robust ms

[Aldijkhuizen]

in our lab we have a waters quatro micro MSMS. this MS has allways been working robust. last year we bought a agilent 6495. this new MS has given much more trouble. is it true that the modern MS is much less robust then the MS ten years ago? is this a general thing or are some vendors making more robust MS? what is in you opinion on the most robust MS?
i ame working in clinical diagnostics so robustness of the hardware is very important.

[leadazide]

In general I disagree.. Modern MS are on par or better than older MS.

But.. they are usually also more sensitive.. and not just sensitive in regards to your compounds of interest but for everything! And if you are transferring a method that works well on a 10 year old LCMS system to a brand new ultra sensitive system you are asking for trouble..

A modern high end MS is so much more sensitive that special care needs to be taking with sample prep, mobile phases, vials and anything related.. This is true for the 6495 but also for any "funnel" based instrument from any vendor compared to the older(or newer) skimmer based systems.

Compare them to cars. The old system is a Ford Focus.. nothing bad about Ford.. very reliable.. will get you from A to B every day. You could even forget to change the oil once in a while and it would still work ok. The newer systems is a F1 racer. They require high level of maintenace, pricy oil and fuel and if you are not a trained driver you will crash!

So on the 6495 you must use LCMS grade solvents and reagents. You must use good consumables. You must have proper sample prep. You must expect to perform regular maintenance to keep performance up. But this would be true if you had a Thermo Quantis or Sciex "What ever their high end is called) or a Waters "likewise"

Sorry for my rant but this is one of my pet pives.. I don't understand people spending hundreds of thousands of dollars on equipment and then treat them like dirt.. and not willing to spend the money on the proper consumables.. and when they start to perform poor.. It is a shitty instrument!! Try driving a F1 with off the shelf tires..

[Rndirk]

I fully agree with leadazide about the system handling part.

We recently bought a Xevo TQ-XS, and increased our standards when it comes to general handling and routine maintenance, compared to our previous LC-MS systems from 3 generations ago. For example, on our old systems we put the mobile phase bottles on the dishwasher after use. Now, we use dedicated bottles for the new system which are cleaned with LCMS grade solvents between use. Methods should not be transferred from old systems to new without a good review.

About the sample preparation: I do not agree that sample preparation has to yield cleaner extracts to be injected on newer systems. To me, this sounds like a contradiction: why would you need a more intensive cleanup on a system that is better at separating analytes from matrix (talking about detection here, not LC). A good chromatographic separation, a good use of the divert valve, and a good choice of dilution/injection volume (less is more!) does wonders. You could of course -correctly- argue that a diluted extract is cleaner than a non-diluted extract!

[Aldijkhuizen]

So if the newer instruments need more atention with cleaner solvents, consumables, maintenance, cleaner samples otherwise they brake down and the older once just keep running (allthough "slower") I think that means the newer once are less robust.

[leadazide]

Hi,

Let me clarify..

The reason newer instruments seem less robust is that they are more sensitive.. Especially funnel based systems compared to older skimmer types..

If you had gone with a 6460 compared to your old waters you would most likely have found it very robust.. But sesitivity comes at a price.

Regarding sample prep issues. Many of these are more related to the LC in front.. With new high end MS people will also usually have high end LC systems with narrower capillaries. This makes them more sensitive to poor sample prep and mobile phases. But the MS rarely stands alone so "bad sensitivity" is usually blamed on the MS but often it comes from the LC.

[James_Ball]

Hi,

Let me clarify..

The reason newer instruments seem less robust is that they are more sensitive.. Especially funnel based systems compared to older skimmer types..

If you had gone with a 6460 compared to your old waters you would most likely have found it very robust.. But sesitivity comes at a price.

Regarding sample prep issues. Many of these are more related to the LC in front.. With new high end MS people will also usually have high end LC systems with narrower capillaries. This makes them more sensitive to poor sample prep and mobile phases. But the MS rarely stands alone so "bad sensitivity" is usually blamed on the MS but often it comes from the LC.

We are thinking of adding a newer LCMSMS to the lab and since Agilent has said they will soon discontinue the 6460 we are instead looking at the 6470. Can the 6470 still be purchased without the iFunnel system? From reading the specs that is an extra add-on so if we don't add that should it be more comparable to the 6460? Our other instrument is the Sciex API3200 so I know for certain we can not just transfer methods, but am hoping that the much smaller injections will help keep it clean.

[leadazide]

Hi,

Yes, the 6470 is without iFunnel.. With the Funnel it is then a 6595. Advantage of the 6470 is that is can be upgraded to a 6495 at a later point if the extra sensitivity is needed..

