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The recent increase in world industrial activities has resulted in higher wastewater discharge containing potentially toxic species (PTEs) into the aquatic environment. This study aimed to evaluate the PES/mesomaterial-based mixed matrix membranes (MMMs) adsorption capacities for PTEs (Cd2+, Cr6+, Ni2+, and Pb2+) in different aqueous systems using a Doehlert design method. The MCM-41 synthesis was performed via the hydrothermal method and modified via the grafting method (NH2-MCM-41 and SH-MCM-41). The MMMs were obtained by the phase inversion method. PTEs quantification was performed by inductively coupled plasma optical emission spectrometry (ICP OES). Preliminary adsorption results showed no significant differences between the membrane adsorption capacities for the PTEs studied. The in-depth study using the PES/SH-MCM-41-based MMMs (MMM-S) showed a significant influence of the independent variable X2 (initial PTEs concentration) in the MMM-S adsorption capacities. Contrary, pH, contact time and amount of SH-MCM-41 into the MMMs does not significantly affect the adsorption process. Also, maximum adsorption capacity values of PTEs were observed in batch adsorption systems with an initial PTEs concentration of 0.332 mmol L−1, at pH 5, under agitation (300 rpm) for 39 min and using a MMM synthesized with 6% of SH-MCM-41. In the permeation system, the MMM-S2 presented the best performance with the lowest permeability rates and the highest removal percentage of PTEs. [ABSTRACT FROM AUTHOR]

This work proposes an analytical method based on digital images to indirectly determine bisulfite in vinegar samples using the colorimetric reaction between Fe(II) and the complexing agent 2,2′-bipyridine. Optimization was conducted using a multivariate methodology. Firstly, a two-level full factorial design was performed to identify the factors with significant effects on the analytical response through a two-level full factorial design (23). The studied variables included pH, 2,2′-bipyridine concentration, and sample volume. Subsequently, a Doehlert matrix was employed to establish the optimal conditions for the significant variables. The recommended procedure involved a reaction pH of 5.7 and a 0.0038 mol L−1 2,2′-bipyridine concentration, with a sample volume of 0.75 mL. The proposed method exhibited a linear response within the range of 0.45 to 300 mg L−1 of bisulfite, with detection and quantification limits of 0.15 mg L−1 and 0.45 mg L−1, respectively. The method's precision, assessed through relative standard deviation, was 3.4% (n = 10, 1.0 mg L−1). Accuracy was evaluated through recovery tests, with results ranging from 97 to 114%. Furthermore, a comparison was made between the bisulfite concentrations determined using the proposed method and those obtained through a reference method based on iodometric titration. The method was successfully applied to determine bisulfite in commercial vinegar samples. The bisulfite concentration varied from (14 ± 1) mg L−1 to (261 ± 3) mg L−1. [ABSTRACT FROM AUTHOR]

The many possible treatments and continuously changing consumer trends present a challenge when selecting antimicrobial interventions during pork processing. Thirty-five potential antimicrobials were screened at commercial working concentrations by individually adding them to miniaturized (69 cm3) disks of pork loin ends, followed by inoculation with Salmonella Typhimurium ATCC 19585. Two organic acids and nine essential oils significantly inhibited Salmonella counts on pork (p < 0.05). However, six compounds that represent different levels of significance (p < 0.05–p < 0.0001) were selected as independent variables to build a Response Surface Methodology model based on a Doehlert matrix (Doehlert Matrix—RSM): lactic acid 1.25%, formic acid 0.25%, cumin 0.25%, clove 0.25%, peppermint 0.5%, and spearmint 0.5%. The goal of the Doehlert Matrix—RSM was to study single and paired effects of these antimicrobials on the change in Salmonella over 24 h. The Doehlert Matrix—RSM model predicted that lactic acid, formic acid, cumin, peppermint, and spearmint significantly reduced Salmonella when added alone, while no significant interactions between these antimicrobials were found. A laboratory-scale validation was carried out on pork loin end slices, which confirmed the results predicted by the model. While this screening did not identify novel synergistic combinations, our approach to screening a variety of chemical compounds by implementing a miniaturized pork loin disk model allowed us to identify the most promising antimicrobial candidates to then formally design experiments to study potential interactions with other antimicrobials. [ABSTRACT FROM AUTHOR]

Hydrodynamic cavitation (HC)‐based treatments have been proposed for the degradation of phenol as a toxic pollutant. The present work aimed to optimize the degradation of phenol using HC by means of Doehlert experimental design, which has not been previously addressed. Initially, operational parameters of hydraulic characteristics of the pump, inlet pressure, solution pH, and initial concentration were optimized; later, the effects of pH solution and H2O2 loading or initial pollutant concentration on phenol degradation were explored using the Doehlert experimental design. It was observed that phenol degradation is strongly dependent on the pH of the solution. Also, the acidic condition favors the formation of hydroxyl radicals and thus, the degradation of phenol. Based on the Doehlert matrix, the 94.1% phenol degradation and 68.60% total organic carbon (TOC) were obtained in 180 min at 304.5 mg/L of hydrogen peroxide at an initial concentration of 20 mg/L, 2.0 pH, and 90 psi inlet pressure, providing a cavitational yield of 6.33 × 10−6 mg/J and minimum treatment cost of US$/L 0.13. Overall, it has been observed that HC can be a promising route for the removal of pollutants (phenol) effectively using hydrogen peroxide as an additive. [ABSTRACT FROM AUTHOR]

