DETAILED GUIDE TO OWN ASSEMBLY OF 3D PRINTERS. In recent years, there has been an increase in the use of 3D printing for the manufacture of three-dimensional objects. Thus, it is clear that 3D printers have presented as a tool with high potential for applications in several fields, including chemistry. However, despite its popularity, it is notable that some 3D printers have a relatively high cost, in addition to not favoring optimizations or repairs, making users dependent on the manufacturers of such tools. Therefore, this article aims to present, particularly to the chemistry community, a detailed guide for assembling a low-cost FDM-type 3D printer with good performance. Consequently, we hope that this guide can contribute to increasing the 3D printing popularization in the field of chemistry because of the various possibilities of applications in this area. D PRINTERS years threedimensional three dimensional objects Thus fields However popularity cost repairs tools Therefore present community lowcost low FDMtype FDM type performance Consequently area

This work proposes a novel approach for colorimetric assays using ubiquitous and inexpensive water beads (WBs) made of a superabsorbent polymer (sodium polyacrylate). The high-water absorption capacity by the WBs was exploited for the preconcentration of iron ions from samples of tap, well, and lake waters. Moreover, the WBs also worked as a substrate for colorimetric detection of iron by the classical reaction of formation of Fe(II)-phenanthroline complex. Digital images acquired with a smartphone were used to obtain the color intensity of the WBs containing the orange color complex. The WBs were able to uptake and preconcentrate iron ions, allowing colorimetric detection with good linearity (R2 = 0.9978) and limits of detection (LOD) and quantification (LOQ) of 0.02 and 0.07 mg L-1, respectively. The proposed method provided recoveries ranging from 93 to 111% for a sample of well water spiked with 0.15 mg L-1 of iron.

Sample preparation is commonly considered a key step to achieve selective, sensitive, and reliable chemical analyses, particularly those involving complex matrices. Although the application of electric fields to improve the speed and efficiency of sample preparation methods has been proven, this approach is still considered to be state-of-the-art; hence, further development is necessary to improve future applications. This review describes the fundamentals, advances, applications, and perspectives of using electric fields to enhance sample preparation techniques such as liquid-liquid and solid-liquid extractions in conventional and microscale devices.

Neste trabalho é apresentado o desenvolvimento de um método rápido e simples, empregando eletroforese capilar, para determinação de 5-hidroxitriptofano (5-HTP) em amostras de suplementos alimentares. O eletrólito de corrida utilizado foi constituído por 20 mmol L-1 de fosfato de sódio (pH 10) e 0,2 mmol L-1 de brometo de cetiltrimetilamônio (CTAB), empregado como inversor de fluxo eletrosmótico. Foram obtidos limites de detecção e quantificação de 3,1 e 10,1 µmol L-1, respectivamente. A curva analítica obtida, para concentrações do analito entre 0-500 µmol L-1, apresentou linearidade com coeficiente de correlação linear (R²) de 0,9995. A precisão instrumental intra-dia (repetibilidade), expressa em desvio padrão relativo (RSD), para a área de pico e tempo de migração do 5-HTP foram de 2,2 e 1,9% (n = 8), respectivamente. O método eletroforético foi empregado na análise de quatro diferentes amostras comerciais de suplementos alimentares e o RSD (n = 3) para as determinações variaram de 2 a 3%. A exatidão do método foi avaliada pela comparação das concentrações de 5-HTP obtidas pelo método proposto e por cromatografia líquida de alta eficiência (HPLC). Os erros relativos variaram entre 0 e 5,9% e não foram observadas diferenças significativas entre as concentrações, ao nível de 95% de confiança.

A rapid and simple capillary electrophoresis (CE) method was developed to determine 5-hydroxytryptophan (5-HTP) in samples of commercial dietary supplements. The optimized background electrolyte (BGE) was composed by 20 mmol L-1 sodium phosphate (pH 10) and 0.2 mmol L-1 cetyltrimethylammonium bromide (CTAB) for electroosmotic flow inversion. The limits of detection (LOD) and quantification (LOQ) for 5-HTP were 3.1 and 10.1 µmol L-1, respectively. The analytical curve demonstrated linearity over a concentration range of 0-500 µmol L-1 with a correlation coefficient (R²) of 0.9995. The intraday instrumental precision (repeatability) as relative standard deviation (RSD) in terms of peak area and migration time of the 5-HTP were 2.2 and 1.9% (n = 8), respectively. The CE method was applied to the analysis of four different samples of commercial dietary supplements and the RSD (n = 3) for the determinations ranged from 2 to 3%. The accuracy of the method was evaluated comparing the measured 5-HTP concentrations to those obtained by a high performance liquid chromatography (HPLC) method. The relative error ranged from 0 to 5.9% (n = 3) and no significant differences between the concentrations were observed at a confidence level of 95%.

