Two-level Fractional Factorial Design Research Articles

Experimental design approach for the quantitative analysis of multicomponents by single marker and HPLC fingerprinting of Thunbergia laurifolia aqueous extract.

Thunbergia laurifolia is used in traditional Thai medicine to reduce fever and treat mouth ulcers. However, the quantitative analysis of chemical markers has not yet been officially defined. The objective of this study is to develop a high-performance liquid chromatography (HPLC) method using a design of experiment (DoE) for the quantitative analysis of multicomponents by single marker (QAMS) and fingerprinting of the T. laurifolia aqueous extract. Critical variables were screened using a two-level fractional factorial design, followed by the optimization of the selected variables using a central composite design. The validated method was applied for quality assessment based on QAMS and fingerprinting of the extract. Optimum conditions of DoE for the analysis of caffeic acid, vicenin-2, and rosmarinic acid were determined. The relative correction factors for caffeic acid and vicenin-2 were calculated using rosmarinic acid as an internal reference standard, and their contents in 30 samples were determined. The differences between the external standard method (ESM) and QAMS were compared. No significant difference was observed in the quantitative determination, proving the consistency QAMS and ESM. HPLC fingerprints of T. laurifolia were established with 8 of 12 characteristic peaks that were structurally characterized using HPLC-diode array detection-electrospray ionization/tandem mass spectrometry. The similarity of the fingerprints in all samples was ≥0.74, and the pattern recognition of the characteristic peaks was satisfied. The proposed method efficiently detected multiple components of the T. laurifolia extract. Thus, the method is beneficial in providing references for enhancing the quality control of other herbal medicines.

Fluconazole Microemulsions: Preparation, Statistical Optimization by Two-Level Factorial Design, and Physicochemical Evaluation

Background:: Candida albicans is the yeast that causes the fungal infection known as candidiasis. One of the standard methods for treating candida is the application of fluconazole. The low solubility of fluconazole in aqueous media is a big problem in the use of this agent. Novel drug delivery systems, such as microemulsions, could be applied to solve this problem. The main aim of this study was to perform statistical optimization of the formulation and physicochemical characterization of fluconazole microemulsion. Methods:: Optimization of the microemulsion formulation was done by using experimental design software, and then fluconazole was loaded onto the best formulation at a concentration of 1 % w/w. The physiochemistry of the microemulsion formulation was assessed by pH measurement, rheology measurement, simultaneous thermal analysis, and Scanning Electron Microscopy (SEM). Results:: The two-level fractional factorial design application demonstrated the optimum formulation to consist of surfactant, co-surfactant, oil content, and water, comprising 58%, 27%, 10%, and 5% of the formulation, respectively. Desirable thermal mass was observed up to 150°C. The formulation was a non-Newtonian shear-thinning liquid in terms of viscosity, with a reported pH between 6.5-7. Conclusion:: Considerably stable, high-quality microemulsion formulations containing fluconazole are presented, which are applicable for antifungal skin candidiasis treatment in clinical trials.

Analysis of tensile behavior of Nylon-CF fabricated using material extrusion

Nylon-CF is an important thermoplastic 3D printable material that can be used to develop high-quality functional parts with slight modifications in low-cost machines like material extrusion (MEX) technology. This paper investigates the tensile behavior of Nylon-CF samples produced by material extrusion. The influence of seven process parameters is studied on response characteristics. The Taguchi design is used to investigate the effect of process parameters on Young’s modulus and yield strength of specimens fabricated as per ASTM D-638. A two-level fractional factorial design supplements the L27 design results. The results show that the layer height, infill pattern, density, and raster angle significantly affect the tensile behavior. The apparent Young’s modulus is also significantly affected by the interaction between layer height, infill pattern, and infill density.