Diclofenac (DCF) can cause several adverse effects in the environment and it should be removed from industrial pharmaceutical wastewaters. Advanced oxidation processes (AOPs) are promising methods for the DCF degradation. But, in many cases, AOPs require acidic pH. However, at this condition, DCF precipitates, which may hinder its oxidation. Thus, in this work, some AOP were studied for the DCF degradation, especially the photo-Fenton process, applying the experimental design technique (Doehlert matrix), operating without and with pH control (between 6.5 and 7.0). As independent variables, the initial ferrous ion concentration ([Fe2+]) and the molar addition rate of H2O2 (FH2O2) were evaluated. Empirical models were proposed and optimized conditions were determined without ([Fe2+] = 0.27mmol L-1 and FH2O2 = 1.64mmol min-1) and with pH control ([Fe2+] = 1.0mmol L-1 and FH2O2 1.64 mmol L-1), with the following predicted mineralization percentages: 93% and 68%, respectively. So, photo-Fenton process without pH control presented the best performances. Furthermore, at this condition, iron concentration respects the limit value established by the Brazilian environmental legislation. That is, in this condition, additional processes, in order to remove iron ions, would not be necessary, that is very interesting for applications on an industrial scale. [ABSTRACT FROM AUTHOR]

In this work, magnetic barium phosphate (FBP) composites with different content of commercial Fe3O4 nanoparticles were easily prepared by a one-step hydrothermal method. FBP composites with a magnetic content of 3% (FBP3) were studied as the example for the removal of an organic pollutant (Brilliant Green, BG) from the synthetic medium. The adsorption study was executed under the variation of different experimental conditions, such as solution pH (5 ~ 11), dosage (0.02 ~ 0.20 g), temperature (293 ~ 323 K), and the contact time (0 ~ 60 min) on the removal of BG. For comparison purposes, the one-factor-at-a-time (OFAT) approach and Doehlert matrix (DM) were both employed to investigate the factor impacts involved. FBP3 showed a high adsorption capacity of 1419.3 ± 10.0 mg/g for at 25 °C and pH = 6.31. The kinetics study revealed the pseudo-second-order kinetic model as the best-fitted model, and the thermodynamic data fit well with the Langmuir model. The possible adsorption mechanisms involved are the electrostatic interaction and/or hydrogen bonding of PO43−...N+/C-H and HSO4−...Ba2+ between FBP3 and BG. Furthermore, FBP3 showed good easy reusability and high capacities for BG removal. Our results provide new insights for developing low-cost, efficient, and reusable adsorbent to remove BG from industrial wastewater. [ABSTRACT FROM AUTHOR]

A unique method for treating wastewater containing a commercial dye (Methyl Violet 2B) has been investigated using a hydrodynamic cavitation-based packed bed reactor (HCPBR) which consists of small glass balls. For the first time, the effects of hydrogen peroxide and iron (II) in HCPBR system were examined. In the current study, the Doehlert matrix-based design was used to optimize variables including solution pH, initial concentration of methyl violet 2B, loading of hydrogen peroxide, and iron. The development of cavity bubbles by glass balls and flow-rate-induced jets is the degrading mechanism used in this reactor. It has been observed that the complete removal of methyl violet 2B was obtained at a Fenton ratio of 0.60 and an acidic pH of 2 based on the optimal variables of the Doehlert matrix. Eventually, the pH of the solution (ranging from 1 to 3) was found to be the most important variable in the effective removal of dye. The total required cost was US $ 0.13/L for the HCPBR system based on glass marbles and US $ 0.11/L for orifice-based hydrodynamic cavitation at an optimized Fenton ratio of 0.60 under the acidic pH of 2. Overall, it was observed that HCPBR system based on glass marbles is an effective and alternative technique for the removal of methyl violet 2B dye based on energy economics and ease of fabrication compared to hydrodynamic cavitation. • Doehlert matrix surface response method used for degradation of dye in a novel HCPBR. • Complete degradation of methyl violet 2B based on design strategies. • Use of H 2 O 2 and iron successfully trigger the extent of degradation. • Comparison of HCPBR and orifice-based hydrodynamic cavitation studied. [ABSTRACT FROM AUTHOR]

Rhodamine B-containing wastewater was thoroughly treated in a photocatalytic reactor operated in a continuous mode with a zig-zag type of flow pattern. The effect of operating parameters such as pH (1−9) and initial dye concentration (10–40 ppm) on Rhodamine B degradation was studied at 1 g/L of TiO 2 and H 2 O 2 in order to determine the optimal operating parameters for combined treatment schemes. At a concentration of 10 ppm and a loading of 1 g/L TiO 2 and H 2 O 2 at a pH of 3, the maximum rate of degradation was 94.02%, and 96.68% obtained and follows pseudo-first order kinetics, respectively. Further studies of the influence of initial dye concentration and solution pH were investigated using an optimized range of TiO 2 and H 2 O 2 loading based on the surface response of the Doehlert matrix design. Based on the surface response, it was observed that the lower initial concentration with a higher loading of TiO 2 and H 2 O 2 accelerates the production of hydroxyl radicals and thereby, higher degradation of pollutants was achieved. Complete degradation with 84.76% COD reduction of Rhodamine B was observed at 0.8 g/L of H 2 O 2 and 2 pH of dye solution with a total treatment cost of US $0.009/L. Overall, the current study found that the novel photocatalytic reactor operated in a continuous mode can treat large volumes of waste water using hybrid methods with optimum catalyst loading, has high potential, and may be successfully applied for the removal of hazardous dyes from aqueous solutions with intensification benefits. [Display omitted] • First time reported Zig-zag type of flow pattern based photocatalytic reactor. • Complete degradation at a large scale of 10 L. • Efficient optimization using Doehlert matrix domain surface response. • Combined treatment of reactor with H 2 O 2 found to be economical route compared to TiO 2. [ABSTRACT FROM AUTHOR]

