For research use only. Not for use in diagnostic procedures.
What does "bin size" mean and what is the rule of thumb for setting bin sizes when setting up acquisition methods for a TOF MS system in Analyst® TF software?
Under the Advanced MS tab in Analyst TF software, there is a field that allows the user to set bin size. The default setting is typically 4.
The Time-Bins-To-Sum parameter determines the number of points across the peak in the mass spectrum (similar to how cycle time affects points across the LC peak). The number of bins refers to the number of data points from the signal handling subsystem that are summed together to create a single data point in the mass spectrum. The higher the bins-to-sum, the more points that are consolidated to make a data point in the spectrum.
Time bins are 25 ps each, so a bins-to-sum = 4 means that every data point in the spectrum spans 4 * 25 ps = 100 ps of time-off-flight. Bins = 40 would be 1000 ps (1 ns) of flight time.
Increasing bins-to-sum (i.e., fewer points across the peak) gives the appearance of higher intensity because each spectral data point has more flight time summed up into it. However, this can also cause a loss of spectral resolution/mass accuracy if the binning is too high. Conversely, if the binning is too low (i.e., more points across the peak) the data will appear to have lower intensity and the peaks may appear noisier/scratchier.
If the data start to look too “angular” or “triangular”, then the bins are too high (too few points across the peak). If the data are oversampled (i.e., more data points than necessary), then the binning can be increased.
General rules of thumb:
When absolute optimum resolution below m/z 200 is required: bins = 2
For large non-isotopically resolved proteins (e.g., intact mAbs): bins = 60
Small non-isotopically resolved proteins (e.g., carbonic anhydrase, BSA): bins = 40
Everything else: bins = 4 (default)