LAUSR

Carbon monoxide (CO) poisoning presents an interesting challenge for postmortem toxicology laboratories. The discontinuation of the Co-Oximeter manufactured by Instrumentation Laboratories (IL) has left many forensic laboratories without this simple but reliable choice for the analysis of CO in blood. A comparable alternative that is quick and simple is analysis using a standard UV-Vis spectrophotometer which offers sufficient precision and accuracy for the measurement of % carboxyhemoglobin (COHb) in postmortem blood. The hurdle for laboratories then becomes the selection of an appropriate spectrophotometric method since a variety of procedures have been published over the years. Four methods were evaluated based on literature findings and/or the appropriateness for postmortem testing. These methods are based on 1) relating %COHb to the ratio of COHb and hemoglobin (Hb) absorbance of a two-component system (two wavelength), 2) multicomponent analysis of all hemoglobin species, 3) multicomponent analysis of a two-component system, and 4) derivative spectroscopy. While all four methods performed similarly in terms of typical validation requirements, the ability to more effectively handle decomposed samples and the ease of sample preparation afforded 3) multicomponent analysis of a two-component system the most suitable for routine postmortem testing.