Adriana Dillenburg Meinhart

Use of multivariate statistical techniques to optimize the simultaneous separation of 13 phenolic compounds from extra-virgin olive oil by capillary electrophoresis.

Characterization of phenolic compounds in olive oil has not been achieved as yet, owing to the complexities of their chemical structures and analytical matrix. The aim of this work is to optimize and validate a method for simultaneous separation and quantification of 13 phenolic compounds from extra-virgin olive oil: tyrosol, hydroxytyrosol, oleuropein glycoside, ferrulic acid, p-coumaric acid, cinnamic acid, p-hydroxybenzoic acid, gallic acid, caffeic acid, luteolin, apigenin, vanillic acid and 3,4-dihydroxybenzoic acid. A statistical central composite design, response surface analysis and the simultaneous optimization method of Derringer and Suich were used to separate all the peaks. These multivariate procedures were efficient in determining the optimal separation condition, using five peak-pair resolutions and runtime as responses. The optimized method employed a fused-silica capillary of 50 μm i.d.× 60 cm effective length with extended light path, 50 mmol L(-1) boric acid electrolyte, 10.2 pH, 25°C, injection of 50 mbar for 25s with application of reverse voltage (-30 kV for 5s) before setting the running voltage (+30 kV) with detection at 210 nm and a run time of 12 min. Peak resolutions are found to be very sensitive to pH values outside the 10.15-10.25 range but acceptable electropherograms can be obtained for a wide range of boric acid concentrations within this pH interval.

Phenolic compounds from yerba mate based beverages--A multivariate optimisation.

This work used a central composite design to optimise a reverse phase high performance liquid chromatographic method for the simultaneous separation of gallic, syringic, 5-caffeoylquinic, caffeic, p-coumaric, ferulic, 3,4-dicaffeoylquinic, 3,5-dicaffeoylquinic, 4,5-dicaffeoylquinc acids, rutin in aqueous extracts of yerba mate (Ilex paraguariensis). The effect of the linear gradient time, the initial and the final methanol concentration in the mobile phase on the peak resolution and peak symmetry was evaluated. The 26 responses obtained were simultaneously optimised using the desirability method of Derringer and Suich. According to results, the increasing in the resolution and peak symmetry was achieved by using lesser levels of methanol in both initial and final gradient elution (-1.68, -1), as well as higher gradient times (+1, +1.68). The optimal condition (13.9-40% of methanol in 39.4 min) were successfully applied for analysis of chimarrão, tererê and mate tea aqueous extracts, which showed as excellent sources of chlorogenic acids.

Doehlert design-desirability function multi-criteria optimal separation of 17 phenolic compounds from extra-virgin olive oil by capillary zone electrophoresis

In Brazil, the consumption of extra-virgin olive oil (EVOO) is increasing annually, but there are no experimental studies concerning the phenolic compound contents of commercial EVOO. The aim of this work was to optimise the separation of 17 phenolic compounds already detected in EVOO. A Doehlert matrix experimental design was used, evaluating the effects of pH and electrolyte concentration. Resolution, runtime and migration time relative standard deviation values were evaluated. Derringers desirability function was used to simultaneously optimise all 37 responses. The 17 peaks were separated in 19min using a fused-silica capillary (50μm internal diameter, 72cm of effective length) with an extended light path and 101.3mmolL(-1) of boric acid electrolyte (pH 9.15, 30kV). The method was validated and applied to 15 EVOO samples found in Brazilian supermarkets.

Chemometrics optimization of carbohydrate separations in six food matrices by micellar electrokinetic chromatography with anionic surfactant

Multivariate statistical design modeling and the Derringer-Suich desirability function analysis were applied to micellar electrokinetic chromatography (MEKC) results with anionic surfactant to separate carbohydrates (CHOs) in different food matrices. This strategy has been studied with success to analyze compounds of difficult separation, but has not been explored for carbohydrates. Six procedures for the analysis of different sets of CHOs present in six food matrices were developed. The effects of pH, electrolyte and surfactant concentrations on the separation of the compounds were investigated using a central composite design requiring 17 experiments. The simultaneous optimization of the responses for separation of six sets of CHOs was performed employing empirical models for prediction of optimal resolution conditions in six matrices, condensed milk, orange juices, rice bran, red wine, roasted and ground coffee and breakfast cereal samples. The results indicate good separation for the samples, with appropriate detectability and selectivity, short analysis time, low reagent cost and little waste generation, demonstrating that the proposed technique is a viable alternative for carbohydrate analysis in foods.

Comparison of capillary electrophoresis and high performance liquid chromatography methods for caffeine determination in decaffeinated coffee

