This paper reports the application of hydrophobic deep eutectic solvents (HDES) as an environmentally friendly alternative for liquid-phase microextraction (LPME) of Allura Red AC and Tartrazine in food products and the spectrophotometric determination of these analytes. The HDES used in this work were prepared by mixing octanoic acid (OctAc) or decanoic acid (DecAc) and tetrabutylammonium bromide (N4444-Br) in a molar ratio of 2:1. An investigation was also carried out regarding the effects of sample pH, sample volume, HDES volume, and concomitants on the analytical performance of the proposed method. The analytical curves obtained for Allura Red AC and Tartrazine in octanoic acid (OctAc)-tetrabutylammonium bromide (N4444-Br) were in the linear concentration ranges of 0.05 to 2.00 mg L-1 and 0.04 to 2.14 mg L-1, with limits of detection of 0.005 and 0.004 mg L-1, respectively. The proposed technique was successfully applied for the determination of Allura Red AC and Tartrazine in food products.

Simple, fast, and inexpensive electroanalytical procedures were developed for the determination of codeine (COD) solely and paracetamol (PCT) and COD simultaneously in pharmaceutical formulations and human body fluids. The methods involve the combination of square-wave voltammetry (SWV) with a cathodically pretreated boron-doped diamond electrode and a 0.2 mol L–1 acetate buffer (pH 4.0) solution as the supporting electrolyte. Significantly low limits of detection were obtained for COD solely or PCT and COD simultaneously: 1.19 or 18 and 14 nmol L–1, respectively. The proposed SWV method was successfully applied in the simultaneous determination of PCT and COD in four samples of pharmaceutical tablets, with results similar (at 98% confidence level) to those obtained using a reference high-performance liquid chromatography (HPLC) method. Additionally, adequate results were obtained when concentrations of PCT and COD were determined in human urine or serum samples by addition-recovery. Clearly, the proposed method is an excellent option for the determination of COD solely or PCT and COD simultaneously.

<p>A novel method for simultaneous voltammetric determination of the antihypertensive drugs, amlodipine besylate (AML) and hydrochlorothiazide (HTZ) in synthetic urine samples was developed. Determination was carried out with a cathodically pretreated boron-doped diamond electrode (CPT-BDD) using square-wave voltammetry (SWV) and Britton-Robinson buffer solution at pH 2 as the supporting electrolyte. AML and HTZ exhibited oxidation peaks at 0.88 V and 1.30 V, respectively. The difference in potentials of 0.42 V allowed the simultaneous determination of these two analytes. The analytical curve showed linear response in the concentration range from 0.200 to 9.09 µmol L^-1 for AML and from 4.00 to 100 µmol L^-1 for HTZ, with a limit of detection (LOD) of 60.0 nmol L^-1 and of 2.00 µmol L^-1 for AML and HTZ, respectively. Recoveries of these analytes ranged from 91.0 to 107%. The proposed method using SWV and a CPT-BDD electrode is simple, fast and low cost, representing a good alternative for simultaneous determination of AML and HTZ in urine samples.</p>

Um procedimento simples é descrito para a determinação de propiltiouracil (PTU) por voltametria de pulso diferencial (DPV) usando um eletrodo de diamante dopado com boro (BDD) pré-tratado catodicamente. Estudos por voltametria cíclica indicam que a oxidação do PTU é irreversível a um potencial de pico de 1,42 V (vs. Ag/AgCl (KCl 3,0 mol L-1)) em uma solução tampão de Britton-Robinson (BR) (pH 2,0). Sob condições otimizadas, a curva analítica obtida foi linear (r = 0,9985) na faixa de concentração de PTU de 1,0 a 29,1 mmol L-1 em solução tampão BR (pH 2,0), com um limite de detecção de 0,90 mmol L-1. O método proposto foi aplicado com sucesso na determinação de PTU em amostras farmacêuticas, com resultados concordantes (a um nível de 95% de confiança) com aqueles obtidos empregando um método titulométrico oficial.

