Abstract: Green Analytical Chemistry (GAC) is a research field that seeks for more sustainable analytical approaches to minimize the toxicity and amounts of wastes without hindering the analytical performance. This is a trend in Analytical Chemistry worldwide and because of the diversity of innovations on this subject, Brazil stands out as the third in the list of the main contributors to GAC, with ca. 11.2% of the published articles. Significant innovations and interesting applications in several fields have been presented and Brazil is continuously moving from Chemistry to Green Chemistry also in the Analytical Chemistry field. Selected contributions for sample preparation, spectro- and electroanalysis, separation techniques, chemometrics, and also procedures for point-of-care measurements are critically reviewed.
ABSTRACT Coupling solid-phase extraction (SPE) to flow systems has promoted a synergistic development. Whereas SPE mechanization leads to improved precision and higher sample throughput, as well as diminishes systematic errors and contamination risks, analyte concentration and separation from the sample matrix provides a remarkable impact on detectability and selectivity in flow analysis. Historical aspects, main cornerstones, tips for system design, and recent applications are critically reviewed, in the context of analyte(s) separation/concentration, sample clean-up, and release of sorbed chemical species involving both packed (e.g. mini-columns, cartridges, and disks) or fluidized (e.g. beads and magnetic materials) particles. Novel (bio)sorbents, selective synthetic materials, and stationary phases for low-pressure chromatography are also discussed. Moreover, the feasibility of SPE for sample treatment before chromatographic separation, as well as the exploitation of direct measurements on the solid phase (optosensing) are emphasized.
A fast, simple and inexpensive procedure is described for the determination of gossypol in cottonseed meal. The procedure is based on a flow injection analysis system and a complexation reaction with spectrophotometric detection at 620 nm. A fluidized bed column was used to implement the on line that was coupled to the extraction flow system in order to analyze the solid samples directly. A linear response was observed from 0.96 to 3.85 mmol L-1, and the detection limit, the coefficient of variation and the sampling rate were estimated at 100 µmol L-1 (99.7% confidence level), 1.90% (n = 20) and 30 h-1, respectively. The reagent consumption was 1.08 mg of Fe(NO3)3, with a volume of 20 mL of effluent per determination. Analyses of the results of commercial samples were consistent with through the official procedure of detoxification of cottonseed meal as described by American Oil Chemists’ Society (AOCS) at the 95% confidence level.
Soils with high levels of iron and aluminum, thus negatively the phosphorous availability, affecting crop yields. A prior determination of the soil capacity to adsorb phosphate is relevant to attaining good agricultural performance. To this end, a multi-pumping flow system with pulsed fluidization is proposed. The procedure takes into account the amount of remaining phosphorus (P-rem) in the solution after the adsorption step to indirectly estimate the soil retention capacity. A 1.0 mg L-1 P solution is passed through a fluidized bed column with 50 mg of soil (particles < 0.15 mm), where the analyte is adsorbed. P-rem was spectrophotometrically quantified by the molybdenum blue method. The coefficient of variation (n = 20), limits of detection and quantification (99.7% confidence level), and sampling rate were estimated as 1.54%, 17 and 51 µg L-1 P, and 87 h-1, respectively. Only 0.27 mg (NH4)6Mo7O24 and 0.10 mg SnCl2 were consumed per determination, generating 2.4 mL of waste. The results followed a linear relationship [y = 0.9702x + 1.483 (r = 0.9635; n = 20)] with the reference procedure. In comparison to the reference procedure, 100, 40 and 180-fold reductions in the required soil amount, waste generation and analytical time were attained.
