Losartan potassium and hydrochlorothiazide are often combined in pharmaceutical formulations for the treatment of hypertension. Therefore, the determination of these compounds in a single run is highly desirable for rapid quality control applications. The present study describes an ultra-fast (ca. 85 injections h-1) and environmentally friendly method based on capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection for simultaneous quantification of potassium, losartan and hydrochlorothiazide. Cation (potassium) and anions (losartan and hydrochlorothiazide) were analyzed in a single run using a background electrolyte composed by 10.0 mmol L-1 boric acid (pH = 9.0, adjusted with sodium hydroxide). The limits of detection were 4.0, 3.0 and 10.0 μmol L-1 for potassium, losartan and hydrochlorothiazide, respectively. The proposed method is simple, fast, with minimal waste generation, and accurate (recovery values between 98 and 102%). The results obtained with the CE method were statistically similar (95% confidence level) to those obtained by high-performance liquid chromatography (losartan and hydrochlorothiazide) and flame photometry (potassium).

The presence of bioaccessible potentially-toxic elements in five different brands of temporary tattoos (packaged with bubble gums) aimed at children and three product brands used by young and adult audiences were analyzed in accordance with the Brazilian Organization of Technical Standards (ABNT) and International Organization for Standardization (ISO) for toy’s safety standards. Bioaccessible barium, copper and strontium were found in the concentration range between 1.78-11.1 μg g-1, 0.0364-0.875 μg g-1, 0.155-9.9 μg g-1, respectively. Bioaccessible lead (2.6 ± 0.1 μg g-1 - 4.36 ± 0.06 μg g-1) and boron (2.14 ± 0.07 - 3.54 ± 0.07 μg g-1) were found in two samples whereas chromium (0.403 ± 0.004 μg g-1) in one sample aimed at children. Bioaccessible aluminum was found in six samples, mostly at products used by children. Other elements whose bioaccessibility was evaluated were Mo (< LOD), Cd (< LOD), V (0.148 ± 0.003 μg g-1) and Co (0.003 - 1.756 μg g-1). All samples met the upper limits permitted by the national toy safety standard, however, chromium, lead, cobalt and barium presented higher bioaccessibility levels than the allowed values by cosmetic regulation that controls products applied directly to the skin.

Sustainable analytical methods are highly demanded in the modern society. Within the green principles, novel procedures that attend the sustainable development goals have been proposed and the internet of things (IoT) can play key role to achieve this goal. The association of IoT with analytical chemistry enables the real-time obtaining of analytical data to control industrial processes as well as for monitoring different environmental scenarios and human health by accessing remotely analytical information. In this context, this review presents the main IoT technologies used for analytical chemistry as well as a tutorial for beginners in the field.

Additive manufacturing is an emerging tool that has contributed to the sustainable fabrication of devices in several areas based on the concept of “zero waste”. Considering extrusion-based manufacturing (or 3D printing), polylactic acid (PLA) has been highlighted due to its biodegradability, obtention from renewable sources, and compatibility for 3D printing. Composites of PLA with conducting fillers, such as carbon-black (CB/PLA), are commercially-available and compatible with extrusion-based 3D printers and 3D pen. Herein, we investigate the electrochemical behavior of several antioxidant species (catechol, hydroquinone, propyl-gallate, octyl-gallate, dopamine, gallic acid and pyrogallol (PY)) on 3D-printed electrodes. Experiments by cyclic voltammetry demonstrated that electrochemical surface treatment in NaOH aqueous solution is an important strategy to improve the response of all antioxidants. Thus, PY was selected to evaluate the analytical performance of the proposed 3D-printed sensor. For this, a fast and simple method using batch-injection analysis with amperometric detection (BIA-AD) has been developed, which showed a limit of detection of 0.15 µmol L-1, wide linear range (0.5 to 300 µmol L-1), good precision (relative standard deviation (RSD) < 3.4%) and selectivity. This method was applied in biodiesel samples, after dilution (400-fold) in electrolyte. Recovery percentages ranging from 82 to 119% attested absence of matrix effect and good accuracy.

