Collection and detection of latent fingermarks contaminated with cosmetics on nonporous and porous surfaces

Desorption Electrospray Ionization Mass Spectrometry Imaging of Powder-Treated Fingermarks on Forensic Gelatin Lifters and its Application for Separating Overlapping Fingermarks

Fingermarks are frequently collected at crime scenes by using gelatin lifters for preservation and transport of the marks to a forensic laboratory for inspection. The gelatin lifters preserve both the imprint of the fingermark pattern necessary for identification purposes and the chemical residue of the mark potentially useful for profiling the person who left the fingermark. The fingermark patterns are traditionally recorded using photography/optical imaging, but methods for chemical analysis of fingermark residues on gelatin lifters are scarce. Here we report the first method for the chemical analysis of fingermarks on gelatin lifters using desorption electrospray ionization mass spectrometry (DESI-MS) imaging. The imaging can be done directly on the gelatin support without any sample preparation, supporting immediate operational use of the method for fingermarks collected at crime scenes. Operational use of the method is further supported by successful chemical imaging of fingermarks enhanced by traditional dusting with forensic powders and lifted off different surfaces (glass, stainless steel, painted aluminum, polystyrene, cardboard, and plastic) as well as fingermarks lifted multiple times. We also demonstrate that the present method can be used to visually separate natural overlapping powder-treated fingermarks, and the chemical composition of the fingermarks can be analyzed on the gelatin support by DESI-MS/MS. The presented method has potential for integration into the traditional workflow for fingermark analysis, and will allow more fingermarks collected at crime scenes to be evaluated both visually and chemically.

Untargeted metabolomics for lifestyle biomarker discovery in human hair

There is a risk of crimes remaining unsolved when no matching DNA profiles or fingermarks are found. If this is the case, forensic investigations are faced with a significant shortage of evidence and information regarding the unknown perpetrator and/or victim as well as any missing persons. However, a rather commonly found biological trace encountered at crime scenes is human hair. As hair acts as a biochemical reservoir, it may contain valuable information regarding one's characteristics and habits. This study aimed to build an analytical method capable of determining a marker set of relevant metabolites in hair, eventually building up a profile of its donor. To find potential markers, an untargeted metabolomics approach was developed to select and identify statistically significant features. For that purpose, a total of 68 hair samples were collected at several hairdresser shops in varying neighbourhoods. Compound extraction was achieved via methanolic incubation overnight and analysis performed using a high-resolution mass spectrometry (HRMS) Orbitrap Q Exactive Focus. The acquired data was uploaded and statistically evaluated using two free online software/libraries, where a total of eight compounds have given a match on both tools. Their presumptive identity was confirmed using reference standards and consequently added to a dynamic target donor profiling list. These results show the potential of using untargeted metabolomics for the search for lifestyle biomarkers capable of differentiating individuals. Such tools are of paramount importance in a forensic setting with little or no evidence available and no clear tactical leads.

Magnetic Nanoparticle-Based Surface-Assisted Laser Desorption/Ionization Mass Spectrometry for Cosmetics Detection in Contaminated Fingermarks: Magnetic Recovery and Surface Roughness

In this work, we propose a matrix-free approach for the analysis of fingermarks (FMs) contaminated with five cosmetic products containing different active pharmaceutical ingredients (APIs) using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). For this purpose, a magnetic SALDI substrate based on Fe₃O₄-CeO₂ magnetic nanoparticles was prepared, characterized, and optimized for the analysis of contaminated FMs without sample pretreatment. Initially, groomed FM and cosmetic products were separately analyzed, and their major components were successfully detected. Subsequently, FMs contaminated with Ordinary serum and Skinoren, Dermovate, Bepanthen, and Eucerin creams were analyzed, and components of FM and cosmetics were detected. The stability of the cosmetics in FMs was studied over an interval of 28 days, and all components showed good stability in FM for 4 weeks. Recovery of contaminated FMs from different surfaces utilizing a few microliters of the magnetic substrate was carried out using a simple external magnetic field from ceramic, plastic, metal, and glass. Successful retrieval of the API and FM components was achieved with magnetic recovery, and glass exhibited the best recovery, whereas ceramic tile demonstrated the lowest recovery. This was supported by atomic force microscopy study, which revealed that the ceramic surface had higher roughness than the other surfaces employed in this study, which adversely affected the magnetic maneuvering. This proof-of-concept investigation extends the application of SALDI-MS in forensic analysis of contaminated FMs by exploring cosmetics as exogenous materials and their stability and recovery from different surfaces.

Quantitative analysis of 17 hypoglycemic drugs in fingerprints using ultra-high-performance liquid chromatography/tandem hybrid triple quadrupole linear ion trap mass spectrometry

RATIONALE

The objective of this study was to develop, optimize, and validate a method for the determination and quantification of 17 hypoglycemic drugs in fingerprints using ultra-high-performance liquid chromatography/tandem hybrid triple quadrupole linear ion trap mass spectrometry (UHPLC/QTRAP-MS/MS). We also aimed to apply the present method to the fingerprints collected from patients with hyperglycemia.