The solid waste of Curcuma longa rhizomes generated after its cold juice process making is mostly unused and discarded even though they can contain essential oil. Conventional techniques such as hydrodistillation can be used to extract essential oil, but this generally results in low essential oil yield and inefficient extraction time. Solid-state fermentation as a pretreatment of distillation could improve the yield of essential oil. In this study, we evaluated the effect of solid state fermentation on the yield of extraction of Curcuma longa solid wastes essential oil. The solid-state fermentation was carried out naturally without any addition of inoculum and the extraction was performed by hydrodistillation. Under experimental conditions at room temperature ( 25 ∘ C ) with a moisture content of 44% and anaerobically in the dark, the treatment of 7 days of solid state fermentation followed by 2 h of hydrodistillation provided the highest yield of 1.21% as compared to non-fermented of 0.35% and of 0.96% relative to the raw plant material representing an increase of 71% and 21% respectively. A set of experiments was then carried out by a Doehlert matrix to optimize the yield of extraction. Two independent variables, namely the distillation time and the fermentation time, were studied. Under optimal experimental conditions of 10 days and 4 h, a yield of 1.96% was obtained validating the statistical model. The solid state fermentation applied before the hydrodistillation step has been successful and proves its potential to improve the efficiency of essential oil extraction. [ABSTRACT FROM AUTHOR]

• Study shows Azolla microphylla 's potential in swine wastewater treatment. • Shorter photoperiods reduce Cu and Zn concentrations. • Longer photoperiods decrease N-NH 4 + levels. • Extended photoperiods or low cytokinin with brief LED exposure lowers SMX. • Biomass productivity reached up to 34.8 t ha-1 yr-1. Phytoremediation is an eco-friendly and affordable option for tackling wastewater pollutants. The study focused on how light-emitting diodes (LED) light exposure, measured by intensity and duration (photoperiod), along with cytokinin, impacts Azolla microphylla 's simulated swine wastewater treatment performance and biomass production. Under optimal treatment conditions, high removals of COD (89.2 % to 90.8 %), N-NH 4 + (72.6 % to 91.2 %), N-NO 3 - (84.4 % to 88.6 %), Cu (75.4 % to 86.4 %), sulfamethoxazole (77.0 % to 79.0 %), P-PO 4 3- (54.1 % to 59.9 %) and DOC (67.4 % to 71.3 %) while Zn presented a more moderate reduction (2.0 % to 9.7 %). Biomass productivity reached up to 34.8 t ha-1 yr-1. Protein production accounted for 23 % to 27 % of dry weight, while lipids ranged from 20 % to 34 % of dry biomass. Carbohydrate content varied from 8 % to 28 % of fresh weight. Higher light intensities, with both high or low values of photoperiods, and low concentrations of cytokinin were identified as optimal conditions for removal of almost all pollutants. However, pollutant removal was impacted differently by LED light and cytokinin concentration. In treatment conditions with the shortest photoperiods (8 h), the lowest residual Cu and Zn concentrations, whereas with longer photoperiods (24 h), the lowest residual concentrations of N-NH 4 + and P-PO 4 3- concentrations were recorded. On the other hand, SMX was the only parameter in which cytokinin had a clear influence on its removal, with the lowest residual concentration observed under 8-hour photoperiods combined with the lowest tested cytokinin concentrations (0.3 mg L-1). For residual COD and N-NO 3 -, no discernible pattern was evident for any of the analyzed factors. Therefore, the study demonstrates the potential for treating simulated swine wastewater using Azolla microphylla , aligned with its ability to produce biomass rich in high-value compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

The study of cigarette authenticity in Brazil is important due to increasing consumption of contraband cigarettes. Nicotine concentration is an important parameter reflecting the quality of tobacco used in the production of these cigarettes. Simple methods for this determination, which produce reduced waste, are environmentally and industrially important. The nicotine concentration of smuggled cigarette tobacco was determined by the QuEChERS method, requiring some modifications, such as decreasing the volume of the extractor solvent, changes in pH, and removal of the sample hydration step. Quantification was performed by gas chromatography using a flame ionization detector. The Doehlert matrix design was used to optimize the method. The extraction recoveries ranged from 97.5% to 99.6%, with relative standard deviation (RSD) ≤ 2.5% and limits of detection and quantification of 0.6 mg L-1 and 2.5 mg L-1, respectively. The method was sensitive and accurate for the detection and quantification of nicotine. The nicotine concentration in contraband cigarettes was found to be lower than that observed in legal cigarettes. The method was successfully applied to real samples of smuggled and legal cigarettes, providing a robust method for routine analysis and proving the need for more studies on quality control of smuggled cigarettes in Brazil.

