Doehlert matrix: a chemometric tool for analytical chemistry—review

Sulfur fractionation using high-resolution continuum source molecular absorption spectrometry with calcium and hydrophobic palladium nanoparticles as chemical modifiers

The unprecedented use of high-resolution continuum source molecular absorption spectrometry (HR-CS MAS) for the fractionation of organic and inorganic sulfur (S) species through monitoring the CS molecule is presented here. Two separate methods for determining organic (CSorg) and inorganic (CSino) sulfur were developed to work sequentially. The optimized temperature program for both methodologies has two pyrolysis steps and one vaporization step (1st Tpyr: 1800 and 2ndTpyr: 800 °C, and Tvap: 2500 °C). The fractionation was achieved by implementing hydrophobic Pd NPs and Ca as chemical modifiers for the CSorg and CSino methods. Method development was performed by applying different statistical models, allowing the definition of optimal conditions for the chemical modifier mass, and minimizing the S species interconversion, i.e., Doehlert design, and central composite design. The limits of detection (LoD) for CSorg and CSino were 2.4 and 2.1 mg L-1, respectively. Recovery tests evaluated the method's specificity and accuracy; over 92 % recovery was found for both CSorg and CSino. Thus, the proposed methods offer a reliable alternative for fractionating organic and inorganic S by using HR-CS MAS.

Effects of LED lights and cytokinin on the phytotreatment of simulated swine wastewater by Azolla spp.: Pollutant removal and biomass valorization

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-NH4+ (72.6 % to 91.2 %), N-NO3- (84.4 % to 88.6 %), Cu (75.4 % to 86.4 %), sulfamethoxazole (77.0 % to 79.0 %), P-PO43- (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-NH4+ and P-PO43- 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-NO3-, 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.

Pseudomonas rhizophila S211 as a microbial cell factory for direct bioconversion of waste cooking oil into medium-chain-length polyhydroxyalkanoates

The present study examines the use of waste cooking oil (WCO) as a substrate for medium-chain-length polyhydroxyalkanoates (mcl-PHA) production by Pseudomonas rhizophila S211. The genome analysis revealed that the S211 strain has a mcl-PHA cluster (phaC1ZC2DFI) encoding two class II PHA synthases (PhaC1 and PhaC2) separated by a PHA depolymerase (PhaZ), a transcriptional activator (PhaD) and two phasin-like proteins (PhaFI). Genomic annotation also identified a gene encoding family I.3 lipase that was able to hydrolyze plant oils and generate fatty acids as favorable carbon sources for cell growth and PHA synthesis via β-oxidation pathway. Using a three-variable Doehlert experimental design, the optimum conditions for mcl-PHA accumulation were achieved in 10% of WCO-based medium with an inoculum size of 10% and an incubation period of 48 h at 30 °C. The experimental yield of PHA from WCO was 1.8 g/L close to the predicted yield of 1.68 ± 0.14 g/L. Moreover, 1H nuclear magnetic resonance spectroscopy analysis confirmed the extracted mcl-PHA. Overall, this study describes P. rhizophila as a cell factory for biosynthesis of biodegradable plastics and proposes green and efficient approach to cooking oil waste management by decreasing the cost of mcl-PHA production, which can help reduce the dependence on petroleum-based plastics.

Search for Biomarkers for the LC-ESI-QqQ Determination of Phenoxymethylpenicillin Treatment in Raw or Cooked Chicken Meat Samples

The high standards required for food safety make it necessary to trace unambiguously raw or cooked food products coming from medicated animals. Nevertheless, considering the lability of β-lactams and their degradation, the detection of the presence of antibiotics in meat either raw or submitted to a cooking process is not easily affordable. To achieve this goal, an evaluation of the effect of common domestic cooking procedures, such as boiling and grilling, on the fate of phenoxymethylpenicillin (PENV) residues was performed. Finally, in this work, the penilloic acid from PENV (MET02) and the corresponding penicilloic acid (PENV-HYDRO) are suggested as biomarkers. These compounds present the highest relative abundances 5 days after the treatment was stopped (5PT) and show enough thermal stability to be considered suitable biomarker candidates for the pharmacological treatment instead of the parent compound. Nevertheless, the peaks corresponding to MET02 are significantly more intense than those for PENV-HYDRO, which makes preferential the use of MET02 to perform the control of samples.