METHODS

The scheduled multiple reaction monitoring information-dependent acquisition-enhanced product ion (SMRM-IDA-EPI) scanning mode was utilized. The chromatographic system consisted of an Acquity UHPLC® BEH C18 column (3.0 × 100 mm, 1.7 μm) and a mobile phase of 0.01% (v/v) formic acid in water and methanol. Analytes were extracted via a precipitation protein procedure. The method was validated in accordance with the US Food and Drug Administration (FDA) guidance and applied to the analysis of fingerprint deposits from subjects who had taken the drugs.

RESULTS

The limits of detection (LODs) and the lower limits of quantification (LLOQs) of 17 hypoglycemic drugs were 0.001 to 0.020 and 0.002 to 0.050 ng/fingerprint, respectively. The correlation coefficients (r) for the calibration curves were > 0.99 in the range of 0.050-50.000 ng/fingerprint. The matrix effect and recovery of 17 hypoglycemic drugs at three concentrations ranged from 81.1 to 117.3% and 80.0 to 109.6%, respectively. The validation data (intra- and inter-day combined) for accuracy ranged from 85.5 to 117.2%, the CV (%) data were ≤19.7%. All analytes were found to be stable stored in the autosampler (4°C) for 24 h. This validated method was successfully applied to detect hypoglycemic drugs in fingerprints from patients with hyperglycemia.

CONCLUSIONS

A quantification method for hypoglycemic drugs in fingerprints was developed, optimized, and validated. This sensitive method could be used for drug monitoring and providing reference information in forensic investigations.

Monitoring the chemical changes in fingermark residue over time using synchrotron infrared spectroscopy

Using synchrotron sourced ATR-FTIR microspectroscopy and THz/Far-IR gas phase spectroscopy to monitor the chemical changes in fingermark residues in the immediate hours following deposition.

The transfer and persistence of metals in latent fingermarks

Transfer and persistence of metals in latent fingermarks derived from objects of forensic interest explored using synchrotron sourced X-ray fluorescence microscopy.

Simultaneous determination and quantitation of hypolipidemic drugs in fingerprints by UPLC-Q-TRAP/MS

An ultra-performance liquid chromatography tandem triple quadrupole compound linear ion trap mass spectrometry (UPLC-Q-TRAP/MS) method was developed and validated for the detection of hypolipidemic drugs in fingerprints. 13 hypolipidemic drugs were well separated by the gradient elution of 0.01% formic acid in water and methanol at a flow rate of 0.4 mL/min within 11 min. The analytes were detected in positive (ESI⁺) and negative (ESI^-) modes and scanned using scheduled multiple reaction monitoring-information dependent acquisition-enhanced product ion (SMRM-IDA-EPI) for best selectivity and sensitivity. The calibration curves showed good linearity in the range of 0.050-50.000 ng/patch with coefficients (r²) higher than 0.9904 for all analytes. Meantime, the LODs and LLOQs were in ranges of 0.001-0.034 and 0.003-0.050 ng/patch. The accuracies, intra-day and inter-day precision ranged from -13.3 to 0.3%, 1.1-10.4% and 3.7-14.5%, respectively. The recoveries ranged from 79.9 to 114.8%, while the absolute and relative matrix effects were in the range of 83.0-107.2% and 2.2-9.7%. By comparing the non-spiked fingerprints from healthy volunteers with the fingerprints obtained from patients, demonstrated that the method was competent for determination and quantitation of hypolipidemic drugs in fingerprints.

The analysis of latent fingermarks on polymer banknotes using MALDI-MS

In September 2016, the UK adopted a new Bank of England (BoE) £5 polymer banknote, followed by the £10 polymer banknote in September 2017. They are designed to be cleaner, stronger and have increased counterfeit resilience; however, fingermark development can be problematic from the polymer material as various security features and coloured/textured areas have been found to alter the effectiveness of conventional fingermark enhancement techniques (FETs). As fingermarks are one of the most widely used forms of identification in forensic cases, it is important that maximum ridge detail be obtained in order to allow for comparison. This research explores the use of matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) profiling and imaging for the analysis of fingermarks deposited on polymer banknotes. The proposed methodology was able to obtain both physical and chemical information from fingermarks deposited in a range of scenarios including; different note areas, depletion series, aged samples and following conventional FETs. The analysis of forensically important molecular targets within these fingermarks was also explored, focussing specifically on cocaine. The ability of MALDI-MS to provide ridge detail and chemical information highlights the forensic applicability of this technique and potential for the analysis of fingermarks deposited onto this problematic surface.

