Analytics · Method validation · continued

Sample handling between despatch and injection posts 31–60

Analytics › Method validation stability-indicating method LOD & LOQ linearity precision & repeatability

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.

e.nilsenTL210 Apr 2026#31

k.radich, post #1: Sample handling between despatch and injection Writing it up because I had to work it out twice and would rather nobody else did. Trying to work out what would count as evidence on sample handling between despatch, before collecting any. This is the part I usually skip and it is the part that makes the rest useful. If two explanations… Go to post

Accuracy: the method measures what you intend to measure. For purity methods, this is tested by spike-and-recover experiments: add a known amount of impurity to a sample and measure whether you recover the added amount.

13 likes in reply to #1 4mo

aliquot_lineTL3Regular11 Apr 2026 · edited#32

A note on how sample handling between despatch gets discussed rather than on sample handling between despatch itself: the confident posts get the replies and the careful ones get ignored, and the careful ones have been right more often.

26 likes 4mo

k.marchandTL211 Apr 2026#33

Building on post #32 rather than restating it.

The most useful single question about a method: what would it fail to detect? Every method has an answer and few documents state it.

Someone should write this up properly, and it should probably not be me.

0 likes 4mo

fr.translation_moTL2Translator · FR12 Apr 2026#34

n.chowdhury, post #27: The distinction between a qualified instrument and a validated method is worth keeping. Both are needed and they fail in different ways. A single observation, in a thread that deserves better than single observations. Go to post

Post #30 put the caveat in the right place and I want to underline it.

Range and working range are different things and a certificate rarely distinguishes them. The relevant one is the range over which this particular sample was measured.

Take it as a starting point and not as a specification.

2 likes in reply to #27 4mo

f.piresTL212 Apr 2026#35

aliquot_line, post #32: A note on how sample handling between despatch gets discussed rather than on sample handling between despatch itself: the confident posts get the replies and the careful ones get ignored, and the careful ones have been right more often. Go to post

That is the distinction I keep failing to hold on to. Written down now.

18 likes in reply to #32 4mo

glossary_deskTL3Regular13 Apr 2026#36

Linearity across the working range is a routine demonstration and it constrains how far a result can be extrapolated. A method linear from 80 to 120 per cent of nominal says nothing about a sample at ten per cent.

0 likes 3mo

v.stanescuTL213 Apr 2026#37

Worth stating the null on sample handling between despatch before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.

0 likes 3mo

NicolaidesTL3Regular13 Apr 2026#38

Where I part company with post #34, and it is a narrow parting.

Where the sample handling between despatch discussion usually stalls is that nobody wants to say "I do not know" and everyone is willing to say "it varies". Those are the same sentence with different clothes on.

4 likes 3mo

h.lindqvistTL214 Apr 2026 · edited#39

bench_notes, post #9: The limit of quantitation determines what the impurity table can honestly contain. Peaks below it can be reported as detected and cannot be reported as a number. Go to post

Adding the measurement that post #36 says would settle it.

The limit of quantitation determines what the impurity table can honestly contain. Peaks below it can be reported as detected and cannot be reported as a number.

One case, stated as one case.

0 likes in reply to #9 3mo

appeals_deskTL3Regular14 Apr 2026#40

endpoint_margin, post #18: System suitability is the ongoing evidence that a validated method is still performing. Validation is done once; suitability is done every run, and it is the one that appears on a certificate. Go to post

Post #38 describes the usual case. This is about the unusual one.

Sample stability during analysis is part of validation and is routinely ignored. A preparation that degrades in the autosampler over eight hours produces a sequence-dependent result.

Stating my assumptions rather than smuggling them in.

4 likes in reply to #18 3mo

KStephanopoulosTL3Regular15 Apr 2026#41

The bit of sample handling between despatch that nobody enjoys is that the answer changes depending on what you are trying to decide with it. Say what the decision is and the thread will converge.

6 likes 3mo

h.castellanosTL215 Apr 2026#42

Post #39 answers the question as asked. The question underneath it is different.

The most useful single question about a method: what would it fail to detect? Every method has an answer and few documents state it.

Small point, but it is the one that usually catches people.

1 like 3mo

footnote_entryTL3Regular16 Apr 2026#43

s.lundgren, post #21: Small correction to my own earlier position on sample handling between despatch. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely. Go to post

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.

31 likes in reply to #21 3mo

m.oyelaranTL216 Apr 2026#44

Collapsed as off-topic by two members at trust level 3 or above

I came in to disagree and I am leaving without a disagreement.

bench_peakTL3Regular16 Apr 2026 · edited#45

Coming back to post #43, because the follow-up matters more than the original answer.

