Applications of laser-ablation-inductively-coupled plasma-mass spectrometry in chemical analysis of forensic evidence
Highlights
► A practical guide to introduce and help forensic scientists in the use of LA-ICP-MS. ► LA-ICP-MS is a versatile tool for the chemical investigation of physical evidence. ► The review is based on the most important articles published in the past 12 years.
Introduction
After the first source of coherent microwave radiation, named microwave amplification by stimulated emission of radiation (MASER) [1], the first source of coherent light radiation, known as light amplification by stimulated emission of radiation (LASER), was developed in 1960. The capacity and the precision of LASER for the collection of data directly from solid materials attracted the attention of researchers [2]. Shortly after the creation of lasers, laser micro-optical emission spectrometry (LM-OES) and laser-ablation mass spectrometry (LA-MS) were investigated for identification and elemental quantitative analysis of solids [3]. More recently, the coupling of laser ablation with inductively coupled plasma-MS (LA-ICP-MS) has shown great potential for the direct elemental analysis of solid samples [4].
The first ICP-MS commercial instruments were available in 1983. They were initially employed on daily routine analysis of aqueous solutions. However, for the analysis of solid samples, the transformation of the sample in a solution was necessary, usually by sample digestion with strong acids and oxidizers. Obviously, any such sample preparation involves the risk of sample contamination, the loss of volatile elements, and, besides, it creates a complex aqueous matrix, which can be source of several spectroscopic and non-spectroscopic interferences. The coupling of ICP-MS with an LA system for sample introduction [4], [5] enabled direct, reliable, sensitive, and quasi non-destructive analysis of major and trace elements of solid samples. In the past 15 years, there has been rapid development of this technique, which has been widely applied to several fields of science (e.g., geology, medicine, science of materials and, more recently, to forensic sciences, where solid samples constitute a large part of the physical evidence submitted to forensic chemistry laboratories).
As a consequence of the increasing interest on LA-ICP-MS, several reviews have been written on the technique itself and its applications to the elemental analysis of different types of samples. Those that stand out are from the Günther Group [3], [6], [7], Durrant [4], Russo et al. [8], and Mokgalaka and Gardea-Torresdey [9]. Recently, Trejos and Almirall [10] published quite an interesting chapter in the Encyclopedia of Analytical Chemistry, entitled “Laser Ablation Inductively Coupled Plasma Mass Spectrometry in Forensic Science”, where they explain the technique, its main characteristics, and give a general view of its potential for the analysis of a wide number of forensic samples, ranging from glass to biological and environmental samples.
This review is a practical guide to help forensic scientists in the use of LA-ICP-MS as a versatile tool for the chemical investigation of common physical evidence found in forensic laboratories [e.g., glass, paints, documents (inks and papers), fibers, cannabis, gems, porcelains, brick stones, and gold and silver]. The review, based on the most important articles published in the past 12 years in forensic chemistry, comprises a basic introduction to the technique, a detailed overview of its applications to the analysis of these samples, and future perspectives. Biological and environmental-forensic samples do not fall within the scope of this review.
Section snippets
Instrumentation
The general configuration of an LA-ICP-MS instrument (Fig. 1) comprises:
- (1)
an LA system, for sample introduction into the plasma, coupled to
- (2)
ICP-MS equipment [3], [6], [11], [12], [13].
A solid sample is placed into the ablation cell, which is mechanically adjusted, and a carrier gas (argon or helium) flows into this cell. Then, an energy-controlled pulsed laser is focused by the optic lens of the microscope onto the sample surface. The high-energy photons generated in the laser are converted into
Forensic applications of LA-ICP-MS
The forensic scientist must work with physical evidence of different types, shape, and size, whose origin must be ascertained and linked to the suspect in order to ensure a successful prosecution. For this reason, reliable analytical techniques are needed (e.g., LA-ICP-MS, which is capable of determining metals, metalloids and even non-metals in solid samples, providing highly discriminating data and preserving the sample, practically, “as it is”). Furthermore, suitable chemometrics methods to
Graphical and statistical processing of data
As stated above, LA-ICP-MS provides a chemical fingerprint of the analyzed materials in forensic applications. Given the great amount of information (variables) obtained with this technique for different samples (objects), raw data must be treated statistically. Analytical signals for every element can be expressed as an average value and its standard deviation. However, even in this simplified form, the matrix of average values is large enough to obtain detailed information on samples by
Conclusions and future trends
LA-ICP-MS is an effective technique for the direct analysis of solids without requiring their dissolution. LA-ICP-MS is especially recommended to overcome the limitations regarding the sample size generally associated with forensic analysis. Its quasi non-destructive nature also allows that samples already analyzed by LA-ICP-MS to be available for complementary analysis. In addition, its excellent sensitivity, accuracy and precision, combined with its capacity for isotopic and multi-elemental
Acknowledgements
The authors would like to thank the Contributing Editor and the Reviewers of TrAC for discussion and helpful comments about first version of this manuscript. The authors are grateful to Álvaro Torre for help with English language. Financial support of the University Institute of Research in Police Sciences (Projects IUICP/PI2010/4 and IUICP/PI2010/9) is also acknowledged.