Optimization of synergistic extraction of calcium ion via an emulsion liquid membrane using dicyclohexano-18-crown-6 and D2EHPA carriers: A design of experiment study

Calcium ions play an important role in various fields, with their stable isotopes being of particular importance in medical research and in the production of superheavy metals. Emulsion liquid membranes (ELMs) offer a promising alternative to conventional methods for metal ion extraction due to their remarkable mass transfer rates. However, the effectiveness of crown ethers as carriers in ELM processes has been hindered by their limited ability to extract calcium ions. The aim of this study is to optimize the extraction of calcium ions using an ELM containing dicyclohexano-18-crown-6 (DC18C6) as a carrier and di-(2-ethylhexyl) phosphoric acid (D2EHPA) as a synergistic carrier. To achieve this objective, a two-level fractional factorial design (FFD) was initially implemented to screen the key factors. Subsequently, a central composite design (CCD) was employed to optimize the four identified key factors. The CCD method yielded a quartic regression model for calcium extraction efficiency. The optimum values were: DC18C6 concentration at 0.035 mol/L, feed phase pH of 4, a feed/emulsion volume ratio of 2.3, and a W/O/W stirring time of 23.4 min. Under these optimal conditions, DC18C6 exhibited negligible extractability, while D2EHPA achieved an extraction efficiency of 62.2%. Combining both carriers, however, significantly increased the extraction efficiency to 97.3%, indicating a synergistic effect that enhanced the extraction of Ca(II) ions. Furthermore, the selectivity of the ELM towards Ca(II) ions was examined in binary solutions of Ca(II)/Li(I), Ca(II)/Na(I), and Ca(II)/Mg(II). The ELM demonstrated selectivity for Ca(II) over Li(I), Na(I), and Mg(II) with separation factors of 4.4, 2.0, and 8.1, respectively. It is noteworthy that the combination of carriers positively influenced calcium selectivity exclusively in the Ca(II)/Mg(II) solution. Conversely, no noticeable effect on selectivity was observed in the Ca(II)/Li(I) solution, while the combination had an adverse effect on calcium selectivity in the Ca(II)/Na(I) solution.

Multi-Criteria Decision-Making of Countermeasure Combination for Mitigating the Stack Effect in High-Rise Office Building

Energy loss and performance deterioration caused by the stack effect are emerging issues in high-rise office buildings (HROB). However, a single countermeasure may not completely remove the stack effect problems, so combinations of countermeasures are often considered in building commissioning or retrofit projects to achieve the desired results. Therefore, a comprehensive study on combinations is necessary for the final decision-making. In this study, a multi-criteria decision-making model is proposed, which is utilized to calculate the ranking of countermeasure combinations for the final decision-making index by assigning weights and conducting comprehensive analysis on four criteria: infiltration energy loss, maximum pressure difference, investment cost, and implementation resistance. Based on a two-level Fractional-Factorial design (FFD), the interaction effects between countermeasures were verified, and the regression models of infiltration energy loss and maximum pressure difference were obtained as well. The investment cost and implementation resistance were defined according to the investigation and survey. An Analytic Hierarchy Process (AHP) was applied to establish the weights of each criterion. A weighted Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method was applied to establish the decision-making index. Through the case study of a HROB located in northern China, it was concluded that the ideal combination can reduce infiltration and pressure difference by 26.88% and 87.58%, respectively, with low-level investment costs and implementation resistance. The results indicate that the multi-criteria model provides a comprehensive ranking of countermeasure combinations, which can serve as a quantitative basis for the final decision-making. Furthermore, this multi-criteria decision-making approach can be extended to other buildings in other regions.

A quality by design approach for the synthesis of palmitoyl-L-carnitine-loaded nanoemulsions as drug delivery systems

Nanoemulsions (NE) are lipid nanocarriers that can efficiently load hydrophobic active compounds, like palmitoyl-L-carnitine (pC), used here as model molecule. The use of design of experiments (DoE) approach is a useful tool to develop NEs with optimized properties, requiring less experiments compared to trial-and-error approach. In this work, NE were prepared by the solvent injection technique and DoE using a two-level fractional factorial design (FFD) as model was implemented for designing pC-loaded NE. NEs were fully characterized by a combination of techniques, studying its stability, scalability, pC entrapment and loading capacity and biodistribution, which was studied ex-vivo after injection of fluorescent NEs in mice. We selected the optimal composition for NE, named pC-NEU, after analysis of four variables using DoE. pC-NEU incorporated pC in a very efficient manner, with high entrapment efficiency (EE) and loading capacity. pC-NEU did not change its initial colloidal properties stored at 4 °C in water during 120 days, nor in buffers with different pH values (5.3 and 7.4) during 30 days. Moreover, the scalability process did not affect NE properties and stability profile. Finally, biodistribution study showed that pC-NEU formulation was predominantly concentrated in the liver, with minimal accumulation in spleen, stomach, and kidneys.