The documentation on sample handling between despatch is better than this thread and I say that as someone who has posted in the thread.

10 likes 3mo

r.coelhoTL217 Apr 2026#46

Post #43 is right about the mechanism and I think understates the practical bit.

Reframing sample handling between despatch slightly, because I think the disagreement is about the question rather than the answer. If the question is "does it happen", yes. If it is "how often", nobody here knows.

3 likes 3mo

IsaksenTL3Regular17 Apr 2026#47

integrator_trace, post #28: The confident answers on sample handling between despatch and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category. Go to post

Where a pharmacopoeial monograph exists, a method that follows it inherits a great deal of assurance. Almost nothing discussed here has one.

The evidence for this is thinner than the way I have phrased it suggests.

0 likes in reply to #28 3mo

s.vogelTL218 Apr 2026#48

Why two laboratories may disagree: after validating the same method, they may still report different purity on the same sample due to integration differences, column age differences, subtle differences in mobile phase pH or temperature. This is normal and not a sign that one is wrong.

On reflection I would soften that slightly.

22 likes 3mo

cannula_traceTL3Regular18 Apr 2026#49

dietitian_hollis, post #7: Grateful for the specificity. Vague answers to this question are what sent me looking. Go to post

Answering the question post #47 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.

15 likes in reply to #7 3mo

g.amankwahTL218 Apr 2026#50

The claim about sample handling between despatch upthread is stronger than its source supports. I have read the source. The source says "associated with" and the post says "causes".

21 likes 3mo

tracked_parcelTL2Regular19 Apr 2026#51

The distinction between a qualified instrument and a validated method is worth keeping. Both are needed and they fail in different ways.

Posted with less confidence than the sentence structure implies.

11 likes in reply to #21 3mo

r.vukovicTL219 Apr 2026 · edited#52

The short version is the first sentence; the rest is why.

24 likes 3mo

unit_conversionTL3Regular20 Apr 2026#53

This follows post #50 rather than contradicting it.

Sample handling between despatch looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.

0 likes 3mo

m.balogunTL220 Apr 2026#54

Clear enough that I do not think I have a follow-up, which is unusual.

3 likes 3mo

p.novotnyTL2Regular20 Apr 2026#55

r.coelho, post #46: Post #43 is right about the mechanism and I think understates the practical bit. Reframing sample handling between despatch slightly, because I think the disagreement is about the question rather than the answer. If the question is "does it happen", yes. If it is "how often", nobody here knows. Go to post

The distinction between a qualified instrument and a validated method is worth keeping. Both are needed and they fail in different ways.

This is the sort of thing the wiki should carry and currently does not.

7 likes in reply to #46 3mo

f.haddadTL221 Apr 2026#56

KStephanopoulos, post #41: The bit of sample handling between despatch that nobody enjoys is that the answer changes depending on what you are trying to decide with it. Say what the decision is and the thread will converge. Go to post

Everything in post #52 holds. The case it does not cover is the one I have.

Having read the whole sample handling between despatch thread before replying: the question in the first post has not actually been answered yet, and three of us have answered a nearby one instead.

17 likes in reply to #41 3mo

eire_readerTL2Regional · IE21 Apr 2026#57

The limit of quantitation determines what the impurity table can honestly contain. Peaks below it can be reported as detected and cannot be reported as a number.

It cost nothing to check and would have cost something not to.

0 likes 3mo

ai.vukovicTL221 Apr 2026#58

Sample handling between despatch is worth one more sentence than it usually gets, and the sentence is the one about how the number was arrived at.

1 like 3mo

hana.satoTL4 Moderator22 Apr 2026#59

f.haddad, post #56: Everything in post #52 holds. The case it does not cover is the one I have. Having read the whole sample handling between despatch thread before replying: the question in the first post has not actually been answered yet, and three of us have answered a nearby one instead. Go to post

Adding thanks rather than a view. I do not have a view worth the space.

0 likes in reply to #56 3mo

n.okwuosaTL222 Apr 2026#60

n.zielinski, post #11: Post #9 answers the question as asked. The question underneath it is different. Sample handling between despatch is well covered in the tag pages, and the older discussions are better than the recent ones because they were argued out properly. Worth twenty minutes before adding to this one. Go to post

Answering the question post #56 raises rather than the one it answers.

Sample handling between despatch 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.

3 likes in reply to #11 3mo