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Question Fake blood for forensics

1 month 2 weeks ago #41588 by BioBee
Hi all,

Does anyone have suggestion on where to get fake blood for forensics practicals?

We recently ordered in a kit called a 'presumptive blood test' and the amount of blood it comes with is hilariously small (for the price we were expecting MUCH more haha).

It would suffice for a demo but the teachers would like to do it as an individual or at least small group practical so would need at least 100-200mls of the stuff.

And yes, halloween blood from poundland has already been suggested :p

Thank you!

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1 month 2 weeks ago #41589 by TecHKnow
Try "Demonstrate how Blood Grouping works" on our Wiki area

Please consider buying me a drink for Christmas by making a donation to the website - Happy Christmas and Thank you!

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1 month 2 weeks ago #41590 by BioBee
Great thanks I'll have a look :)

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1 month 1 week ago #41592 by Baldilocks
Sorry for the delay but I've been away.

I've been meaning to write this up ever since I retired - then I discovered that my full notes were wiped by the school IT before my replacements could print it out - then I found some notes and reagents in my shed a couple of years ago.

My idea was to make something that could give an idea of the ABO differntiation but without the cost and without any nasty chemicals. I believe that I succeeded.

This is NOT an agglutination reaction, so it does not mimic the Eldon cards or other similar biological tests. It is much more akin to ‘blue line’ pregnancy tests.

The blood.

This was made from about 80% glycerol and 20% water. This gave a realistic ‘gloopiness’

The red colour was a red food colour known as a ‘lake’. These are well known precipitates that are made in the presence of strong dye solutions. As the precipitate drops out of the solution some of the dye is trapped in the structure and is no longer soluble. This is why smarties no longer work for chromatography experiments and eating them no longer stains the tongue (as much). If you read the ingredients of smarties, skittles etc. you will see a long list of lakes.

The red colour was one of several that I tried from an ebay supplier of food/cosmetic colours. The ones that didn’t work failed because they had ferric oxide as an ingredient, and one of the tests was for iron salts!

Now for the interesting bit – the antigens.

A is potassium ferrocyanide (Potassium hexacyanidoferrate(II) ) - sharp intake of breath. Despite the name. this stuff is NOT toxic, it is used as an anti-caking agent added to table salt. The beauty of it is that it gives a bright blue reaction when it meets a ferric salt (the original blueprint), so the anti-A is weak ferric citrate (or even Irn-Bru).

B is thymolphthalein, almost identical to phenolphthalein in every respect except that it turns blue on exposure to anti-B, which is sodium carbonate solution.

O blood obviously has neither of the above while AB has both.

The method of determining involves a microscope slide sized piece of blotting paper (I got mine from Rymans) with a pencil mark in the centre, A written near one end and B near the other. A drop of ‘blood’ is placed in the centre and, because the ‘blood cells’ (red lakes) are not soluble they stay put while the ‘serum’ (glycerol + antigens) diffuse both ways outwards. After a short while, a drop of each of anti-A and anti-B are dropped onto the pencil marks and allowed to diffuse towards the ;serum’. When they meet they will give a blue line for positive or nothing for negative.


Other uses of the same blotting paper technology that I tested were:
Essentially identical blood without the red colour, now called serum, urine, wine or whatever you choose, which is tested for drugs, performance enhancing dope or poison.

I also tried it with Benedicts or Fehlings, (Can’t remember which) using a heatproof cooking sheet and an electric iron to develop it. All I can remember were the labels on the ‘urine’ specimen bottles – Mustapha Whee, Anita P, N Uresis, I N Continent, Dai Abieties, M Bustin etc. etc.

All the reagents were issued in eye-dropper bottles that I found really cheap on ebay or Amazon, for example: www.amazon.co.uk/s?k=starall+dropper+bottle
offers 50 for £3.65, or 7p each.

The only ingredient that is NOT (to my knowledge) available as food grade is the thymolphthalein so the risk assessment needs to be done for that. The lakes WILL stain cotton.

I probably have some more info at home but I’m not there at the moment.

Ian

“Do not believe everything you read on the Internet.” -Abraham Lincoln
The following user(s) said Thank You: TecHKnow, Kasey

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