Predicting the Past of Dried Blood Spots: Time Since Deposition and Toxicology

Blood is among the most frequently encountered evidence types at crime scenes and establishing the time since deposition (TSD) of bloodstains can be critical in certain cases. A method to establish the TSD of bloodstains is not routinely applied yet, because of because of age estimation inaccuracies caused by environmental conditions, influence of the substrate, inter-person variation and sample quantity. A bottom-up proteomics approach in combination with nano-liquid chromatography hyphenated to tandem mass spectrometry with electrospray ionisation and surface acoustic wave nebulisation coupled to mass spectrometry was used to assess the molecular profile of dried blood spots (DBS) aged up to 8 days. A major reduction in the workflow time of DBS analysis was achieved by the application of a novel developed microfluidic immobilised-enzyme reactor for the digestion of DBS proteins. A model was developed to predict the TSD of DBS from its molecular composition and is currently able to classify aged from non-aged DBS samples. The analysis of toxicology from micro-volumes of blood would also be beneficial in a variety of forensic scenarios. The collection of DBS onto cards or the collection of micro-volumes of blood onto the novel volumetric absorptive microsampling (VAMS) device would allow simple, quick and non-invasive sampling in situations where the volume of blood is limited or repetitive sampling is needed. No medical trained personnel are needed, there is no location restriction, samples can be stored at room temperature and samples can be transported by regular post. Methods were developed for the quantification of two drugs of abuse, salbutamol and pseudoephedrine, from blood sampled onto VAMS devices including from the blood of healthy volunteers collected after administration with either one of the drugs.