What parameters can increase MS scan rate?

[Anthony_Ng]

Hi all,

We have a LC couple with low level single quad MS. For DAD, we can decrease the peak width (response time) to minimize the peak broadening by detector electronics.

What about Mass Spec? Apart from decreasing the mass scan range, what else we can do to increase the scan rate? (What is the effect of Step size, Time filter, peakwidth....)

Thanks in advance!

[lmh]

I think the following is true, but would be grateful for the input of someone who knows more:

For full scans, realistically, there may not be much you can do, but it depends on your instrument. Agilent single quads come with a fast scan option, which increases the ion energy (I think this involves changing voltages in the octapole, but I'm not sure) and changes the optimisation of the quad. This isn't a win-win situation: the increased scan speed is at the expense of decreased sensitivity and mass resolution.

I think the higher end Agilent single quads come with an even faster scan, too.

Probably other manufacturers have similar options on their instruments.

I don't think the time filter is going to make data appear faster. It is merely a real-time smoothing filter. It needs to be shorter if your peaks are narrower, but it cannot make points appear more quickly than they can be physically collected.

Peak width, in Agilent-language, is used to ensure that there are enough scans across a peak, but it's not clear to me whether scan speed is actually adjusted, or whether it merely complains if you try to do something that would give inadequate scans across the specified peak. You should try to enter a realistic value, and hope you can find step-sizes and scan ranges that don't result in complaints from your software.

Keeping scans as narrow-ranged as possible (i.e. don't go up to 2000 unless you have to) should speed things up. In SIM mode, of course, there isn't such a scan-speed issue.

[jh1]

Try changing the sampling rate value if the option is available to you, it should increase or decrease the time spent monitoring each ion allowing you more scans or more sensitivity in each scan.

Also as mentioned already SIM is a great way to increase scanning rates, if you're only interested in a small number of ions it's quite easy to get a large number of scans across each peak.