HES vs AEI sources

[MorganS]

Hello all,

My lab is considering buying a new GC-MS. We hesitate between the Thermo and Agilent models (ISQ7000 and 8890-5977B). On the one hand, Agilent offers the High Efficiency Source (HES) to achieve very low levels of concentration. And on the other side, Thermo offers the Advanced EI source source that matches the model above the ExtractaBrite EI source.

Is there really a lot of difference between these source models? Since we want to achieve very low concentration levels (low ng / L) in clean matrices (tap water and surface water), we should better go with the HES and AEI sources?

[James_Ball]

Hello all,

My lab is considering buying a new GC-MS. We hesitate between the Thermo and Agilent models (ISQ7000 and 8890-5977B). On the one hand, Agilent offers the High Efficiency Source (HES) to achieve very low levels of concentration. And on the other side, Thermo offers the Advanced EI source source that matches the model above the ExtractaBrite EI source.

Is there really a lot of difference between these source models? Since we want to achieve very low concentration levels (low ng / L) in clean matrices (tap water and surface water), we should better go with the HES and AEI sources?

Are you looking to direct inject the water, or to extract and concentrate the samples?

If extract and concentrate, what initial and final volume are you planning to use?

The standard and extractor source from Agilent can achieve those levels for most thing if you are extracting and concentrating. We currently quantify Alpha HCH at 10ng/l and Chlorpyrifos at 30ng/l with the 5975 with standard source by extracting 1L water and concentrating to 1ml solvent.

Either of those sources should go even lower in concentrations. But also consider ease of use, ease of cleaning, and how well the software works for your application for each manufacturer.

[MorganS]

Hi James,

Thank you for your response.

We will extract and concentrate the water samples via SPME Arrow and in-tube extraction (ITEX) depending on the analyte. The initial volume would be around 20 mL for SPME Arrow extraction and around 1 mL for ITEX.

[James_Ball]

Hi James,

Thank you for your response.

We will extract and concentrate the water samples via SPME Arrow and in-tube extraction (ITEX) depending on the analyte. The initial volume would be around 20 mL for SPME Arrow extraction and around 1 mL for ITEX.

That would put the sensitivity of the instrument at about 1pg/ml to be equal to 1ng/L so if the sample for SPME has 1pg/ml you will extract at most 20pg analyte. If the source can see that 20pg on column then that would theoretically be your LOD for that analyte by that method. I haven't looked to see what the HES and Extractor source list at average detection limit but I know some are near 10fg levels.

There are always differences if you use SIM or full scan to take into account. You may want to check with the vendors if you can send a standard to them and have them do an analysis and be sure they see your analyte and meet your required detection limits before purchase.

[ThomasStegemann]

Check out the AEI! I am always quite impressed by the sensitivty of this source

[benhutcherson]

Honestly, either instrument in competent hands should achieve the sensitivity that you need.

A few things that I would think about:

1. Even with relatively clean samples, to keep that level of sensitivity you will probably want to clean the source frequently. On paper, Thermo wins this since you can clean the source without venting the instrument. In practice, from what I've seen, this doesn't really save a huge amount of time(esp. with a turbo pump Agilent) since the source is still going to take a few hours to stabilize and the instrument to settle down. Subjectively, I also find Agilent sources easier to clean, but then a Thermo is a rare adventure for me(we only have one in the department and I only touch it when I'm asked to) whereas I can do Agilents in my sleep.

2. Chromeleon is a very different software package from Chemstation/Mass Hunter. From what I've seen, both are excellent and equally capable, but in some ways their operating philosophy is different. Familiarity with one or the other would sway me toward staying with that one, but at the end of the day you can likely accomplish whatever you need with either software. I'd see if you can arrange a demo of both to see if you immediately "click" with one better.

3. If you are in an environment(big company or university, for example) where there are other GC/GC-MS users around, it's worth finding out what they have. To me, this can almost be a make or break thing. Service visits can be VERY expensive, and having someone around who knows the instruments and can help you out a whole lot both because they can save you money and also can usually respond to things faster than outside service can. A good instrument guy(or gal) can figure out a lot on pretty much any brand of instrument, but expect a lot of muttering and fumbling while they look for how to do things that they could go right to on their preferred brand of instrument. Not that I'm a GOOD instrument guy, but we are mostly an Agilent shop with one lone Thermo GC-MS. I can fix many Agilent issues over the phone/email, or if not often identify the problem with a minute in front of the instrument. I rarely get asked to look at the Thermo, but when I do it takes me 10x or longer what it takes to do the same on an Agilent.

Those are just my thoughts-I don't think you can go WRONG with either instrument.

[MorganS]

That would put the sensitivity of the instrument at about 1pg/ml to be equal to 1ng/L so if the sample for SPME has 1pg/ml you will extract at most 20pg analyte. If the source can see that 20pg on column then that would theoretically be your LOD for that analyte by that method. I haven't looked to see what the HES and Extractor source list at average detection limit but I know some are near 10fg levels.

There are always differences if you use SIM or full scan to take into account. You may want to check with the vendors if you can send a standard to them and have them do an analysis and be sure they see your analyte and meet your required detection limits before purchase.

I rely a lot on microextraction to reach low concentrations. I use SIM all the time for quantitative analysis. According with Thermo vendors AEI source is 3-6X more sensitive. For Agilent, It's a 10X greater analytical sensitivity with the HES than the standard EI.

[MorganS]

Honestly, either instrument in competent hands should achieve the sensitivity that you need.

