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Messages - djb17

1
Compound identification / Duplicate annotations from Compound Discoverer
Hi all,

I'm seeing a noticeable number duplicate annotations for the analytes generated from Compound Discoverer. Specifically, there are cases where the molecular weight are the same, but some (or all) of the retention times are different.

What is the best way of handling such cases during downstream analyses?

Thanks!
2
Vendor specific software / QC correction in Compound Discoverer (ThermoFisher)
Hello,

ThermoFisher's compound discoverer provides two different methods of correcting for drift using either linear or cubic spline regression.

I'm not too well versed in statistics and was wondering if someone could help me understand how this is done (especially cubic spline).

For example, what would be my coefficients (beta's) if I was using linear regression to correct for drift?

Thank you.
3
Mass spectrometry / Re: Experimental design for multiple-batch study
Given that, how different are the distributions?
Say there are 3 conditions, where all samples were randomly assigned to. It would be fine to have one batch with 30/40/50 samples from each treatment (assuming they are run in a randomized order). However, it wouldn't be good to have a distribution of something like 50/0/60. Even worst would be 10/0/100.

I'm talking about the extreme case (e.g. 10/0/100). So is it correct to say that, even if the pooled QC was created from all of the samples in the experiment, the resulting data would have issues because of the unbalanced distribution of the samples (after correction, normalization, etc...)?

If this is the case, what happens during the experiment as a result of the imbalance that leads unusable/low-quality data?

Thank you so much for your feedbacks! Learning so much from you all  :D
4
Mass spectrometry / Re: Experimental design for multiple-batch study
Thanks for the reply.

It's not an experiment where we have 'paired samples', so we are okay with respect to that.

I wonder if it would be okay if an experiment set up where:

  • There are multiple batches.
  • Within each batch, samples with different conditions are not evenly distributed.
  • A pooled sample consisting of small amounts of all samples in batches is created. QC samples are analyzed in addition to the samples in each batch (which ideally would allow for inter + intra batch drift).

After the batch correction (inter + intra) using QC samples, will the quality of the data be okay given that the distribution of the conditions were not even?

Thanks again.
5
Mass spectrometry / Experimental design for multiple-batch study
Hi all,

I have been thinking about setting up an experiment with around 600 samples (3 batches of 200) with 3 different conditions. Would it be optimal to set up the batches such that the proportion of 3 different conditions are the same throughout the different batches?

Thank you.