A simple procedure is described for the determination of propylthiouracil (PTU) by differential pulse voltammetry (DPV) using a cathodically pretreated boron-doped diamond (BDD) electrode. Cyclic voltammetry studies indicate that the oxidation of PTU is irreversible at a peak potential of 1.42 V (vs. Ag/AgCl (3.0 mol L-1 KCl)) in a Britton-Robinson (BR) buffer solution (pH 2.0). Under optimized conditions, the obtained analytical curve was linear (r = 0.9985) for the PTU concentration range of 1.0 to 29.1 mmol L-1 in a BR buffer solution (pH 2.0), with a detection limit of 0.90 mmol L-1. The proposed method was successfully applied in the determination of PTU in pharmaceutical samples, with results in agreement at a 95% confidence level with those obtained using an official titration method.

A determinação de triptofano usando voltametria de varredura rápida com um ultramicroeletrodo de fibra de carbono (CF-UME) é descrita. O eletrodo CF-UME foi submetido a um pré-tratamento eletroquímico. Parâmetros tais como número de aquisição de ciclos, velocidade de varredura, intervalo de potencial e pré-tratamento eletroquímico da superfície foram otimizados. Sob condições ideais, três curvas analíticas foram obtidas para o triptofano (entre 30 e 300 µmol L-1) usando três diferentes CF-UME pré-tratados através de um procedimento de tratamento eletroquímico otimizado. Observou-se uma dependência na sensibilidade e concentração do triptofano com o raio do eletrodo, com limites de detecção entre 16,7 e 22,7 µmol L-1. O método foi aplicado na determinação de triptofano em amostras comerciais com erros entre -0,99 e +13,2% em relação a um método comparativo

Tryptophan determination using a fast-scan voltammetric method at carbon fiber ultramicroelectrodes (CF-UME) is described. CF-UME electrode was submitted to electrochemical pretreatment. Parameters such as number of acquisition cycles, scan rate, potential interval and electrochemical surface pretreatment were optimized. Under optimized conditions, three analytical curves were obtained for tryptophan (between 30 and 300 µmol L-1) using three different CF-UMEs pretreated by means of an optimized electrochemical treatment procedure. It was observed a dependence on the sensitivity and tryptophan concentration linear range with the radius of the electrode, with limits of detection between 16.7 and 22.7 µmol L-1. The method was applied in the determination of tryptophan in commercial samples, with errors between -0.99 and +13.2% in relation to a comparative method.

Neste trabalho, a aplicação de um microssistema analítico construído com tecnologia LTCC (cerâmica cossinterizada a baixa temperatura) com incorporação monolítica de uma cela óptica de fluxo para determinação de dipirona em formulações farmacêuticas é descrita. O sistema de detecção baseou-se na formação de um cromóforo azul entre a dipirona e Fe(III) monitorado fotometricamente em 630 nm usando um minifotômetro de LED lab-made construído com um diodo emissor de luz como fonte de radiação e um fotodiodo de Si como detector. O minifotômetro elaborado apresentou um bom desempenho com respeito à elevada relação sinal ruído, baixo ruído e sensibilidade satisfatória. A curva analítica foi linear na região de concentração de dipirona de 1,0 × 10-4 a 3,5 × 10-3 mol L-1 tendo sido obtido um limite de detecção de 4,5 × 10-5 mol L-1 e um tempo total de análise de 20 s equivalente à uma frequência analítica de 195 h-1 com pouca geração de resíduos por análise (480 µL).

In this work, an analytical microsystem based on LTCC (low-temperature co-fired ceramic) technology with monolithic incorporation of an optical flow cell for determination of dipyrone in pharmaceuticals is described. The detection system is based on the formation of a blue chromophore between dipyrone and Fe(III) photometrically monitored at 630 nm using a lab-made LED mini-photometer constructed with a light emitting diode as a radiation source and a Si photodiode as a detector. The lab-made mini-photometer elaborated presented a good performance in regard to high signal/noise ratio, low drift and good sensitivity. The analytical curve was linear in the dipyrone concentration range from 1.0 × 10-4 to 3.5 × 10-3 mol L-1, limit of detection of 4.5 × 10-5 mol L-1 and total time of analyses of 20 s yielding an analytical frequency of 195 h-1 with a low waste generation per analysis (480 µL).

