Paper Spray Mass Spectrometry for the Forensic Analysis of Black Ballpoint Pen Inks

Standardization of the analytical procedure based on deep eutectic solvent for the extraction and measurement of tricyclic antidepressants drugs in post-mortem blood samples

Measuring drugs in post-mortem blood samples is one of the most important challenges in forensic medicine. The development of sensitive analytical techniques for the measurement of drugs in biological samples is of great use in forensic medicine. In this research an easy, safe and environmental friendly vortex-assisted liquid phase microextraction (VA-LPME) based on deep eutectic solvent (DES) followed by high performance liquid chromatography-ultraviolet detector (HPLC-UV) was developed for the extraction, preconcentration and analysis of tricyclic antidepressants drugs (TCAs) in post-mortem blood samples. DES synthesized from thymol as hydrogen bond acceptor (HBA) and ethylene glycol (EG) as hydrogen bond donor (HBD) with a molar ratio of 2:1 was used as an extractant. After adding DES to the sample solution, the resulting mixture was vortexed in order to increase the contact surface and increase the extraction efficiency. Next, phase separation was done using centrifugation. Some effective parameters on the extraction were studied and optimized. Under the optimum conditions, intra- and inter-day %RSDs of the method based on 7 replicate measurements of 100 μg L-1 of TCAs in blood samples were in the range of 2.4-5.1 and 3.7-6.8 %, respectively. The analytical performance of the method showed linearity over the concentration of 3-500 μg L-1 with the detection limits ranging from 1.0-2.0 μg L-1. The trueness of the method was confirmed by spiking different concentrations of TCAs in real blood samples and obtaining relative recoveries in the range of 91.2-108 %.

Combination of a Green and a Traditional Method for Estimating Relative and Absolute Ink Age: A Case Study of Ballpoint Pen Ink Dating in Vietnam

The dating of ink in questioned documents remains a significant challenge in forensic investigations in Vietnam and other countries. Many forensic examination methods have been usually applied to ensure the highest accuracy of the assessment results while maintaining high environment awareness. In this study, paper characteristics were physically tested to confirm source similarity, and the relative ink dating was established by high-performance thin-layer chromatography (HPTLC). Absolute ink dating by solvent and dye identification was performed by Raman spectrometry-a green technique, using a time-dependent degradation model for crystal violet and the comparison between 2-phenoxyethanol peak intensities. We found that the relative dating of the questioned document was 14 ± 3 months lesser than that of the reference samples, i.e., the absolute age of the questioned samples was estimated to be 24 ± 3 months. The combination of the conventional HPTLC method with the dynamic crystal violet degradation Raman model provides promising results for relative and absolute ink dating of ballpoint pens, which can be applied for documents written 1-15 years prior to the time of examination. The combination of the abovementioned methods demonstrated an acceptable error margin, affording highly practical applications in modern forensic science.

Direct coupling of paper spray mass spectrometry and four-phase electroextraction sample preparation

This paper presents a novel coupling between a four-phase electroextraction (EE) system and paper spray mass spectrometry (PS-MS) for the extraction, pre-concentration, and direct analysis of target compounds in different samples. The approach, EE-PS-MS, is based on the sorption of analytes directly on the tip of a triangular-shaped chromatographic paper, with subsequent prompt analysis by PS-MS. Thus, no off-line extraction step is required before the PS analysis, improving the protocol efficiency and reducing the analysis time. In addition to functioning as a porous material to absorb the target compounds, the chromatographic paper also served as the support for one of the aqueous phases of the optimized four-phase electroextraction system. Extraction conditions, such as the composition of the donor and organic phases, applied electric potential, and extraction time, were optimized. Three different applications, involving biofluid, food, and water quality analysis, were evaluated as a proof-of-concept. These applications involved the determination of (i) cocaine and lidocaine in saliva, (ii) malachite green in tap water, and (iii) bisphenol A (BPA) in red wine. When compared with direct PS-MS, the novel EE-PS-MS protocol improved the sensitivities by factors ranging from 14 to 110, depending on the analyte and the sample. The electroextraction procedures were performed on a laboratory-built 66-well plate, which offered the functionality of simultaneous sample handling and, most importantly, improved analytical throughput.

