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interactions among different factors [ 10 ]. To overcome these shortcomings, Box and Wilson suggested the use of response surface methodology (RSM) [ 11 ]. RSM is an effective and efficient mathematical statistics method to construct models, evaluate the

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systematic approach that includes multidimensional combinations of input variables using design of experiments such as Response Surface Methodology (RSM) to obtain optimal conditions with better quality assurance [ 10 ]. Design Space (DS) is a key step in the

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, while a response surface methodology based on central composite design (RSM-CCD) program was carried out for the maximum yields. In our previous work, six kinds of solvents (methanol, anhydrous, ethanol, 95% ethanol, ethyl acetate and petroleum ether

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Progress in Agricultural Engineering Sciences
Authors: Szilvia Bánvölgyi, Eszter Dusza, Fiina K. Namukwambi, István Kiss, Éva Stefanovits-Bányai, and Gyula Vatai

(°C) Time (h) Solvent concentration Water (%) Alcohol (%) −1 30 1 100 0 0 45 3 50 50 1 60 5 0 100 Response surface methodology (RSM) technique was used to optimize the extraction conditions aimed at maximum recovery of polyphenol. The RSM is an

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Raquel Cristóvão, Priscilla Amaral, Ana Tavares, Maria Coelho, Magali Cammarota, José Loureiro, Rui Boaventura, Eugénia Macedo, and Fernando Pessoa

Abstract  

In this work, the laccase catalyzed degradation of reactive textile dyes was studied in supercritical carbon dioxide media. A two level Box–Behnken factorial design with two factors and response surface methodology (RSM) were performed to investigate and optimize the effects of pressure and temperature on reactive red 239 (RR239), reactive yellow 15 (RY15) and reactive black 5 (RB5) dye degradations by commercial laccase in supercritical carbon dioxide media. Mathematical models were developed for each dye showing the effect of each factor and their interactions on color removal. Pressure and the interaction between temperature and pressure were the main factors affecting the decolorization. The optimum conditions for RB5 and RY15 were found to be high pressure values (>120 bar), whilst the temperature presented a minor effect on their degradation at these pressures. For RR239, both variables influenced the decolorization and the optimum conditions appear to be at low values of pressure and high values of temperature.

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Response surface methodology (RSM) was used to optimize solid– liquid ultrasonic-assisted extraction (UAE) conditions for the maximization of the stigmasterol content from an Ayurvedic plant Tecomella undulata (T. undulata) bark. The Box—Behnken design (BBD), form of RSM, was employed for the optimization of ultrasonic extraction parameters, viz., temperature (°C), drug-to-solvent ratio (mg/10 mL), and time (min). Quantification of stigmasterol was performed using high-performance thin-layer chromatography in visible range (HPTLC–vis). HPTLC analysis of stigmasterol was carried out in the absorbance mode at 510 nm using toluene—ethyl acetate—formic acid (8.0:1.5:0.5, v/v) as the solvent system. This system was found to give compact spots for stigmasterol at R f 0.44 ± 0.01. The optimal UAE processing parameters were the following: extraction time, 46 min; temperature, 50°C; and drug-to-solvent ratio, 528 mg/10 mL, with stigmasterol yield of 2.45 ± 0.073%. This study proves that the use of BBD for the optimization of UAE process provides more accuracy than single factorial optimization. The optimized UAE was a more efficient technique over conventional Soxhlet extraction (CSE) due to the higher stigmasterol content along with the low ingredient and time consumption. To the best of the authors’ knowledge, no studies have been published previously addressing specifically the optimization of ultrasonic extraction of stigmasterol from T. undulata bark using BBD.

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Summary

Radix Isatidis has widely useful activities including anti-virus, anti-bacterial. Tryptanthrin, indigo, and indirubin are active ingredients in R. Isatidis. Response surface methodology (RSM)-optimized infrared-assisted extraction (IRAE) was developed and combined with HPLC for simultaneous determination of tryptanthrin, indigo, and indirubin from R. Isatidis. IRAE were investigated through extraction yields of the three components and optimized by RSM. The optimum conditions were as follows: infrared power of 129 W, solid/liquid ratio of 1:40 g/mL, and irradiation time of 22.5 min. IRAE conditions obtained by RSM were not only accurate, but also had practical value reflecting the expected optimization. Subsequently, this novel IRAE method was evaluated by extraction yield of the components of R. Isatidis samples from different regions. Compared with common extraction methods including maceration extraction (ME), reflux extraction (RE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), IRAE showed higher yield with advantages of no limitation of solvent selection, low cost, convenience under optimum extraction conditions. These results suggested the potential of RSM-optimized IRAE for extraction and analysis of the water-/fat-soluble compositions of Chinese herbal medicine. A simple chromatographic separation for simultaneous determination of tryptanthrin, indigo, and indirubin from Chinese herbal medicine R. Isatidis was performed on a C18 column (Diamonsil 150 mm × 4.6 mm i.d., 5 μm) with a mobile phase isocratic consisting of methanol and water at a flow-rate of 0.8 mL min−1. The retention times of tryptanthrin, indigo, and indirubin were 15.4, 31.9, and 58.6 min, respectively. The linear equations were obtained as follows: y = −3094.5744 + 21208.792x for tryptanthrin (R = 0.9998, 0.9–18.0 μg mL−1), y = 4730.0448 + 30180.567x for indigo (R = 0.9997, 0.5–10.0 μg mL−1) and y = −6582.9045 + 67069.312x for indirubin (R = 0.9997, 0.4–8.0 μg mL−1). The result showed that RSM-optimized IRAE was a simple, efficient pretreatment method for the analysis of complex matrix.

