From Basic Research to Routine Use in the Courtroom: Elemental Analysis and Comparisons of Materials with Laser Ablation Inductively Coupled Plasma Mass Spectrometry

First lecture/Primeira palestra

From Basic Research to Routine Use in the Courtroom: Elemental Analysis and Comparisons of Materials with Laser Ablation Inductively Coupled Plasma Mass Spectrometry

The chemical analysis and comparison of a number of solid matrices of interest to forensic scientists is made possible by the progression from fundamental research and method development, validation in several forensic laboratories and the publication of international standards. The story of high-sensitivity elemental analysis of materials including glass, paint, soils, precious metals, diamonds, paper and ink on paper begins with the reporting of analytical techniques in the scientific literature and continues with the adaptation and optimization of the analytical methods by forensic scientists to suit these specific matrices. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been called the "gold" standard for solid-sampling and high-sensitivity elemental characterization of materials providing sub-ppm detection limits of elemental analytes encompassing almost 70% of the periodic table. In addition, LA-ICP-MS provides true quantitative analysis data that can be used in numerical/statistical hypothesis testing to determine "match" and also to populate databases that are useful to determine the probability of a match for a given elemental profile. The story develops further when several forensic laboratories collaborate on method development and optimization as reported by the European Union funded NITECRIME effort (2000-2005) [1] and continued by the NIJ funded Elemental Analysis Working Group (EAWG) effort (2008-2012) [2]. The next chapters include interlaboratory trials that report high-quality performance of these methods for the analysis of glass in forensic laboratories [3] and the publication of international (ASTM) analytical consensus standards for the examination these materials [4]. More than 30 forensic laboratories around the world now routine employ the use of LA-ICP-MS for materials characterization on every continent (except Antartica) and the history of elemental analysis provides a good model on how forensic method development should progress from basic research to routine use and acceptance in the courtroom.

1. C Latkoczy, M Dücking, S Becker, D Günther, J Hoogewerff, JR Almirall, JA Buscaglia, A Dobney, R Koons, S Montero, G van der Peyl, W Stoecklein, T Trejos, J Watling, V Zdanowicz, Evaluation of a standard method for the quantitative elemental analysis of float glass samples by LA-ICP-MS, J. of Forensic Sciences, 2005, 50 (6), 1327-1341.

2. T Trejos, R Koons, S Becker, T Berman, J Buscaglia, M Duecking, T Eckert-Lumsdon, T Ernst, C Hanlon, A Heydon, K Mooney, R Nelson, K Olsson, C Palenik, E Pollock, D Rudell, S Ryland, A Tarifa, M Valadez, P Weis and JR Almirall, Cross-validation and evaluation of the performance of methods for the elemental analysis of forensic glass by µ-XRF, ICP-MS and LA-ICP-MS, Anal. Bioanal.Chem., 2013, DOI 10.1007/s00216-013-6978-y.

3. T Trejos, R Koons, P Weis, S Becker, T Berman, C Dalpe, M Duecking, J Buscaglia, T Eckert-Lumsdon, T Ernst, C Hanlon, A Heydon, K Mooney, R Nelson, K Olsson, E Schenk, C Palenik, E Pollock, D Rudell, S Ryland, A Tarifa, M Valadez, A van Es, V Zdanowicz and JR Almirall, Forensic analysis of glass by μ-XRF, SN-ICP-MS, LA-ICP-MS and LA-ICP-OES: evaluation of the performance of different criteria for comparing elemental composition, J. Anal. At.Spectrom.,2013, 28, 1270-1282. DOI: 10.1039/C3JA50128K.

4. (2013) Standard Test Method for the Determination of Trace Elements in Soda-Lime Glass Samples Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry for Forensic Comparisons. ASTM (in press).

Second lecture/Segunda palestra

Analytical LIBS in the Forensic Science Laboratory

The use of chemical analysis and comparison of materials that are of interest to forensic scientists is possible by the progression from fundamental research and method development, validation in several forensic laboratories and the publication of international standards. While analytical standards such as ASTM do not currently exist for the application of LIBS in forensic analysis, evidence is mounting that analytical LIBS is fit-for-purpose for the elemental analysis of materials including glass, paint, soils, precious metals, diamonds, paper and ink on paper. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been called the "gold" standard for solid-sampling and high-sensitivity elemental characterization of materials providing sub-ppm detection limits while providing true quantitative analysis data that can be used in numerical/statistical hypothesis testing to determine "match" and also to populate databases that are useful to determine the probability of a match for a given elemental profile. More than 30 forensic laboratories around the world now routine employ the use of LA-ICP-MS for materials characterization but there is an opportunity for many more laboratories to adopt LIBS as an analytical alternative to the expensive and complex LA-ICP-MS methods. This presentation compares the analytical figures of merit of LIBS to LA-ICP-MS for the analysis of several matrices of importance to forensic scientists. For example, a LIBS method for the analysis of the bulk elemental composition is presented whereby only 10 mg of soil is needed for the analysis [1]. The very small analytical sample (picoliters drops have been demonstrated for analysis of LIBS [2]) results in sub-picogram absolute detection limits for the LIBS experiment [2]. A comparison of the type of information gathered from LIBS and how the data is interpreted is also presented. Recent advances in instrumentation and data analysis schemes now makes analytical LIBS a viable alternative to LA-ICP-MS and other elemental analysis methods within the forensic science laboratory.

1. SC Jantzi and JR Almirall, Elemental analysis of soils by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS) with multivariate discrimination using tape-mounting as an alternative to pellets for small forensic transfer specimens, Applied Spectroscopy, 2014, 68(9), 963-974.

2. E Cahoon and JR. Almirall, Quantitative Analysis of Liquids from Aerosols and Microdrops using Laser Induced Breakdown Spectroscopy, Anal. Chem., 2012, (doi:10.1021/ac202834j).