A study of the intermolecular interactions of lipid components from analogue fingerprint residues

A compositionally simplified analogue of a latent fingermark was created by combining single representatives of each major component of a natural fingermark. Further modified analogues were also produced each having one component removed. The aim of this study was to investigate the intermolecular interactions that occurred within these analogue samples using Fourier Transform Infrared (FT-IR) Microspectroscopy. FT-IR microspectroscopy showed that the absence of squalene and cholesterol significantly restricted the interactions between the other organic constituents within the analogue samples. Investigating the intermolecular interactions of organic compounds within a simplified analogue solution could indicate corresponding interactions that occur within natural fingermarks. These potential interactions could go on to be the target of further investigation of latent fingermark chemistry, and ultimately contribute to a better understanding of the aging processes and degradation mechanisms that take place post-deposition.

Infrared spectroscopy and spectroscopic imaging in forensic science

Infrared spectroscopy and spectroscopic imaging, are robust, label free and inherently non-destructive methods with a high chemical specificity and sensitivity that are frequently employed in forensic science research and practices. This review aims to discuss the applications and recent developments of these methodologies in this field. Furthermore, the use of recently emerged Fourier transform infrared (FT-IR) spectroscopic imaging in transmission, external reflection and Attenuated Total Reflection (ATR) modes are summarised with relevance and potential for forensic science applications. This spectroscopic imaging approach provides the opportunity to obtain the chemical composition of fingermarks and information about possible contaminants deposited at a crime scene. Research that demonstrates the great potential of these techniques for analysis of fingerprint residues, explosive materials and counterfeit drugs will be reviewed. The implications of this research for the examination of different materials are considered, along with an outlook of possible future research avenues for the application of vibrational spectroscopic methods to the analysis of forensic samples.

Towards Fingermark Dating: A Raman Spectroscopy Proof-of-Concept Study

Fingermarks have, for a long time, been vital in the forensic community for the identification of individuals, and a possibility to non‐destructively date the fingermarks would of course be beneficial. Raman spectroscopy is, herein, evaluated for the purpose of estimating the age of fingermarks deposits. Well‐resolved spectra were non‐destructively acquired to reveal spectral uniqueness, resembling those of epidermis, and several molecular markers were identified that showed different decay kinetics: carotenoids > squalene > unsaturated fatty acids > proteins. The degradation rates were accelerated, less pronounced for proteins, when samples were stored under ambient light conditions, likely owing to photo‐oxidation. It is hypothesized that fibrous proteins are present and that oxidation of amino acid side chains can be observed both through Raman and fluorescence spectroscopy. Clearly, Raman spectroscopy is a useful technique to non‐destructively study the aging processes of fingermarks.

Determining the chronology of deposition of natural fingermarks and inks on paper using secondary ion mass spectrometry

This study thoroughly explores the use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) for determining the deposition sequence of fingermarks and ink on a porous paper surface.

Chemical changes exhibited by latent fingerprints after exposure to vacuum conditions

The effect of vacuum exposure on latent fingerprint chemistry has been evaluated. Fingerprints were analysed using a quartz crystal microbalance to measure changes in mass, gas chromatography mass spectrometry to measure changes in lipid composition and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to determine changes in the content of water, fatty acids and their esters after exposure to vacuum. The results are compared with samples aged under ambient conditions. It was found that fingerprints lose around 26% of their mass when exposed to vacuum conditions, equivalent to around 5 weeks ageing under ambient conditions. Further exposure to vacuum causes a significant reduction in the lipid composition of a fingerprint, in particular with the loss of tetradecanoic and pentadecanoic acid, that was not observed in ambient aged samples. There are therefore implications for sequence in which fingerprint development procedures (for example vacuum metal deposition) are carried out, as well as the use of vacuum based methods such as secondary ion mass spectrometry (SIMS) and matrix-assisted laser desorption ionisation (MALDI) in the study of fingerprint chemistry.

Micro- and macro-attenuated total reflection Fourier transform infrared spectroscopic imaging. Plenary Lecture at the 5th International Conference on Advanced Vibrational Spectroscopy, 2009, Melbourne, Australia

Fourier transform infrared (FT-IR) spectroscopic imaging has become a very powerful method in chemical analysis. In this review paper we describe a variety of opportunities for obtaining FT-IR images using the attenuated total reflection (ATR) approach and provide an overview of fundamental aspects, accessories, and applications in both micro- and macro-ATR imaging modes. The advantages and versatility of both ATR imaging modes are discussed and the spatial resolution of micro-ATR imaging is demonstrated. Micro-ATR imaging has opened up many new areas of study that were previously precluded by inadequate spatial resolution (polymer blends, pharmaceutical tablets, cross-sections of blood vessels or hair, surface of skin, single live cells, cancerous tissues). Recent applications of ATR imaging in polymer research, biomedical and forensic sciences, objects of cultural heritage, and other complex materials are outlined. The latest advances include obtaining spatially resolved chemical images from different depths within a sample, and surface-enhanced images for macro-ATR imaging have also been presented. Macro-ATR imaging is a valuable approach for high-throughput analysis of materials under controlled environments. Opportunities exist for chemical imaging of dynamic aqueous systems, such as dissolution, diffusion, microfluidics, or imaging of dynamic processes in live cells.