Determining the range of process parameters for friction stir welding using steepest ascent approach

In the present research work, friction stir welding (FSW) of dissimilar aluminium alloy series (i.e., 7xxx and 8xxx) is performed at various rotational speeds (1900–2500 rpm), welding speeds (60–80 mm min−1), and tilt angle (1.8°–2.4°) to find out the optimal ranges of process parameters for main experiments. The experiments are designed as per the steepest ascent approach by using three factors two-level fractional factorial design. The tensile strength is considered as an output parameter for deciding the optimal levels of process parameters. The graphical analysis of the steepest ascent provides the optimal ranges of process parameters, i.e., 1818 to 2104 rpm for rotation speed, 42 to 63 mm min−1 for tool travel speed and 0.9 to 1.8° for tool tilt angle. Furthermore, microstructural and fractography analyses are also carried out to study the morphology and nature of joints. The microstructure shows the different welding zones such as the nugget zone, thermomechanical affected zone, and heat affected zone. The fractography analysis reveals the ductile nature of joint.

Parameter screening of a VPSA cycle with automated breakthrough control for carbon capture

Vacuum pressure swing adsorption (VPSA) is an efficient technology that can be used for carbon capture from combustion stationary sources. However, VPSA is a cyclic and complex process that involves several operational variables that can have an influence on the key performance indicators: purity, recovery, productivity, and energy consumption. Typically, the concentration of carbon dioxide (CO2), flowrate and gas temperature may vary depending on the excess of air on the combustion process, type of fuel, purity of the fuel, the efficiency of the combustion equipment, the energetic demand, among many other. An industrial CO2 capture technology must be able to adapt to these possible process changes. In this work, a new automated control strategy was applied, instead of using the conventional time scheduling, in a seven-step VPSA process for CO2 capture. The column breakthrough points were used to control the feeding, rinse and purge steps (stop points) together with three flowrates used in these steps and the vacuum pressure used in the regeneration step. A two-level fractional factorial design 27−3, was used to study the influence of these control variables on the key performance indicators, applying the analysis of variance (ANOVA). The results show that the critical parameters of this new control strategy were the vacuum pressure and the feed and rinse stop points. With the automated breakthrough control, it was possible to capture 81 % of the CO2 from a simulated dry flue gas obtaining a CO2 purity of 98 %, a productivity of 0.26 kgCO2/(kgadsorbent·h) and an energy consumption of 0.18 kWh/kgCO2.

Nanosized belite phases obtained by flame spray pyrolysis: Assessment of process conditions on the mineralogy and reactivity

The synthesis of highly reactive dicalcium silicate phases by the alternative method flame spray pyrolysis (FSP) was investigated. Five main conditions of the synthesis process were varied and analyzed by applying a two-level fractional factorial design 25–2 resolution III, with a replica of a chemical system defined by a mixture of Ca(O2CCH2CH3)2/Si(C2H5O))4 dissolved in ethanol/water/triethanolamine to evaluate the formation of polymorphs and their reactivity. For this, a physical and mineralogical characterization was carried out that included X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) specific surface area analysis, thermogravimetric analysis (TGA-DSC), and transmission electron microscopy (TEM). The investigation reveals that the process parameters have a remarkable importance on the final properties of the samples, favoring the formation of belite phases with high reproducibility. The hydraulic samples present a complete hydration reaction after 24 h of contact with water, giving a clear image of the potential of this technique for the development of highly reactive materials that can be part of sustainable construction in the future.

