We recently purchased a Thermo LCQ Advantage and I am beginning to develop a carbamate analysis method. We currently use HPLC with post column derivitization and UV detection. I would like to speak with anyone who is currently analyzing carbamtes using LC/MS.

Thanks,

Mike M.

Hi Mike
I have obtained separation and detection of N-methylcarbamates such as carbaril, aldicarb and metomil, with HPLC and MSD detection (single quadrupole Agilent 1100 series).
The separation was performed on a cyano column (LUNA 50*3 mm - 3.0 µm) with acetonitrile - ammonium formate 5 mM as mobile phase and gradient elution:
acetonitrile % 10 20 60
time (min) 0 5 18
flow 0,35 mL/min
note that ammonium formate 5 mM is able to produce a sligthly acidic mobile phase.
With this conditions and "standard" settings for this electrospray interface (capillary voltage 4000V, nebuliser pressure [nitrogen] 40 psi, drying gas [nitrogen] 10 L/min), I have obtained a good signal in positive ionisation mode. Generally a low fragmentor voltage (40-60V) is sufficient to produce fragments ions from parent molecules giving information for confirmatory purposes; with fragmentor voltage toward 20 V the signal of pseudomolecular [M-H]+ ion is maximized.
Consider that I have tried only this conditions with the aim of exploring the possibilities of ammonium formate as modifier. Therefore this condition was not tested for quantitative purposes.
sorry for my english.
Good luck.

What was the pH?

Anon,

Thanks for your help. I appreciate the feedback. I recently accuired a method usign Amonium Acetate 10mM and ACN. I am going to give that a try. I would still like to hear from anyone else who is doing this application.

Thanks

Mike M.

We are not routinely running carbamates, but have had small confirmation runs of methomyl, carbaryl and carbofuran that were very promising. Sensitivity seems to be similar to many other pesticides with which we have experience, and we have not experienced severe quantitation problems. However, LC/MS quantitation will probably not be as solid as UV or FLD, other things being equal. It is a much more complex, dynamic detector, and the real problem is the interface to the detector. We have several of these beasts, and difficult, unsettling problems come up from time to time.

I have an LCQ Deca, APCI interface. I use 0.1% acetic acid in the water and MeOH, and use a gradient on the C18 column. Because you have MS/MS available, the exact gradient isn't critical, but I used a general purpose 10-90% organic in 15 minutes--about the same as we use on conventional equipment.

While there are always surprises (poor ionization for 1 or more compounds), I don't foresee any major problems converting this analysis to LC/MS, unless you need exceptional sensitivity.

We are currently debating the use of ammonium acetate, however, when analyzing triazines. Again, we use APCI interfaces. If we do not use ammonium acetate, but only 0.1% acetic acid, we get about 4 times the response. It appears that the acetate does not maximize ionization for some compounds. You may want to check this out for carbamates.

I am also debating with myself the wisdom of replacing a relatively cheap, simple, reliable post-column system (FLD, NOT UV detection--I think you mistyped) with an LC/MS for this analysis. Except for some sample types--in our case citrus fruits which have high fluorescense background from the citrus oil in the rind, is it a smart move? There are many other compounds and matrices that the LC/MS would be a better--maybe the only--alternative. I suppose it depends on the individual lab's problems.

In any case, enjoy the ride!! The LCQ's are almost magical on a good day, and way more often than not are a joy to run.