Capacitive sensing of an amphetamine drug precursor in aqueous samples: Application of novel molecularly imprinted polymers for benzyl methyl ketone detection.

Highly selective molecularly imprinted polymers (MIPs) towards benzyl methyl ketone (BMK) were synthesized for application as recognition elements in a capacitive sensor. A computational approach was employed to select the most appropriate monomers and cross-linkers. Using the selected compounds, different polymerization techniques and protocols were compared in order to study the effect on the MIP performance and characteristics. MIPs synthesized by bulk polymerization using itaconic acid and 1-vinylimidazole as monomers and p-divinylbenzene as cross-linker possess the highest affinity towards the target analyte. Prior to capacitive analysis, the developed particles were immobilized on the surface of gold transducers using tyramine as a linker. The validity of the developed sensor was checked by the BMK detection in spiked tap water and real water samples. A linear working range from 50 to 1000 µM was found while the limit of detection (LOD) was determined to be 1 µM in tap water. To the best of our knowledge, both the developed MIPs towards BMK and the electrochemical sensor for its detection have not been published or marketed to date.

Novel multiplex capacitive sensor based on molecularly imprinted polymers: A promising tool for tracing specific amphetamine synthesis markers in sewage water.

The development of a sensing system for amphetamine (AMP), N-formyl amphetamine (NFA), and benzyl methyl ketone (BMK) in sewage is a strict requirement for enabling the on-site detection and tracing of the consumption of AMP, and the production and/or transportation of these target analytes. The present research is therefore devoted to the development of an on-site capacitive sensing system, based on molecularly imprinted polymers (MIPs) as recognition elements. To this end, the commercially available CapSenze capacitive sensor system was miniaturized by implementing an application-specific integrated circuit (ASIC), dedicated to the bias and read-out of the chemical sensor. MIPs towards AMP were purchased, whereas the ones towards NFA and BMK were synthesized in house. Gold transducers, consisting of six working electrodes with their corresponding reference electrodes and one common auxiliary electrode, were designed together with a flow cell to enable analyses. The applied water samples were filtered through a 20 micron filter before application in the sensors' flow cell. The limits of detection in filtered sewage water were determined to be 25 µM for NFA and BMK and 50 µM for AMP. The overall performance of the sensing system was tested by analysis of blind-coded sewage samples, provided by legal authorities. To the best of our knowledge, this is the first research presenting multiplex MIP-based detection of amphetamine synthesis markers using a capacitive sensor, miniaturized via ASIC technology. The presented technique is undoubtedly a potential solution for any analysis requiring constant reliable on-site monitoring of a substance of interest.

Recent advances in electrochemical monitoring of zearalenone in diverse matrices.

The current manuscript summarizes different electrochemical sensing systems developed within the last 5 years for the detection of zearalenone (ZEN) in diverse matrices such as food, feed, and biofluids. ZEN is one of the most prevalent non-steroidal mycotoxins that is often found in pre- and post-harvest crops. Crops contamination with ZEN and animal exposure to it via contaminated feed, is a global health and economic concern. The European Union has established various preventive programs to control ZEN contamination, and regulations on the maximum levels of ZEN in food and feed. Electrochemical (bio)sensors are a very promising alternative to sensitive but sophisticated and expensive chromatographic techniques. In the current review, recent developments towards electrochemical sensing of ZEN, sorted by type of transducer, their design, development, and approbation/validation are discussed, and the use of specialized electrochemical instrumentation is highlighted.

Recent developments in electrochemical detection of illicit drugs in diverse matrices.

Drug abuse is a global problem, requiring an interdisciplinary approach. Discovery, production, trafficking, and consumption of illicit drugs have been constantly growing, leading to heavy consequences for environment, human health, and society in general. Therefore, an urgent need for rapid, sensitive, portable and easy-to-operate detection methods for numerous drugs of interest in diverse matrices, from police samples, biological fluids and hair to sewage water has risen. Electrochemical sensors are promising alternatives to chromatography and spectrometry. Last decades, electrochemical sensing of illegal drugs has experienced a very significant growth, driven by improved transducers and signal amplifiers helping to improve the sensitivity and selectivity. The present review summarizes recent advances (last 10 years) in electrochemical detection of the most prevailing illicit drugs (such as cocaine, heroin, and (meth)amphetamine), their precursors and derivatives in different matrices. Various electrochemical sensors making use of different transducers with their (dis)advantages were discussed, and their sensitivity and applicability were critically compared. In those cases where natural or synthetic recognition elements were included in the sensing system to increase specificity, selected recognition elements, their immobilization, working conditions, and analytical performance were discussed. Finally, an outlook is presented with suggestions and recommendations for future developments.

Capacitive sensor for detection of benzo(a)pyrene in water.

An affinity sensor based on capacitive transduction was developed to detect benzo(a)pyrene (BaP) in river water. Two types of recognition elements, the synthetic receptor analogues molecularly imprinted polymers (MIPs) and natural monoclonal antibody (mAb) were tested for this type of biosensor. Different polymerization strategies to obtain MIPs were compared. One approach comprised a preliminary batch synthesis of beads that were subsequently coupled covalently to an electrode surface. Another approach consisted of the in-situ synthesis of MIPs directly onto the electrode surface using electropolymerization. The latter approach provided the best results. To choose the optimal recognition element mAb and MIP-modified electrodes different sets were evaluated with regards to their sensitivity, selectivity, linear range and re-usability. The mAb-modified electrodes were considerably more sensitive toward BaP (ng L-1 range vs µg L-1 range for the MIP-modified one), and showed a broader linear working range than the MIP-modified electrodes. The latter revealed more suitable for group-selective determination of PAHs. The developed capacitive sensor was tested for the detection of BaP in naturally-contaminated water samples collected in different places of Ghent, Belgium. The results obtained with the sensor were coherent and reproducible, and were in a good agreement with the confirmation technique, HPLC-FlD.