Range: the concentration range over which the method has been validated. Going outside the validated range is going outside the method's demonstrated performance.
Worth separating two things that the opening post runs together.
Where a pharmacopoeial monograph exists, a method that follows it inherits a great deal of assurance. Almost nothing discussed here has one.
Reporting a result to more decimal places than the method's precision supports is a small dishonesty that appears everywhere. A method with a two per cent relative standard deviation does not support a figure quoted to a hundredth.
A qualification I should have led with rather than closed on.
The arithmetic in post #36 is right; the assumption feeding it is the part to check.
Transfer between laboratories: a method can be transferred from one lab to another, but the receiving lab needs to demonstrate that they can achieve the same performance. This requires comparative testing and sometimes small method refinements.
Answering the question post #79 raises rather than the one it answers.
A method transferred between laboratories needs a demonstration that it performs equivalently, not just a document describing it. Transfer is where a great many between-laboratory disagreements originate.
This follows post #89 rather than contradicting it.
Reporting a result to more decimal places than the method's precision supports is a small dishonesty that appears everywhere. A method with a two per cent relative standard deviation does not support a figure quoted to a hundredth.
One of those cases where knowing the mechanism does not help the decision.
Stability-indicating method: one that can separate a compound from its degradation products. Critical for assay methods that claim to measure actual degradation (as opposed to purity, which is orthogonal).
Happy to be the one who is wrong here if it settles the question.
Read the full topic (113 posts)
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Specificity, linearity, accuracy, precision, range, robustness — with real criteria
Specificity, linearity, accuracy, precision, range, robustness — with real criteria Writing it up because I had to work it out twice and would rather nobody else did. Trying to establish the boundary…
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+44 | 48 | 12k | 1d |
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LOD and LOQ: definitions people get wrong
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2 | 43k | 8mo | |
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Coming back to: When to suspect the method rather than the sample
When to suspect the method rather than the sample I have a specific reason for asking rather than idle curiosity, and the context is below. Two reports on the same lot, and I would like help deciding whether…
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+116 | 135 | 42k | 19mo |
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Repeatability versus intermediate precision
Repeatability versus intermediate precision — setting out what I have, and where I think it stops being reliable. Trying to establish the boundary conditions on repeatability versus intermediate precision.…
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+119 | 134 | 34k | 13mo |
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Revisiting: Sample handling between despatch and injection
Posting this under the heading it deserves: Revisiting: Sample handling between despatch and injection Everything below is what sits behind that. Reading back through what has been written here about Sample…
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+5 | 9 | 1.1k | 6mo |
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Where the integrator drew the baseline, and how much it moved the number
Where the integrator drew the baseline, and how much it moved the number — setting out what I have, and where I think it stops being reliable. Posting the method first, because I know what the first three…
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+20 | 24 | 1.6k | 8mo |
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Relative retention time as a better inter-laboratory comparator — does this still hold?
Relative retention time as a better inter-laboratory comparator — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. What changes if the standard…
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+11 | 15 | 21k | 21mo |
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Coming back to: Specificity, linearity, accuracy, precision, range, robustness — with real criteria
On the subject in the title: Specificity, linearity, accuracy, precision, range, robustness — with real criteria Working notes rather than a conclusion. Trying to establish the boundary conditions on…
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+93 | 99 | 1.4k | 6d |
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Why one laboratory's 98.4% and another's 96.1% may not contradict — one year on
Asking directly, because I could not find a straight answer: Why one laboratory's 98.4% and another's 96.1% may not contradict — one year on Posting the method first, because I know what the first three…
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+10 | 14 | 13k | 5mo |
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Coming back to: What consumer-accessible tests can and cannot determine
Asking directly, because I could not find a straight answer: What consumer-accessible tests can and cannot determine Something about consumer-accessible tests does not reconcile and I would like a second pair…
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+4 | 8 | 25k | 22mo |