We present an electroanalytical method using square-wave anodic stripping voltammetry on electrochemically-treated screen-printed gold electrodes to the simultaneous determination of lead(II), copper(II) and mercury(II) in struvite (natural fertilizer produced from urine). Electrochemical treatment via cyclic voltammetry of the working electrodes increased surface rugosity that improved the electroanalytical responses for the three metals. Under optimized conditions and using a deposition time of 90 s, the proposed method presented the following limit of detection values: 1.3 µg L-1 for lead(II), 2.0 µg L-1 for copper(II) and 0.9 µg L-1 for mercury(II). Struvite samples were easily dissolved in supporting electrolyte solution (0.05 mol L-1 HCl). Satisfactory recovery values between 91 and 111% were obtained for the analysis of spiked samples. Hence, we can infer that the proposed electroanalytical method is an effective alternative for the determination of trace metals, since it provides precise and accurate direct analyses, with rapid responses without interference from sample matrix and enabling in field analysis.

This communication demonstrates that a 3D printing pen, commercially-available as a toy for kids, can be used to draw thermoplastic electrochemical sensors using conductive filaments over any desirable format and substrate. A polylactic acid filament containing graphene or carbon black was passed through the 3D pen that works as a handheld 3D printer (fused deposition modeling type). As proof-of-concepts, we select three designs, the first one analogous to a conventional carbon-paste electrode, the second one containing the three electrodes in a cylindrical tube and the third one similar to commercial screen-printed electrodes. The 3D pen was used to draw the thermoplastic electrodes inside the pockets of all devices until reaching the copper wires to establish electric contact. Customized 3D printed substrates were used to guide the application of the 3D pen. The fabricated electrodes were applied for the detection of dopamine and trace metals as well as to generate electrochemically a Prussian Blue modified sensor. Many other designs, conductive filaments and substrates can be combined with a 3D pen to draw electrochemical sensors as well as other electrochemical devices, with applications ranging from medical point-of-care platforms, energy-storage devices as well as for teaching purpose.

Tea infusions are a source of mineral nutrients, including manganese. Although it is classified as an essential element, the excess of manganese is toxic for humans and its toxicity depends on its bioavailability. In this context, we propose a simple procedure to determine free and total manganese in black tea infusions by square-wave voltammetry (SWV). Free manganese was directly quantified in the samples after simple sample dilution in 0.1 mol L−1 acetic acid/acetate buffer (pH = 4.5) while total manganese determination was carried out after sample digestion with oxidant mixture (HNO3 + H2O2). For comparison, cloud point extraction was performed to remove organic-bound manganese and the content of free metal (not extracted) measured by flame atomic absorption spectrometry (F AAS) agrees with the values obtained by the proposed SWV procedure. The limit of detection and quantification were estimated for manganese determination as 0.06 and 0.20 µg L−1, respectively, with a linear range observed between 20 and 250 µg L−1. The coefficient of variation was 9.7% (50 µg L−1, n = 10). The procedure was applied to determination of free and total manganese in black tea bags and the results were compared with literature procedures employing F AAS.

This work presents the development and characterization of a new chemically modified electrode exploiting recordable Au-rewritable compact discs (AuCDs) as substrate for drop casting of a chemically-reduced graphene-oxide slurry focusing on simple and low-cost electrochemical sensors. Increase in electrochemical responses in cyclic voltammetric and amperometric measurements were achieved using the proposed sensor. Both scanning electron microscopy and atomic force microscopy data showed increase in rugosity (about 46% higher) for the chemically reduced graphene oxide (CRGO) AuCD surface while Raman spectroscopy confirmed the presence of structural defects of graphene. The calculated charge transfer resistances (Rct) and heterogeneous electron transfer rate constants (k0) were 1638 Ω and 0.0022 cm s-1 for the bare substrate, and 91 Ω and 0.0027 cm s-1 for the modified electrode, evidencing the facilitated electron transfer of the CRGO-AuCD surface. The dopamine (DP) amperometric detection using CRGO-AuCD provided low detection limit (0.12 µg L-1) compared with other modified electrodes already reported, high precision (relative standard deviation (RSD) < 5%) and analytical frequency (370 h-1). As a proof-of-concept, DP determination in synthetic saliva samples was performed and a satisfactory recovery value (98.6 ± 0.9%) was obtained.

