Nitrogen generator for LC/MSMS

[orelie]

Hello,

We are going to equip our lab with an LC/MSMS (Xevo TQD or Agilent 6490) and therefore we need to buy a nitrogen generator.

According to you experiences, would you advise a generator including the air compressor (eg Zefiro 35L/min) or to buy compressor and generator separately (eg NG6 35L/min)? We have already the air compressor (not oil free) used for AAS and we would add a dryer+ filters.

Is the maintenance of generator with compressor easy to do ourselves? Can this machine stay in the chromatography room or it will be too noisy (the seller says noise <55dB so it is OK)?

Thank you very much,

Orelie

[CE Instruments]

Buy one inclusive of a compressor, that way you will have no problems with contamination etc. and two companies who each blame each other if something goes wrong. Little point using the compressor from the AA, if you can afford an LC/MS you can afford a new Nitrogen generator. The stand alone Nitrogen generators are usually for large flow or those with laboratory air.

[orcicdejan]

We've been using Peak Scientific generator with included compressor for about two years now, for our LC-MS/MS (Agilent 6410), and it seems to be very robust, with minimal maintenance required. It is also pretty quiet, generating less noise than LC-MS/MS itself. Previously, we used Jun-air compressor with separate generator, and we were not satisfied - it was unable to generate nitrogen flow high enough, and it also broke quite often.

[James_Ball]

We've been using Peak Scientific generator with included compressor for about two years now, for our LC-MS/MS (Agilent 6410), and it seems to be very robust, with minimal maintenance required. It is also pretty quiet, generating less noise than LC-MS/MS itself. Previously, we used Jun-air compressor with separate generator, and we were not satisfied - it was unable to generate nitrogen flow high enough, and it also broke quite often.

I am using a Parker Balston model that sounds similar. It has a high and low internal pump. We have an ABI3200 this is used on. Right now I am having trouble getting the nitrogen quality above 90% and still have enough pressure to run the instrument, but I think I found the problem is the pressure relief valve that relieves pressure when you power down the generator.

I was wondering, does everyone leave the generator running constantly or shut it down when the instrument is idle? Always need the vacuum going of course but what about the nitrogen?

We have gone through one of the pumps about once a year, the other was very noisy by two years old and was replaced at three, but if we can idle the instrument without needing the high purity nitrogen I believe we could extend the life on the generator considerably.

[orcicdejan]

Ours is turned on all the time (except when we shut down the entire instrument), and we had no problems. However, with Jun-air, the lifetime was affected indeed - since it could not generate sufficient air flow, the pump had to work almost constantly (instead of pressurizing the tank, shutting down the pump and then slowly releasing the air to the generator), so we had to replace some parts quite often.

[orelie]

Thank you very much for your answers!
We will definitively go for a generator with included compressor it seems more simple and performant .

[lmh]

We're on Domnick Hunter generators, which are now serviced by Parker I think. I can't quite work out who is related to who in the N2-generator world.

Don't expect a quiet generator to stay quiet. The compressors get noisier as they get older.

Don't expect the compressors to last more than a year. They are mechanical and wear out.

Do check the price of servicing, either on contract or if you buy parts to do it yourself. We gave up on one manufacturer because their service contract was phenomenally more expensive than their competitors, and parts purchased from them turned out to be repackaged kits from the company that supplied the compressors (we couldn't buy direct from compressor-company as it was a special part number supplied exclusively to N2-company) - and the mark-up on price was truly phenomenal. We got round this by peeling off the label that nitrogen-company stuck on top of compressor-company's label, and ordering the part number we found underneath...

We run ours continuously; at least one instrument is supposed to sit in a low flow of nitrogen when not in use.

If you decide to put noisy generators at a distance from the instrument, make the tubing very, very wide or you'll get a pressure-drop. We're currently on half-inch (12mm) medical-grade stainless steel tubing supplied by 2 30L generators.

[Zmeevic]

Only Peak Scientific, it's better than Parker Balston.
For example, NM32LA. It's enough for one LC-MS\MS, may be for two.

[lmh]

To clarify: most LC-MS systems doing traditional flow LC (not nano-flow, i.e. under 1mL/min but over 10uL/min) will use a maximum of around 15L/min nitrogen (but beware, some use more). Generators with a "30" or similar number in their model-number are probably designed to supply 30L/min, i.e. to satisfy two typical LC-MS instruments. But again, be careful, and check the actual specification.
With most generators, the purity of gas declines as the flow increases, so to some extent the output depends on what level of impurity the manufacturer thinks you will tolerate.
Generators with built-in compressors will get worse over the course of a year, and will need the compressors servicing or replacing at the end of that time. "Worse" means more noise, and less gas. In particular, the pressure may fall more between cycles of the generator, to the extent that eventually mass specs using electrospray will start to complain about low nebuliser pressure (or whatever it's called in your instrument).
It's never fair to compare a new unit from company A with an old one from company B.
I would disregard statements that company A is better than B unless you get them from someone who's compared a representative sample (n>=5) of generators from both companies! I know who I prefer, and I wouldn't necessarily agree with the previous poster, but I don't think it fair for me to comment on individual companies.

[shemesh199]

Why do you guys want to buy a nitrogen generator especially after reading the above stories.

Stick with a purchase agreement for regular delivery of high pressure liquid nitrogen tanks

There are so many things that can go wrong with the generator, You can always "guarantee" that gas will never be an issue.

Also, you might spend 2-4k on delivery per year depending on usage, but the generator can cost 10k and cause a nightmare.

I have been at 4 instituions using LC-MS-MS all without nitrogen generators.

I guess it is really a preference.

Best of luck!

[thohry]

I recommend you buy a Peak N2 generator. We have been using one for an Agilent 6460, some of my friends' labs also use. It's quiet, robust and the gas quality is just OK for an LC/MS/MS.

[paul_b]

We use house compressed air with a pair of Peak NM-30L nitrogen generators, one has given 16 years and the other 10 years (so far) trouble free sevice. If you have a good house air supply they are a good option - particularly if your house air has a backup unit for servicing etc. Standalone instruments are quite bulky, fairly noisy and will have a significant maintenance cost, but you may have no choice.

[clarkkdc]

Has anyone ever seen the NitroFill nitrogen generators? My understanding is they are typically used for filling tires, but the purity looks good (99%) as well as the pressure output (~100 psi). They run much much cheaper, so I'm wondering if there is a hidden reason for this.

[Or Not]

I would second what shemesh199 said - you might see if a microbulk liquid nitrogen tank would be an option. No moving parts, very reliable. We have a 1000L microbulk tank that supplies 10 LCMS systems, and I believe we pay around $750 per month for everything (nitrogen, tank rental and service, delivery charges, telemetry). Smaller sizes are available. I think the installation charge for the tank was about $1000.

[jturpin]

Are any of you who are using nitrogen generators using a receiver tank for the nitrogen? This allows the generator to cycle off occasionally, reducing the wear on the compressors. I would like opinions on the acceptable material for a tank for use with LC/MS.