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- Posts: 25
- Joined: Sat Apr 09, 2022 4:08 pm
I have recently been having a bit of play with some MRM methods, and after doing a comparison between 2 of my methods, noticed that one produced a greater response than the other despite running the same sample.
This wasn't particularly surprising (they were after all slightly different methods), but what did surprise me was that the method which was set to detect a greater number of daughter ions seemed to provide greater response than an otherwise identical method which was designed to detect a more limited set of daughter ions.
It was always drummed into me that the fewer ions selected in a SIM/MRM type method, the greater the proportion of the cycle time available for their detection and thus the greater the response; so the results appeared counterintuitive. I now suspect that the reason for the result is that the methods were set to display response as a function of both quant and qual ions and hence the method detecting more ions was simply displaying a response encompassing signal from more ions and hence was bigger.
However this got me thinking about whether or not there is an optimum dwell time for MRM and SIM beyond which the law of diminishing return rears its head and where this is? The SIM work I do requires only a quant and a single qual ion (2 ions + RT) which means that the dwell times for each ion are in the region of about 120ms. I was curious as to whether these dwell times were excessive and whether I would lose anything by dropping the dwell times to say 80 ms and adding another ion which would increase response? I will obviously try this out, but would be curious to get an idea of what to expect beforehand if anyone would be willing to let me know their thoughts on this?
Kind Regards
TD2