If the 6460 has the sensitivity you need and the only reason for the 6470 is that you need a new instrument in the 6460 class, have a look at the Ultivo. It is the direct successor of the 6460 and has the exact same specification on paper.. but will usually out perform the 6460 in a direct comparison. Also this is 1/3 the size of the 6460!! The only thing to be aware of is that the Ultivo has a mass range up to 1400 where the 6460 has up to 3000.. Unless you are looking at proteins or some fairly exotic compounds I would argue that 1400 on a QqQ is enough for most applications.

[leadazide]

Hi,

Yes, the 6470 is without iFunnel.. With the Funnel it is then a 6595. Advantage of the 6470 is that is can be upgraded to a 6495 at a later point if the extra sensitivity is needed..

If the 6460 has the sensitivity you need and the only reason for the 6470 is that you need a new instrument in the 6460 class, have a look at the Ultivo. It is the direct successor of the 6460 and has the exact same specification on paper.. but will usually out perform the 6460 in a direct comparison. Also this is 1/3 the size of the 6460!! The only thing to be aware of is that the Ultivo has a mass range up to 1400 where the 6460 has up to 3000.. Unless you are looking at proteins or some fairly exotic compounds I would argue that 1400 on a QqQ is enough for most applications.

[leadazide]

Hi,

Yes, the 6470 is without iFunnel.. With the Funnel it is then a 6595. Advantage of the 6470 is that is can be upgraded to a 6495 at a later point if the extra sensitivity is needed..

If the 6460 has the sensitivity you need and the only reason for the 6470 is that you need a new instrument in the 6460 class, have a look at the Ultivo. It is the direct successor of the 6460 and has the exact same specification on paper.. but will usually out perform the 6460 in a direct comparison. Also this is 1/3 the size of the 6460!! The only thing to be aware of is that the Ultivo has a mass range up to 1400 where the 6460 has up to 3000.. Unless you are looking at proteins or some fairly exotic compounds I would argue that 1400 on a QqQ is enough for most applications.

[James_Ball]

Thanks a lot for the information, always good to hear it from an actual user, not just the marketing guys.

The main reason for choosing the 6470 over the Ultivo is we have an offer from Agilent for a factory refurb that brings the price quite a bit below the Ultivo new, and that we can do that upgrade in the future if we get into the PFOA/PFAS analysis which will need the increased sensitivity. In the past we have also done some Vitamin B12 analysis and I believe that is pushing the 1400 mass limit.

[Rndirk]

In the past we have also done some Vitamin B12 analysis and I believe that is pushing the 1400 mass limit.

Hey James, just a small comment from experience: you will notice that all cobalamins (B12 vitamers) ionize much better as [M+H]2+ in ESI, which is in the 600-700 m/z range.

About perfluorinated compounds: I don't know which instrumental limits you need to reach, but we were able to validate surface- and waste waters on our older LCMS instrument. Lowest calibration point is 1 µg/L with 10µL injection. MS-wise these compounds are straightforward/easy to develop: they all ionize as [M-H]- in ESI, sensitivity is quite good.

[James_Ball]

In the past we have also done some Vitamin B12 analysis and I believe that is pushing the 1400 mass limit.

Hey James, just a small comment from experience: you will notice that all cobalamins (B12 vitamers) ionize much better as [M+H]2+ in ESI, which is in the 600-700 m/z range.

About perfluorinated compounds: I don't know which instrumental limits you need to reach, but we were able to validate surface- and waste waters on our older LCMS instrument. Lowest calibration point is 1 µg/L with 10µL injection. MS-wise these compounds are straightforward/easy to develop: they all ionize as [M-H]- in ESI, sensitivity is quite good.

Thanks for the tip. We tried the perfluorinated method for the last UCMR3 and just could not get down to the detection limits needed for that with the 3200, but then a 6470 is at least 10x more sensitive so that should work well. Agilent has an application for the 6495 that is a direct injection of the water sample with no extraction/concentration, but if the 6470 would be more robust, I think I would do the extraction first.

[Steve Reimer]

For the perfluorinated compounds, some states (I won't mention which) are trying to push their limits down to <10 ng/L for water.

[Rndirk]

Sorry for further derailing the topic with PFC talk but I think the OP has been answered...

We're measuring down to 50 ng/L on surface waters, according to current limits here (in the EU), using a standard SPE protocol.

About direct injection: I'm always a huge fan of simplified sample preparation techniques. But in this specific case it's very hard to get rid of all PFC background in the instrument. Using a more sensitive instrument which can detect 10 ng/L by simple (large volume) injection, which is certainly possible with current triple quads, you will have to deal with getting the instrumental background at least, and consistently, below 5 ng/L.

Using an extraction and concentration type of sample prep, the instrument is measuring at a much higher level, where a background of 5-100 ng/L is negligible (if it gives a signal at all).