Optimization of adaptation parameters from adhesion cell culture in serum-containing media to suspension in chemically defined media by superlative box design

A new design of experiments-superlative box design (SBD), was adopted to optimize the adaptation of Chinese hamster ovary cells from adhesion culture to serum-free suspension culture. It is a general trend to use a serum-free medium instead of a serum-containing medium. The advantage of serum-free medium (chemically defended) is that it does not contain unknown components and avoids safety issues. SBD requires fewer experiments while ensuring a sufficient number of experiments and uniformity in the distribution of experiments amongst all the factors. Six factors were considered in this experimental design with 43 runs plus three more repeating center runs. The cell line was adapted to serum-free media by gradually reducing serum, and from adherent to suspension by rotating at various speeds in a shake flask. Response surface methodology was applied to find the optimum condition. The optimized cell density reached 7.02 × 105 cells/mL, calculated by the quadratic model. Experiments validated the predicted cell adaptation with the maximum cell density. Three suspension runs were selected randomly to perform in the bioreactor to validate cell stability and production homogeneity. This study provides an efficient method to transfer adherent cells to suspension cells and is the first to successfully use SBD and establish a parameter quadratic optimization model.

Classification of produced water samples using class-oriented chemometrics and comprehensive two-dimensional gas chromatography coupled to mass spectrometry

Produced water (PW) is a type of wastewater that arises during oil and gas production. Due to its potential environmental impact, PW is one of the most closely monitored forms of wastewater in the petroleum industry. The total oil and grease (TOG) content in the water is a crucial parameter for assessing the environmental impact of PW. Traditional methods for analyzing TOG in PW can be time-consuming and may not be compatible with green chemistry principles. In this study, an alternative method for classifying PW samples is proposed using a one-class classifier (OCC) model, which has proven useful for classification problems. To achieve this goal, headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography (GC×GC) were employed to obtain TOG profiles from PW. A series of simulated PW samples containing TOG were generated using a mixture design comprising four petrochemicals at concentrations ranging from 10 mg L-1 to 50 mg L-1. The polydimethylsiloxane (PDMS) fiber showed the most representative extraction of analytes. The optimization of the HS-SPME method was performed using a Doehlert design with two variables, and the final conditions were set at 80 °C and 70 min for extraction temperature and time, respectively. A pixel-based data approach was used to implement data-driven soft independent modeling by class analogy (DD-SIMCA). Although DD-SIMCA is a developing area in GC×GC studies, the proposed model produced outstanding results with a sensitivity of 94.3 %, specificity of 95.0 %, and accuracy of 94.5 %, considering the complex and broad compositional range of the modeled mixtures. These findings demonstrated the effectiveness of the OCC model approach in classifying PW samples according to environmental regulations.

A Data-Driven Approach to Molten Salt Synthesis of N-Rich Carbon Adsorbents for Selective CO2 Capture

Applying a design of experiments methodology to the molten salt synthesis of nanoporous carbons enables inverse design and optimization of nitrogen (N)-rich carbon adsorbents with excellent CO2 /N2 selectivity and appreciable CO2 capacity for carbon capture via swing adsorption from dilute gas mixtures such as natural gas combined cycle flue gas. This data-driven study reveals fundamental structure-function relationships between the synthesis conditions, physicochemical properties, and achievable selective adsorption performance of N-rich nanoporous carbons derived from molten salt synthesis for CO2 capture. Taking advantage of size-sieving separation of CO2 (3.30 Å) from N2 (3.64 Å) within the turbostratic nanostructure of these N-rich carbons, while limiting deleterious N2 adsorption in a weaker adsorption site that harms selectivity, enables a large CO2 capacity (0.73 mmol g-1 at 30.4 Torr and 30 °C) with noteworthy concurrent CO2 /N2 selectivity as predicted by the ideal adsorbed solution theory (SIAST = 246) with an adsorbed phase purity of 91% from a simulated gas stream containing only 4% CO2 . Optimized N-rich porous carbons, with good physicochemical stability, low cost, and moderate regeneration energy, can achieve performance for selective CO2 adsorption that competes with other classes of advanced porous materials such as chemisorbing zeolites and functionalized metal-organic frameworks.

