Forensic classification from one-dimensional analytical signals is attractive for lower-cost instrumentation, but useful representations must retain discriminative structure and tolerate variation encountered in casework. We transformed each signal into a fractional derivative spectrum map (FDSM), a two-dimensional representation whose rows contain fast Fourier transform (FFT)-based derivatives spanning orders 0–2, and classified it with a compact convolutional neural network. The approach was evaluated using 4137 authentic gas chromatography–mass spectrometry (GC–MS) ignitable-liquid casework samples and a Fourier transform infrared (FT-IR) cotton-versus-regenerated-cellulose task trained on 385 reference spectra and tested on 250 casework spectra. From the GC–MS total-ion chromatogram alone, FDSM-based models achieved an accuracy of 0.903 and a macro-F1 of 0.783–0.784, corresponding to approximately 98% and 90%, respectively, of the values reported for a published full-m/z benchmark. Across both analytical domains, FDSM-based models retained substantially higher macro-F1 than raw-signal models under low-frequency baseline and scattering perturbations. Fractional and integer stacks produced similar macro-level performance on clean data, while fractional order steps improved GC–MS performance under selected baseline and scattering conditions. The benefit of derivative preprocessing narrowed for more flexible classifiers. These results establish FDSM as a compact, tunable representation for robust classification from single-channel forensic signals and motivate further evaluation using direct single-channel measurements and broader multi-instrument datasets.
Synthetic cathinones represent a major group of New Psychoactive Substances (NPS) monitored and seized within the European Union. Acconding to the European Drug Report 2026, substituted methylmethcathinones (MMCs), chloromethcathinones (CMCs), and the emerging bromomethcathinones (BMCs) have become increansingly relevant in European drug seizures. In 2024, MMC, CMC, BMC and N-ethylnorpentedrone (NEP) cathinones together represented more than 80% of the total quantity of NPS reported seized in European Union. While Nuclear Magnetic Resonance (NMR) is the gold standard for determining ring substitution, its application is often hindered by the presence of cutting agents in forensic samples, which necessitate laborious purification steps. This study introduces a novel, dual-analytical framework for the fast profiling of 2-MMC, 3-MMC, 4-MMC, 2-CMC, 3-CMC, 4-CMC, 4-BMC and N-ethylpentedrone (NEP) using authentic seized samples provided by the Spanish National Police. We report a high-throughput, eco-friendly GC–MS method using ethanol as a sustainable solvent, achieving baseline resolution of all isomers within a 6-min run time, even in the presence of caffeine as a common adulterant.Furthermore, we describe, for the first time, a systematic FTIR spectroscopic analysis of in-plane CH bending vibrations (1000–950 cm−1) as a robust diagnostic tool for discriminating between ortho, meta, and para positional isomers of synthetic cathinones. This integrated approach —combining ‘green’ chromatography for fast screening with definitive FTIR isomeric identification of synthetic cathinones— offers forensic laboratories a reliable, fast and efficient analytical tool to fight the evolving challenges of the illicit drug market.
This review provides a comprehensive overview of the instrumental analysis of textile fibers for forensic purposes, focusing on the evolution and application of various chromatographic and direct techniques. The discussion encompasses a broad spectrum of methodologies, including Liquid Chromatography coupled with Ultraviolet-Visible detection (LC-UV), Liquid Chromatography-Mass Spectrometry (LC-MS, LC-MS/MS), High-Resolution Mass Spectrometry (HRMS), and Gas Chromatography-Mass Spectrometry (GC-MS). Special emphasis is placed on the transition from conventional HPLC to modern Ultra-High Performance Liquid Chromatography (UHPLC) platforms, highlighting improvements in sensitivity, resolution, and the reduction of analysis time.The analytical workflow is explained in detail, starting from miniaturized sample preparation and extraction strategies connected to specific fiber types (e.g., cotton, wool, polyester, acrylic) and dye classes. The study describes the relationships between dye chemistry, stationary phase selectivity (predominantly C18 and Phenyl-Hexyl), and mobile phase optimization, including the use of ion-pairing reagents for ionic dyes. Furthermore, the review addresses the critical challenge of sample size requirements, demonstrating how modern high-resolution techniques enable the successful identification of dyes in single-fiber fragments as short as 0.5 mm. By comparing the capabilities of UV–Vis and various mass spectrometric detection techniques, this paper evaluates the current state of the art in forensic textile analysis, providing a roadmap for selecting appropriate instrumental strategies based on the chemical nature of the analytes and the limitations of examined materials.
Effective surface sampling is crucial for detecting and analysing chemical warfare agents (CWAs) following contamination events. In this study, seven swipe materials, including four activated carbon cloth (ACC)–based materials, were evaluated using two low-toxicity liquid CWA simulants: methyl salicylate and benzyl salicylate. Both model compounds were used to study sampling and recovery in the context of CWA contamination across physicochemically diverse compounds. The materials assessed comprised two ACCs (FM70 and FM50K) and two composite wipes incorporating these ACCs as the sorptive layer. Sampling performance was quantified by high-performance liquid chromatography (HPLC) following collection from four substrates of varying porosity and composition: glass, car door metal, brick, and medium-density fibreboard (MDF). Extraction efficiencies varied significantly with both sampling material and surface type. For methyl salicylate, recovery from ACC materials followed the order FM50K > FM70 wipe > FM50K wipe > FM70, whereas for benzyl salicylate, the trend was FM50K wipe > FM70 wipe > FM50K > FM70. Overall, sampling with filter paper resulted in higher recovery than the cotton swab sampling approach under the experimental conditions investigated. Lower recoveries were observed on porous compared to non-porous surfaces. Notably, on the car door substrate, recoveries obtained using ACC-based wipes were comparable to or slightly greater than those achieved via direct solvent extraction of the surface coupons. Across three of the four substrates tested, the composite wipe configuration mitigated performance losses associated with surface porosity, indicating advantages over pure ACC materials for practical sampling applications. These findings demonstrate that both substrate characteristics and sample configuration strongly influence recovery and provide comparative performance data to inform the material selection for surface sampling of CWA contamination.
Crystal Violet (CV), a commonly used triarylmethane dye in blue ballpoint inks, is of interest in chemical ink-dating approaches, yet its degradation kinetics under standardized and environmentally relevant exposure conditions remain underexplored. Here, we quantified CV degradation in ink strokes from three commercial blue ballpoint pens exposed to (i) indoor daylight transmitted through window glass, (ii) dark-storage conditions, and (iii) accelerated xenon-arc aging (ISO 12040). Samples were positioned in accordance with ISO 2810, and CV degradation was monitored by HPLC-DAD via changes in the normalized A(CV)/A₀(CV) peak-area ratio over ten days. All inks showed a pronounced initial decrease in detectable CV under both indoor daylight and xenon-arc exposure, followed by a slower degradation phase, while samples kept in darkness exhibited only minor changes. Meteorological parameters (temperature, cloudiness, and sunshine duration) provided environmental context for interpreting degradation under naturally varying indoor daylight conditions. An exponential decay model provided excellent fits for both indoor daylight and accelerated aging (R2 ≈ 0.97–0.99), describing the observed degradation profiles across inks from different manufacturers.By combining controlled and environmentally relevant exposures with HPLC-DAD analysis, meteorological data, and kinetic modelling, this study provides a quantitative framework for characterizing CV degradation on paper. The findings demonstrate the strong influence of exposure conditions on CV degradation and support its use as a complementary chemical indicator in forensic ink-aging assessment rather than as an independent measure of chronological ink age.
