Testing Standards

Purity Is The Cheap Test. Here Are The Four Your Supplier Probably Skipped.

Purity is the one number every listing prints, because it is the cheapest one to get. It says nothing about how much is in the vial, what metals came along for the ride, or whether anything is growing in it. Here is what a full certificate is supposed to show.

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You compare two listings. Both say 99%. Same vial size. One costs less. Easy call.

Except that 99% only answers one question. Of the material in the vial, how much is the target molecule?

It does not tell you how many milligrams are actually there. It does not tell you about heavy metals. It does not tell you whether the vial is sterile, or whether it carries endotoxin. Four questions. Four separate tests. And most listings answer none of them.

1Purity is a ratio. You are paying for an amount.

A glass can be 99% orange juice and still be half empty. The 99% describes what is in the glass. It says nothing about how much.

A vial works the same way. The label says 10mg. Purity cannot confirm that. Only a measured content test can, and it costs extra, so most suppliers never order it.

One published AKRO lot shows exactly what this looks like on paper: labelled 10mg, measured 9.87mg, purity 99.4% by HPLC. Two numbers. Two tests. Both printed.

If nobody measured the milligrams, nobody knows how many you paid for.

2Heavy metals do not show up in a purity number

Purity looks at the target molecule against everything else that responds to the same test. Metals picked up from equipment, water or raw materials can sit in the vial and never move that number.

That needs its own method. On a proper certificate you will see it named, usually ICP-OES or ICP-MS, with a result next to it.

No metals line means no metals test. Not a clean result. No result.

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3Sterile and endotoxin free are two different findings

Sterility testing asks whether anything grows. Endotoxin testing asks something else entirely. Endotoxins are fragments left behind by bacteria, and they survive the processes that kill live bacteria.

So a vial can pass sterility and still carry endotoxin. You only know if both tests were run. On a certificate, look for USP <71> for sterility and LAL for endotoxin.

Sterile is one finding. Endotoxin free is another. Ask which one, if either, is on the page.

Values from one published AKRO lot record (tested Sep 21, 2026, ISO/IEC 17025 accredited lab). Fields differ from lot to lot, so read the record for the lot you are buying.

4Why most suppliers stop at purity

Money. Purity comes off one standard run. Content, metals, sterility and endotoxin are four more methods, often at an outside lab, every single lot.

A supplier who skips them is not hiding a bad result. They simply do not have one. Neither do you.

A missing test is not a pass. It is a blank you are paying to ignore.

5The sixty second check

Open the certificate for the lot you are about to buy. Skip the purity line. Look for these instead.

• Measured content in milligrams. Next to the labelled amount, not instead of it.
• A heavy metals line with a named method. ICP-OES or ICP-MS and a result.
• Sterility and endotoxin, listed separately. Two lines, two results.
• A named lab you can look up. Not just the word "tested".

Four lines. Under a minute. It sorts suppliers faster than any price comparison.