Artículos ELAN

New fluorescent reporters capable of Ultra-sensitively detecting trinitrotoluene on surfaces: A proof-of-concept for finding hidden nitroaromatics in the workroom

Sun, 01 Oct 2023 00:00:00 GMT

New fluorescent reporters capable of Ultra-sensitively detecting trinitrotoluene on surfaces: A proof-of-concept for finding hidden nitroaromatics in the workroom Revilla Cuesta, Andrea; Abajo Cuadrado, Irene; Medrano, María; Martín Salgado, Mateo; Pecori, Giuditta; Rodríguez Rodríguez, Mª Teresa; Hernando Muñoz, Carla; García Calvo, José; Arcos Martínez, Julia; Torroba Pérez, Tomás We describe the proof of concept of a portable testing setup for the detection of trinitrotoluene (TNT), a common component in hidden explosive devices. The system allows for field-testing and generation of real-time results to test for TNT traces in surfaces by simply using a filter paper and a fluorescent reporter. In this way, the controlled trapping and detection of the analyte by a chemical sensor gives reliable results at extremely low concentrations of TNT on surfaces under real life conditions suitable for daily use in ordinary sampling for example at airlines luggage storage or sport locker rooms. The reported fluorescent methodology is very sensitive and selective, allowing for the trapping and detection of TNT by a fluorescent reporter to give reliable results at very low concentrations. As a complement, we report the preparation of a modified Sylgard film that is useful under real conditions for qualitative fluorescent detection of hidden traces of TNT on surfaces or fingers by a swab method. The combination of quantitative and qualitative detection of TNT traces on surfaces constitutes a comprehensive new method for the detection of hidden nitroaromatic explosives in the workplace.

Electrochemical detection of fentanyl with screen-printed carbon electrodes using square-wave adsorptive stripping voltammetry for forensic applications

Tue, 01 Sep 2020 00:00:00 GMT

Electrochemical detection of fentanyl with screen-printed carbon electrodes using square-wave adsorptive stripping voltammetry for forensic applications Ott, Colby E.; Cunha Silva, Hugo; Kuberski, Sara L; Cox, Joseph A.; Arcos Martínez, Julia; Arroyo Mora, Luís E. Square-wave adsorptive stripping voltammetry (SWAdSV) is proposed as a fast, simple, and sensitive approach toward the detection, identification, and semi-quantitation of fentanyl in seized drug samples using screen-printed carbon electrodes. Electrochemical oxidation of fentanyl resulted in the formation of two anodic peaks, one at 0.75 V (peak I) and the second at 0.88 V (peak II) versus a Ag/AgCl pseudo reference electrode. Voltammetric measurements were conducted under optimized experimental conditions using fentanyl standards ranging from 0.076 μg/mL to 6.9 μg/mL, which resulted in a limit of detection of 0.037 μg/mL. Reproducibility was assessed as the average percent relative standard deviation of the slopes of calibration curves and was 2.6% for oxidation peak I and 7.4% for oxidation peak II in cell. Detection capabilities were assessed in a 5-mL cell and in a 100 microliter drop. Interference studies were conducted with cocaine, methamphetamine, quinine, caffeine, and acetaminophen. The mechanism for the electrochemical oxidation of fentanyl to norfentanyl is also described. Accuracy and suitability of the method for seized drug analysis was assessed using 11 simulated samples. Suitability of the method for future analysis of fentanyl in oral fluid was assessed.

Inhibited enzymatic reaction of crosslinked lactate oxidase through a pH-dependent mechanism

Sun, 01 Dec 2019 00:00:00 GMT

Inhibited enzymatic reaction of crosslinked lactate oxidase through a pH-dependent mechanism Cunha Silva, Hugo; Pires, Filipa Velez; Cabral, A. Cristina Dias; Arcos Martínez, Julia Lactate oxidase (LOx), recognized to selectively catalyze the lactate oxidation in complex matrices, has been highlighted as preferable biorecognition element for the development of lactate biosensors. In a previous work, we have demonstrated that LOx crosslinking on a modified screen-printed electrode results in a dual range lactate biosensor, with one of the analysis linear range (4 to 50 mM) compatible with lactate sweat levels. It was advanced that such behavior results from an atypical substrate inhibition process. To understand such inhibition phenomena, this work relies in the study of LOx structure when submitted to increased substrate concentrations. The results found by fluorescence spectroscopy and dynamic light scattering of LOx solutions, evidenced conformational changes of the enzyme, occurring in presence of inhibitory substrate concentrations. Therefore, the inhibition behavior found at the biosensor, is an outcome of LOx structural alterations as result of a pH-dependent mechanism promoted at high substrate concentrations.

Development of a selective chloride sensing platform using a screen-printed platinum electrode

Mon, 01 Apr 2019 00:00:00 GMT

Development of a selective chloride sensing platform using a screen-printed platinum electrode Cunha Silva, Hugo; Arcos Martínez, Julia A new and selective voltammetric method for chloride determination is proposed, based on platinum and chloride interactions. A screen-printed platinum electrode (SPPtE) functions as a sensing platform, which promotes the formation of chloro-adsorbed species on the electrode surface, acting as an effective means of anion-determination in several matrices. The pretreatment of the SPPtE and careful control of the cathodic stripping voltammetric parameters yielded a well-defined electrochemical signal. This cathodic peak was due to the adsorption of chlorine, which had previously been oxidized from chloride anions in the initial anodic deposition step. It offers a simple, low-cost, fast, reproducible (RSD < 6%) and precise method for selective chloride determination, with limit of detection of 0.76 mM, and a sensitivity of − 24.147 µA mM −1 for a broad determination range of up to 150 mM. Chloride determination was correctly performed with single drops of environmental, pharmaceutical and food samples. In addition, the sensor was successfully adapted as a flexible screen-printed platinum electrode sensor using Gore-Tex® as support for printing.