What consumer-accessible tests can and cannot determine — a second dataset

I had read the opposite somewhere and cannot now find where, which tells me something.

Taking post #32 at face value and following it one step further.

Nobody has said the unglamorous part of consumer-accessible tests yet, so: most of the variation is explained by things that are boring to write about and easy to check.

Consumer-accessible tests: I would want to see the raw numbers rather than the summary before agreeing. Summaries lose exactly the information that would settle this.

Where I part company with post #57, and it is a narrow parting.

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.

Building on post #61 rather than restating it.

Where I have landed on consumer-accessible tests, having got it wrong once in public: the direction is clear, the magnitude is not, and anyone quoting a precise magnitude has borrowed it from somewhere that did not measure it.

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.

Happy to be corrected if someone holds better data than mine.

Careful with the language on consumer-accessible tests. "Not detected" and "not present" are different findings and the first is a statement about the method.

Consumer-accessible tests looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.