This paper presents a simple and low-cost capillary electrophoresis method for ultra-fast simultaneous determination of naphazoline (NPZ) and one of the following active ingredients: diphenhydramine (DIP), pheniramine (PHEN) or chlorpheniramine (CPHEN). The proposed method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) equipped with a short length capillary column (10 cm). One sample can be analyzed every 35 s (ca. 100 injections per hour) with resolutions between peaks greater than 1.4. The optimized background electrolyte (BGE) was composed by 20 mmol L-1 histidine and 10 mmol L-1 3,4-dimethoxycinnamic acid (pH = 9.5, adjusted with NaOH). Limits of detection were 25 µmol L-1 for NPZ, DIP, and PHEN and 13 µmol L-1 for CPHEN. The results obtained with the developed procedure were compared to those obtained by high-performance liquid chromatography (HPLC) and no statistically significant differences were observed (95% confidence level).

Formaldehyde is a carcinogenic compound that was employed as fungicide in the past. Despite its disuse, some foods such as mushrooms naturally produce formaldehyde, showing the importance of its determination. In this work, a mechanized flow system based on solenoid valves is proposed for spectrophotometric formaldehyde determination in mushrooms. The analyte was extracted from fresh and dried mushrooms samples by steam distillation with deionized water in the presence of phosphoric acid. The determination was based on the reaction between formaldehyde and acetylacetone in presence of ammonium acetate (Hantzsch reaction), leading to the formation of 3,5-diacetyl-1,4-dihydrolutidine (DDL, λmax = 412 nm). Linear response from 0.2 to 7.0 mg L-1 was achieved, with detection limit estimated at 0.02 mg L-1 (99.7% confidence level). Coefficient of variation and sample throughput were 1.1% (n = 15) and 17 h-1, respectively. Per determination, 11 mg of acetylacetone and 30 mg of ammonium acetate were consumed, generating 4.2 mL of waste. The procedure was applied to formaldehyde determination in fresh and dried shiitake, and fresh shimeji, and the results agreed with those attained by reference method at the 95% confidence level.

This article critically reviews the spectrometric, chromatographic and electroanalytical methods applied for the identification and quantification of organic and inorganic compounds containing Se and their applications in food, biological and natural water samples. The main characteristics, advantages and disadvantages of each analytical method are presented, and special attention is paid to sample preparation strategies prior to identification and quantification. Perspectives of research on new analytical procedures with improved speed, sensitivity, selectivity, accuracy, and mainly environmentally friendly, are also reported.

In this paper, we present a simple and low-cost capillary electrophoresis method for ultra-fast determination of active ingredients present in three different pharmaceutical formulations: (i) scopolamine (SCO) and dipyrone (DIP); (ii) orphenadrine (ORP), caffeine (CAF) and DIP; (iii) mepyramine (MEP), CAF, DIP, and ascorbic acid (AA). The proposed method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D). The samples can be analyzed in a single run (< 1 minute) using 10 mmol L-1 3,4-dimethoxycinnamate (DMX) and 12 mmol L-1 triethanolamine (TEA) as a background electrolyte (pH = 8.5). A linear working range (r > 0.993) was obtained from 0.10 to 0.50 mmol L-1 for SCO, from 0.25 to 1.25 mmol L-1 for ORP and MEP, from 0.50 to 2.50 mmol L-1 for DIP and CAF, and from 1.00 to 3.00 mmol L-1 for AA. The limits of detection were 0.02, 0.05, 0.03, 0.04, 0.02, and 0.06 mmol L-1 for SCO, DIP, ORP, CAF, MEP, and AA, respectively. In addition, the proposed method also provided adequate intra (< 4%) and inter-day (< 14%) precision values, as well as satisfactory recovery values for spiked pharmaceutical samples (from 92% to 103%).

Este trabalho reporta a determinação simultânea de paracetamol e naproxeno usando a detecção amperométrica de múltiplos pulsos em um eletrodo impresso modificado com nanotubos de carbono de parades múltiplas (MWCNT-SPE) adaptado em uma célula de análise em fluxo (FIA) construída em laboratório. Uma sequência de dois pulsos de potencial (+0,30 e 0,70 V por 70 ms cada) foi aplicada continuamente de tal forma que paracetamol foi selectivamente oxidado em +0,30 V e ambos compostos (paracetamol e naproxeno) são oxidados em +0,70 V. Subtração da corrente depois de usar um fator de correção foi empregada para a determinação de naproxeno sem a interferência do paracetamol. O método FIA proposto apresenta alta seletividade e sensibilidade, exatidão adequada (resultados em concordância com cromatografia líquida de alta eficiência), elevada frequência analítica (90 h-1) e baixo custo uma vez que um único SPE pode ser usado durante todo o dia de trabalho adaptado em uma célula em fluxo.