References (93)
- et al.
Spectrochim. Acta, Part B
(2007) - et al.
Trends Anal. Chem.
(2005) - et al.
Talanta
(2002) - et al.
Spectrochim. Acta, Part B
(1999) - et al.
Int. J. Mass Spectrom.
(2005) - et al.
Spectrochim. Acta, Part B
(2009) - et al.
Trends Anal. Chem.
(2007) - et al.
Chem. Geol.
(2004) - et al.
Spectrochim. Acta, Part B
(2007) - et al.
Spectrochim. Acta, Part B
(2007)
Spectrochim. Acta, Part B
Appl. Surf. Sci.
Spectrochim. Acta, Part B
Appl. Surf. Sci.
Spectrochim. Acta, Part B
Int. J. Mass Spectrom.
Spectrochim. Acta, Part B
Talanta
Spectrochim. Acta, Part B
Talanta
Spectrochim. Acta, Part B
Spectrochim. Acta, Part B
Talanta
Sci. Justice
Forensic Sci. Int.
Spectrochim. Acta, Part B
Appl. Radiat. Isot.
Rapid Commun. Mass Spectrom.
Forensic Sci. Int.
Phys. Rev.
J. Anal. At. Spectrom.
Fresenius J. Anal. Chem.
Anal. Bioanal. Chem.
Appl. Spectrosc. Rev.
J. Anal. At. Spectrom.
J. Anal. At. Spectrom.
J. Anal. At. Spectrom.
J. Anal. At. Spectrom.
Acta
J. Anal. At. Spectrom.
Spectrochim. Acta, Part B
Environ. Forensics
Cited by (59)
Quantitative bioanalysis by inductively coupled plasma mass spectrometry for clinical diagnosis
2024, TrAC - Trends in Analytical ChemistryCharacterization of metal components in white-based polyester single fibers by X-ray fluorescence spectrometry and X-ray absorption fine structure analysis utilizing synchrotron radiation for forensic discrimination
2023, Spectrochimica Acta - Part B Atomic SpectroscopyMethods and techniques for in vitro subcellular localization of radiopharmaceuticals and radionuclides
2021, Nuclear Medicine and BiologyLaser-induced excitation mechanisms and phase transitions in spectrochemical analysis – Review of the fundamentals
2021, Spectrochimica Acta - Part B Atomic SpectroscopyAutomotive paint analysis: How far has science advanced in the last ten years?
2020, TrAC - Trends in Analytical ChemistryCitation Excerpt :Paint analysis is therefore an important branch of forensic science as it is useful in these cases where only paint fragments remain [1,3]. The analysis aims to compare evidence from the crime scene either with a paint fragment of the suspect vehicle or with a paint sample in a paint database [2]. Currently, the most widely used protocol for the assessment and identification of automotive paints in these cases consists of the following steps: a) by observing the characteristics of the fragment, one can determine the number of layers and whether it is the original equipment manufacturer (OEM) or an aftermarket respray; b) visual comparison with color/pigment tables of paint manufacturers is then performed; c) the infrared (IR) spectrum of each layer is collected; d) the spectra are compared to spectra obtained from reference IR databases, for example, the Paint Data Query (PDQ) from the Royal Canadian Mounted Police, and the European Paint Group (EPG) database from the European Network of Forensic Science Institutes; and e) the combination of these results generates a list of possible vehicles that may have been involved in the scene to facilitate police investigation [4].
Handbook of Analytical Techniques for Forensic Samples: Current and Emerging Developments
2020, Handbook of Analytical Techniques for Forensic Samples: Current and Emerging Developments