Development of a green liquid-phase microextraction procedure using a customized device for the comprehensive determination of legacy and current pesticides in distinct types of wine samples

In this work, we reported the development of a novel, simple, and green liquid-phase microextraction (LPME) procedure based on the use of a customized device for the determination of 47 multiclass pesticides in red, white, and rosè wine samples by GC-MS. The main parameters that affect the LPME were optimized using multivariate statistical techniques such as centroid-simplex mixture design and Doehlert design. The optimal conditions were: 70 μL of toluene as extractor solvent; concentration of NaCl (2.7%, m v-1); pH 4; and an extraction time of 30 min, under vortex-assisted agitation (at 500 rpm). After validation, it was possible to obtain LOQ values as low as 7.63 ng L-1 and extraction recoveries ranging from 81.7% to 119% for most of the target pesticides. The application of exploratory analysis, specifically Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), provided evidence indicating contamination in the different types of wine samples, primarily by systemic fungicides.

Use of Doehlert Matrix as a Tool for High-Throughput Screening of Organic Acids and Essential Oils on Miniaturized Pork Loins, Followed by Lab-Scale Validation That Confirmed Tested Compounds Do Not Show Synergistic Effects against Salmonella Typhimurium

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.

Using Data-Driven Learning to Predict and Control the Outcomes of Inorganic Materials Synthesis

The design of inorganic materials for various applications critically depends on our ability to manipulate their synthesis in a rational, robust, and controllable fashion. Different from the conventional trial-and-error approach, data-driven techniques such as the design of experiments (DoE) and machine learning are an effective and more efficient way to predictably control materials synthesis. Here, we present a Viewpoint on recent progress in leveraging such techniques for predicting and controlling the outcomes of inorganic materials synthesis. We first compare how the design choice (statistical DoE vs machine learning) affects the type of control it can offer over the resulting product attributes, information elucidated, and experimental cost. These attributes are supported by discussing select case studies from the recent literature that highlight the power of these techniques for materials synthesis. The influence of experimental bias is next discussed, followed finally by our perspectives on the major challenges in the widespread implementation of predictable and controllable materials synthesis using data-driven techniques.

Laser powder bed fusion (LPBF) of commercially pure titanium and alloy development for the LPBF process

Laser powder bed fusion (LPBF) of titanium or titanium alloys allows fabrication of geometrically more complex and, possibly, individualized implants or osteosynthesis products and could thus improve the outcome of medical treatments considerably. However, insufficient LPBF process parameters can result in substantial porosity, decreasing mechanical properties and requiring post-treatment. Furthermore, texturized parts with anisotropic properties are usually obtained after LPBF processing, limiting their usage in medical applications. The present study addresses both: first, a design of experiments is used in order to establish a set of optimized process parameters and a process window for LPBF printing of small commercially pure (CP) titanium parts with minimized volume porosity. Afterward, the first results on the development of a biocompatible titanium alloy designed for LPBF processing of medical implants with improved solidification and more isotropic properties are presented on the basis of conventionally melted alloys. This development was performed on the basis of Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au, a near-α alloy presented by the authors for medical applications and conventional manufacturing, with yttrium and boron additions as additional growth restriction solutes. In terms of LPBF processing of CP titanium grade 1 powder, a high relative density of approximately 99.9% was obtained in the as-printed state of the volume of a small cubical sample by using optimized laser power, scanning speed, and hatch distance in combination with a rotating scanning pattern. Moreover, tensile specimens processed with these volume settings and tested in the as-printed milled state exhibited a high average yield and ultimate tensile strength of approximately 663 and 747 N/mm2, respectively, combined with a high average ductility of approximately 24%. X-ray diffraction results suggest anisotropic mechanical properties, which are, however, less pronounced in terms of the tested specimens. Regarding alloy development, the results show that yttrium additions lead to a considerable microstructure refinement but have to be limited due to the occurrence of a large amount of precipitations and a supposed higher propensity for the formation of long columnar prior β-grains. However, phase/texture and microstructure analyses indicate that Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au-0.1B-0.1Y is a promising candidate to achieve lower anisotropy during LPBF processing, but further investigations on LPBF printing and Y2O3 formation are necessary.

Multivariate optimization of dispersive liquid-liquid microextraction using ionic liquid for the analysis of ultraviolet filters in natural waters

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.