Decaffeinated coffee accounts for 10 percent of coffee sales in the world; it is preferred by consumers that do not wish or are sensitive to caffeine effects. This article presents an analytical comparison of capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) methods for residual caffeine quantification in decaffeinated coffee in terms of validation parameters, costs, analysis time, composition and treatment of the residues generated, and caffeine quantification in 20 commercial samples. Both methods showed suitable validation parameters. Caffeine content did not differ statistically in the two different methods of analysis. The main advantage of the high performance liquid chromatography (HPLC) method was the 42-fold lower detection limit. Nevertheless, the capillary electrophoresis (CE) detection limit was 115-fold lower than the allowable limit by the Brazilian law. The capillary electrophoresis (CE) analyses were 30% faster, the reagent costs were 76.5-fold, and the volume of the residues generated was 33-fold lower. Therefore, the capillary electrophoresis (CE) method proved to be a valuable analytical tool for this type of analysis.O comercio de cafe descafeinado constitui 10% das vendas mundiais de cafe, sendo preferido pelos consumidores que nao desejam ou sao sensiveis aos efeitos da cafeina. Este artigo apresenta uma comparacao analitica de metodos por eletroforese capilar (CE) e cromatografia liquida de alta eficiencia (HPLC) para a quantificacao de cafeina residual em cafe descafeinado, quanto aos parâmetros de validacao, custos, tempo de analise, composicao e tratamento dos residuos gerados, bem como quantificacao de cafeina em 20 amostras comerciais. Ambos os metodos apresentaram parâmetros de validacao adequados. O teor de cafeina nao diferiu estatisticamente pelos dois metodos. A vantagem do metodo por HPLC foi o limite de deteccao 42 vezes mais baixo. Nao obstante, o limite de deteccao da CE foi 115 vezes menor do que o permitido pela legislacao brasileira. A analise por CE foi 30% mais rapida, os custos com reagentes foram 76,5 vezes mais baixos e o volume de residuos gerados foi 33 vezes menor. Portanto, o metodo por CE mostrou-se uma valiosa ferramenta analitica para este tipo de analise.

Chlorogenic acid isomer contents in 100 plants commercialized in Brazil

This study analysed 100 plants employed in Brazil as ingredients to infusions for their caffeic acid, 3-caffeoylquinic acid (3-CQA), 4-caffeoylquinic acid (4-CQA), 5-caffeoylquinic acid (5-CQA), 3,4-dicaffeoylquinic acid (3,4-DQA), 3,5-dicaffeoylquinic acid (3,5-DQA), and 4,5-dicaffeoylquinic acid (4,5-DQA) contents. The samples were collected from public markets and analysed using ultra-high performance liquid chromatography (UPLC). The highest concentrations of chlorogenic acids were found in yerba mate (Ilex paraguariensis), 9,2g·100g-1, white tea (Camellia sinensis), winters bark (Drimys winteri), green tea (Camellia sinensis), elderflower (Sambucus nigra), and Boehmeria caudata (known as assa-peixe in Brazil), 1,1g·100g-1. The present work showcased the investigation of chlorogenic acids in a wide range of plants not yet studied in this regard and also resulted in a comparative table which explores the content of six isomers in the samples.

Optimization of Electrophoretic Separations of Thirteen Phenolic Compounds using Single Peak Responses and an Interactive Computer Technique

An interactive computer method is proposed for the electrophoretic separation of 13 phenolic compounds from extra-virgin olive oil using single peak response values. A central composite design was executed for optimization of the sodium tetraborate concentration, pH and applied voltage. Statistical models were determined for eight resolution responses and thirteen effective mobilities. Six of the resolution models had highly significant ANOVA lack of fit values, limiting their accuracies for use in Derringer´s desirability function search for optimal separation conditions. None of the 13 effective mobility models suffered from significant lack of fit. Since it is not possible to define effective mobility target values for the desirability function, an interactive computer program developed in our laboratories was applied to the single peak models. Mouse or cursor movements were executed to define experimental conditions in model simulations of the electropherogram. These simulations resulted in superior peak separations, especially for the apigenin and luteolin peaks, in 35 min, compared with those obtained in close to 50 min with the resolution models. Verification experiments performed 2 and 3 years later confirmed the robustness of the models.

Chlorogenic acids and flavonoid extraction during the preparation of yerba mate based beverages

This study determined the content of chlorogenic acids (CA) and rutin during successive aqueous extraction of yerba mate for tererê and chimarrão from four yerba mate types (smooth, native, traditional and coarse ground). Aqueous extracts were prepared aiming to simulate homemade procedure by partially (chimarrão) or completely (tererê) immersing the herb into hot (chimarrão) or cold (tererê) water (30 times consecutively). The content of CA and rutin in the aqueous extracts was compared to those in methanolic extracts (exhaustive extraction). Tererê aqueous extracts gave higher amounts of all phenolic compounds (2.5 to 6 times higher than chimarrão). Among chimarrão, course-ground aqueous extracts had on average 15% more PC (phenolic compounds). By comparing the content in aqueous and methanolic extracts, after 30 successive extractions, on average 14% of the total amount of CA in yerba mate leaves and 9% of rutin were transferred to the chimarrão extracts, whereas tererê achieved between 40% and 100% of transference. Thus, this study shows that CA and rutin are continuously extracted during the preparation of aqueous extracts of chimarrão and tererê, favoring a high intake of these antioxidant species by consumers.

Multivariate Optimization of Chlorogenic Acid Extraction From Brazilian Coffee

Brazil is the largest producer and exporter of coffee in the world; the beverage is recognized as the main source of chlorogenic acids (CA), which have beneficial effects on human health. In this study, a multivariate optimization of extraction conditions was performed, aiming to maximize the extraction of chlorogenic acids isomers (3-caffeoylquinic acid (3-CQA), 4-caffeoylquinic acid (4-CQA), 5-caffeoylquinic acid (5-CQA), 3.4-dicaffeoylquinic acid (3.4-DQA), 3.5-dicaffeoylquinic acid (3.5-DQA), and 4.5-dicaffeoylquinic acid (4.5-DQA)). The optimal extraction condition was obtained using ethanol and water in the proportions of 32.4:67.6, and a 22-min extraction period, resulting in a fast, precise, accurate, and cost-effective method, with low toxic waste generation. Optimized extraction conditions were employed to investigate the CA content in different types of ground roasted coffee available on the market (traditional, extra strong, gourmet, decaffeinated, and organic). Results showed that, although these products are differentiated by their value of trade, no difference in the chlorogenic acids content was found.