Descreve-se um eletrodo de carbono modificado com fosfato de cobre (II) imobilizado em uma resina de poliéster (Cu3(PO4)2-Poly) para a determinação de rutina em amostras farmacêuticas por voltametria de onda quadrada. O eletrodo modificado permite a determinação de rutina em potencial (0.20 V vs Ag / AgCl (3,0 mol L-1 KCl)) menor que o observado em um eletrodo não modificado. Verificou-se que a corrente de pico foi linear com a concentração de rutina na faixa de 9,9 × 10-8 a 2,5 × 10-6 mol L-1, com um limite de detecção de 1,2 × 10-8 mol L¹. A resposta do eletrodo foi estável, sem variação significativa dentro de várias horas de operação contínua. A morfologia da superfície do eletrodo modificado foi caracterizada por microscopia eletrônica de varredura (MEV) e pelo sistema de energia dispersiva de raios-X (EDX). Os resultados obtidos foram precisos e exatos. Ademais, estes resultados estão de acordo com aqueles obtidos pelo método cromatográfico a um nível de confiança de 95%.

A carbon composite electrode modified with copper (II) phosphate immobilized in a polyester resin (Cu3(PO4)2-Poly) for the determination of rutin in pharmaceutical samples by square-wave voltammetry is described herein. The modified electrode allows the determination of rutin at a potential (0.20 V vs. Ag/AgCl (3.0 mol L-1 KCl)) lower than that observed at an unmodified electrode. The peak current was found to be linear to the rutin concentration in the range from 9.9 × 10-8 to 2.5 × 10-6 mol L-1, with a detection limit of 1.2×10-8 mol L-1. The response of the electrode was stable, with no variation in baseline levels within several hours of continuous operation. The surface morphology of the modified electrode was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) system. The results obtained are precise and accurate. In addition, these results are in agreement with those obtained by the chromatographic method at a 95% confidence level.

Um procedimento simples de análise por injeção em fluxo foi desenvolvido para a determinação de captopril em formulações farmacêuticas empregando um novo reator em fase sólida contendo tiocianato de prata imobilizado em resina poliuretana obtida a partir de óleo de mamona. O método foi baseado na formação de um mercapto composto de prata, no reator em fase sólida, obtido entre o captopril e Ag (I) imobilizada. Durante a reação, íons SCN- eram liberados e reagiam com Fe3+, gerando o complexo FeSCN2+, que foi continuamente monitorado em 480 nm. A curva analítica foi linear no intervalo de concentração de captopril entre 3,0 × 10-4 a 1,1 × 10-3 mol L-1 com um limite de detecção de 8,0 × 10-5 mol L-1. Recuperações entre 97,5-103% e desvio padrão relativo de 2% para uma solução contendo 6,0 × 10-4 mol L-1 de captopril (n = 12) foram obtidos. A frequência de amostragem foi de 40 h-1 e os resultados obtidos para captopril em formulações farmacêuticas utilizando este procedimento e o da Farmacopeia, estão de acordo em um nível de confiança de 95%.

A simple flow-injection analysis procedure was developed for determining captopril in pharmaceutical formulations employing a novel solid-phase reactor containing silver thiocyanate immobilized in a castor oil derivative polyurethane resin. The method was based on silver mercaptide formation between the captopril and Ag(I) in the solid-phase reactor. During such a reaction, the SCN- anion was released and reacted with Fe3+, which generated the FeSCN2+ complex that was continuously monitored at 480 nm. The analytical curve was linear in the captopril concentration range from 3.0 × 10-4 mol L-1 to 1.1 × 10-3 mol L-1 with a detection limit of 8.0 × 10-5 mol L-1. Recoveries between 97.5% and 103% and a relative standard deviation of 2% for a solution containing 6.0 × 10-4 mol L-1 captopril (n = 12) were obtained. The sample throughput was 40 h-1 and the results obtained for captopril in pharmaceutical formulations using this procedure and those obtained using a pharmacopoeia procedure were in agreement at a 95% confidence level.