A few things that I would think about:

1. Even with relatively clean samples, to keep that level of sensitivity you will probably want to clean the source frequently. On paper, Thermo wins this since you can clean the source without venting the instrument. In practice, from what I've seen, this doesn't really save a huge amount of time(esp. with a turbo pump Agilent) since the source is still going to take a few hours to stabilize and the instrument to settle down. Subjectively, I also find Agilent sources easier to clean, but then a Thermo is a rare adventure for me(we only have one in the department and I only touch it when I'm asked to) whereas I can do Agilents in my sleep.

2. Chromeleon is a very different software package from Chemstation/Mass Hunter. From what I've seen, both are excellent and equally capable, but in some ways their operating philosophy is different. Familiarity with one or the other would sway me toward staying with that one, but at the end of the day you can likely accomplish whatever you need with either software. I'd see if you can arrange a demo of both to see if you immediately "click" with one better.

3. If you are in an environment(big company or university, for example) where there are other GC/GC-MS users around, it's worth finding out what they have. To me, this can almost be a make or break thing. Service visits can be VERY expensive, and having someone around who knows the instruments and can help you out a whole lot both because they can save you money and also can usually respond to things faster than outside service can. A good instrument guy(or gal) can figure out a lot on pretty much any brand of instrument, but expect a lot of muttering and fumbling while they look for how to do things that they could go right to on their preferred brand of instrument. Not that I'm a GOOD instrument guy, but we are mostly an Agilent shop with one lone Thermo GC-MS. I can fix many Agilent issues over the phone/email, or if not often identify the problem with a minute in front of the instrument. I rarely get asked to look at the Thermo, but when I do it takes me 10x or longer what it takes to do the same on an Agilent.

Those are just my thoughts-I don't think you can go WRONG with either instrument.

1. I completely agree. With a turbo pump, the adequate vacuum is reached in 2 hours.

2. I worked a lot with Chromeleon, mainly on LC-MS/MS and LC-Q-Exactive, but never on GC-MS. But I think it should be pretty much the same thing on GC. I tried Chemstation/Mass Hunter with Agilent vendors to see if it suited me, but it doesn't. It does not take away from Agilent, but I have a hard time finding myself with Chemstation / Masshunter, even though the software has evolved a lot since its last release.

3. I know that the service of both companies is good. Maybe a little better for Agilent who is cheaper and can be on-site very quickly. I'm probably the person who knows these instruments best in our team. I was able to repair an old VArian GC-MS by sending emails/phone calls and by simply reading the hardware. However, we already have an Agilent GC-ECD in our lab.

Finally, my main concern for my choice is the software and the sensitivity of the device. For the same price, we have on one side the Agilent with HES (a more sensitive source) and with Chemstation / Mass Hunter and on the other hand the Thermo GC with a software that I prefer but a regular EI source.

But you're right, there is no wrong choice.

[benhutcherson]

I would say that having another Agilent in your lab would make the decision easier, but one of the big selling points of the Thermo Trace line of GCs is that they use the same septa/liners/gold seals/ferrules as Agilent. So, in that sense, both instruments will be fine since you'll still only have to stock one set set of consumables.

IF it were me, I'd probably buy the Agilent system, but there again it falls back to familiarity for me.

WRT to outside service-I can email our local Agilent FSE and she will generally answer the same day, or in the worst case the next morning. Most of my contact with Thermo has been on the LC-MS side of things, but on the whole I've found that they can be a bit more sluggish about even responding(I tried to have them service our AA once-it was about 3 weeks before they even contacted me, by which point we'd fixed the problem ourselves). Even sales can be a bit more difficult-I recently went through getting quotes on a GC-QQQ(not sure what, if anything, I'm going to end up with)-I called our Agilent rep and he had it to me the next day, while it was probably a month before I even talked to the local Thermo rep(although he did get me the quote probably a day and a half after he came to visit).

Since you know Chromeleon for LC-MS, I think you might find yourself a bit more comfortable and ready to jump into working with the Thermo instrument. One other thing to consider-Chromeleon can control most other maker's chromatography instruments(not coupled chromatography-MS, but something like an Agilent GC-ECD would be fine as long as its not old enough to be HP-IB). If you talk to your sales rep, you can probably twist their arm into an extra Chromeleon license with the GC-MS to run your Agilent GC also so that both are on the same software. That was a trick the Thermo rep actually suggested to me for Agilent if I bought the GC-QQQ from them(get them to throw in an extra Mass Hunter license for my 5975), so I imagine it works both ways.

[James_Ball]

That would put the sensitivity of the instrument at about 1pg/ml to be equal to 1ng/L so if the sample for SPME has 1pg/ml you will extract at most 20pg analyte. If the source can see that 20pg on column then that would theoretically be your LOD for that analyte by that method. I haven't looked to see what the HES and Extractor source list at average detection limit but I know some are near 10fg levels.

There are always differences if you use SIM or full scan to take into account. You may want to check with the vendors if you can send a standard to them and have them do an analysis and be sure they see your analyte and meet your required detection limits before purchase.

I rely a lot on microextraction to reach low concentrations. I use SIM all the time for quantitative analysis. According with Thermo vendors AEI source is 3-6X more sensitive. For Agilent, It's a 10X greater analytical sensitivity with the HES than the standard EI.

Agilent also has the Extractor source which falls midway between the HES and the standard source so that would match up with the Thermo and it is less expensive than the HES and much fewer parts when it comes time to clean. Agilent also has the option to use hydrogen to constantly clean the source or prevent it from getting dirty as fast, which can also play into the overall operating cost if you have to vent it less often.

But as mentioned they are both good instruments, I just never had any luck with Chromelion on our single UPLC, just seems utterly confusing the way it does things lol, but most will say that about Agilent too. If you do single quad, and Agilent I would install the MSDChemstation Data Analysis version F which should still be an option, so much easier than MassHunter Quant and Qual as separate programs.