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25I-NBOH is a new potent serotonin 5-HT2A receptor agonist recently identified in blotter paper seizures. This compound is a thermolabile molecule that undergoes degradation under routine gas chromatography–mass spectrometry analysis leading to misidentification. In this paper, the voltammetric behavior of 25I-NBOH and 2C-I was investigated and their electroanalytical characteristics were determined. A novel, fast and sensitive electrochemical method for the detection of 25I-NBOH using a SPCE is described and all method characteristics demonstrated the method to be analytically valuable. This method is selective and achieves full differentiation between 25I-NBOH, 2C-I and 25I-NBOMe. [ABSTRACT FROM AUTHOR]

A new methodology to estimate firing distance based on the direct analysis of organic components of gunshot residues (GSRs) on the bullet impact surface using Fourier transform near-infrared (FT-NIR) spectroscopy is proposed. Mathematical models relating firing distance with spectral information were developed using data obtained from a series of shots performed with a Glock model 17C (114 mm barrel length and 9 × 19 mm cartridges) at different distances, from 20 to 90 cm, against a white 40 × 40 cm square cloth (70% polyester/30% cotton) target. The study was repeated with two different types of ammunition. Spectra were obtained around the bullet entrance hole at 4 perpendicular directions and at 5 radial distances in diffuse reflectance mode with the assistance of a fiber optic probe. Principal component analysis showed that FT-NIRS displayed sensitivity in the recognition of the differences between the GSRs from the two different types of ammunition. Partial least squares regression models allowed the estimation of firing distance for both types of ammunition. Prediction errors lower than 11 cm were obtained for shots up to 90 cm. [ABSTRACT FROM AUTHOR]

DNAzyme based electrochemical biosensors have the characteristics of high sensitivity and selectivity, but traditional DNAzyme based electrochemical biosensors need the immobilization of DNAzyme on the electrode surface first, and the procedures are time consuming and tedious, which limit their real application. In this study, a simple but sensitive immobilization free DNAzyme based electrochemical biosensor has been proposed and lead has been chosen as a model target because of the severe effects of lead toxicity. The different diffusivity and electrostatic repulsion between long and short DNA on the negatively charged ITO electrode can be used to discriminate the short and long DNA. Lead dependent DNAzyme was hybridized with its substrate (which was modified with methylene blue at the 3′ terminal) beforehand. Since the DNAzyme/substrate complex contains a large negative charge, it cannot diffuse easily to the negatively charged ITO electrode surface and little electrochemical signal has been detected. The presence of lead would trigger the cleavage of the DNAzyme/substrate complex and cause the release of a methylene blue-labeled short-oligonucleotide into the solution. The methylene blue-labeled short-oligonucleotide can diffuse easily to the surface of the negatively charged ITO electrode and results in the enhanced electrochemical response being detected. Each lead can cleave a lot of DNAzyme/substrate complex to realize signal amplification. The enhanced electrochemical signal has a linear relationship with the Pb2+ concentration in the range of 0.05–1 μM with a detection limit of 0.018 μM (S/N = 3). The proposed biosensor has been applied to detect Pb2+ in water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent chemosensor of Pb2+ in the near-infrared (NIR) region, which is based on the Pb2+-tuned restored fluorescence of a weakly fluorescent fluorophore–gold nanoparticle (AuNPs) assembly, has been reported. In this fluorophore–AuNP assembly, NIR fluorescent dye brilliant cresyl blue (BCB) molecules act as fluorophores and are used for signal transduction of fluorescence, while AuNPs act as quenchers to quench the nearby fluorescent BCB molecules via electron transfer. In the presence of Pb2+, fluorescent BCB molecules detached from AuNPs and restored their fluorescence due to the formation of a chelating complex between Pb2+ and glutathione confined on AuNPs. Under the optimal conditions, the present BCB–AuNP assembly is capable of detecting Pb2+ with a concentration ranging from 7.5 × 10−10 to 1 × 10−8 mol L−1 (0.16–2.1 ng mL−1) and a detection limit of 0.51 nM (0.11 ng mL−1). The present BCB–AuNP assembly can be used in aqueous media for the determination of Pb2+ unlike common organic fluorescent reagents, and also shows advantages of NIR fluorescence spectrophotometry such as less interference, lower detection limit, and higher sensitivity. Moreover, the present method was successfully applied for the detection of Pb2+ in water samples with satisfactory results. [ABSTRACT FROM AUTHOR]