LC-MS/MS for multiresidue analysis

[emadatala]

Dear Colleagues,

I am working in pesticide residue analysis lab, we are going to buy the first LC-MS/MS in our lab to quantify 200-300 compounds in one multiresidue method and must get good sensitivity (at 0.01 ug/ml or lower). We usually analyze food samples.
There are many brands in the markets they looks pretty, especially from
Micromass (Quattro Ultima or Primier) and Applied Biosystems (API3000, 4000, 5000), it is very difficult to choose between them in terms of system sensitivity, duty cycle, precision, friendly software and low troubleshootings.

So my question what is the best system that can fulfill our requirments? the most important isuue is to detect as many compounds as possible in the same time window with good sensitivity.

Also, do Agilent developed any MS system that can fulfill these requirements?

Any sugestions will be highly appreciated
Best regards

Emad

[JNF]

Hi,


Up to a few years ago the only machine (or rather software) that allowed the monitoring of several compounds at reasonable sensitivity was Micromass’s. This was not due to the better inherent properties of the hardware but rather the software allowed the use of overlapping periods so that one could monitor the compounds at their expected retention time instead of during all analysis time. I am not sure if other MS produces introduced this feature into their software. It can be a very useful tool if you are doing pesticide screening.

Ciao
JNF

[Kostas Petritis]

Emadatala,

The high-end instruments you mentioned (i.e. Micromass Premier and Applied Biosystems 4000 and 5000) can do the job in terms of sensitivity. Now you also need apparently ultra fast dwell times of less than 10 ms and keep that sensitivity. Actually assuming that you need to analyze 200 compounds and you need to have two datapoints per sec (if your chromatography is good you will need that) then you need to work with a dwell time of 2.5 msec which is quite ambitious. Also if you are in Europe, I think that the new legislation asks for two transitions per compound which will bring your dwell time down to 1.25 ms... quite challenging.

Anyway, the latest instruments can go down to 10 ms maybe 5ms without loss of sensitivity but for lower I do not know. This is something that you will have to ask them to demo you (i.e. sensitivity vs. dwell time).

Agilent does not have a triple quadrupole yet but in this ASMS conference they announced that they are working on it and will have something commercially available shortly with good specs (of course shortly can be one more year...).

So your choice for now is between Micromass and Applied with an edge on Micromass in terms of software and an edge on API 5000 in terms of sensitivity (although sometimes it is compound specific...).

[james little]

We have a Quattro Micro and a Applied Biosystems 4000 Qtrap. I like both instruments.

For your application, probably need the Quattro Premier or even better the Quattro Premier XE. Think the latter has higher negative ion sensitivity. You might also want to switch back and forth between negative and positive and even APCI/Electrospray. I have a Waters ESCI probe which allows switching between postive and negative ions.

If you want to monitor many ions, will want to switch between groups of ions during the run. The only problem with Applied Biosystems software is that there is a bug in their quantitation software that stops you from using an internal standard from within one group of ions (period in their software?) with an analyte in another group of ions. Sure they could fix if you wanted to buy one from them.

Gooo luck.

[james little]

We have a Quattro Micro and a Applied Biosystems 4000 Qtrap. I like both instruments.

For your application, probably need the Quattro Premier or even better the Quattro Premier XE. Think the latter has higher negative ion sensitivity. You might also want to switch back and forth between negative and positive and even APCI/Electrospray. I have a Waters ESCI probe which allows switching between postive and negative ions.

If you want to monitor many ions, will want to switch between groups of ions during the run. The only problem with Applied Biosystems software is that there is a bug in their quantitation software that stops you from using an internal standard from within one group of ions (period in their software?) with an analyte in another group of ions. Sure they could fix if you wanted to buy one from them.

[MG]

James, with Analyst 1.1, it was possible to use ISTD from one period with an analyte in another period. But, things had to be entered in a certain order in the software, in order for it to work. Also, I can't remember if it worked in Quick-Quant or not, but I do remember that certain features don't work in Quick-Quant. So it was a little buggy. I can't say if the functionality is still there in the newer versions, because it's been some years since I've done much multiple-period work. Just play around with it and you'll probably figure out the sequence that Analyst needs for this to work.

For example, if entering ISTD in Period#1, but you haven't yet entered an analyte that will use it, Analyst might complain that nothing is using the ISTD and try to delete it when you advance to the next period. So just enter a bogus analyte (like TIC) in Period#1 and set it to use the ISTD, then advance to Period#2, enter your analyte and have it use the same ISTD (it should show up at that point), then go back to Period#1 and delete the bogus analyte. That's all from memory but hopefully it helps.

[james little]

Thanks for the advice MG.

I had called technical support for help on the problem, but the person I talked to offered no encouragement for it working.

I will give it a try.