not subject to all the radiation safety rule since it contains a smaller quantitiy of radioactive materials. This is much easier to move since no wipe test in involved, and it is MUCH simpler to ship internationally. I don't know if Varian makes a detector like this, but if I were you I would ask the Varian people some very specific questions, such as milli-Curies of old detector vs. new.

I'm not surprised at the Varian service engineer's response, I was told once by a former Varian detector R&D scientist that it is normal for two brand new identical detectors mounted on the same GC to differ in response by a factor of 10. I have my own opinion on that statement, and I think you probably have the same opinion.

[Margaret Coe]

You people are great - 3 replies in one day.

The new detectors did pass the Varian specifications. The Varian guy was completely puzzled about why our old one was so much more sensitive, and could offer no explanation. He wasn't a typical service engineer / electronics guy, but a specialist troubleshooter. I was quite impressed by his knowledge, and I've been doing GC for a couple of decades. He really knew his product.

The new ones were labelled as having the same milli-Curies as the old one.

You're right, it is a hassle shipping them internationally, but I wanted to see if there was anywhere that could help. So far, I have one name, of a place in North Carolina, who I haven't been able to contact yet. I only have a phone number, and the time difference makes it difficult.

If you know of any others that offer re-foiling or cleaning, please pass on the name or contact details. E-mail address would be really good, from this time zone.

We're fairly sure it was contaminated from the Helium cylinder we were using at that time; done all kinds of troubleshooting. It had really weird symptoms at first, so we didn't figure it out for more than a month; plenty of time for lots of contamination. This is a routine QC lab, with 20 - 40 samples per day, for FID & ECD components, so we have to keep going every day, and get at least some results out.

Unfortunately, the contamination got all through the GC lines, electronic flow controller, filters etc, and it took ages to replace and/or clean everything. We still see the occasional lump on the FID side, but we haven't cleaned anything there, as it is just a minor thing compared to the ECD.

Thanks for all your helpful suggestions. I look forward to the contact details.

[AICMM]

Ms. Coe,

From a customer of mine:



CJ Bruyn
http://www.cjbruynco.com/
cjbruyn@msn.com
800-252-7896
360-671-0182

360-671-8686 Fax

1053 Sehome Ave.
Bellingham, WA 98229-8866 USA

They should be able to help you with the paperwork as well.

Best regards.

[Margaret Coe]

Thanks for that. They only service HP/Agilent ECDs; just in case anyone else needs this service.

[macgyver]

Dean Rood's excellent book "Troubleshooting and Maintenance Guide for Gas Chromatographers" has a couple of procedures for cleaning ECDs. Here's a summary...

1. Hydrogen is supplied to the ECD as either carrier gas (at a high flow rate - he doesn't say what) or as a substitute for the auxillary gas. Heat the detector to 350 degrees and leave the detector in this configuration for more than 24 hours. After 24 hours, return it to normal configuration and let it settle down for a couple of hours and then test. If this doesn't work, try the second cleaning procedure.

2. Connect a short piece of deactivated fused silica (or a short piece of old column) between the injector and detector. Set the carrier to a low flow rate, the detector to 350 deg, injector to above 200 deg, oven to above 150 deg and make 50-100 injections of 50-100 uL water. The vaporised water steam cleans the ECD cell. The ECD will take about a day before it's background comes down. This method will not release any radioactive material and is suitable for all 63Ni sources

He suggests that steam cleaning followed by hydrogen bakeout gives the cleanest detector and that giving it a good clean like this should extend its lifetime by 3 to 12 months.

I've not had any personal experience with either of these methods, but they sound reasonably. Others on the group may be able to tell you if it's worth the trouble.

[macgyver]

Google Books have Dean Rood's book online for preview including the relevant pages about ECD cleaning (pp 160 & 161):
http://books.google.com/books?id=t5JMMg ... q=&f=false

[skunked_once]

So far, I have one name, of a place in North Carolina, who I haven't been able to contact yet. I only have a phone number,

You must have the number for Detector Service Center in Cary, NC, USA.

911 W Durham Rd
Cary, NC 27513
919-469-0259

We've used there services in the past to restore the ECD on our old Tracor (who remembers them?) gas chromatographs. They gave good service. I posted this for others who may be interested.

[Margaret Coe]

Thanks, macgyver. I'll give those ideas a try, when time permits. Here's hoping. I'll let you all know what happens.