Identification of Luminescent Markers for Gunshot Residues: Fluorescence, Raman Spectroscopy, and Chemometrics.

Gunshot residue (GSR) is an evidence of major importance in firearm-related crimes. The recent introduction of nontoxic ammunition has made impossible the characterization of GSR particles by the current methods employed by forensic experts. To overcome this drawback, the introduction of luminescent markers was proposed, allowing on-site visual detection of luminescent gunshot residue (LGSR) at the crime scene. Three different luminescent markers coordinated with europium for specific and selective encoding of ammunition have been proposed. To promote a variety of versatile tools for GSR analysis, spectroscopic techniques combined with chemometric methods can be applied to achieve a reliable, fast, and nondestructive means to identify LGSR and discriminate among the different markers. Luminescence (emission and excitation), normal, and resonance Raman spectroscopies associated with principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were evaluated. The classification model using the complementary information on emission and excitation spectra, a.k.a. data fusion, provided a 100% correct classification for all markers. A comprehensive study has been developed to show that the insertion of luminescent markers enables not only the easy localization of GSR residues but also the possibility of ammunition encoding through the use of multivariate classification methods.

Rapid separation of post-blast explosive residues on glass electrophoresis microchips.

This study describes the development of an analytical methodology based on the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4 D) for the separation and detection of inorganic anions in post-blast explosive residues. The best separation condition was achieved using a running buffer composed of 35 mmol/L lactic acid, 10 mmol/L histidine and 0.070 mmol/L cetyl(trimethyl ammonium) bromide. For C4 D measurements, the highest sensitivity was obtained applying a 700 kHz sinusoidal wave with excitation voltage of 20 Vpp . The separation of Cl- , NO3- , NO2- , SO42- , ClO4- and ClO3- was performed within ca. 150 s with baseline resolution and efficiencies between 4.4 × 104 and 1.7 × 105 plates/m. The found limits of detection ranged between 2.5 and 9.5 µmol/L. Last, real samples of post-blast explosive residues were analyzed on the ME-C4 D devices obtaining successfully the determination of Cl- , NO3- and SO42- . The achieved concentration values varied between 12.8-72.5 mg/L for Cl- , 1.7-293.1 mg/L for NO3- and 1.3-201.3 mg/L for SO42- . The data obtained using ME-C4 D devices were in good agreement with the concentrations found by ion chromatography. The approach reported herein has provided short analysis time, instrumental simplicity, good analytical performance and low cost. Furthermore, the ME-C4 D devices emerge as a powerful and portable analytical platform for on-site analysis demonstrating to be a promising tool for the crime scene investigation.

Authenticity screening of seized whiskey samples using electrophoresis microchips coupled with contactless conductivity detection.

This report describes for the first time the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4 D) to investigate the authenticity of seized whiskey samples, which were probably adulterated by simple dilution with tap water. The proposed microfluidic platform was explored for the monitoring of anionic species (Cl- and F- ) in both original and tampered samples. The best separations were achieved within 70 s using a running buffer composed of lactic acid and histidine (pH = 5.9). ME-C4 D devices were used to analyze samples from three different brands (five samples each). Based on the presence of inorganic anions like Cl- , F- , SO42- and NO2- in different amounts, the authenticity of seized whiskeys was compared to original samples. According to the reported data, the proposed microfluidic platform can be useful to help regulatory authorities in the investigation and monitoring of authenticity of commercialized whiskey beverages.

White Light-Photolysis for the Removal of Polycyclic Aromatic Hydrocarbons from Proximity Firefighting Protective Clothing.

The presence of polycyclic aromatic hydrocarbons (PAHs) on firefighters' personal protective equipment is a concern. One form of preventing from these compounds is to decontaminate proximity firefighting protective clothing (PFPC). Traditional decontamination methods do not promote total removal of pollutants and alter the properties of PFPC. The objective of this work was to evaluate the effectiveness of white light-photolysis (WLP), an advanced oxidation process (AOP), for removing PAHs from PFPC, while maintaining the integrity of the fabric fibers. Experiments were carried out, varying reaction time and concentration of H2O2. With WLP (without H2O2), it was possible to remove more than 73% of the PAHs tested from the outer layer of PFPC in 3 days. The WLP provided the greatest removal of PAHs, compared with the most common mechanical decontamination techniques (laundering and wet-soap brushing). The fibers' integrity after exposure to the white light was evaluated with infrared spectroscopy and scanning electron microscopy/energy dispersive X-ray spectrometry. In addition, a tearing strength test was performed. No remarkable fabric degradation was observed, indicating a possible, routine-compatible, simple, and inexpensive method of decontamination of PFPC, based on photolysis, which is effective in the degradation of PAHs and maintains the integrity of fabric fibers.

Determination of the alcoholic content in whiskeys using micellar electrokinetic chromatography on microchips.