The construction of a low cost mini sensor containing a bismuth-film electrode (BiFE), as work electrode, a silver electrode as pseudo reference electrode, and copper as counter electrode is proposed. The application of this mini sensor using a low cost electrochemical cell for in loco voltammetric determinations of inorganic and organic analytes is also described.

This study reports on the construction of a turbidimeter employing light emitting diodes as radiation source at a wavelength of 405 nm, a photodiode as detector, a temperature sensor and a microcontroller used for data acquisition and processing. The turbidimeter was applied to determine sulfate concentrations in natural water employing barium chloride as reagent. Potential interferences and recovery studies were performed and an interference of 3.5 % and a recovery between 97.8 and 108 % were estimated. The analytical performance of in situ turbidimeter for the determination of sulfate was evaluated and compared with two commercial spectrophotometers and a good agreement was obtained.

A análise turbidimétrica e nefelométrica sequencial (STN) para duas aplicações analíticas empregando um nefelômetro e turbidímetro microcontrolado portátil (PMTN) é proposta. O PMTN é constituído de diodos emissores de luz, fotodiodos, microcontrolador como unidade de processamento central (CPU) e um um LCD (liquid crystal display) como amostrador. Os métodos STN foram aplicados para a determinação de N-acetilcisteína em formulações farmacêuticas nos intervalos de concentração de 8,0 × 10-5 a 5,0 × 10-3 mol L-1 (nefelometria) e de 5,0 × 10-5 a 1,2 × 10-3 mol L-1 (turbidimetria) com limites de detecção (LOD) de 2.6 × 10-6 e 7,5 × 10-6 mol L-1, respectivamente. As análises STN também foram executadas para a determinação de tiamina na faixa de concentração de 5,0 × 10-6 a 2,5 × 10-4 mol L-1 e de 5,0 × 10-6 a 1,0 × 10-4 mol L-1 com LOD de 5,91 × 10-8 e 3,11 × 10-8 mol L-1 respectivamente no modo nefelométrico e turbidimétrico.

Sequential turbidimetric and nephelometric (STN) analysis for two distinct analytical applications employing a portable microcontrolled turbidimeter and nephelometer (PMTN) is proposed. The PMTN is based on light emitting diodes, photodiodes and, a microcontroller as a central processing unit with a LCD (liquid crystal display) as displayer. The STN methods were applied to determine N-acetylcysteine and two analytical curves in the concentration ranges from 8.0 × 10-5 to 5.0 × 10-3 mol L-1 and from 5.0 × 10-5 to 1.2 × 10-3 mol L-1 were obtained to nephelometry and turbidimetry, respectively. Limits of detection (LOD) of 2.6 × 10-6 and 7.5 × 10-6 mol L-1 were acquired for these procedures. The STN analyses were also performed to determinate thiamine and two analytical curves in the concentration ranges from 5.0 × 10-6 to 2.5 × 10-4 mol L-1 and from 5.0 × 10-6 to 1.0 × 10-4 mol L-1 with LOD of 5.91 × 10-8 and 3.11 × 10-8 mol L-1 were acquired for nephelometry and turbidimetry, respectively.

A factorial design applied in a voltammetric stripping method for the measurement of Ag(I) in natural water is described. The procedure is based on the effective pre-concentration of silver ions on electrode surface. The calibration graph was linear in the silver concentration range from 7.92 x 10"7 to 1.07 x 10"5 mol L"1 with a detection limit of 3.81 x 10-7 mol L-1. The determination of Ag(I) in natural water samples was carried out satisfactory with the proposed electrode.

