The possibility of detecting some organic compounds directly in a petroleum/water interface was described. Aqueous phase was composed by 1 x 10-3 mol L-1 NaCl solution and the oil phase was carried out using crude oil forming an oil/water interface. Carbon based screen-printed electrodes was used in conjunction with square-wave voltammetry technique, constituting the main tools of this technical note. Petroleum was contaminated with phenol, naphthalene and cyclohexane. The oxidation potentials for these three molecules were 0,72, 0,81 and 0,87 V vs. Ag, respectively. Phenol was chosen to study the stability of currents during the process. After 15 minutes, the currents of this process were stable. Although the formation of a passivation film, the qualitative detection of the molecules was possible. Finally, the main advantage of this methodology is the possibility of detecting contaminants in oil without the necessity of complicated pre-treatment steps.

A sensitive voltammetric method for trace measurements of gold(III) ions using a screen-printed carbon electrode modified with poly-L-histidine is described. The new procedure is based on the accumulation of the tetrachloroaurates complex at the electrode surface under an open circuit potential condition, followed by a cathodic stripping scan of potential. Parameters such as film preparation, pH, accumulation potential and deposition time have been optimized to obtain the best voltammetric response. Using optimal experimental conditions, analytical curves for gold ions were obtained using a linear sweep (LSV), differential pulse (DPV), and square wave voltammetry (SWV). Limits of detection of 6.0 × 10-6 mol L-1, 1.7 × 10-6 mol L-1 and 4.0 × 10-6 mol L-1 were estimated for the LSV, DPV and SWV, respectively. The method was successfully applied to the determination of gold ions in human urine samples.

The need for agile and proper identification of drugs of abuse has encouraged the scientific community to improve and todevelop new methodologies. The drug lysergic acid diethylamide (LSD) is still widely used due to its hallucinogenic effects. The use ofvoltammetric methods to analyze narcotics has increased in recent years, and the possibility of miniaturizing the electrochemical equipmentallows these methods to be applied outside the laboratory; for example, in crime scenes. In addition to portability, the search for affordable andsustainable materials for use in electroanalytical research has grown in recent decades. In this context, employing paper substrate, graphite pen-cil, and silver paint to construct paper-based electrodes is a great alternative. Here, a paper-based device comprising three electrodes was drawnon 300 g/m2watercolor paper with 8B pencils, and its efficiency was compared to the efficiency of a commercially available screen-printedcarbon electrode. Square wave voltammetry was used for LSD analysis in aqueous medium containing 0.05 mol/L LiClO4. The limits of detec-tion and quantification were 0.38 and 1.27 mol/L, respectively. Both electrodes exhibited a similar voltammetric response, which was alsoconfirmed during analysis of a seized LSD sample, with recovery of less than 10%. The seized samples were previously analyzed by GCMStechnique, employing the full scan spectra against the software spectral library. The electrode selectivity was also tested against 3,4-methylene-dioxymethamphetamine (MDMA) and methamphetamine. It was possible to differentiate these compounds from LSD, indicating that the devel-oped paper-based device has potential application in forensic chemistry analyses.

Histamine (HIS) is a major public health problem due to its toxic properties. High levels can cause a chronic toxicity as poisoning and can be used as a signal of food hygiene. Thus, a new electrochemical sensor for HIS detection in fish is presented herein, prepared by tailoring a molecularly imprinted polymer (MIP) sensing material on a gold screen-printed electrode (Au-SPEs), in which the polymeric film was generated in-situ. This film was obtained by electropolymerizing aniline under conditions that preserved the chemical structure of HIS. Raman spectroscopy followed the chemical changes occurring at each stage of the electrode modification. The device performance was assessed by evaluating the changes in electron transfer properties of a standard redox probe [Fe(CN)6]4/[Fe(CN)6]3, by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS was also used to calibrate the sensor, being the standard solutions prepared under different background media (electrolyte or a blank sample of fish extract). The device displayed a linear response from 500nM to 1mM, with a limit of detection of 210nM, and a selective behaviour against tyramine, another amine related to fish degradation. The sensing system was further employed to monitor the HIS content in samples in different time points of storage at ambient temperature. The obtained results were in agreement with the ELISA method, while offering more reproducible data. In general, the optimized sensor allowed reproducible and accurate analysis of fish samples subject to degradation and was completely assembled in-situ, in a very simple and straightforward approach. The device is low cost and suitable for further adaptation to on-site analysis, as required in food control.