Talk:Kastle–Meyer test

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The previous form of this page contained a great deal of misinformation, though the author can be forgiven, as there is a great deal of misinformation about this test floating around. I have personal experience in preparing the analytical solutions to perform this test, and was nearly driven crazy trying to divine why nothing I tried gave me a positive test using authentic samples of blood (I was cheap and decided to make my own test kit). It wasn't until I came across a research paper assessing the relative effectiveness of various forensic tests did I see that the phenolphthalein solution was boiled with zinc dust prior to use. I'm really at a loss for why this isn't popularly known, maybe it's some kind of half-assed trade secret on the part of the test kit manufacturers? --Uberhobo 17:55, 25 August 2007 (UTC)

Update April 2008
Thanks to User:Sekiyu for the revisions. I'm not familiar with the name 'phenolphthalin' for the reduced form of phenolphthalein and I'd be cautious in using it as it is important to make the distinction, and yet the names are so very similar. (In the same way that 'hypo-' and 'hyper-' prefixes are disparaged in many medical situations).

Ewen (talk) 09:42, 29 April 2008 (UTC)

I agree that the similarity between the two names is confusing, but that is the accepted name. Whenever possible, I tried to make the distinction between the reduced -lin form and the oxidized -lein form, and no one wants to read "2-(Bis[4-hydroxyphenyl]methyl)benzoic acid" vs. "3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone." Even Sigma Aldrich's chemical entry for it warns against the confusion between the two. Sekiyu (talk) 15:28, 29 April 2008 (UTC)


 * Sure. I hope my minor editing of your revision is OK, by the way? I think I'll stick to 'reduced phenolphthalein' myself. Quite the mouthful but not so confusing. Ewen (talk) 15:35, 29 April 2008 (UTC)

Strong Bases
What if a strong base was added to the blood sample (such as cleaning out a bathtub with very basic drain cleaner), wouldn't this cause the Phenolphthalein to change color also? 64.180.188.6 (talk) 20:25, 26 October 2008 (UTC)


 * I can see where you're coming from, but the answer is no. You're probably talking about how phenolphthalein changes color to pink in the presence of a basic solution, that experiment we've all done in chemistry class.  The Kastle Meyer (KM) reagent is actually already basic in pH -- it is when the reduced phenolphthalein in the reagent is oxidized to phenolphthalein by the presence of heme (or some other oxidizer) that it is the phenolphthalein you are familiar with, which indeed, will turn pink in the presence of its alkaline solvent.  Now, if you cleaned out that bathtub with bleach (an oxidizer), you definitely would have a false positive.  If you were trying to conceal a crime, this obviously would not be a great move as the tub would be regarded with even closer scrutiny by law enforcement.  Hope that helps! Sekiyu (talk) 06:40, 14 April 2009 (UTC)

False information
This article formerly contained errors, in the limitations section.

The cox study found that NONE of the tested substances caused false positives with KM

False positives were only found with the orthotolidine and tetramethylbenzidine tests in cox's study.... he even concludes that KM and LMG are two of the most specific tests!! — Preceding unsigned comment added by 82.42.246.140 (talk) 15:59, 24 February 2013 (UTC)


 * Sorry, but what 'cox study'? Could you dig out a reference please? Ewen (talk) 19:49, 26 February 2013 (UTC)

Sorry, i deleted the false information, but here it is: http://www.ncbi.nlm.nih.gov/pubmed/1955838 / http://projects.nfstc.org/workshops/resources/articles/A%20Study%20of%20the%20Sensitivity%20and%20Specificity%20of%20Four.pdf

it used to be cited as a reference saying that all sorts of things caused false positives with KM.. which is the complete opposite of what the study found82.42.246.140 (talk) 20:31, 26 February 2013 (UTC)