Experimental design approach, screening and optimization of system variables, analytical method development of flurbiprofen in nanoparticles and stability-indicating methods for high-pressure liquid chromatography

BackgroundThe development of chromatographic method and the validation of a sensitive, simple, efficient, and reversed-phase high-performance liquid chromatography (RP-HPLC) approach were adopted for the drug flurbiprofen (FBP) in nanoparticles formulation by using a design of experiment (DoE). The critical method variables (CMVs) were screened using a statistical two-level fractional factorial design (FFD) followed by optimization of the selected CMVs that influence the analytical responses (ARs) of the RP-HPLC process by using two-level full factorial design.ResultsStatistical models are used to investigate the effects of system factors including column temperature, flow rate, and methanol in orthophosphoric acid (OPA) on the dependent responses, retention time, peak area, tailing factor, and theoretical plates in HPLC. The ideal column temperature (25 °C), flow rate (1 ml/min), and mobile phase (methanol 85 percent v/v in 0.05 percent OPA in water) were selected independently from the response surface at three levels (1, + 1, and 0) for further validation at constant solvent pH 2.75. Optimized method in the RP-HPLC resulted a retention time of 4.75 min, a peak area of 3975.12, a tailing factor of 0.73, and a total of 9697.7 theoretical plates followed by validation in accordance with the current ICH recommendations Q2 (R1). Linearity, precision, accuracy, assay, limit of detection (LOD), limit of quantification (LOQ), and robustness were all included in validation. The calibration curve was linear (r2 = 0.9997, slope = 70.72) for the concentration of 10 to 50 µg/ml, with a limit of detection of 0.14 µg/ml. Furthermore, stability-indicating methods demonstrate that drug degradation is highest in the presence of basic circumstances (about 96.49%), followed by oxidation (about 76.41%), and acidic conditions (about 48.12%), whereas drug is stable in some extent under neutral, photo (sunlight), and dry heat conditions.ConclusionsEffect of independent variables on dependent responses was screened and optimized by using statistical software design. A method for drug development could be successfully implemented for the estimation of drug in nanoparticles formulation as well as for the routine analysis in bulk and pharmaceutical formulations. The high recovery and low relative standard deviation support the suitability of proposed method that could be employed.Graphical

Multi-commutated flow system for inorganic selenium speciation in infusion tea samples by chemical vapor generation atomic fluorescence spectrometry

This work proposes an automated strategy for the inorganic selenium speciation in infusion tea samples, employing an MSFIA-CVG-AFS system and sodium tetrahydroborate for chemical vapor generation. The selenium total is determined after an online prereduction step of selenium (VI) to selenium (IV) in alkaline media, using a UV reactor with a 15 W Hg lamp. Selenium (IV) is quantified directly on the sample, and selenium (VI) is determined by the difference between the total selenium and selenium (IV) concentrations. The optimization of the chemical parameters: hydrochloric acid – hydrobromide acid solution concentration, potassium iodide concentration, sodium hydroxide concentration, and sodium tetrahydroborate concentration was performed using a (24−1) two-level fractional factorial design. The validation parameters were determined for total selenium and selenium (IV), and the results found were: limits of detection and quantification of 0.05 and 0.18 μg L−1, respectively; a linear range of 0.18–5.0 μg L−1, precision expressed as the relative standard deviation of 2.1% for a sample number of 10, for both analytes. The system allows the speciation analysis with an injection throughput of 15 injections per hour. This analytical method was applied for inorganic selenium speciation in nine infusions of tea samples purchased commercially in supermarkets in Palma de Mallorca City, Spain. The concentrations of selenium (IV) and total selenium varied from 0.2 to 0.6 μg L−1 and 0.4–2.0 μg L−1, respectively. The accuracy method was evaluated using spike tests, and the recoveries achieved varied from 91 to 111%.

