This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
A home refractometer is not measuring what people hope it is measuring in these preparations, and the readings are dominated by everything other than the peptide.
If anyone has run this properly I would rather read that than my own guess.
Agreed, and I will stop repeating the version of this I had been repeating.
Lateral-flow devices: like a rapid COVID test. They have a reagent strip and produce a colour result. They are quick but not precise and not intended for quantitative work.
This follows post #34 rather than contradicting it.
Reading this Reflectance and photometric devices thread as someone who came in with a fixed view: the third and seventh replies moved me and the confident ones did not.
Fair, and the limits you put on it are the part I will remember.
I have been on both sides of the Reflectance and photometric devices argument in this category within eighteen months, which should tell you how strong the evidence for either side is.
A home refractometer is not measuring what people hope it is measuring in these preparations, and the readings are dominated by everything other than the peptide.
It is the sort of thing that seems obvious in retrospect and was not at the time.
I would rather this thread reach "we do not know" about Reflectance and photometric devices than reach a confident answer that nobody can support when asked.
Post #41 describes the usual case. This is about the unusual one.
I changed my mind about Reflectance and photometric devices after someone here asked me for the source and I could not produce one. That is worth saying out loud because it is the ordinary way it happens.
Adding the measurement that post #41 says would settle it.
The right question for any home test is: what physical quantity does it measure, and what would have to be true for that quantity to answer your question? Most disappointment comes from skipping it.
If that reads as pedantic, it is, and it has saved me twice.
A note on scope: what I am saying about Reflectance and photometric devices applies to the case in the first post and I would not extend it further without checking.
Post #45 is the version of this I will quote in future. One addition.
Where the Reflectance and photometric devices reasoning breaks down for me is the step from the group result to the individual case. That step is almost never argued for.
Helpful, and short, which on this subject is harder than long.
The most useful home practice is not a test at all: photograph the vial, the cake, the label and the document on arrival. It costs nothing and it is the evidence you will wish you had.
Worth one more sentence than it usually gets.
I read post #45 twice before replying, because I had assumed the opposite.
Precision of home tests: most consumer-accessible devices are not precise to the level people want ("is this 99% pure or 97% pure"). They give a yes/no or a rough category, not a quantitative number.
Source for the Reflectance and photometric devices figure, since it was asked for. It is in the discussion rather than the abstract, which is why the version circulating is stronger than the paper is.
Reading the surrounding paragraph is worth the two minutes. The authors are more careful than their summarisers.
Lateral-flow devices: like a rapid COVID test. They have a reagent strip and produce a colour result. They are quick but not precise and not intended for quantitative work.
I have deliberately not rounded that, because the rounding is where the argument starts.
Building on post #53 rather than restating it.
Genuine question rather than a rhetorical one: has anyone here actually observed Reflectance and photometric devices, as opposed to read about it? The thread is long and I cannot tell.
A home refractometer is not measuring what people hope it is measuring in these preparations, and the readings are dominated by everything other than the peptide.
The honest cost comparison is a home kit against a single independent submission. For most people the second answers the question and the first answers a different, smaller one.
Adding this to the thread rather than to the wiki, because I am not confident enough for the wiki.
Coming back to post #58, because the follow-up matters more than the original answer.
The most useful home practice is not a test at all: photograph the vial, the cake, the label and the document on arrival. It costs nothing and it is the evidence you will wish you had.
I am aware this is the third time this month I have made this point.