Correction: An impedimetric immunosensor for diagnosis of Brazilian spotted fever in blood plasma.

Correction for 'An impedimetric immunosensor for diagnosis of Brazilian spotted fever in blood plasma' by Marx Osório Araújo Pereira et al., Anal. Methods, 2024, https://doi.org/10.1039/d3ay01308a.

Simple and selective screening method for the synthetic cathinone MDPT in forensic samples using carbon nanofiber screen-printed electrodes.

3',4'-Methylenedioxy-N-tert-butylcathinone (MDPT), also known as tBuONE or D-Tertylone, is a synthetic cathinone (SC) frequently abused for recreational purposes due to its potent stimulant effects and similarity to illegal substances like methamphetamine and ecstasy. The structural diversity and rapid introduction of new SC analogs to the market poses significant challenges for law enforcement and analytical methods for preliminary screening of illicit drugs. In this work, we present, for the first time, the electrochemical detection of MDPT using screen-printed electrodes modified with carbon nanofibers (SPE-CNF). MDPT exhibited three electrochemical processes (two oxidations and one reduction) on SPE-CNF. The proposed method for MDPT detection was optimized in 0.2 mol L-1 Britton-Robinson buffer solution at pH 10.0 using differential pulse voltammetry (DPV). The SPE-CNF showed a high stability for electrochemical responses of all redox processes of MDPT using the same or different electrodes, with relative standard deviations less than 4.7% and 1.5% (N = 3) for peak currents and peak potentials, respectively. Moreover, the proposed method provided a wide linear range for MDPT determination (0.90-112 µmol L-1) with low LOD (0.26 µmol L-1). Interference studies for two common adulterants, caffeine and paracetamol, and ten other illicit drugs, including amphetamine-like compounds and different SCs, showed that the proposed sensor is highly selective for the preliminarily identification of MDPT in seized forensic samples. Therefore, SPE-CNF with DPV can be successfully applied as a fast and simple screening method for MDPT identification in forensic analysis, addressing the significant challenges posed by the structural diversity of SCs.

An impedimetric immunosensor for diagnosis of Brazilian spotted fever in blood plasma.

Brazilian spotted fever (BSF) is a serious disease of medical importance due to its rapid evolution and high lethality. The effectiveness of the treatment mainly depends on the rapid diagnosis, which is currently performed by indirect immunofluorescence and PCR tests, which require high costs and laboratory structure. In order to propose an alternative methodology, we sought to develop an impedimetric immunosensor (IM) based on the immobilization of specific IgY antibodies for IgG anti Rickettsia rickettsii, using blood plasma from capybara (Hydrochoerus hydrochaeris), for characterization, validation and applications of the ready IM. IM selectivity was observed when comparing capybara reagent IgG (IgGcr) readings with non-reagent IgG (IgGnr). A reagent IgG calibration curve was obtained, from which the limits of detection (LOD) and quantification (LOQ) of 1.3 ng mL-1 and 4.4 ng mL-1 were calculated, respectively. The accuracy tests showed that different concentrations of IgGcr showed a maximum deviation of 20.0%, with CI between 90.00% and 95.00%. Intermediate precision tests showed a relative standard deviation of 2.09% for researcher 1 and 2.61% for researcher 2, and the F test showed no significant difference between the recovery values found between the two analysts, since Fcal 1.56 < 5.05 and P-value 0.48 > 0, 05. Therefore, an impedimetric immunosensor was developed to detect anti BSF IgG in capybara blood plasma, which greatly contributes to the improvement of diagnostic tests, cost reduction and ease of execution.

Comprehensive detection of lysergic acid diethylamide (LSD) in forensic samples using carbon nanotube screen-printed electrodes.

Lysergic acid diethylamide (LSD) is a prevalent psychoactive substance recognized for its hallucinogenic properties, often encountered in blotter papers for illicit consumption. Given that LSD ranks among the most widely abused illicit drugs globally, its prompt identification in seized samples is vital for forensic investigations. This study presents, for the first time, an electrochemical screening method for detecting LSD in forensic samples, utilizing a multi-wall carbon nanotube screen-printed electrode (SPE-MWCNT). The LSD detection process was optimized on SPE-MWCNT in a phosphate buffer solution (0.1 mol L-1, pH 12.0) using square wave voltammetry (SWV). The combined use of SPE-MWCNT with SWV displayed robust stability in electrochemical responses for both qualitative (peak potential) and quantitative (peak current) LSD assessment, with a relative standard deviation (RSD) of less than 5% across the same or different electrodes (N = 3). A linear detection range was established between 0.16 and 40.0 µmol L-1 (R2 = 0.998), featuring a low limit of detection (LOD) of 0.05 µmol L-1. Interference studies with twenty-three other substances, including groups of phenethylamines typically found in blotting papers (e.g., NBOHs and NBOMes) and traditional illicit drugs, were performed, revealing a highly selective response for LSD using the proposed method. Consequently, the integration of SPE-MWCNT with SWV offers a robust tool for qualitative and quantitative LSD analysis in forensic applications, providing rapid, sensitive, selective, reproducible, and straightforward preliminary identification in seized samples.

Determination of organophosphorus compounds in water and food samples using a non-enzymatic electrochemical sensor based on silver nanoparticles and carbon nanotubes nanocomposite coupled with batch injection analysis.

This work presents, for the first time, a fast and highly sensitive electrochemical method for determination of three organophosphorus compounds (OPs), diazinon (DZN), malathion (MLT), and chlorpyrifos (CLPF), using a modified pyrolytic graphite electrode (PGE) coupled to batch injection analysis system with multiple pulse amperometric detection (BIA-MPA). The PGE was modified by a nanocomposite based on functionalized carbon nanotubes (CNTf) and silver nanoparticles (AgNPs). The OPs samples were directly analyzed on the modified working electrode surface by BIA-MPA system in Britton-Robinson (BR) buffer 0.15 mol L-1 at pH 6.0. The MPA detection of DZN, MLT and CLPF was performed using two potential pulses, which were sequentially applied on modified PGE at -1.3 V (100 ms) and +0.8 V (100 ms) for selective determination of these three OPs and working electrode cleaning, respectively. Under optimized conditions, the sensor presented a linear range of 0.1-20 µmol L-1 for DZN, 1.0-30 µmol L-1 for MLT and from 0.25 to 50 µmol L-1 for CLPF. The limits of detection (LOD) and quantification (LOQ) of 0.35 and 1.18 µmol L-1 for DZN, 0.89 and 2.98 µmol L-1 for MLT, and 0.53 and 1.78 µmol L-1 for CLPF were obtained. The proposed method exhibited high sensitivity of 0.068, 0.030 and 0.043 mA L µmol-1 for DZN, MLT and CLPF detection, respectively. Furthermore, the BIA-MPA system provided an analytical frequency of 71 determinations per hour for direct determination of these OPs in water and food samples. The modified PGE coupled to BIA-MPA system showed a high stability of electrochemical response for OPs detection with relative standard deviation (RSD) of 1.60% (n = 20). The addition-recovery studies of the proposed method were carried out in tap water, orange juice, and apple fruit real samples, which showed suitable recovery values between 77 and 124%. The analytical performance of the developed sensor provides an attractive alternative method for OPs determination with great potential for a fast and sensitive application in contaminated samples with these pesticides.