Spiramycin (SPY) is an antibiotic belonging to the class of macrolides. Its main structurally related components are SPY I, SPY II and SPY III. The aim of this work was to optimize and validate a simple and fast method of quantification of SPY I in tablets in the presence of SPYs II and III by HPLC based on multivariate approach. Initially, different conditions were tested by means of a complete factorial design 23. Afterward, the chromatographic parameters were optimized using the Doehlert Matrix and response surface methodology, which allowed to obtain an efficient separation for SPY I with relatively short retention time (16 min). The new method was validated using phosphoric acid 0.1% and methanol (67:33, v/v) as mobile phase, flow rate at 1.0 mL min−1, C8 column (250 mm × 4.6 mm × 5 µm) as stationary phase and UV detection at 232 nm. The method proved to be selective, linear, accurate, with good reproducibility, robust, useful, simple, and efficient for the quantification of SPY I in pharmaceutical tablets. Thus, multivariate approach proved to be an excellent strategy for method optimization with a reduced number of experiments without the need for additional cost with expensive equipment or chromatographic columns. [ABSTRACT FROM AUTHOR]

The study of cigarette authenticity in Brazil is important due to increasing consumption of contraband cigarettes. Nicotine concentration is an important parameter reflecting the quality of tobacco used in the production of these cigarettes. Simple methods for this determination, which produce reduced waste, are environmentally and industrially important. The nicotine concentration of smuggled cigarette tobacco was determined by the QuEChERS method, requiring some modifications, such as decreasing the volume of the extractor solvent, changes in pH, and removal of the sample hydration step. Quantification was performed by gas chromatography using a flame ionization detector. The Doehlert matrix design was used to optimize the method. The extraction recoveries ranged from 97.5% to 99.6%, with relative standard deviation (RSD) ≤ 2.5% and limits of detection and quantification of 0.6 mg L-1 and 2.5 mg L-1, respectively. The method was sensitive and accurate for the detection and quantification of nicotine. The nicotine concentration in contraband cigarettes was found to be lower than that observed in legal cigarettes. The method was successfully applied to real samples of smuggled and legal cigarettes, providing a robust method for routine analysis and proving the need for more studies on quality control of smuggled cigarettes in Brazil. [ABSTRACT FROM AUTHOR]

In this work, a methodology for chemical speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry is proposed. Doehlert design and desirability function were used to find the optimum conditions for hydride generation (1.0 mol L−1 HCl and 0.9% m v−1 NaBH4). The accuracy of the analytical method was evaluated by analysis of reference material fly ash (BCR 176R), addition and recovery tests for inorganic As species, and comparison of independent methods for Sb determination in urban dust samples. The determination of the total concentrations of As and Sb and their inorganic species presented good accuracy, between 80 ± 1 and 101 ± 6%. Precision was expressed as the relative standard deviation and was better than 4.7% (n = 3). The limit-of-quantification values were 0.23 and 1.03 mg kg−1 for As and Sb, respectively. The methodology was applied to eight samples of dust collected in an urban area of Salvador and Jaguaquara cities, Bahia, Northeast, Brazil, with an aerodynamic size lower than 38 μm. Concentrations of pentavalent inorganic species (iAs5+ and iSb5+) in relation to trivalent species (iAs3+ and iSb3+) were found in urban dust collected in the city of Salvador, which are regarded as more toxic for both elements. The enrichment factor and geoaccumulation index (Igeo) values showed that for some samples, the concentrations of iAs and iSb presented strong enrichment and, and regarding environment, strong to moderately polluted by iAs and iSb, with an indication of anthropogenic contributions. The occurrence of these inorganic constituents in the urban area of Salvador can be related with intense industrial activities and vehicular traffic. [ABSTRACT FROM AUTHOR]

In this work, we combined a hierarchical nano-array effect of silicon nanowires (SiNWs) with a metallic surface of silver nanoparticles (AgNPs) to design a surface-enhanced Raman spectroscopy (SERS) scattering substrate for sensitive detection of Rhodamine 6G (R6G) which is a typical dye for fluorescence probes. The SiNWs were prepared by Metal-Assisted Chemical Etching (MACE) of n-Si (100) wafers. The Doehlert design methodology was used for planning the experiment and analyzing the experimental results. Thanks to this methodology, the R6G SERS response has been optimized by studying the effects of the silver nitrate concentration, silver nitrate and R6G immersion times and their interactions. The immersion time in R6G solution stands out as the most of influential factor on the SERS response. [ABSTRACT FROM AUTHOR]

The objective of this study was to optimize UV/H2O2 and ozonation systems by means of an experimental design using as a response the efficiency of the operational conditions to remove the methylene blue (MB) dye. Two classes of experimental planning were used: the Doehlert matrix (DM) and the central composite design (CCD). The most important variables for each process were hydrogen peroxide concentration, the ratio of illuminated volume/total volume of the reactor and recirculation flow rate for UV/H2O2, and ozone flow rate, consumed ozone and MB concentration for the ozonation. The DM was more efficient in optimizing the systems, since it used a smaller number of experiments and achieved similar results when compared to the CCD. After optimization, the disinfection efficiency of the systems was tested with secondary effluent evaluating the inactivation of microbiological indicators, Escherichia coli and total coliforms, using the optimized and the worst condition previously obtained with MB removal as response. The inactivation efficiencies in the optimum conditions were about 99%, allowing an efficient disinfection as well as the production of an effluent with quality to be reused according to specific legislations, while at the worse conditions, the inactivation did not reach standards for reuse. [ABSTRACT FROM AUTHOR]