This work reports the simultaneous determination of paracetamol and naproxen using multiple-pulse amperometric detection on a multi-walled carbon nanotube modified screen-printed electrode (MWCNT-SPE) adapted in a homemade flow-injection analysis (FIA) cell. A sequence of two potential pulses (+0.30 and +0.70 V for 70 ms each) was applied continuously in such a way that paracetamol is selectively oxidized at +0.30 V and both compounds (paracetamol and naproxen) are oxidized at +0.70 V. Current subtraction after using a correction factor was employed for determination of naproxen without the interference of paracetamol. The proposed FIA method presents high selectivity and sensitivity, adequate accuracy (results in agreement with high-performance liquid chromatography), elevated analytical frequency (90 h-1), and low-cost once a single SPE strip can be used during the whole working day adapted in a flow-cell.

A oxidação electroquímica de clorexidina é investigada pela primeira vez e sua determinação amperométrica usando um sistema de análise por injeção em fluxo (FIA) é demonstrada. Um pico de oxidação bem definido foi observado próximo de 1,3 V em uma solução 0,1 mol L-1 de HClO4 em eletrodo de carbono vítreo. O mecanismo da oxidação eletroquímica de clorexidina é dependente do pH e envolve a transferência de um único elétron, possivelmente através da formação de cátion radical. Os parâmetros do sistema FIA foram otimizados e um limite de detecção de 0,3 µmol L-1 foi obtido. O método proposto foi aplicado em enxaguantes bucais e desinfetantes de pele e comparados com cromatografia líquida de alta eficiência.

The electrochemical oxidation of chlorhexidine is investigated for the first time and its amperometric determination using a flow-injection analysis (FIA) system is demonstrated. An oxidation peak was observed at around 1.3 V in a 0.1 mol L-1 HClO4 solution at a glassy-carbon electrode. The mechanism of the electrochemical oxidation of chlorhexidine is pH-dependent and involves a single-electron transfer possibly via radical cation formation. The FIA parameters were optimized and a detection limit of 0.3 µmol L-1 was obtained. The proposed method was applied in mouth rinses and skin disinfectants samples and compared with high-performance liquid chromatography.

Um método eletroanalítico original e rápido para a determinação de naproxeno em formulações farmacêuticas usando análise por injeção em batelada (BIA) com detecção amperométrica pulsada é descrito. Eletrodo de carbono vítreo foi usado como eletrodo de trabalho e solução tampão fosfato 0,05 mol L-1 como eletrólito suporte. O método amperométrico envolveu a aplicação contínua de dois pulsos de potencial ao eletrodo de trabalho com intuito de detectar naproxeno pela sua oxidação eletroquímica (+1,5 V por 200 ms) e de limpar a superfície do eletrodo de produtos de adsorção (+1,0 V por 100 ms), evitando contaminação do eletrodo. O método proposto possui várias vantagens para análises de rotina, incluindo: baixo desvio padrão relativo (3,0%, n = 10), elevada frequência analítica (90 h-1), exatidão satisfatória (baseado em determinações comparativas por espectrofluorimetria) e baixo limite de detecção (0,3 µmol L-1).

A novel and fast electroanalytical method for naproxen determination in pharmaceutical formulations using batch injection analysis (BIA) with pulsed amperometric detection is described. Bare glassy carbon electrode was used as working electrode and 0.05 mol L-1 phosphate buffer solution as supporting electrolyte. The amperometric method involved the continuous application of two sequential potential pulses to the working electrode in order to detect naproxen by its electrochemical oxidation (+1.5 V for 200 ms) and to clean the electrode surface from adsorption products (+1.0 V for 100 ms), avoiding electrode contamination. The proposed method has several advantages for routine analysis, including: a low relative standard deviation between injections (3.0%, n = 10), high analytical frequency (90 h-1), satisfactory accuracy (based on comparative determinations by spectrofluorimetry) and low limit of detection (0.3 µmol L-1).