Reagent-Pencil and Paper Spray Mass Spectrometry: A Convenient Combination for Selective Analyses in Complex Matrixes

The recent developments on fieldable miniature mass spectrometers require efforts to produce easy-to-use and portable alternative tools to assist in point-of-care analysis. In this paper, the reagent-pencil (RP) technology, which has been used for solvent-free deposition of reagents in paper-based microfluidics, was combined with paper spray ionization mass spectrometry (PS-MS). In this approach, named RP-PS-MS, the PS triangular piece of paper was written with the reagent pencil, consisting of mixtures of graphite and bentonite (used as a support) and a reactive compound, and allowed to react with a given analyte from a sample matrix selectively. We conducted typical applications as proof-of-principles to verify the methodology's general usefulness in detecting small organic molecules in distinct samples. Hence, various aldehydes (2-furaldehyde, valeraldehyde, and benzaldehyde) in spiked cachaça samples (an alcoholic drink produced from fermentation/distillation of sugarcane juice) were promptly detected using a reagent pencil doped with 4-aminophenol (the reactive compound). Similarly, we recognized typical ginsenosides and triacylglycerols (TAGs) in ginseng aqueous infusions and soybean oil samples, respectively, using lithium chloride as the reactive compound. The results indicate that the reagent-pencil methodology is compatible with PS-MS and provides an easy and fast way to detect target analytes in complex samples. The advantage over the usual solution-based deposition of reagents lies in the lack of preparation or carrying different specific solutions for special applications, which can simplify operation, especially in point-of-care analysis with fieldable mass spectrometers.

Depth-Dependent Chemical Analysis of Handwriting by Nanospray Desorption Electrospray Ionization Mass Spectrometry

Nanospray desorption electrospray ionization (nano-DESI) has been utilized in direct sampling mass spectrometry (MS) that requires highly spatially resolved sampling with minimal sample destruction. In this study, we explored the applicability of nano-DESI MS for the forensic chemical analysis of ink directly from handwriting on paper. Nano-DESI readily ionizes dyes, including the polyanionic ones, with minimal fragmentation and produces chemical fingerprints of ballpoint pens directly from a paper surface. Further, we specifically focused on how the potential of nano-DESI that changes the mass spectral profiles over time could reflect the differential distribution of analytes in a vertical direction because mildly extracted analytes are immediately transferred and analyzed in real time. To test this, we wrote the character "X" with various combinations of two different pens and analyzed the crosspoints by nano-DESI MS. As a result, the time-course changes in the chemical fingerprints of the ink, which were consistent with the order of the pen strokes, were successfully obtained by nano-DESI MS in most cases. After confirming the capability of the depth-dependent analysis of nano-DESI MS, we analyzed a simulated forgery in which the original and forged writings were made before and after affixing a seal and clearly distinguished the two portions based on the time-dependent changes in the profile of the ink compound.

Interpol review of questioned documents 2016-2019

This review paper covers the forensic-relevant literature in questioned documents from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol Review Papers 2019.pdf.

The current role of mass spectrometry in forensics and future prospects

Mass spectrometry (MS) techniques are highly prevalent in crime laboratories, particularly those coupled to chromatographic separations like gas chromatography (GC) and liquid chromatography (LC). These methods are considered "gold standard" analytical techniques for forensic analysis and have been extensively validated for producing prosecutorial evidentiary data. However, factors such as growing evidence backlogs and problematic evidence types (e.g., novel psychoactive substance (NPS) classes) have exposed limitations of these stalwart techniques. This critical review serves to delineate the current role of MS methods across the broad sub-disciplines of forensic science, providing insight on how governmental steering committees guide their implementation. Novel, developing techniques that seek to broaden applicability and enhance performance will also be highlighted, from unique modifications to traditional hyphenated MS methods to the newer "ambient" MS techniques that show promise for forensic analysis, but need further validation before incorporation into routine forensic workflows. This review also expounds on how recent improvements to MS instrumental design, scan modes, and data processing could cause a paradigm shift in how the future forensic practitioner collects and processes target evidence.

Forensic Analysis of Commercial Inks by Laser-Induced Breakdown Spectroscopy (LIBS)

Laser-induced breakdown spectroscopy (LIBS) was tested for all of the relevant issues in forensic examinations of commercial inks, including classification of pen inks on one paper type and on different paper types, determination of the deposition order of layered inks, and analysis of signatures and toners on one questioned document. The scope of this work was to determine the potential of a single LIBS setup that is compatible with portable instruments for different types of ink analysis, rather than building a very large database for inks and papers. We identified up to seven metals characteristic for the examined inks, which allowed to fully discriminate all eight black inks on one type of printing paper. When the inks were tested on ten different papers, the correct classification rates for some of them were reduced for reasons thoroughly studied and explained. The replicated tests on three crossing points, each one involving a pair of blue or black inks, were successful in five cases out of six. In the test simulating documents of forensic interest (questioned documents), LIBS was able to correctly identify the differences in three inks used for signatures on one of the three pages and the use of different printing inks on each page of the document.