Automated method using direct-immersion solid-phase microextraction and on-fiber derivatization coupled with comprehensive two-dimensional gas chromatography high-resolution mass spectrometry for profiling naphthenic acids in produced water

Naphthenic acids (NAs) are naturally occurring organic acids in petroleum and are found in waste waters generated during oil production (produced water, PW). Profiling this class of compounds is important due to flow assurance during oil exploration. Compositional analysis of PW is also relevant for waste treatment to reduce negative impacts on the environment. Here, comprehensive two-dimensional gas chromatography coupled with high-resolution mass spectrometry (GC×GC-HRMS) was applied as an ideal platform for qualitative analysis of NAs by combining the high peak capacity of the composite system with automated scripts for group-type identification based on accurate mass measurements and fragmentation patterns. To achieve high-throughput profiling of NAs in PW samples, direct-immersion solid phase microextraction (DI-SPME) was selected for extraction, derivatization and preconcentration. A fully automated DI-SPME method was developed to combine extraction, fiber rinsing and drying, and on-fiber derivatization with N-methyl-N‑tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA). Data processing was based on filtering scripts using the Computer Language for Identifying Chemicals (CLIC). The method successfully identified up to 94 NAs comprising carbon numbers between 6 and 18 and hydrogen deficiency values ranging from 0 to -4. The proposed method demonstrated wider extraction coverage compared to traditional liquid-liquid extraction (LLE) - a critical factor for petroleomic investigations. The method developed also enabled quantitative analysis, exhibiting detection limits of 0.5 ng L^-1 and relative standard deviation (RSD) at a concentration of NAs of 30 µg L^-1 ranging from 4.5 to 25.0%.

The improvement of guava (Psidium guajava) juice quality using crude multi-enzymatic extracts obtained from yeasts

Guava juice is cloudy and viscous, which hinders filtration, decreases yield, and causes the loss of quality after its processing and during storage. This study aimed to evaluate enzymatic treatment effects using crude multi-enzymatic extracts (CME) obtained from Rhodotorula mucilaginosa, Rhodotorula orizycola, and Pseudozyma sp. produced by submerse fermentation in the extraction of juice guava. Mixtures of 100 ml of guava pulp and multi-enzymatic extracts proposed by Doehlert planning were incubated under constant agitation at 150 rpm and 50°C, and a Doehlert design was applied as a multivariate optimization strategy. The optimal conditions using the multi-enzymatic extract were: 0.4% (v/v) of CME for 131 min for the multi-enzymatic treatment using Pseudozyma sp.; 3.0% (v/v) of CME for 154 min using the R. mucilaginosa CME; and 5.0% (v/v) of CME for 90 min using R. oryzicola. The maximum viscosity reduction values for the juices treated with the CME of yeasts were 10.33%, 86.38%, and 13.33% for the juices treated with the CME of Pseudozyma sp., R. mucilaginosa, and R. orizycola, respectively. The physical-chemical properties were improved after treatment with CMEs, yielding a reduction of clarity, increase of total soluble solids and reducing sugars, and decreasing the acidity (pH) for all treatments with enzymatic extracts of all strains. The yeasts studied showed a potential for CME production to be applied to juice, improving the quality of the juice, and R. mucilaginosa was the most prominent yeast due to most significant reduction of viscosity in guava juice.

Multivariate optimization applied to the synthesis and reuse of a new sugarcane bagasse-based biosorbent to remove Cd(II) and Pb(II) from aqueous solutions

This study reports the use of multivariate tools to optimize the synthesis of a new agricultural-based biosorbent derived from sugarcane bagasse (SB) for the removal of Cd(II) and Pb(II) from aqueous solutions, as well as to optimize the process of desorption of these ions from the spent biosorbent using an acidic solution. The effects of the reaction parameters temperature (T), time (t), and the ratio of 1,2,3,4-butanetetracarboxylic acid dianhydride (BTCAD) to raw SB (wBTCAD wraw SB-1) on the chemical modification of raw SB with BTCAD and on the equilibrium adsorption capacity (qe) for Cd(II) and Pb(II) were investigated by application of a 23 Doehlert experimental design (DED), followed by optimization using a statistical desirability tool to produce the best adsorbent in terms of performance and cost. The best reaction condition was wBTCAD wraw SB-1 of 4.0 g g-1, t of 1 h, and T of 70 ºC. The optimal synthesis condition resulted in a modified sugarcane bagasse (MSB) that provided qe values for Cd(II) and Pb(II) of 0.50 and 0.61 mmol g-1, respectively, obtained under the following conditions: 0.311 mmol Cd(II) L-1, 0.632 mmol Pb(II) L-1, pH 5.0, 4 h, 0.2 g L-1 MSB, 130 rpm, and 25 °C. The desorption of Cd(II) and Pb(II) from MSB was investigated by a 22 DED, with optimization using the desirability tool to obtain the best desorption condition in terms of HNO3 solution concentration ([Formula: see text]) and t. The desorption efficiencies for Cd(II) and Pb(II) were 90 ± 4% and 88 ± 3%, respectively, obtained using 0.7 mol L-1 HNO3, t of 42 min, and 1.0 g L-1 MSB-M(II) (M = Pb or Cd). Infrared spectroscopy was used to investigate the natures of the interactions involved in the adsorption of Cd(II) and Pb(II) on MSB, as well as possible changes in the chemical structure of MSB after desorption. The synthesis of MSB can be performed under mild reaction conditions (t = 1 h, T = 70 ºC), and the solvents used can be recovered by distillation. BTCA is commercially available at moderate cost and can alternatively be obtained employing microbial succinic acid, metal-free catalysis, and modest use of petrochemical feedstocks. Furthermore, MSB can be reused, which could contribute to increasing the economic feasibility of water and wastewater treatment processes.