A flow-based analytical procedure exploiting multicommutation is proposed for captopril determination and the construction of dissolution curves. The procedure is based on the redox reaction between Cu(II) and the drug with the subsequent complexation of Cu(I) with 4,4'-dicarboxy-2,2'-bichinoline (BCA) and spectrophotometric detection. A linear response was observed between 25 and 300 µmol L-1 captopril and the detection limit was estimated as 7 µmol L-1 (99.7% confidence level). The coefficient of variation (n = 20) and sampling rate were 2.2% and 47 determinations per hour, respectively, consuming 290 µg of BCA and generating 3.6 mL of waste per determination. The results for seven pharmaceutical samples agreed with those obtained by the reference volumetric procedure at the 95% confidence level. The dissolution profiles attained with a lab-made dissolution apparatus agreed with those reported in the literature, with a coefficient of variation of 1.8% for three replicates of the reference product
Um procedimento analítico em sistema de análises em fluxo com multicomutação é proposto para a determinação de captopril e construção de curvas de dissolução de medicamentos. O método é baseado na reação do fármaco com Cu(II), com posterior complexação de Cu(I) com 4,4'-dicarboxi-2,2'-biquinolina (BQA) e detecção espectrofotométrica. Foi observada resposta linear entre 25 e 300 µmol L-1 captopril, com limite de detecção de 7 µmol L-1 (99,7% de confiança). O coeficiente de variação (n = 20) e a frequência de amostragem foram 2,2% e 47 determinações por hora, respectivamente, com consumo de 290 µg de BQA e geração de 3,6 mL de resíduo por determinação. Os resultados para 7 amostras de preparações farmacêuticas concordaram com os obtidos pelo procedimento volumétrico de referência com 95% de confiança. Perfis de dissolução obtidos com um aparato construído no laboratório foram concordantes com os relatados na literatura, com coeficiente de variação de 1,8% para três replicatas do produto de referência
A flow system based on the sandwich technique is proposed for the sequential determination of ascorbic acid, dipyrone, acetylcysteine, captopril and paracetamol. The procedure is based on the reduction of Cu(II) by the analytes followed by the spectrophotometric measurement of the complex of Cu(I) with 2,2'-biquinoline 4,4'-dicarboxylic acid. Linear responses were achieved in the µmol L-1 range, with coefficients of variation better than 1.7%. Sampling rate was estimated as 60 determinations per hour, consuming 230 µg of BQA and generating 2.5 mL of waste per determination. Results for commercial samples agreed with those obtained by procedures recommended by the American and European pharmacopeias at the 95% confidence level.
A simple, fast and low cost procedure for spectrophotometric determination of captopril in pharmaceutical preparations is described. The procedure is based on a flow-injection system exploiting the on-line formation of the triiodide reagent, which is consumed in the presence of the analyte generating a transient signal. Linear response was observed up to 200 µmol L-1 with a detection limit of 1.0 µmol L-1 (99.7% confidence level). The coefficient of variation (n = 20) and the sampling rate were estimated as 1.2% and 72 determinations per hour, respectively. The main excipients found in pharmaceutical preparations did not affect the captopril determination. The zone sampling approach was exploited to implement on-line dilutions, aiming direct analysis of sample extracts. Results of the analysis of commercial samples agreed with the obtained by the titrimetric reference procedure described in the US-Pharmacopeia at the 95% confidence level. The reagent consumption was estimated as 18 µg of KMnO4 and 10 mg of KI per determination, with a cost of US$ 2.50 per 1000 determinations.
Um procedimento simples, rápido e de baixo custo é descrito para a determinação de captopril em preparações farmacêuticas. O procedimento é baseado em um sistema de análises por injeção em fluxo explorando a formação em linha de triiodeto, o qual é consumido na presença do analito gerando um sinal transiente. Resposta linear foi observada até 200 µmol L-1 com limite de detecção de 1,0 µmol L-1 (99,7% de confiança). O coeficiente de variação (n = 20) e a freqüência de amostragem foram estimados em 1,2% e 72 determinações por hora, respectivamente. Os principais excipientes encontrados em preparações farmacêuticas não afetaram a determinação de captopril. Reamostragem na zona dispersa foi explorada para implementar diluições em linha, visando a análise direta de suspensões das amostras. Resultados da análise de amostras comerciais foram concordantes com os obtidos pelo procedimento volumétrico de referência descrito na Farmacopéia americana com nível de confiança de 95%. O consumo de reagente foi estimado em 18 µg KMnO4 e 10 mg KI por determinação, com custo de US$ 2,50 por 1000 determinações.
A simple and low-cost flow cell with 30 cm optical path for spectrophotometric measurements is described. It presents desirable characteristics such as low attenuation of the radiation beam and internal volume (75 µL) comparable to that of a 1-cm conventional cell (80 µL). Despite the increase in optical path, the effect on sample dispersion was also similar to that attained in the commercial cell. The performance of the cell was assessed by the determination of phosphate based on the molybdenum blue method, yielding a linear response range between 0.05 and 0.8 mg L-1 phosphorus (r=0.999). The increase in sensitivity (30.4-fold) in comparison with that obtained with a conventional 1-cm flow cell agreed with that estimated by the Lambert-Beer law.
A new passive sampling system for monitoring NO2 in air has been developed to measure gas concentrations in indoor and outdoor air. The sampler is inexpensive, and easy to construct and operate. Nitrogen dioxide forms a derivative after reaction with a filter coated with triethanolamine and ethyleneglycol. The nitrogen dioxide derivative is extracted from the filter, and the concentration is determined by colorimetry. To test the sampler for measuring ambient level nitrogen dioxide, measurements were carried out inside homes and in a range of workplace environments.