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Summary

This paper describes the optimization and validation of an analytical method for HPLC analysis of acetazolamide in tablets using Box-Behnken design. This multivariate approach enables substantial improvement of chromatographic performance using fewer experiments, without additional cost of columns or other equipment. By use of quadratic regression analysis, equations were developed describing the behavior of the response as simultaneous functions of the selected independent variables. Accordingly, the optimum conditions were determined. For quality-control samples these were use of a C18 column with acetonitrile-phosphoric acid buffer solution (0.01 m, pH 7.1) 15:85 (ν/ν) as mobile phase at a flow rate of 1.0 mL min−1. Diode-array detection was performed at 266 nm. The method was validated, in accordance with ICH guidelines, for accuracy, precision (intra-day and inter-day coefficient of variation <2.0%), selectivity, and linearity (R 2 = 0.9993) over the concentration range 10–300 μg mL−1. The method is simple, rapid, sensitive, and accurate and the retention time is less than 4 min. The method is therefore suitable for routine quality-control monitoring of acetazolamide in tablets.

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Summary

The objective of this study was to develop a new rapid and robust high-performance thin-layer chromatographic (HPTLC) method for the estimation of rivaroxaban (RRB) in tablet dosage form using a quality by design approach. Chromatography was performed using a pre-coated silica gel aluminum plate 60 F254 (10 cm × 10 cm) as the stationary phase and toluene–methanol (7:3, V/V) as the mobile phase. Detection was carried out at 250 nm. The linear regression analysis data for the calibration plots showed r2 > 0.99 with a concentration range from 100–600 ng per band. A Box-Behnken experimental design with a response surface methodology was applied to study the effects of chamber saturation time, band length, and solvent front on the R F value and area of RRB. The R F value was predicted to be 0.63 ± 0.05 for RRB to optimize the chromatographic conditions based on the preliminary trials. The optimized HPTLC method was validated according to the International Conference on Harmonization (ICH) guideline Q2 (R1). The results of this study indicate that the quality by design (QbD) concept could be effectively applied to optimize a HPTLC method with a minimum number of experimental runs. The developed HPTLC method was successfully applied for routine analysis of RRB in tablet dosage form.

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A robust and eco-friendly stability-indicating high-performance thin-layer chromatography (HPTLC) method was developed for the stability study of thiocolchicoside using analytical quality-by-design approach. Full factorial design was used for screening potential variables affecting method development. Box‒Behnken design was used subsequently for investigation of the main, interactive, and quadratic effects of these variables on response. Four potential variables were selected on the basis of scientific knowledge for the development of a method for the stability study of thiocolchicoside. The selected potential factors, namely, volume of water (mL), saturation time (min), migration distance (mm), and volume of mobile phase (mL) were screened by 24 full factorial designs by selecting resolution as a critical method attribute. Pareto chart analysis showed that 3 variables, namely, volume of water (mL), saturation time (mm), and migration distance (mm), out of 4 potential variables were significantly affecting the response variable (resolution). Optimization with response surface methodology further clarified the relationship between critical variables and resolution using Box–Behnken design. The experimental design model was found to be quadratic, and the design space was developed on the basis of suggested model for optimization of critical method variables for maximum desirable resolution and for the development of a control strategy of the HPTLC method for the stability study of thiocolchicoside. The developed method was validated for linearity, range, specificity, precision, accuracy, limit of detection and limit of quantification as per the International Conference on Harmonization guidelines (ICH) Q2 (R1). The developed method was applied for the estimation of thiocolchicoside in its pharmaceutical dosage forms. The degradation products formed in acidic and alkaline media were isolated and characterized by their infrared (IR), nuclear magnetic resonance (NMR), and mass spectral data.

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