The analysis of EDTA in dried bloodstains by electrospray LC-MS-MS and ion chromatography

Analytical methods were developed to determine the presence of ethylenediaminetetraacetic acid (EDTA) in dried bloodstains to provide probative information when allegations of evidence tampering have been made in criminal cases. A simple screening method using ion chromatography to analyze stains was found to be quantitative to the 5 ppm level. The presence of EDTA was then confirmed using negative and positive ion mode liquid chromatography-tandem mass spectrometry (LC-MS-MS) methods. A blind trial of these methods on 42 samples correctly determined the bloodstains that did and did not contain the preservative EDTA. One interesting observation in these results was the adsorption and postanalysis release of EDTA in the chromatographic system. In order to avoid cross contamination of samples resulting from this phenomena, it was found to be necessary to use EDTA-free blood extracts as blanks in the LC-MS analysis of bloodstains.