Abstract A methodology combining experimental design methodology, liquid chromatography, excitation emission matrixes (EEM) and bioassays has been applied to study the performance of O 3 and O 3 /UVA-vis in the treatment of a mixture of eight phenolic pollutants. An experimental design methodology based on Doehlert matrixes was employed to determine the effect of pH (between 3 and 12), ozone dosage (02–1.0 g/h) and initial concentration of the pollutants (1–6 mg/L each). The following conclusions were obtained: a) acidic pH and low O 3 dosage resulted in an inefficient process, b) increasing pH and O 3 amount produced an enhancement of the reaction, and c) interaction of basic pH and high amounts of ozone decreased the efficiency of the process. The combination of O 3 /UVA-vis was able to enhance ozonation in those experimental regions were this reagent was less efficient, namely low pH and low ozone dosages. The application of EEM-PARAFAC showed four components, corresponding to the parent pollutants and three different groups of reaction product and its evolution with time. Bioassys indicated important detoxification (from 100% to less than 30% after 1 min of treatment with initial pollutant concentration of 6 mg/L, pH = 9 and ozone dosage of 0.8 g/h) according to the studied methods (D. magna and P. subcapitata). Also estrogenic activity and dioxin-like behavior were significantly decreased. Graphical abstract Image 10 Highlights • UV-A-vis light improves ozonation at acid pH and low O 3 concentration. • EEM is a good technique to detect intermediates in the oxidation process. • PARAFAC is able to decompose the EEM into more simple components, allowing monitoring of the generated intermediates. • This process resulted in a decrease in estrogenic and dioxine-like properties as well as detoxification (standard bioassays) [ABSTRACT FROM AUTHOR]

Abstract Based on Doehlert matrix, Silver Antimony Sulfide (AgSbS 2) thin films were prepared by chemical bath deposition (CBD) technique onto glass slides. Doehlert matrix was used to correlate between the effect of several factors and to predict the optimal condition of thickness (e = 4 μm). XRD and SEM techniques were used to study the structural, microstructural and morphological properties of the obtained film. XRD data confirm the formation of the desired phase as well as their purity. SEM analysis reveals that the obtained film was formed by truncated-plate shaped grains morphology. AgSbS 2 film shows good absorption coefficient (α) in the range of 104 cm−1. The optical band gap (E g) of this film was determined based on transmittance and reflectance data and it was found to be equal to 1.65 eV. DFT calculation was applied to investigate the electronic structure their material and to confirm the experimental optical results. The obtained AgSbS 2 film was examined as a new photocatalysis material for the degradation of MB dye. AgSbS 2 shows good photocatalytic activity with a degradation efficiency of 80% for three hours. Graphical abstract Image 1 Highlights • AgSbS 2 thin film with a definite thickness (e=4 μm) was successfully synthesized based on Doehlert matrix design. • Energy band structure, density of states and dielectric function were investigated by Density Functional Theory (DFT) calculation. • The obtained material could be useful for photovoltaic application. • AgSbS 2 thin film was tested as a new photocatalysis material. [ABSTRACT FROM AUTHOR]

Highlights • Chemometric techniques employed for optimization in food analysis are shown. • Description, advantages, and drawbacks of the experimental designs are presented. • A comparison between the response surface methodologies for food analysis has been performed. Abstract This work presents a critical review of multivariate techniques employed for optimization of methods developed in food analysis. A comparison between the response surface methodologies has been performed, it evidencing advantages and drawbacks of these. Applications of the main chemometric tools (central composite and Box Behnken designs and Doehlert matrix) often utilized for optimization of sample preparation procedures and also instrumental conditions of analytical techniques for determination of organic and inorganic species in food samples are shown. Also, a brief discussion on the use of multiple responses and robustness test in food analysis has been presented. [ABSTRACT FROM AUTHOR]

This review presents fundamentals and a critical evaluation of the multivariate optimization techniques employed by the analytical chemistry. Characteristics of the surface response methodologies (SRM) are shown and compared. Additionally, a bibliographic survey was performed in the web of science database using as keywords names of the chemometric tools utilized for experimental designs. Papers classified in the analytical chemistry area demonstrated that the two-level full factorial design had often been used for preliminary assessment of factors. For determination of critical conditions using quadratic models, the central composite design (CCD) is the technique most utilized by the analytical chemists. Remarks about standardized effects and the Pareto chart, description of the several multiple response functions employed in experimental designs, efficiencies of the SRM's and robustness tests are also discussed. [ABSTRACT FROM AUTHOR]

Mobile devices were used to quantify ethanol content—via colorimetry—in cachaça samples to great analytical precision. Ethanol from the spirits reacted with ceric ammonium nitrate (CAN) and nitric acid (NA) to form a red-colored complex. Images from the reaction were taken over time using a smartphone device and processed using software PhotoMetrix Pro® via partial least squares (PLS). A priori, Doehlert matrix was used for optimization of reagents concentration in the complexation reaction, with hierarchical cluster analysis (HCA) as estimation method and a flatbed scanner as measuring tool. When compared with the UV-VIS reference method, results from mobile device imaging presented a root mean square error of prediction (RMSEP) of 0.0677% (v/v). A t test showed there is no significant difference between methods (P < 0.05). [ABSTRACT FROM AUTHOR]