Evaluation of thermosensitive chitosan hydrogel containing gefitinib loaded cellulose acetate butyrate nanoparticles in a subcutaneous breast cancer model

In the present study, gefitinib loaded cellulose acetate butyrate nanoparticles (Gnb-NPs) were prepared and then incorporated into thermo-sensitive chitosan/β-glycerophosphate hydrogels for intratumoral administration in mice bearing breast cancer. Accordingly, Gnb-NPs were prepared using the solvent evaporation process and optimized by applying a two-level fractional factorial design. Properties of NPs, including particle size, zeta potential (ZP), polydispersity index (PdI), encapsulation efficiency (EE) % and drug loading (DL) %, were investigated; the optimized Gnb-NPs were then loaded in chitosan hydrogels (Gnb-NPs-Hydrogel). The formulated Gnb-NPs-Hydrogel was assessed in terms of gelling time, release behavior, injectability, swelling and degradation behavior. The anti-cancer efficacy of Gnb-NPs-Hydrogel was evaluated in vitro against the 4 T1 breast cancer cell line and in vivo in breast tumor bearing mice. The optimized formulation showed spherical particles with the size of 156.50 ± 2.40 nm, PdI of 0.20 ± 0.002, ZP of −4.90 ± 0.04 mV, EE of 99.77 ± 0.09 % and DL of 20.59 ± 0.05 %. Incorporating Gnb-NPs into the hydrogel led to the decrease of the drug release rate. Gnb-NPs-Hydrogel displayed a greater cytotoxic effect in comparison to the free Gnb and Gnb-Hydrogel in 4 T1 cancer cells. Furthermore,intratumorallyinjectedGnb-NPs-Hydrogel showed the strongest antitumor efficacy in vivo. The superior performance of Gnb-NPs-Hydrogel, thus, demonstrated its potential for the treatment of breast cancer.

An empirical analysis of homicides in Mexico through Machine Learning and statistical design of experiments

Homicide is one of the most important mortality causes that has reduced the Mexican life expectancy. That is why the aim of this work is to identify some sociodemographic and economic factors that can help explain homicides in Mexico and measure their impact, assuming the current conditions prevail. To do that, several Machine Learning (ML) methods were evaluated. The C5.0 model is best suited for the data at hand. After fine-tuning the algorithm, we used the estimated model to identify the main factors that explain homicides. Among these factors, eleven were selected that can be influenced by direct changes in domestic public policy, laws and/or regulations. These were used as input in a two-level fractional factorial Statistical Design of Experiments (DOE) to estimate their main effects and possible interactions. Although several of these factors had statistically significant effects on homicide rate, the one that had the biggest and direct impact from a practical perspective, was the Rule of Law Index (RLI). In fact, if we assumed that all states had the median RLI of 0.37, implementing domestic policies and procedures to move them all to the best RLI level could significantly reduce homicide rates.

Bioremediation of Textile Industrial Effluents Using Nutraceutical Industrial Spent: Laboratory-Scale Demonstration of Circular Economy.

This research reports the first-ever study on abundantly available, environmentally friendly, low-cost and ready-for-use Nutraceutical Industrial Cumin Seed Spent (NICUS) as an innovative adsorbent for bioremediation of a bisazo Acid Red 119 (AR119) dye, a probable mutagen from textile industrial effluents (TIEs). The experiment at the laboratory scale is designed to suit the concepts of sustainability and valorisation under the domain of circular economy. The experimental qe value obtained was 96.00 mg g−1. The optimised conditions of parameters are as follows: pH of 2; adsorption time, 210 min; adsorbent dosage, 0.300 g L−1; particle size, 175 µM; initial dye concentration, 950 mg L−1; orbital shaking, 165 rpm and temperature, 50 °C, producing an impressive value of 748 mg of dye adsorbing on 1 g of dry NICUS. The adsorption capacity of NICUS obtained from the quadratic model developed for process optimisation gave values of 748 mg g−1. As a prelude to commercialisation, five variables that affect the adsorption process were experimentally studied. For the feasibility and efficiency of the process, a two-level fractional factorial experimental design (FFED) was applied to identify variables that influence the adsorption capacity of NICUS. The identified variables were applied to scale experiments by three orders. Nine isotherm models were used to analyse the adsorption equilibrium data. The Vieth–Sladek adsorption isotherm model was found to be the best fit. The pseudo-second-order reaction was the appropriate mechanism for the overall rate of the adsorption process. Mechanistic studies related to mass transfer phenomena were more likely to be dominant over the diffusion process. Techniques such as SEM, FTIR and CHN analysis were used to characterise NICUS. The dye-adsorbed NICUS obtained as “sludge” was used as a reinforcing material for the fabrication of composites using plastic waste. The physicomechanical and chemical properties of thermoplastic and thermoset composite using dye-adsorbed NICUS were evaluated and compared with NICUS composites. Prospects of integrating Small and Medium Enterprises (SMEs) into the circular economy of Nutraceutical Industrial Spent (NIS) are discussed.