Optimization of GC-MS Method for Analysis of Basil Essential Oils from Algeria: Design of Experiments and Exploratory Pattern Recognition

An optimization procedure for multistep temperature-programmed capillary gas chromatography was developed for the analysis of basil essential oil. The current study was planned after performing the following three steps: a preliminary chromatographic study, primary parameter screening, and final method optimization by using 23 factorial and Doehlert designs (DOE). The optimized conditions were obtained by using a split ratio of $1/2$ , a gas flow rate of 1.3 mL/min, and a heating rate of 2°C/min. This set of conditions was later used for the optimization of the final method. The optimal experimental conditions were subsequently obtained by response surface optimization (isotherm duration = 6.2 min and slope = 1.06°C/min). The compositions of essential oils from six varieties of basil (Ocimum B. (1), Ocimum B. purpurescens opal (2), Ocimum B. minimum (3), Ocimum. B. cinnamon (4), Ocimum B. (marcellas) (5), and Ocimum B. Citriodora (6)) grown in four regions of Algeria (Ouargla, south of Algeria (O); Mostaganem, west of Algeria (M); Algiers, north of Algeria (A), and Constantine, east of Algeria (C)) were determined. A statistical study was performed based on hierarchical ascending classification and principal component analysis to elucidate the relationships between the basil varieties, their region of growth, and their essential oil composition. In addition to identifying several chemotypes, such as linalool, linalool/eugenol, linalool acetate, methyl eugenol, methyl chavicol, eugenol, methyl cinnamate E, and geraniol, a new compound, namely, octadecenamide (Z) (oleamide), was detected in the essential oil of Ocimum basilicum L. from Algiers (A1).

Multivariate experimental design provides insights for the optimisation of rechloramination conditions and water age to control disinfectant decay and disinfection by-product formation in treated drinking water

The stability of drinking water disinfectant residuals is known to be influenced by multiple variables. To evaluate the effects of various influencing variables on disinfectant stability, a multivariate analysis of chloramine decay and associated disinfection by-products (DBPs) formation was investigated in a series of bench-scale experiments. Of nine water quality variables previously identified, monochloramine dose, pH, and bromide concentration were selected as key water quality variables based on previous investigations and modelling. Co-effects of these key variables on monochloramine decay and formation of 33 halogenated and nitrogen-containing DBPs were investigated using response surface experimental design. Rechloramination conditions, including monochloramine dose, pH and bromide concentration, were optimised via a 3-factorial multivariate analysis of monochloramine stability in post-treatment drinking water. Effects of influencing variables on disinfectant decay and DBP formation were assessed and graphically presented as response surfaces with minimal experiments using Doehlert matrix experimental design compared to other multivariate experimental designs. Concentrations of trihalomethanes (THMs), haloacetic acids (HAAs), and N-nitrosamines were found to increase with water age, whereas opposite phenomenon was observed in the net production of haloacetonitriles (HANs). Increasing pH was found to stabilise monochloramine but it could cause DBP speciation to shift. Furthermore, increasing bromide concentration elevated Br-DBP formation. In bromide-containing water, pH = 7.8-8.0 should be considered as higher pH increases Br-THMs formations and lower pH increases formations of Br-HAAs and Br-HANs. However, water age or pH has insignificant impacts on DBP formation after significant monochloramine decay or at low initial monochloramine dose. These findings indicate that effective combined control measures to maintain monochloramine stability should include the application of high monochloramine dose (>1.5 mg-Cl₂.L^-1) under conditions of moderate to high pH (pH = 7.8-8.0) and minimal bromide concentration. This study provides relevant insights to water utilities aiming to design effective disinfectant residual management strategies for controlling monochloramine decay and DBP formation.