This work proposes a flow injection analysis system for sulfaguanidine determination in pharmaceutical and food samples. The method was based on the reaction of sulfaguanidine with nitronium ion to produce a colored complex whose absorbance was measured at 545 nm. The flow injection analysis system’s significant parameters were checked by a fractional factorial design 27-2 and optimization by a Doehlert matrix. The flow injection analysis system shows optimum values at 0.28, 2.00, and 0.11% (w/v) for N-naphtil ethylenediamine, ammonium sulfamate, and sodium nitrite concentrations, respectively. The possible interferents present in pharmaceutical and food samples were assessed by a multivariate technique and depicted on probability charts, indicating no significant interferences at the 95% level of confidence interval. The method showed detection and quantification limits of 0.012 and 0.039 mg L−1, an analytical frequency of 30 readings h−1 and precision always lower than 5.0% expressed as the relative standard deviation. The obtained results were in accordance with those obtained by high-performance liquid chromatography. [ABSTRACT FROM AUTHOR]

The electrochemical incineration of diethylenetriaminepentaacetic acid (DTPA) with boron-doped diamond (BDD) anode had been initially performed under galvanostatic conditions. The main and interaction effects of four operating parameters (flow rate, applied current density, sulfate concentration and initial DTPA concentration) on mineralization performance were investigated. Under similar experimental conditions, Doehlert matrix (DM) and central composite rotatable design (CCRD) were used as statistical multivariate methods in the optimization of the anodic oxidation processes. A comparison between DM model and CCRD model revealed that the former was more accurate, possibly due to its higher operating level numbers employed (7 levels for two variables). Despite this, these two models resulted in quite similar optimum operating conditions. The maximum TOC removal percentages at 180 min were 76.2% and 73.8% for case of DM and CCRD, respectively. In addition, with the aid of quantum chemistry calculation and LC/MS analysis, a plausible degradation sequence of DTPA on BDD anode was also proposed. [ABSTRACT FROM AUTHOR]

The discoloration of a textile dye derivative bromothymol blue (BTB) in aqueous solution with Fenton process (FP) has been studied. The performance of the FP depends on various operating parameters such as the initial concentration of hydrogen peroxide [H2 O2 ]0, the initial ferrous ion concentration [Fe2+]0 and the pH of the reaction medium. The optimal conditions of these variables, for the discoloration of BTB with FP, have been investigated by the use of Doehlert matrix. It has been demonstrated that under the optimal conditions ([H2 O2 ]0 = 1.61 mM, [Fe2+]0 = 0.18 mM and pH = 2.85), FP leads to a maximum discoloration yield of BTB (67.58%± 4.39) after 1 h of treatment. These values were also experimentally validated. The obtained discoloration yield was 70.4%. After 6 h of BTB treatment in aqueous solution by FP, the color removal achievement was 91.54% and, the chemical oxygen demand (COD) removal reached 63%. Carboxylic acids and inorganic ions have been identified and followed during the mineralization of BTB with FP. [ABSTRACT FROM AUTHOR]

In this work, a vortex-assisted dispersive liquid-liquid microextraction method, using an ionic liquid as the extracting solvent was developed, for the simultaneous analysis of three UV filters in different water samples. The extracting and dispersive solvents were selected in a univariate way. Then, the parameters such as the volume of the extracting and dispersive solvents, pH and ionic strength were evaluated using a full experimental design 24, followed by Doehlert matrix. The optimized method consisted of 50 μL of extracting solvent (1-octyl-3-methylimidazolium hexafluorophosphate), 700 μL of dispersive solvent (acetonitrile) and pH of 4.5. When combined with high-performance liquid chromatography, the method limit of detection ranged from 0.3 to 0.6 μg L−1, enrichment factors between 81 and 101%, and the relative standard deviation between 5.8 and 10.0%. The developed method demonstrated effectiveness in concentrating UV filters in both river and seawater samples, being a simple and efficient option for this type of analysis. [Display omitted] • The optimization of microextraction of UV-filters using DLLME was achieved through factorial designs. • The recovery values obtained in real samples were satisfactory (81–120%). • The optimized method provided limits of detection between 0.3 and 0.6 μg L−1. • The developed methodology was applied for the analysis of UV-filters in fresh and seawater samples. [ABSTRACT FROM AUTHOR]

The excessive use of pesticides and the demand for environmentally friendly compounds have driven the focus to detailed studies of the environmental destination of these compounds. Degradation by hydrolysis of pesticides, when released into the soil, can result in the formation of metabolites with potentially adverse effects on the environment. Moving in this direction, we investigated the mechanism of acid hydrolysis of the herbicide ametryn (AMT) and predicted the toxicities of metabolites through experimental and theoretical approaches. The formation of ionized hydroxyatrazine (HA) occurs with the release of the SCH 3 - group and the addition of H 3 O+ to the triazine ring. The tautomerization reactions privileged the conversion of AMT into HA. Furthermore, the ionized HA is stabilized by an intramolecular reaction that provides the molecule in two tautomeric states. Experimentally, the hydrolysis of AMT was obtained under acidic conditions and at room temperature with HA as the main product. HA was isolated in a solid state through its crystallization as organic counterions. The mechanism of conversion of AMT to HA and the experimental investigation of the reaction kinetics allowed us to determine the dissociation of CH 3 SH as the rate-controlling step in the degradation process that culminates in a half-life between 7 and 24 months under typical acid soil conditions of the Brazilian Midwest – region with strong agricultural and livestock vocation. The keto and hydroxy metabolites showed substantial thermodynamic stability and a decrease in toxicity compared to AMT. We hope that this comprehensive study will support the understanding of the degradation of s-triazine-based pesticides. [Display omitted] • Mechanism of the acid hydrolysis of Ametryn (AMT) herbicide into the hydroxiatrazine (HA). • Due to tautomerism, the HA occurs as a stable and versatile product when AMT is delivered in an acidic medium. • The conversion of AMT in HA occurs as an apparent pseudo-first-order reaction with low kinetic rates. • HA was isolated by forming salts with chloride, nitrate, mesylate, and oxalate anions. [ABSTRACT FROM AUTHOR]