Sensitivity analysis of self-centering column base connections with shape memory alloy bolts

This paper performs a statistical sensitivity analysis of the cyclic response of self-centering column base connections equipped with shape memory alloy (SMA) bolts. Experimentally validated finite element models are first developed for self-centering column base connections with SMA bolts. The effect of fifteen potentially influential design factors on the cyclic response of self-centering column base connections is statistically assessed using a two-level fractional factorial design. Moreover, the limit state behavior of column base connection models is evaluated and discussed by considering four limit states, including decompression, yield-like point, self-centering, and ultimate limit state. The sensitivity analysis results show that the column axial compressive force, SMA bolt diameter, and column web slenderness are the most influential factors affecting at least four response parameters with percentage contributions greater than 80%. The results from this study confirm the self-centering capability of column base connections with SMA bolts. The self-centering limit state is reached in 44% of the designed connection models; however, it is shown that reaching this limit state does not impact the self-centering capability of the connections. All the connection models can recover their undeformed shape with minimal residual rotations. The results also indicate that only 30% of the column base connections provide a minimum equivalent viscous damping ratio of 8%. Therefore, the results highlight the need for improving the energy dissipation capability of column base connections for seismic applications.

Paper mulberry fruit juice: a novel biomass resource for bioethanol production

By way of broadening the use of diverse sustainable bioethanol feedstocks, the potentials of Paper mulberry fruit juice (PMFJ), as a non-food, sugar-based substrate, were evaluated for fuel ethanol production. The suitability of PMFJ was proven, as maximum ethanol concentration (56.4 g/L) and yield (0.39 g/g) were achieved within half a day of the start of fermentation, corresponding to very high ethanol productivity of 4.7 g/L/hr. The established potentials were further optimally maximized through the response surface methodology (RSM). At the optimal temperature of 30 °C, yeast concentration of 0.55 g/L, and pH of 5, ethanol concentration, productivity, and yield obtained were 73.69 g/L, 4.61 g/L/hr, and 0.48 g/g, respectively. Under these ideal conditions, diverse metal salts were afterward screened for their effects on PMFJ fermentation. Based on a two-level fractional factorial design, nutrient addition had no positive impact on ethanol production. Thus, under the optimal process conditions, and without any external nutrient supplementation, bioethanol from PMFJ compared favorably with typical sugar-based energy crops, highlighting its resourcefulness as a high-value biomass resource for fuel ethanol production.Graphical

Optimised Reduction of Surgical Gloves Pinholes using Forward Search Method

This research investigates the factors that affect the existence of pinholes in surgical gloves during the manufacturing process. Since eight factors affect the existence of pinholes in surgical gloves, a two-level fractional factorial design 28-4 was used to study the main effects and the first-order interactions of the multiple variables. Multiple linear regressions are used to model the data. This paper also examines the presence of influential points in the data using the influential measures in linear regression such as Cook’s Distance, DFFITS, DFBETAS, Studentized Residual, Standardized Residual, Hadi's measure, and the robust forward search. The impact of influential points is further assessed through deletion of potential influential points and model selection using adjusted R2, information criterion, and stepwise selection to see whether these influential points significantly improved the existing model.