Development of a simplified spectrophotometric method for nitrite determination in water samples

A new eco-friendly, rapid, and sensitive spectrophotometric method was developed to determine small quantities of nitrite, based on a diazotization mechanism. In an acidic solution, sulfathiazole was first diazotized with sodium nitrite, followed by adding phosphate buffer to form a yellow-colored compound, which showed maximum absorption at 450 nm, without the need for the addition of coupling agents such as N-(1-naphthyl) ethylenediamine. The effects of reagents amount and the optimal experimental conditions were examined by Central composite design. The simplified method presented a wide linear range of nitrite between 0.091 μg mL^-1 and 1.47 μg mL^-1, a sensitivity of 0.447 Abs mL µg^-1, a determination coefficient of 0.998, and a low limit of detection of 0.053 μg mL^-1. The simplified method was found to be comparable to the Griess method. It was evaluated for the measurements of nitrite using the accuracy profile approach. The validation procedure results established that 80% of the future results would be within the acceptability limit of 10% over the validation domain ranging from 0.174 μg mL^-1 to 1.37 μg mL^-1. The developed method was furtherly applied in the determination of nitrite using a developed paper-based analytical device that detected a nitrite concentration of 3 μg mL^-1 which is considered by the World Health Organization to be the maximal permissible limit of nitrite in drinking water.

Analysis of short-chain bioactive peptides by unified chromatography-electrospray ionization mass spectrometry. Part II. Comparison to reversed-phase ultra-high performance liquid chromatography

In the first part of this study, a unified chromatography (UC) analysis method, which is similar to supercritical fluid chromatography (SFC) but with wide mobile phase gradients of pressurized CO₂ and solvent, was developed to analyse short-chain peptides, with UV and mass spectrometry (MS) detection. In this second part, the method is compared to a reference reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) method, based on the analysis of 43 peptides, including 10 linear peptides and 33 cyclic ones. First, the orthogonality between the two methods was examined, based on the retention patterns. As the UC method was developed on a polar stationary phase (Ascentis Express OH5), the elution orders and selectivities were expected to be significantly different from RPLC on a non-polar stationary phase (ACQUITY CSH C18). Secondly, the success rate of the methods was examined, based on successful retention / elution of the peptides and the absence of observed co-elutions between the main peak and impurities. A successful analysis was obtained for 81% of the peptides in UC and 67% in RPLC. Thirdly, the performance of the methods for the intended application of impurity profiling of peptide drug candidates was assessed, based on the comparison of peak purities, the number of impurities detected and the thorough examination of impurity profiles. Excellent complementarity of the two methods for the specific task of impurity profiling, and for the separation of isomeric species was observed, with only one isomeric pair in this set remaining unresolved. The method sensitivity was however better with RPLC than UC. Finally, the operational costs in terms of solvent cost per analysis were the same between the two methods.

Extraction Induced by Emulsion and Microemulsion Breaking for Metal Determination by Spectrometric Methods - A Review

This review focuses on extraction induced by the destabilization of emulsified systems combined with spectrometric techniques for metal analysis in oily samples. This approach is based on the formation and breaking of an emulsion (extraction induced by emulsion breaking - EIEB) or microemulsion (extraction induced by microemulsion breaking - EIMB) to transfer the analytes from the oil sample to the aqueous phase, which is separated in the process. Its simplicity, speed, and low cost have contributed to its growing popularity among researchers. However, the potential of EIEB and EIMB is far from being fully exploited. Therefore, this paper aims to provide relevant information to expand the applicability of these methods. The principle of the methods is discussed, and a brief description of emulsified systems is presented. The parameters affecting the extraction efficiency and calibration strategy are also critically discussed. Furthermore, the analytical applications of the methods are reviewed. Trends and opportunities in this field are also considered.

Dodecylpyridinium chloride removal by persulfate activation using UVA radiation or temperature: experimental design and kinetic modeling

