Dear fellow beloved Chemists,
I am just now heavily involved in detecting organochlorine and organophosphorus pesticides by GC/MS/MS. I was just curious what the best mode of detection was the best technique i.e. Single Ion Monitoring or Multiple Reaction Monitoring? I am having serious difficulties with the group's scan times cutting into the middle of some peaks. Also if anyone has insight into testing Dithiocarbamates by using automated GC/MS Headspace please do tell. Thank you in advance.-Paul D. Dodson
Hi!
The best MS mode will depend on the conditions of the sample. For example, if you're targeting a pesticide in drinking water then SIM mode is probably good enough for the desired LoQs. If you're targeting it in wastewater, then you will most likely need a different approach to clean the background (like SRM).
You should anyway start by optimizing the run with standards so that get problems with peak data acquisitions.
Finally, there are plenty of methods published to do what you're doing and even standard procedures from EPA and ISO. I recommend that you read them before starting in the lab. It will save you lots of time.
Cheers
Dear Mario and Hanghui, Thank you for taking the time to give me your insights. We have a Shimadzu TQ8040 and it can only scan in EI (scan mode), SIM and MRM (No SRM). The automated MRM technique for finding the optimal collisional Energies (CEs) is seriously lacking detailed explanations and not working. I was just going to switch to SIM until I can get the experience on MRM. Mario, have you seen serious problems from matrix interference in SIM mode? Thank you Gentlemen-Paul
Hi Paul,
First of all I would like to say that Maria Silva's recommendation is best for you. Here you mentioned that your instrument work in MRM mode but not SRM. Here you have to clear the concept of scan in MRM mode. MRM stands for multiple reaction monitoring which just another name of SRM (selected reaction monitoring). By triple quadruple (TQ) mass analyzer if you tried to detect your analyte in SIM (single ion monitoring) mode, you can't achived better sensitivity. In this case MRM mode is the better alternate.
Another issue here you mentioned that automated MRM technique not working in your instrument, that is unfortunate for you. But fortunately you can develop MRM method manually also for the optimization of collision energy for selected transition.
Best of luck.
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