[Analytica Chimica Acta] Paper-based microfluidic devices on the crime scene: a simple tool for rapi
This paper describes for the first time the use of paper-based analytical devices at crime scenes to estimate the post-mortem interval (PMI), based on the colorimetric determination of Fe2+ in vitreous humor (VH) samples. Experimental parameters such as the paper substrate, the microzone diameter, the sample volume and the 1,10-phenanthroline (o-phen) concentration were optimized in order to ensure the best analytical performance. Grade 1 CHR paper of diameter 5 mm, a sample volume of 4 μL and an o-phen concentration of 0.05 mol/L were chosen as the optimum experimental conditions. A good linear response was observed for a concentration range of Fe2+between 2 and 10 mg/L and the calculated values for the limit of detection (LOD) and limit of quantification (LOQ) were 0.3 and 0.9 mg/L, respectively. The specificity of the Fe2+colorimetric response was tested in the presence of the main interfering agents and no significant differences were found. After selecting the ideal experimental conditions, four HV samples were investigated on paper-based devices. The concentration levels of Fe2+achieved for samples #1, #2, #3 and #4 were 0.5 ± 0.1, 0.7 ± 0.1, 1.2 ± 0.1 and 15.1 ± 0.1 mg/L, respectively. These values are in good agreement with those calculated by ICP-MS. It important to note that the concentration levels measured using both techniques are proportional to the PMI. The limitation of the proposed analytical device is that it is restricted to a PMI greater than 1 day. The capability of providing an immediate answer about the PMI on the crime scene without any sophisticated instrumentation is a great achievement in modern instrumentation for forensic chemistry. The strategy proposed in this study could be helpful in many criminal investigations.
Paulo T. Garciaa, Ellen F.M. Gabriela, Gustavo S. Pessôab, Júlio C. Santos Júniorc, Pedro C. Mollo Filhod, Ruggero B.F. Guiduglid, Nelci F. Höehrc, Marco A.Z. Arrudab, e, Wendell K.T. Coltroa, e, , a Instituto de Química, Universidade Federal de Goiás, 74690-900, Goiânia, GO, Brazil b Instituto de Química, Universidade Estadual de Campinas, 13084-862, Campinas, SP, Brazil c Faculdade de Ciências Médicas, Universidade Estadual de Campinas, 13083-881, Campinas, SP, Brazil d Instituto Médico Legal, Superintendência da Polícia Técnico Científica, 05314-000, São Paulo, SP, Brazil e Instituto Nacional de Ciência e Tecnologia de Bioanalítica, 13084-971, Campinas, SP, Brazil Received 27 August 2016, Revised 25 January 2017, Accepted 10 April 2017, Available online 26 April 2017 Show less https://doi.org/10.1016/j.aca.2017.04.040