Test for presence of blood

June 1, 2007 11:03 AM

For obscure journalistic reasons, I need to determine whether a sample of liquid contains blood.

I can't really go into detail, but: Let's say I have a vial of liquid. I am investigating reports that it contains trace amounts of human blood. Is there a kind of lab that would perform such a test, and how much would that cost? Or is there an easy test I could do with a chemistry set? Any help much appreciated.

posted by johngoren to Science & Nature (11 answers total)

You can buy a "blood in stool" test kit, and probably use it with effective results.
posted by nomisxid at 11:18 AM on June 1, 2007

There are kits that use antibodies to blood to determine if there's, well, blood in a sample.

If there's a *lot* of blood, adding bleach will turn the sample green.

You could, also, just look at it under a microscope. Blood cells are pretty obvious (they look like little rolled-up condoms).
posted by porpoise at 11:23 AM on June 1, 2007

A urine dipstick would probably do the trick; they are available here at $47.00 for a pack of 100, but I didn't really do any comparison shopping.
posted by purplemonkie at 11:26 AM on June 1, 2007

Apparently horseradish & copper can also give false positives for the luminol based tests, which is what most of the ones you'll find in kits are.
posted by scalefree at 11:27 AM on June 1, 2007

The guaiac or guiaiacum test will show the presence of very small traces of heme. If heme is not present it's unlikely that blood is.
posted by ikkyu2 at 12:00 PM on June 1, 2007

You say you need to ascertain whether or not the sample is human blood, which is more complicated. That requires genetic analysis.

These folks sell test kits which they claim can confirm the presence of human blood. They also have tests for other precious bodily fluids, in case you've got any other vials of mystery liquid that need identifying.

Unfortunately, they don't list a price, which makes me think they're not particularly cheap. If you find out the cost, please post it here, as this has made me curious.
posted by Gamblor at 12:45 PM on June 1, 2007

Also, the kits I mentioned look like they're commonly used in sexual assault investigations, so there might be other companies with similar products. Forgive me if I don't do an elaborate search at work to confirm that suspicion.

I certainly don't mean to question your motives, but I just want to throw this out there: On the off chance that that's what you're planning on using this test for, please contact the police directly. Just sayin'.
posted by Gamblor at 12:55 PM on June 1, 2007

Everything I know about forensics I learned from CSI. They use Phenolphthalein
posted by soundslikeobiwan at 1:13 PM on June 1, 2007

If maybe after all this is done, you could follow up and share with us why, that would be great. I am dying of curiosity.
posted by fiercecupcake at 1:56 PM on June 1, 2007

Don't use phenolphthalein -- it doesn't show traces of blood so much as it is an indicator of pH, and even then, very inaccurately. I mean, if you can't see the blood, it can't tell you much of anything, especially if the solution is acidic (like urine), because a small amount of blood (being almost neutral) can't 'even out' all of the acids in urine. Hell, one time phenolphthalein even turned a lovely pale orange in a basic solution, god knows why.
posted by flibbertigibbet at 6:25 PM on June 1, 2007

Thanks for the help. It's actually not at all murder or violence related, and is more of a public health issue. I'm going to try one of these tests myself--however, I'm now thinking I'll need a third party firm or chemistry professor to verify my research independently.
posted by Kirklander at 11:41 AM on June 3, 2007