The degradation of dodecylpyridinium chloride (DPC) by SO₄^•- and HO^• radicals, generated by UVA and thermal-activated persulfate (PS) was investigated. Temperatures of 30-50°C were used for the heat activation of PS. In the case of UVA/PS, the effects of [PS]₀ and specific photon emission rate (E_P,0) were studied through a Doehlert design coupled with statistical analysis and response surface methodology. The results showed high DPC removal (99.8%) and pseudo-first-order degradation rate (k_obs = 0.0971 min^-1) for [DPC]₀ = 4.60 ± 0.11 mg L^-1, [PS]₀ = 7.75 mmol L^-1, and E_P,0 = 0.437 μmol photons L^-1 s^-1, with a major role of SO₄^•- radicals in comparison with HO^•. The specific DPC degradation rate found under these conditions was higher than that observed for thermal activation at 50°C and [PS]₀ = 5.5 mmol L^-1 (k_obs = 0.0712 min^-1) over the same time, although complete DPC removal was also achieved in the latter. The positive effect of E_P,0 on DPC degradation by the UVA/PS process depends on PS concentrations, with k_obs values increasing linearly with [PS]₀ in the range 7.75-10 mmol L^-1, whereas lower E_P,0 values can be compensated by increasing [PS]₀ up to about 10 mmol L^-1, without significant scavenging. The second-order rate constants of DPC with HO^• and SO₄^•-, estimated by comprehensive kinetic modeling, were 8.26 × 10⁹ and 4.44 × 10⁹ L mol^-1 s^-1, respectively. Furthermore, higher [DPC]₀ would negatively affect the DPC degradation rate by the UVA/PS process, while 62% DPC removal was obtained in WWTP water, which can be considered good given the complexity of the real matrix. Finally, our results shed light on the possibility of using available UVA radiation (4.5%) in solar irradiance on the Earth's surface, making this treatment process more sustainable and cost-effective.

A GC-SSIM-CRDS system: Coupling a gas chromatograph with a Cavity Ring-Down Spectrometer for onboard Twofold analysis of molecular and isotopic compositions of natural gases during ocean-going research expeditions

Carbon dioxide (CO₂) and methane (CH₄) are two climate-sensitive components of gases migrating within sediments and emitted into the water column on continental margins. They are involved in several key biogeochemical processes entering into the global carbon cycle. In order to perform onboard measurements of both the molecular and stable carbon isotope ratios (δ¹³C) of CH₄ and CO₂ of natural gases during oceanic cruises, we have developed a novel approach coupling gas chromatography (GC) with cavity ring-down spectroscopy (CRDS). The coupled devices are connected to a small sample isotope module (SSIM) to form a system called GC-SSIM-CRDS. Small volumes of natural gas samples (<1 mL) are injected into the GC using a headspace autosampler or a gas-tight syringe to separate the chemical components using a Shincarbon ST packed column and for molecular quantification by thermal conductivity detection (TCD). Subsequently, CO₂ from the sample is trapped in a 7 mL loop at 32 °C before being transferred to the CRDS analyzer for sequential determination of the stable carbon isotope ratios of CH₄ and CO₂ in 24 min. The loop is an open column (without stationary phase). This approach does not require the use of adsorbents or cooling for the trapping step. Optimization of the separation step prior to analysis was focused on the influence of two key separation factors 1) the flow of the carrier gas and 2) the temperature of the oven. Our analytical system and the measurement protocol were validated on samples collected from gas seeps in the Sea of Marmara (Turkey). Our results show that the GC-SSIM-CRDS system provides a reliable determination of the molecular identification of CH₄ and CO₂ in complex natural gases, followed by the stable carbon isotope ratios of methane and carbon dioxide.

Thermostable trypsin-like protease by Penicillium roqueforti secreted in cocoa shell fermentation: Production optimization, characterization, and application in milk clotting

The increased demand for cheese and the limited availability of calf rennet justifies the search for milk-clotting enzymes from alternative sources. Trypsin-like protease by Penicillium roqueforti was produced by solid-state fermentation using cocoa shell waste as substrate. The production of a crude enzyme extract that is rich in this enzyme was optimized using a Doehlert-type multivariate experimental design. The biochemical characterization showed that the enzyme has excellent activity and stability at alkaline pH (10-12) and an optimum temperature of 80°C, being stable at temperatures above 60°C. Enzymatic activity was maximized in the presence of Na⁺ (192%), Co²⁺ (187%), methanol (153%), ethanol (141%), and hexane (128%). Considering the biochemical characteristics obtained and the milk coagulation activity, trypsin-like protease can be applied in the food industry, such as in milk clotting and in the fabrication of cheeses.