This report describes the development of a methodology based on micellar electrokinetic chromatography for the separation of alcohols on chip-based systems aiming the determination of alcoholic content in whiskey samples. The separation conditions were optimized the best results were achieved using 50 mmolL-1 phosphate buffer containing 30 mmolL-1 sodium dodecyl sulfate. The alcoholic content was determined in 16 seized whiskey samples from 4 different brands as well as in the original samples. The methodology presented herein allowed the correct classification of 75% of the seized samples as adulterated and the data obtained did not statistically differ from those recorded by a reference technique. The proposed analytical approach emerges as a promising tool to provide a rapid screening of the beverages authenticity and it may be useful to be widely explored for the quality control.

Analysis of Luminescent Gunshot Residue (LGSR) on Different Types of Fabrics.

The collection of gunshot residue on fabric can be an arduous task due to the microscopic size of particles (blind collection) and sheddability of some fabrics. The introduction of luminescent markers and consequent formation of luminescent gunshot residue (LGSR) can facilitate this analysis. In this study, different fabrics were analyzed in order to verify the persistence of the LGSR on them, the possibility of collecting and analyzing particles by video spectral comparator (VSC) and SEM/EDS. Also, different colored fabrics were used as targets in order to investigate influence of fabric color on LGSR visualization. Furthermore, the influence of the fabric type in the distribution of the LGSR deposited around the projectile´s hole entrance was evaluated. The fabric sheddability did not alter collection of the particles or analysis. It was possible to observe and collect LGSR on all tested fabrics, even after the fabric had been shaken, or in colored fabrics.

Determination of chronological order of crossed lines of ballpoint pens by hyperspectral image in the visible region and multivariate analysis.

Determining the chronological order of crossed lines is a recurrent problem in forensic analysis of documents. One of the most important requirement of these analyses is the use of non-destructive techniques to maintain the integrity of the documents for further analysis as judicial evidences. Thus, this work proposes an objective, non-destructive, easy-to-execute analysis protocol for forensic analysis, using the hyperspectral mode of the VSC6000®, which is an equipment found in most laboratories of questioned documents. Seven blue ballpoint pens of different brands were used to make crossings on white paper, a total of 49. The spectra were obtained from 400 to 1000 nm, and analyzed with HYPER-Tools. Initially, univariate analysis was used, selecting discriminating wavelengths to visualize the images and determine the chronological order of the crossings, and then, when necessary, a multivariate approach using Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS) was applied. The interpretation of the order was made visually, taking into account characteristics of the strokes, such as the continuity and amount of ink. In this way, it was possible to determine the chronological order of 31/49 crossings, which corresponds to an overall rate of 63% accuracy. The method was validated by performing a double-blind test with 8 crossings, which indicated only a small influence of the analyst. The method was also applied to the analysis of a police inquiry, which was provided by the Federal Police and compared with the routine analyzes. The results were concordant but the proposed method provided a more objective analysis than the ones currently in practice at the Police.

Redox titration on foldable paper-based analytical devices for the visual determination of alcohol content in whiskey samples.

This report describes the development of foldable paper-based analytical devices (PADs) to perform redox titrations. Paper devices were designed to contain three spot tests, which were wax printed and folded to create a three-layer structured platform and to promote the sample transport based on vertical flow. The proposed devices were explored for the visual determination of the alcoholic content in whiskey samples. For this purpose, a classical permanganometry reaction was employed to allow the indirect determination of ethanol based on the required amount of oxalic acid to react with the excess of permanganate in acidic medium. The endpoint of the redox titrations performed in different alcoholic concentrations was measured and revealed a good linear behavior for the ethanol concentration range between 0% and 50% (R2 = 0.992), achieving a limit of detection equal to 2.1%. The alcoholic content was determined in a total of 44 whiskey samples seized by the Brazilian Federal Police. When compared to genuine samples and using an established cut-off limit, 73% of the seized samples were correctly classified as whiskeys containing adulterated alcoholic content. The proposed method was compared to a reference protocol and no difference was observed at the confidence level of 95%. The instrumental simplicity, the low cost, the sample volume requirement, the short analysis time and mainly the inherent portability make these devices quite attractive for on-site forensic applications.

Discrimination of whisky brands and counterfeit identification by UV-Vis spectroscopy and multivariate data analysis.

The discrimination of whisky brands and counterfeit identification were performed by UV-Vis spectroscopy combined with partial least squares for discriminant analysis (PLS-DA). In the proposed method all spectra were obtained with no sample preparation. The discrimination models were built with the employment of seven whisky brands: Red Label, Black Label, White Horse, Chivas Regal (12years), Ballantine's Finest, Old Parr and Natu Nobilis. The method was validated with an independent test set of authentic samples belonging to the seven selected brands and another eleven brands not included in the training samples. Furthermore, seventy-three counterfeit samples were also used to validate the method. Results showed correct classification rates for genuine and false samples over 98.6% and 93.1%, respectively, indicating that the method can be helpful for the forensic analysis of whisky samples.

A paper-based colorimetric spot test for the identification of adulterated whiskeys.