EDTA is an important ligand used in many industrial products as well as in agriculture, where it is employed to assist in phytoextraction procedures and the absorption of nutrients by plants. Due to its intensive use and recalcitrance, it is now considered an emerging pollutant in water, so there is great interest in techniques suitable for its monitoring. This work proposes a method based on formation of the Mn(III)-EDTA complex after oxidation of the Mn(II)-EDTA complex by PbO 2 immobilized on cyanoacrylate spheres. A design of experiments (DOE) based on the Doehlert matrix was used to determine the optimum conditions of the method, and the influence of the variables was evaluated using a multiple linear regression (MLR) model. The optimized method presented a linear response in the range from 0.77 to 100.0 μmol L − 1 , with analytical sensitivity of 7.7 × 10 3 L mol − 1 , a coefficient of determination of 0.999, and a limit of detection of 0.23 μmol L − 1 . The method was applied using samples fortified at different concentration levels, and the recoveries achieved were between 97.0 and 104.9%. [ABSTRACT FROM AUTHOR]

Pure γ-MnS thin films have been deposited on glass slides by chemical bath deposition (CBD) method. The effect of principal experimental parameters on the film growth has been studied using the experimental design methodology. The factorial design has shown that deposition time, bath temperature and manganese precursor concentration were the main influential parameters. The prepared thin films have been characterized using the X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and optical absorption spectroscopy. The film produced crystallized in the hexagonal γ-MnS wurtzite phase and presented a preferential orientation in the (002) plane. MnS thin films, in good stoichiometric ratio and uniformly covering the glass surface, consisted of hexagonal or spherical grains. The bandgap energy is found to be in the range of 3.6–3.9 eV. [ABSTRACT FROM AUTHOR]

A headspace solid phase dynamic extraction coupled with gas chromatography-mass spectrometry (HS-SPDE-GC/MS) method for the analysis of the volatile fraction of beer was optimized using response surface methodology. A preliminary two-level full factorial design was performed, with extraction temperature, extraction strokes, and fill/eject speed as the main factors. The results showed that number of extraction strokes and temperature significantly affected the peak area response of the volatile compounds ( p ≤ 0.05). To determine the ideal conditions for extraction, a second optimization of the significant factors was carried out using a Doehlert matrix design. The optimal conditions were identified as an extraction temperature of 60 °C and 55 extraction strokes. The optimized method was applied for the analysis of five commercial beers. A variety of compounds from different chemical classes were extracted from each sample, reflecting the effective application of the SPDE method for volatile compound extraction across different beers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Factorial and Doehlert designs for ultrasound-assisted extraction optimisation. [•] The sample preparation is rapid, easy, inexpensive and reproducible. [•] Information about micronutrient concentrations in coconut milk samples is provided. [Copyright &y& Elsevier]

Highlights: [•] A CE-DAD method to separate 17 phenolic compounds from olive oil was optimised. [•] Resolution, runtime and migration time RSD values were evaluated as responses. [•] This was the first optimisation study to evaluate 37 responses simultaneously. [•] Derringer’s desirability function was used to simultaneously optimise the responses. [•] The method was validated and applied to 15 samples found in Brazilian supermarkets. [ABSTRACT FROM AUTHOR]

Abstract: After production and formulation, but before being brought to market, gasoline must conform to the specifications set by regulatory agencies. Octane numbers are among the most important physico-chemical parameters to be evaluated because they are directly related to the performance and power of the engine. This study will evaluate the influence of the gasoline’s components on its octane numbers. To identify and quantify the major organic compounds in the gasoline sold within the metropolitan area of Salvador, Bahia, Brazil, gas chromatography was used. Toluene, m-xylene, n-hexane, n-heptane and 2-methyl-2-butene were selected for this study. Several gasoline samples with different ratios of the selected compounds were formulated, and their octane numbers were measured in a CFR engine. Based on the results, the system was optimized using the Doehlert matrix as a mathematical tool, which allowed the effects of the different hydrocarbons on the octane numbers to be visualized. From the experimental results, important information has been gathered for use by the producers and formulators of gasoline to facilitate the production of a higher quality fuel with a lower environmental impact. [Copyright &y& Elsevier]