Design of experiment analysis on tensile properties of PLA samples produced by fused filament fabrication

The fused filament fabrication (FFF) is one of the most common forms of 3D printing with many hobbyists and as well as professional printers adopting this technology. With numerous printing parameters available for each print, having the knowledge to optimize the printing process to obtain a custom mechanical properties is clearly advantageous. This paper aims to analyze the elastic mechanical properties of PLA specimens manufactured through FFF process. To reduce experimental runs, the L27 Taguchi orthogonal array was used to analyze the influence of seven parameters, (i) infill pattern, (ii) layer height, (iii) infill density, (iv) printing velocity, (v) raster orientation, (vi) outline overlap, and (vii) extruder temperature, and three interactions, (i) infill pattern/layer height, (ii) infill pattern/infill density and, (iii) layer height/infill density on both Young’s modulus (E) and yield strength (Rp0.2). To remove any doubt about certain parameters, a two-level fractional factorial design with four factors (24–1) was used to supplement Taguchi approach. Results show that the infill density, infill pattern, printing velocity, and printing orientation are the most influential parameters, whereas layer height, extruder temperature, and outline overlap have no significant influence on Young’s modulus and Yield strength. We show that the analysis of interactions could play a leading role in optimization parameters by removing doubt concerning some parameters. This work could be further developed to propose a model to help designers to obtain either tailor-made or a robust mechanical property with minimum variation and uncertainty in product.

Multiple response optimization of ultrasound-assisted procedure for multi-element determination in Brazilian wine samples by microwave-induced plasma optical emission spectrometry

In the present work, a method was developed, optimized, and validated for the determination of aluminum, manganese, lead, copper, cadmium, and zinc by microwave-induced plasma optical emission spectrometry of wine samples from the São Francisco Valley, northeastern Brazil. The samples were subjected to a sonochemical treatment aiming at the degradation of the sample matrix. To optimize the analytical procedure, initially, a two-level fractional factorial design was used to study five experimental variables and determine which ones significantly affected the analytical response. In a second step, the significant variables were optimized using the Doehlert matrix as the response surface methodology and the desirability function as a strategy to optimize multiple responses. The optimum conditions established were concentrations of nitric acid (2.3 mol L−1) and hydrogen peroxide (9%). The developed method is simple, fast, and precise, has a low operational cost and low limits of detection and quantification. The accuracy confirmed by spike tests with recoveries ranging from 104 to 118% and comparative analysis of the results obtained using the proposed method and digestion total procedure. The method was applied for multi-element determination in three wine samples.

Bioenergy Production through Mono and Co-Digestion of Tomato Residues

The agro-industry of tomato generates three types of residues: ripe rotten tomato (unfit for consumption) (RT), green (unripe) tomato (GT), and tomato branches including leaves and stems (TB). These materials are commonly wasted or used as feed for livestock. Energy production through anaerobic digestion is an alternative way to manage and simultaneously valorise these materials. Initially, the operating conditions of mono anaerobic digestion were investigated using RT. Thus, a design of experiments based on a two-level fractional factorial design with resolution V was performed to determine the factors that affect biochemical methane potential (BMP). The substrate to inoculum ratio (SIR), total volatile solids concentration (VSt), working volume (WV), presence of nutrients (Nu), and the pre-incubation of the inoculum (Inc) were investigated. The results showed that SIR is the most important factor. The maximum BMP for RT was 297 NmLCH4/gVS with SIR = 0.5; tVS = 20 g/L; WV = 20%; no pre-incubation and the presence of nutrients. Using these optimum operating conditions, co-digestion was investigated through a mixture design approach. The substrates RT and GT presented similar BMP values, whereas TB led to a significantly lower BMP. Indeed, when high concentrations of TB were used, a significant decrease in methane production was observed. Nonetheless, the highest BMP was achieved with a mixture of 63% RT + 20% GT + 17% TB, with a production of 324 NmLCH4/gVS, corresponding to a synergetic co-digestion performance index of about 1.20. In general, although the substrate RT generates the highest BMP, the mixture with GT did not impair the methane yield. Overall, the co-digestion of tomato residues must be conducted with SIR close to 0.5 and the content of tomato branches in the reaction mixture should be kept low (up to 20%).