A instrumentação para a determinação fotométrica do fluxo eletrosmótico (EOF) em dispositivos microfluídicos é descrita neste trabalho. A instrumentação é baseada em componentes acessíveis e consiste em um microscópio trinocular e no fotodiodo integrado OPT101. Um diodo emissor de luz (LED) de alta intensidade foi utilizado como fonte de radiação. Para as determinações foram utilizadas soluções aquosas dos corantes azul patente V e azul de metileno. O sistema foi utilizado no monitoramento do EOF em microdispositivos de poli(dimetilsiloxano) (PDMS) e híbridos de toner/vidro. As mobilidades do EOF determinadas em pH 7,0 foram (5,75 ± 0,01)10-4 cm² V-1 s-1 e (3,2 ± 0,1)10-4 cm² V-1 s-1 para os dispositivos de toner/vidro e PDMS, respectivamente. Medidas reprodutíveis foram obtidas em todos os experimentos, levando a uma alta precisão na determinação. O método proposto foi comparado com o método tradicional de determinação do EOF que envolve a medida da corrente nos microcanais.

An instrumental setup for electroosmotic flow (EOF) determination in microfluidic devices is described. The system is based on a trinocular microscope and an integrated photodiode OPT101. The radiation was provided by a high-intensity white LED. For the determinations, patent blue V and methylene blue aqueous solutions were used. The setup was applied for EOF monitoring in hybrid toner/glass and PDMS microchips. For the toner/glass device, the EOF mobility was determined to be (5.75 ± 0.01) 10-4 cm² V-1 s-1 at pH 7.0. For PDMS devices the measured EOF mobility was (3.2 ± 0.1) 10-4 cm² V-1 s-1. Reproducible measurements were obtained in all experiments, which produced results with small errors. The proposed method was compared to the conventional current monitoring method.

Este trabalho apresenta a determinação de diversos analitos em água de coco por eletroforese capilar com detecção condutométrica sem contato (CCD). Foram analisadas 5 diferentes amostras: duas não processadas (naturais) e três industrialmente processadas (comerciais). As amostras foram injetadas sem tratamento prévio e apenas uma simples diluição foi necessária. A técnica foi aplicada para quantificação de 12 analitos: cloreto, sulfato, fosfato, malato, ascorbato, potássio, sódio, cálcio, magnésio, frutose, glicose e sacarose, sendo que seus respectivos limites de detecção (LOD) são: 0,09; 0,12; 0,50; 0,97; 1,2; 0,05; 0,17; 0,12; 0,08; 5,4; 7,4 e 8,9 mg L-1. Para realizar estas análises, foram utilizados quatro tampões de corrida diferentes.

This work presents the determination of several analytes in coconut water by using capillary electrophoresis with contactless conductivity detection (CCD). It was analyzed 5 different samples: two unprocessed (natural) coconut water and three processed (commercial) ones. The samples were injected without pretreatment and only a simple dilution was necessary. The technique was applied to quantify 12 analytes: chloride, sulfate, phosphate, malate, ascorbate, potassium, sodium, calcium, magnesium, fructose, glucose, and sucrose with limit of detection (LOD) of 0.09, 0.12, 0.50, 0.97, 1.2, 0.05, 0.17, 0.12, 0.08, 5.4, 7.4, and 8.9 mg L-1, respectively. These analysis were done utilizing four different running buffers.

Um sistema sensível e seletivo para boro, utilizando um sistema de análise por injeção em fluxo com detecção piezelétrica, é apresentado. O detector é um cristal piezelétrico de quartzo com eletrodo separado recoberto com filme de poliepicloridrina modificada com N-metil-D-glucamina. A capacidade do filme em reter boro possibilita ampliar a faixa de resposta linear e a sensibilidade, variando o volume de amostra injetada. Neste trabalho, o volume de amostra variou de 0,5 a 5,0 mL. Dentre diversos íons analisados, germanato foi o único interferente. Entretanto, essa interferência pode ser eliminada com a adição de sulfeto à amostra. O método se mostrou eficiente na determinação de boro em amostras de água natural (de 1,71 a 309 µg L-1) e produtos derivados da uva (de 2,06 a 6,21 mg L-1). Um pré-tratamento com peróxido de hidrogênio em meio básico foi necessário devido à grande quantidade de carboidratos presentes no suco de uva.

An automated flow injection analysis system with piezoelectric detection is proposed as a sensitive and selective method for boron. The detector is an electrode-separated piezoelectric quartz crystal coated with N-methyl-D-glucamine-modified poly(epichlorohydrin). The film ability to retain boron allows the adjustment of the linear dynamic range and the sensitivity by varying the injected sample volume. In the present work, the sample volumes were varied from 0.5 to 5.0 mL. Among several ionic species, germanate is the only one that can interfere in the method. Nevertheless, it can be eliminated by addition of sulfide to the sample. The method was successfully applied to the determination of boron concentration in samples of natural water (from 1.71 to 309 µL-1) and products derived from grape juice (from 2.06 to 6.21 mg L-1). A pretreatment with hydrogen peroxide in alkaline medium was required due to the great amount of sugars in the grape products.