A colorimetric point-of-care paper-based analytical device (PAD) is developed for detecting adulterated beverages using whiskey falsified with caramel color as a model. Combining principal component analysis and calibration curves facilitated identification of adulteration in samples seized by the Brazilian Federal Police, at only ∼$0.02 per sample.

Application of the Metal-Organic Framework [Eu(BTC)] as a Luminescent Marker for Gunshot Residues: A Synthesis, Characterization, and Toxicity Study.

The 3D metal-organic framework (MOF) [Eu(BTC)] (where BTC = trimesic acid) was synthesized in 20 min by a microwave-assisted hydrothermal method with a yield of 89%. A structural and spectroscopic study, performed by X-ray diffraction, thermogravimetry, and photoluminescence spectroscopy, showed that this framework has high crystallinity, thermal stability, and luminescence. This MOF had a red-orange luminescence when excited with ultraviolet (UV) radiation (λ = 254 nm) and a high potential for use as a luminescent marker for gunshot residues (GSR). When added to 9 mm nontoxic ammunition, it greatly improved quality of the crime scene investigation, allowing for direct visualization of the luminescent GSR on the shooter's hand and firearm and at the firing range using only a portable UV lamp. The marked luminescent GSR was easily collected and characterized by nondestructive techniques, including with a Video Spectral Comparator and scanning electron microscopy/energy-dispersive spectroscopy, wherein the presence of Eu3+ ions was confirmed. Furthermore, the oral acute toxicity of this MOF was assessed in adult female Wistar rats using the Organisation for Economic Cooperation and Development 423 guidelines. This study classified the MOF [Eu(BTC)] in a less toxic Globally Harmonized System category (category 5), with a LD50 (lethal dose) of 5000 mg/kg, ensuring a wide security range for its application.

Discrimination and quantification of cocaine and adulterants in seized drug samples by infrared spectroscopy and PLSR.

Middle infrared spectroscopy and multivariate analysis have been applied for the development of methods to perform both quantitative and qualitative analysis of real drug samples seized by the Brazilian Police Federal (BPF). Currently, quantification of cocaine and determination of adulterants in seizures is performed using gas chromatography with flame ionization detection. However, this technique requires a relatively complex sample preparation, higher time of analysis, the destruction of sample and a high cost. In this context, this paper presents a simpler method to quantify cocaine and its major adulterants in seized materials. Out of 375 seizures, taken within a time frame of 2009-2013. A total of 1085 samples were analyzed of which 500 were selected for the calibration set and 585 for the validation set. Cocaine concentration in seized samples was determined by using middle infrared spectroscopy and partial least squares regression (PLSR), obtaining an average prediction error of 3.0% (w/w), precision of 2.0 and 11.8% (w/w) of minimum detectable cocaine concentration in a range varying from 24.2 to 99.9% (w/w). Results indicate that the developed method is able to discriminate between cocaine hydrochloride and free base samples, to quantify cocaine content as well as to estimate the concentration of main adulterants phenacetin, benzocaine, caffeine, lidocaine and aminopyrine.

Classification of Brazilian and foreign gasolines adulterated with alcohol using infrared spectroscopy.

The smuggling of products across the border regions of many countries is a practice to be fought. Brazilian authorities are increasingly worried about the illicit trade of fuels along the frontiers of the country. In order to confirm this as a crime, the Federal Police must have a means of identifying the origin of the fuel. This work describes the development of a rapid and nondestructive methodology to classify gasoline as to its origin (Brazil, Venezuela and Peru), using infrared spectroscopy and multivariate classification. Partial Least Squares Discriminant Analysis (PLS-DA) and Soft Independent Modeling Class Analogy (SIMCA) models were built. Direct standardization (DS) was employed aiming to standardize the spectra obtained in different laboratories of the border units of the Federal Police. Two approaches were considered in this work: (1) local and (2) global classification models. When using Approach 1, the PLS-DA achieved 100% correct classification, and the deviation of the predicted values for the secondary instrument considerably decreased after performing DS. In this case, SIMCA models were not efficient in the classification, even after standardization. Using a global model (Approach 2), both PLS-DA and SIMCA techniques were effective after performing DS. Considering that real situations may involve questioned samples from other nations (such as Peru), the SIMCA method developed according to Approach 2 is a more adequate, since the sample will be classified neither as Brazil nor Venezuelan. This methodology could be applied to other forensic problems involving the chemical classification of a product, provided that a specific modeling is performed.

Inkjet Printing of Lanthanide-Organic Frameworks for Anti-Counterfeiting Applications.

Photoluminescent lanthanide-organic frameworks (Ln-MOFs) were printed onto plastic and paper foils with a conventional inkjet printer. Ln-MOF inks were used to reproduce color images that can only be observed under UV light irradiation. This approach opens a new window for exploring Ln-MOF materials in technological applications, such as optical devices (e.g., lab-on-a-chip), as proof of authenticity for official documents.