Karolina Sipa

Simple sensing protocols for the detection of illicit drugs are needed. Electrochemical sensing is especially attractive in this respect, as its cost together with the analytical accuracy aspires to replace still frequently used colorimetric tests. In this work, we have shown that the interfacial transfer of protonated heroin can be followed at the electrified water-1,2-dichloroethane interface. We have comprehensively studied the interfacial behavior of heroin alone and in the presence of its major and abundant cutting agents, caffeine and paracetamol. To maximally increase developed sensing protocol applicability we have designed and 3D printed a platform requiring only a few microliters of the aqueous and the organic phase. The proposed sensing platform was equipped with a cavity hosting a short section of Ag/AgCl electrode, up to 20 µL of the aqueous phase and the end of the micropipette tip being used as a casing of a fused silica capillary having 25 µm as the internal pore diameter. The volume of the organic phase was equal to around 5 µL and was present inside the micropipette tip. We have shown that under optimized conditions heroin can be detected in the presence of caffeine and paracetamol existing in a sample with 10,000 times excess over the analyte of interest. The calculated limit of detection equal to 1.3 µM, linear dynamic range spanning to at least 50 µM, good reproducibility, and very low volume of needed sample is fully in line with forensic demands.

Polyamides have found a number of applications in the commercial sector. These materials belong to a large group of chemical compounds - polymers. The interest in these polymers is still growing as new materials can be formed through chemical functionalization or simply addition of different nanomaterials. Polyamides have many unique properties (e.g. chemical resistance, tensile and abrasion resistance, high thermal stability, non-flammability and high mechanical strength even after long periods of use), and compounds such as Nylon® or Kevlar® are leading components in the production of textiles, laboratory equipment, everyday objects or structural elements. Polyamides are used in automotive industry, aviation, and even as protective materials for the military. Several methods to synthesize polyamides exists to date. The most popular are reactions between carboxylic acid chlorides and amines, polycondensation of carboxylic acids with amines or polycondensation of amino acids. Especially spectacular is a reaction of pulling polyamide thread from the liquid-liquid interface known as the "nylon rope trick" experiment (https://www.youtube.com/watch?v=S6asCwVG8zU). Here, the reaction between 1,6-diaminohexane dissolved in the aqueous phase and adipoyl chloride being present in the immiscible with water organic phase is fast and spontaneous. In this work, we have proved that the synthesis of the polyamides at the liquid-liquid interface can be controlled using electrochemistry. In this respect, the electrochemically driven interfacial ion transfer or electrochemically modulated local pH changes are used to trigger the polycondensation within the locus defined by the liquid-liquid interface. The introduction to the electrified soft junction and its modification with polyamide is discussed in the concerned work

In this work, the synthesis of Nylon‐6.6 together with silver nanoparticles (presumably Ag₂O, Ag NPs) was carried out at a polarized liquid‐liquid interface (LLI). The reduction of silver ions to Ag‐NPs was driven by an electrochemically controlled electron transfer reaction between silver cations initially dissolved in the aqueous phase and ferrocene species present in the organic phase. The formation of Ag₂O is assumed to originate from Ag⁺ precipitation to AgOH further converted into Ag₂O. The polyamide formation was derived from the interfacial polycondensation reaction happening between 1,6‐diaminohexane and adipoyl chloride. We studied the possibility to form given material simultaneously (interfacial polycondensation and Ag⁺ reduction occurring in one step) and sequentially (electrochemical Ag⁺ reduction by ferrocene from the organic phase was performed after polyamide deposition). The Ag‐based NPs‐polyamide material was synthesized at the macroscopic and microscopic LLI. As the support for the latter, fiberglass membranes was used. The resulting material was characterized by infra‐red (IR) spectroscopy and scanning electron microscopy (SEM).

The interfacial polycondensation of titanium dioxide was studied at the bare and fiberglass membrane supported polarized liquid–liquid interface (LLI). Titanium dioxide synthesis was derived from the titanium (IV) tetrabutoxide (initially dissolved in the 1,2-dichloroethane) interfacial hydrolysis followed by its condensation. Experimental parameters, such as the pH of the aqueous phase and the influence of titanium alkoxide concentration in the organic phase on the electrochemical signal and material morphology, were investigated. The latter was achieved with fiberglass membranes used as the LLI support during TiO₂ interfacial deposition. Cyclic voltammetry was used for the in situ studies, whereas scanning electron microscopy, energy-dispersive X-ray spectroscopy, and infrared spectroscopy were used during ex situ examination. The interfacial polycondensation reaction could be studied using electrified LLI and resulted in the material being a TiO₂ film alone or film decorated with particles.

An electrochemical study of the anthelmintic drug bithionol using edge plane pyrolytic graphite electrode (EPPGE) is presented for the first time by applying different electrochemical techniques, such as cyclic voltammetry (CV), square‐wave voltammetry (SWV), square‐wave adsorptive stripping voltammetry (SWAdSV), and alternating current (AC) impedance spectroscopy. Mechanistic aspects of the electrode reaction were studied implying a quasireversible electrode reaction from an adsorbed state of the reactant, coupled with a follow‐up chemical reaction to a final electroinactive product. The overall mechanism appears totally irreversible under conditions of CV at moderate scan rate, while being quasireversible under conditions of the fast SWV. Furthermore, an optimisation of the analytical procedure for quantitative determination of bithionol was conducted by applying SWV in an adsorptive stripping mode. The calibration curve was constructed in the concentration range of 0.1–1.0 μmol L⁻¹ (R²=0.9984) with a sensitivity of 3.6 μA L μmol⁻¹ and LOD of 26.7 nmol L⁻¹. The simple and sensitive SWAdSV procedure was proved to be suitable for the analysis of spiked urine samples.