O controle do conteúdo de íons inorgânicos em combustíveis veiculares tem uma importante função na manutenção do motor. Um método novo e versátil para análise rápida de íons em etanol é apresentado. Eletroforese capilar foi utilizada para quantificar cátions (sódio, potássio, cálcio, magnésio e amônio) e ânions (sulfato, cloreto e nitrato). A injeção direta da amostra no capilar apresentou falta de repetibilidade nos resultados. A evaporação prévia do etanol, seguida pela resuspensão do material residual, levou a resultados confiáveis. Os limites de detecção para os oito íons estiveram na faixa de 0,06 a 0,18 mg L-1. Limites de detecção inferiores podem ser obtidos com o aumento do tempo de injeção e/ou da pressão de injeção.

The control of the content of inorganic ions in vehicular fuels plays an important role in the engine maintenance. A novel and versatile methodology to carry out rapid analysis of ions in ethanol is presented. Capillary electrophoresis was used to quantify cations (sodium, potassium, calcium, magnesium, and ammonium) and anions (sulfate, chloride, and nitrate). The injection of the sample directly in the capillary shows some lack of repeatability of the results. The prior evaporation of the ethanol, followed by a re-suspension of the residual material, leads to reliable results. The detection limits of the eight ions range between 0.06 and 0.18 mg L-1. Lower detection limits could be attained by increasing the injection time and/or the injection pressure.

This paper presents a new way for the construction of silver electrodes utilizing recordable CDs. The new electrodes were explored for the quantification of chloride (by potentiometry/FIA), cyanide (by amperometry/FIA) and for lead analysis (by square wave voltammetry). For the flowing measurements, a digital multimeter, connected to a microcomputer (via RS 232 interface) was used to collect directly the potential signal (for Cl- measurements) or to take the output signal from a potentiostat (for CN- measurements). The square wave voltammetry analysis was performed in a commercial instrument. The results shown good performance of the new electrodes and the detection limit (s/n = 3) attained for these three analytes were: 0.2, 50, and 200 µg L-1 for Pb2+, Cl-, and CN- respectively.

Um sensor a cristal piezelétrico de quartzo com eletrodos separados e superfície quimicamente modificada foi proposto. A silanização com N-2-aminoetil-3-aminopropiltrimetoxisilano permitiu a imobilização do grupo N-2-aminoetil-3-aminopropilsilano sobre a superfície de um cristal de quartzo de 3,5 MHz. Uma cela em fluxo foi fabricada em poli(metacrilato de metila) com dois eletrodos de latão. Nesta cela, a solução entra em contato somente com um lado do cristal e o eletrodo é recoberto com um filme de poliéster, prevenindo assim a corrosão do eletrodo. Esta inovação reduz o custo da cela e proporciona o desacoplamento DC. O cristal modificado mostrou-se mais sensível a íons cobre (II) do que a magnésio(II), níquel(II), zinco(II) e cobalto(II). Para injeções de 100 miL de amostra, o limite de detecção para cobre(II) foi de 6 mimol L-1 que é um resultado significativo comparado com aqueles obtidos com cristal não modificado.

An electrode-separated piezoelectric quartz crystal sensor with a chemically modified surface was proposed. The modification was carried out by a silanization procedure with N-2-aminoethyl-3-aminopropyltrimethoxysilane, yielding the immobilised N-2-aminoethyl-3-aminopropylsilane group over the surface of a 3.5 MHz piezoelectric quartz crystal. A flow cell was manufactured with poly(methyl methacrylate) and brass, instead of noble metals, for the electrodes. In this cell, the solution touches only one side of the crystal and the related electrode is coated with a polyester film, which prevents corrosion and does not disturb the oscillation process. This innovation reduces the cost of the cell and renders an electronics non DCcoupled to the solution. The modified crystal proved to be more sensitive to copper(II) ions than magnesium(II), nickel(II), zinc(II), and cobalt(II). For 100muL sample injections, the limit of detection for copper(II) was 6 mumol L-1, which is an impressive result when compared with that for an unmodified crystal.

A piezoelectric detector based on a commercial quartz crystal of 3.57MHz is shown. A PTFE cell attached to the GC-column outlet holds the polymer-coated crystal, whose terminals were removed. Two TTL oscillators (reference and sensor) are used and the beating of their frequencies is monitored through a home-made counter card inserted in a microcomputer. The original thermal conductivity detector was also interfaced, but through a 12-bit analog-to-digital converter. In spite of the well-known fact that QCM has low sensitivity at high temperatures, results show significant peak deformation for low temperatures. In addition, the phenomenon is also dependent on the chemical composition of the absorbent film besides instantaneous partial pressure and chemical composition of the analyte.