Can a home kit substitute for a laboratory report? A careful no posts 121–132

Worth separating two things that post #117 runs together.

Colorimetric tests: colour intensity correlates with concentration, but the relationship is non-linear at extremes and the correlation depends on the exact conditions (pH, temperature, timing). Reading the colour visually introduces subjectivity.

Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up.

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 #121 rather than contradicting it.

What you can use home tests for: confirmation that a solution contains peptide (as opposed to being saline alone), rough screening for very different compounds (semaglutide versus totally unrelated compound). What you cannot use them for: precise purity assessment or verification that the identity is correct.

On post #121 — agreed on the reasoning, with one qualification.

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

post #125 answers the question as asked. The question underneath it is different.

Enzyme assays: if you have an enzyme that reacts specifically with your compound, an enzyme-based assay can work. These are sometimes available commercially but are less common than antibody-based tests.

False positives and false negatives: no test has 100% sensitivity and 100% specificity. A negative result does not guarantee absence; a positive result does not guarantee presence. The predictive value depends on prevalence.

Sample handling matters: if a sample is contaminated or degraded before testing, the test gives you the result for the degraded sample, not for fresh material. That is not a failure of the test; it is the test working correctly.

Enzyme assays: if you have an enzyme that reacts specifically with your compound, an enzyme-based assay can work. These are sometimes available commercially but are less common than antibody-based tests.

What physical quantity does the device measure? A colorimetric or lateral-flow method typically responds to a class of chemistry rather than to a specific molecule. It can distinguish "peptide present" from "nothing present" but generally cannot distinguish the intended peptide from a closely related one.