My understanding of mass-error checker is a few years old and may have been superseded. If it has been, I would genuinely like to know rather than keep repeating it.
Posting this under the heading it deserves: Second pass at: The mass-error checker and its intended scope Everything below is what sits behind that.
Posting a small dataset on mass-error checker. It is mine, it is uncontrolled, and the method is stated so it can be discounted appropriately.
What I would like is not agreement but a second dataset collected by someone with no stake in mine. If one exists I would rather read it than argue for this one.
Worth separating two things that the opening post runs together.
A definition problem is doing most of the work in this mass-error checker discussion. Once the term is pinned down I suspect the disagreement mostly goes away and what is left is small.
Two sentences on mass-error checker and then I will stop, because the rest is speculation and the thread is better without mine.
What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.
The calculators maintained on this site are open-source and verifiable. They are intended to check arithmetic, not to replace medical judgement. Using them is optional and they are provided for convenience.
The honest answer is that it depends, and here is what it depends on.
Post #4 answers the question as asked. The question underneath it is different.
A calculator that shows its working is worth ten that give an answer. The whole value is being able to see which step you disagree with.
That is the version I use. It may not be the version that is correct.
My understanding of mass-error checker is a few years old and may have been superseded. If it has been, I would genuinely like to know rather than keep repeating it.
An observation about mass-error checker that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.
Tools that run entirely in the browser send nothing anywhere, which matters more to some people here than others and is worth stating either way.
I have changed my mind on this once already, so take it as current rather than settled.
Mass-error checker is worth one more sentence than it usually gets, and the sentence is the one about how the number was arrived at.
Dose equivalence calculator: compounds have different potencies. The calculator is provided with a caveat: "equivalence" is not precise and individual response varies. It is a rough starting point, not a dose prescription.
Post #13 is right about the mechanism and I think understates the practical bit.
Mass-error checker sits at the boundary between what this community can usefully discuss and what it cannot, and I think it falls on the discussable side, narrowly.
Agreed on all of that, and I have nothing to add to it.
On post #13 — agreed on the reasoning, with one qualification.
Unit-conversion tools are only as good as the assumption they make about the syringe. Ask what barrel and what graduation interval it assumed before trusting the units figure.
A guess, clearly labelled as one.
Post #17 answers the question as asked. The question underneath it is different.
The parts-per-million mass-error calculation is simple enough to do mentally to one significant figure, which is a good habit because it catches an order-of-magnitude slip immediately.
I would not lead a decision with this, but I would not ignore it either.
I think the mass-error checker question is answerable and has not been answered, which is a more optimistic position than most of this thread.
Adding a null result on mass-error checker. I looked, carefully, and found nothing, and null results deserve posting precisely because they never are.
This follows post #18 rather than contradicting it.
A saved calculation is worth more than a remembered one. Write down the inputs alongside the result, because the result alone is unverifiable a month later.
Thank you — that answers what I came here to find out.
A note on how mass-error checker gets discussed rather than on mass-error checker itself: the confident posts get the replies and the careful ones get ignored, and the careful ones have been right more often.
Significant figures in the output should not exceed what the inputs support. A concentration calculated from a nominal vial mass is not known to four decimal places.
I have separated what I observed from what I concluded, which does not always happen.
Reporting rather than recommending, on mass-error checker. What happened is above. Whether it should have is a different question and not one I am qualified to answer.
Sensible. I would want the same detail before I acted on it either.
On post #24 — agreed on the reasoning, with one qualification.
Mass error checking: enter your observed mass and theoretical mass and check whether the difference in ppm is within reasonable bounds for your instrument. Useful sanity check on LC-MS results.
Reporting the observation and leaving the explanation open deliberately.
Precision and significant figures: the calculators do not round to match your input precision. If you input values to one decimal place, the output might have more. Use significant figures appropriate to your input precision.
Old habit: I write down the expected answer before I calculate it.
I read post #28 twice before replying, because I had assumed the opposite.
A calculator that shows its working is worth ten that give an answer. The whole value is being able to see which step you disagree with.
I would put this at better than even and not much better.