Converting time intervals to distance

SilviaCastilla

Hi, I am conducting line scans in zoned crystals from core to rim and already have EPMA data. I want to match the line scan data to my EPMA data by creating concentration vs. distance profiles using the time series option. However, the time series is based on elapsed times, which don’t necessarily align with specific spots of interest. I’d like to know if it’s possible to split the signal from each line scan into multiple time segments that correlate with my EPMA spots. For instance, if I measured 20 points along a crystal with the microprobe, I’d like to segment the line scan into 20 sections. Also, In doing this, how can I account for signal smearing? Thank you!

Bence

Hi @SilviaCastilla

I've just added a first draft of a new tool for subsetting selections, available on GitHub:

https://github.com/iolite-LA-ICP-MS/iolite4-python-examples/tree/master/ui

It's the SelectionSubsetter.py script. There is a Note explaining how to download it here: https://notes.iolite.xyz/posts/downloadingfromgithub/

If you put that script in your Plugins/User interface folder you can use that to automatically break your selections into, for example, 20 sub-selections. iolite will then report a mean/median, uncertainty etc for each of the sub-selections. You can work out the distance along your profile by multiplying the median time for each sub-selection by the ablation scan rate.

Regarding correcting for signal smear, it is possible but getting the settings wrong can easily lead to incorrect results. To do this properly, we'd need to know more about your analytical setup etc. Please let us know what you have in mind.

Kind regards,
Bence

SilviaCastilla

Hi Bence,

Thank you so much for your reply!

I was able to upload the code you shared, and it works great. I really appreciate your help with this.

For context, I conducted a line scan from rim to core using a 20-micron circular aperture and a scan rate of 2 microns/second. The total ablation time was 140 seconds, with 10 seconds of warm-up. I’d like to divide this line scan into 15 segments while correcting for signal smearing. I want to ensure the segmented selections accurately represent the intended intervals without overlap.

Thank you again for your assistance!

Kind regards,
Silvia

Bence

Hi Silvia,

Depending on what ablation cell you're using, it's unlikely you'll have washout beyond a second or two (possibly less than 1 second). This washout affects the entire line, and so when you sync your mass spec data with your laser log file, you'll correct for some of this effect (slightly).

Without having to apply deconvolution, you can check how much your signal is smeared by looking at when the laser switches off. If you see a long, slowly decaying tail, it might be a problem. If you see your signal decay within a second, that's likely the effect any previous segment would have on the start of your current segment.

Please let me know how it goes.

Kind regards,
Bence