Abstract: Alternative methods for quality control in the petroleum industry have been obtained using Near-infrared Spectroscopy (NIRS) combined with multivariate techniques such as PLS (Partial Least-Square). The process of development and refinement of PLS models usually follows a nonsystematic and univariate procedure. The Standard Error of Cross Validation (SECV), the Standard Error of Prediction (SEP) and the determination coefficient (r2 regr.) are usually the only guides used in pursuit of the best model. In the present work, a novel approach was proposed using a Doehlert experimental design with three input variables (wavenumber range, preprocessing technique and regression/validation technique) varied at 5, 7 and 3 levels, respectively. Besides SECV, SEP and r2 regr., some additional response variables, such as the slope, r2 and pvalue from the external validation, as well as the number of PLS factors, were simultaneously assessed to find the optimum conditions for PLS modeling. The optimum setting for each input variable was simultaneously defined through a multivariate approach using a desirability function. With the proposed approach, the main and interaction effects could also be investigated. The methodology was successfully applied to obtain PLS models to monitor the gasoline quality through the process of product loading in trucks. To prevent product contamination or adulteration, fast prediction of key properties was obtained from FT-NIR spectra within the 7300–3900cm−1 region with SECV in the range 0.04–0.63% w/w for composition (Aromatics, Saturates, Olefins and Benzene) and 0.0008 for Relative Density 20/4°C. Each optimized PLS model was obtained with less than 40 modeling runs, demonstrating the efficiency of the proposed approach. [Copyright &y& Elsevier]

Abstract: The transesterification of triglycerides by means of alkaline catalysts is the most widely used route for biodiesel production and reaction optimisation by multivariate methods has been used for biodiesel production from different vegetable oils. However, the application of simultaneous optimisation for biodiesel production from beef tallow has received little attention. In an effort to optimize the beef tallow biodiesel production, a combination of the full factorial design and the Doehlert matrix was applied, and the effects of temperature, reaction time, catalyst concentration and alcohol:tallow molar ratio and their reciprocal interactions were assessed. The response variables under study were purity and yield of the final biodiesel product. In the selected condition [alcohol:tallow molar ratio(M)=7.5:1, catalyst:tallow mass ratio(C)=1.5%, reaction time(t)=20min and temperature=50°C], the conversion yield of tallow biodiesel was 88.4% and the purity was 99.4%. The final biodiesel obtained was analysed and showed to have good quality characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Microstructure of vitreous ceramic samples manufactured from kaolinitic-clay and feldspars raw materials from Cameroon was investigated in the range 1150–1250°C by X-ray diffraction and scanning electron microscopy and by measuring some technological properties. Moreover, the simultaneous influence of feldspars content, heating temperature and soaking time on water absorption and firing shrinkage was evaluated by adopting the response surface methodology (Doehlert matrix), using the New Efficient Methodology for Research using Optimal Design (NEMROD) software. The results show that a spinel phase, mullite, glassy phase and some amount of hematite were formed. However, the spinel phase and potassic feldspar, as compared to the sodic one, disappeared at moderate firing temperature and soaking time. Apparently, mullite developed from spinel phase, which is formed from the demixion of metakaolin. On the other hand, it is found that the effects of fluxing content and firing temperature on the measured properties were almost similar and more influent than soaking time. Antagonistic and synergetic interactions existed between the considered parameters, and their importance differed for the considered properties. By using this mathematical tool, suitable operating conditions for manufacturing vitreous bodies were determined. [Copyright &y& Elsevier]

The oxidation of organic and inorganic pollutants present in tannery effluents has been realised by electrochemical way. The influence of the electrochemical reactor parameters was carried out by the use of Doehlert matrix. The obtained results have shown that the current intensity and the electrolysis time were the main influent parameters on the removal ratio of chemical oxygen demand (COD), total organic carbon (TOC), electrochemical oxidation of trivalent chromium and sulphite ions. [Copyright &y& Elsevier]

Abstract: This paper reports the multivariate optimization of a liquid–liquid extraction procedure for the determination of 15 EPA-polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography with fluorescence detection. A Doehlert design was used to find optimum conditions for the procedure through Response Surface Methodology. Three variables (total volume of hexane, number of extraction steps and duration of such steps) were elected as factors in the optimization study. A principal component analysis (PCA) was run with optimized data, resulting in four groups of PAHs, ordered according to their molecular weight. Final working conditions were established in order to achieve a more robust methodology in relation to all fifteen PAHs under study. Best results could be observed when 77mL of hexane were divided in four consecutive extraction steps with 18min each. These experimental conditions were applied in the analysis of a spiked river water sample, and the recoveries varied between 80.9 and 106%, with an average value of 97.1±6.8%. The application of the methodology to river water showed that the method has a good average precision for the studied PAHs. [Copyright &y& Elsevier]

Abstract: The degradation of an azo dye, the direct orange 61 (DO 61), has been studied by electro-Fenton process using a Pt anode and a carbon felt cathode. The great oxidation ability of this process is due to the large production of hydroxyl radicals ( OH) in the medium from electrochemically assisted Fenton’s reaction which takes place between electrogenerated H2O2 and Fe2+ formed by cathodic reduction of O2 and Fe3+, respectively. These radicals are able to oxidize any organics until their mineralization. A factorial experimental design was used for determining the influent parameters on the DO 61 degradation in aqueous medium by electrochemically generated OH radicals. The results obtained have shown that the current intensity and the dye initial concentration were the main influent parameters on the degradation rate. Thus, under the obtained conditions, kinetic analysis of DO 61 degradation showed a pseudo-first order reaction. The optimal experimental parameters for DO 61 mineralization have been investigated by the use of Doehlert matrix. It has been demonstrated that under the optimal conditions determined by this method, electro-Fenton process can lead to a complete mineralization of the dye solution after 6h (98% of TOC removal) giving carboxylic acids and inorganic ions as final end-products before mineralization. The results show the efficiency of the electro-Fenton process to remove organic pollutants from aqueous medium. [Copyright &y& Elsevier]