Exploring a route to a selective and sensitive portable system for explosive detection- swab spray ionisation coupled to of high-field assisted waveform ion mobility spectrometry (FAIMS)

Paper spray mass spectrometry is a rapid and sensitive tool for explosives detection but has so far only been demonstrated using high resolution mass spectrometry, which bears too high a cost for many practical applications. Here we explore the potential for paper spray to be implemented in field applications with portable mass spectrometry. This involved (a) replacing the paper substrate with a swabbing material (which we call “swab spray”) for compatibility with standard collection materials; (b) collection of explosives from surfaces; (c) an exploration of interferences within a ± 0.5 m/z window; and (d) demonstration of the use of high-field assisted waveform ion mobility spectrometer (FAIMS) for enhanced selectivity. We show that paper and Nomex® are viable collection materials, with Nomex providing cleaner spectra and therefore greater potential for integration with portable mass spectrometers. We show that sensitive detection using swab spray will require a mass spectrometer with a mass resolving power of 4000 or more. We show that by coupling the swab spray ionisation source with FAIMS, it is possible to reduce background interferences, thereby facilitating the use of a low resolving power (e.g. quadrupole) mass spectrometer.

On-substrate derivatization for detection of highly volatile G-series chemical warfare agents via paper spray mass spectrometry

RATIONALE

The analysis of chemical warfare agents (CWAs) from ambient atmosphere presents an analytical challenge due to their ease of degradation and volatility. Herein is described a method for derivatizing CWAs directly onto a paper spray substrate prior to analysis. This derivatization allows for much longer times of analysis without sample degradation and with little to no sample preparation.

METHODS

Derivatization was performed using 2-[(dimethylamino)methyl] phenol both in-vial and directly on paper spray cartridges. Solution studies were carried out over time and samples were analyzed via liquid chromatography/tandem mass spectrometry (LC/MS/MS) operated in positive ion mode. Paper spray substrates impregnated with the derivatizing agent prior to CWA vapor capture were also analyzed over time using a mass spectrometer operated in positive ion mode.

RESULTS

Use of 2-[(dimethylamino)methyl] phenol as a paper spray substrate dopant enables derivatization of G-series compounds into lower volatility complexes. The reaction occurs in solution and in the vapor phase. This new technique effectively traps and captures G-series agents for analysis while extending the time for which the compound remains absorbed. The complex is highly suitable for direct analysis via paper spray mass spectrometry.

CONCLUSIONS

Derivatization of paper spray substrates was shown to greatly increase the time for analysis of CWAs. This technique, combined with the vapor phase capture stage outlined previously, allows for rapid, quantitative CWA detection by paper spray ionization with little or no sample preparation.

Applications of liquid-based separation in conjunction with mass spectrometry to the analysis of forensic evidence

In the past few years, there has been a significant effort by the forensic science community to develop new scientific techniques for the analysis of forensic evidence. Forensic chemists have been spearheaded to develop information-rich confirmatory technologies and techniques and apply them to a broad array of forensic challenges. The purpose of these confirmatory techniques is to provide alternatives to presumptive techniques that rely on data such as color changes, pattern matching, or retention time alone, which are prone to more false positives. To this end, the application of separation techniques in conjunction with mass spectrometry has played an important role in the analysis of forensic evidence. Moreover, in the past few years the role of liquid separation techniques, such as liquid chromatography and capillary electrophoresis in conjunction with mass spectrometry, has gained significant tractions and have been applied to a wide range of chemicals, from small molecules such as drugs and explosives, to large molecules such as proteins. For example, proteomics and peptidomics have been used for identification of humans, organs, and bodily fluids. A wide range of HPLC techniques including reversed phase, hydrophilic interaction, mixed-mode, supercritical fluid, multidimensional chromatography, and nanoLC, as well as several modes of capillary electrophoresis mass spectrometry, including capillary zone electrophoresis, partial filling, full filling, and micellar electrokenetic chromatography have been applied to the analysis drugs, explosives, and questioned documents. In this article, we review recent (2015-2017) applications of liquid separation in conjunction with mass spectrometry to the analysis of forensic evidence.