GC Image User Forum

I would like to do some external processing on a BT file. However, I am not able to figure out the scaling applied to the template coordinates to convert to retention times. How are the template coordinates scaled?

To process template peaks using a method supported by the software, the template peaks can be exported to a csv, modified, and reimported.
1. View > Template Table > select Peaks tab > Save Table
2. Perform external processing on the csv format
3. re-import via Template > Import Compound List

We don't support external processing of our .bt files and the format is not guaranteed to stay consistent. That said, if you still would like to try to perform your own processing, the coordinates found within the template file are given in the image pixel dimensions (i.e., the number of modulations in col I and the number of samples per modulation in col II). To convert to retention time coordinates, use the values stored in the 'template' tag near the top of the file as follows.

For template peaks:

• Retention Time I (in minutes) = starttimecol1 + peakfirstcol * modulation / 60

• Retention Time II (in seconds) = starttimecol2 + peaksecondcol / samplingrate

For template graphics (note that the y coordinate is for RTI and the x coordinate is for RTII):

• Retention Time I (in minutes) = starttimecol1 + y * modulation / 60

• Retention Time II (in seconds) = starttimecol2 + x / samplingrate

Thank you!