Neste trabalho descreve-se a titulação condutométrica do cloridrato de propranolol em formulações farmacêuticas usando nitrato de prata como titulante. O método é baseado na formação de um sal insolúvel (AgCl(s)) entre o cloreto da molécula do cloridrato de propranolol e os íons Ag(I) do titulante AgNO3. O efeito das concentrações PROP-AgNO3 e o intervalo de tempo entre adições sucessivas de titulante no formato da curva de titulação foram estudados. Recuperações para quatro amostras variaram de 96,8 a 105%. O método proposto foi aplicado na determinação do cloridrato de propranolol em diversas formulações farmacêuticas, com resultados concordantes com àqueles obtidos empregando-se o método oficial espectrofotométrico, a um nível de confiança de 95 %.

In this paper the conductometric titration of propranolol hydrochloride in pharmaceutical formulations using silver nitrate as titrant is proposed. The method was based on the formation of an insoluble salt (AgCl(s)) between the chloride of propranolol hydrochloride molecule and Ag(I) ions of the titrant AgNO3. The effect of the PROP-AgNO3 concentrations and the interval of time between the successive additions of the titrant on the shape of the titration curve were studied. The obtained recoveries for four samples ranged from 96.8 to 105%. The proposed method was successfully applied in the determination of propranolol hydrochloride in several pharmaceutical formulations, with results in close agreement at a 95 % confidence level with those obtained using official spectrophotometric method.

This review reports the use of solid amalgam electrodes in the electroanalytical determination of organic and inorganic compounds. The different types of amalgam electrodes are presented, and attention is paid to solid amalgam electrode, and here is presented details about the pre-treatment for activation and renovation and also possible modifications in its surface. The wide potential range, higher signal-to-noise ratio, mechanical stability enabling their application in flowing systems, and principally their resistance toward passivation, indicate that the solid amalgam electrodes are environmentally friendly alternatives to mercury electrodes, without loss in the sensitivity and reproducibility in voltammetric responses.

Um nefelômetro microcontrolado portátil e de baixo custo é proposto para a determinação de potássio em água de coco e bebidas energéticas. O nefelômetro foi construído utilizando dois LEDs (diodos emissores de luz) como fontes de radiação em 465 nm e 880 nm, dois fotodiodos como fotodetectores e um controlador de interface periférica (PIC) para aquisição e processamento dos dados. O nefelômetro foi utilizado para determinar íons potássio pelo monitoramento do precipitado formado na reação entre íons K+ e tetrafenilborato em meio básico na presença de álcool polivinílico. A curva analítica foi linear para potássio na faixa de concentração de 5,0×10"6 a 5,0×10"4 mol L"1, com um limite de detecção de 4,0×10"7 mol L"1. Um desvio padrão relativo de 0,2 % para uma solução de potássio 1,6×10"4 mol L"1 (n = 10) foi obtido. Respostas rápidas e confiáveis e baixo consumo de energia são outras características do nefelômetro proposto.

A low-cost portable microcontrolled nephelometer for the determination of potassium in coconut water and energy beverages is proposed. The nephelometer was constructed using two LEDs (light emitting diodes) as radiation sources at 465 nm and 880 nm, two photodiodes as photodetectors, and a peripheral interface controller (PIC) to acquisition and processing data of the nephelometer. The nephelometer was used to determine potassium ions by monitoring the precipitate formed from the reaction between K+ and tetraphenylborate anion in a basic medium in the presence of polyvinyl alcohol. The analytical curve was linear in the potassium concentration range from 5.0×10"6 to 5.0×10"4 mol L"1, with a limit of detection of 4.0×10"7 mol L"1. A relative standard deviation of 0.2 % for 1.6 × 10"4 mol L"1 potassium solution (n = 10) was obtained. Fast and reliable responses, low power consumption are other attractive features of the proposed nephelometer.