Optimal degradation of organophosphorus pesticide at low levels in water using fenton and photo-fenton processes and identification of by-products by GC-MS/MS

This study aiming to determine the optimal conditions to degrade an organophosphate pesticide diazinon (DZN) at low levels concentrations (μg.mL^-1) and to identify the by-products generated. The degradation processes utilized were the Fenton and photo-Fenton. The iron concentration [Fe²⁺], the hydrogen peroxide concentrations [H₂O₂], and the solution pH are the investigated parameters. The Doehlert three-parameter experimental design was applied to model and optimize both degradation processes. The mathematical models suggested were assessed and validated by application of analysis of variances ANOVA. In the case of Fenton process, the greatest yield of degradation (79%) was obtained at [Fe²⁺] = 35 mg.L^-1 (0.63 mmol.L^-1), [H₂O₂] = 423 mg.L^-1 (12.44 mmol.L^-1), and pH = 5.0. In photo-Fenton process, the maximum yield of degradation (96%) was obtained under the conditions of [Fe²⁺] = 29 mg.L^-1 (0.52 mmol.L^-1), [H₂O₂] = 258 mg.L^-1 (7.59 mmol.L^-1) and pH = 4.6. QuEChERS (quick, easy, cheap, effective, rugged, and safe), as extraction technique, and GC-MS/MS (gas chromatography coupled with triple quadrupole mass spectrometry) were used to identify the by-products degradation of DZN. The identified compounds are diazoxon, triethyl phosphate, triethyl thiophosphate, 2-isopropyl-5-ethyl-6-methylpyrimidine-4-ol, 2-isopropyl-6-methylpyrimidine-4-ol (IMP) and hydroxydiazinon. Three possible pathways for diazinon degradation have been suggested and the hydroxylation, oxidation and hydrolysis are likely probable degradation mechanisms.

A green and sustainable method for monitoring the chemical composition of soybean: an alternative for quality control

INTRODUCTION

Soybean is one of the most important crops in the world, an important source of isoflavones, and used to treat various chronic diseases. High-performance liquid chromatography (HPLC), associated with multivariate experiments and green solvents, is increasingly used to develop comprehensive elution methods for quality control of plants and derivatives.

OBJECTIVE

The work aims to establish a HPLC fingerprinting method for soybean seeds employing Green Chemistry Principles, a sustainable solvent with low toxicity, and a comprehensive experimental design that reduces the number of experiments.

MATERIALS AND METHODS

The fingerprinting method was optimised through Design of Experiments by evaluating seven chromatographic variables: initial percentage of ethanol (X1), final percentage of ethanol (X2), temperature (X3), percentage of acetic acid in water (X4), flow rate (X5), run time (X6), and stationary phase (X7). The dependent variable was the number of peaks (n).

RESULTS

An initial factorial design for screening purposes indicated that the most significant quantitative parameters to separate soybean metabolites were X1 and X3. The conditions were optimised by a Doehlert design, to obtain a HPLC-PAD (photodiode array detector) fingerprinting of the polar extract of soybean seeds with the markers identified by liquid chromatography electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS). The optimum fingerprinting method was determined as 5-55% of ethanol in 30 min, at 35°C, and flow rate of 1 mL/min, by employing a phenyl-hexyl column (150 mm × 4.6 mm).

CONCLUSION

The developed green method enabled markers of soybean to be separated and identified and could be an eco-friendlier alternative for soybean quality control that covered seven Green Analytical Chemistry Principles.

Statistical Multiobjective Optimization of Thiospinel CoNi2S4 Nanocrystal Synthesis via Design of Experiments

Thiospinels, such as CoNi₂S₄, are showing promise for numerous applications, including as catalysts for the hydrogen evolution reaction, hydrodesulfurization, and oxygen evolution and reduction reactions; however, CoNi₂S₄ has not been synthesized as small, colloidal nanocrystals with high surface-area-to-volume ratios. Traditional optimization methods to control nanocrystal attributes such as size typically rely upon one variable at a time (OVAT) methods that are not only time and labor intensive but also lack the ability to identify higher-order interactions between experimental variables that affect target outcomes. Herein, we demonstrate that a statistical design of experiments (DoE) approach can optimize the synthesis of CoNi₂S₄ nanocrystals, allowing for control over the responses of nanocrystal size, size distribution, and isolated yield. After implementing a 2^5-2 fractional factorial design, the statistical screening of five different experimental variables identified temperature, Co:Ni precursor ratio, Co:thiol ratio, and their higher-order interactions as the most critical factors in influencing the aforementioned responses. Second-order design with a Doehlert matrix yielded polynomial functions used to predict the reaction parameters needed to individually optimize all three responses. A multiobjective optimization, allowing for the simultaneous optimization of size, size distribution, and isolated yield, predicted the synthetic conditions needed to achieve a minimum nanocrystal size of 6.1 nm, a minimum polydispersity (σ/d̅) of 10%, and a maximum isolated yield of 99%, with a desirability of 96%. The resulting model was experimentally verified by performing reactions under the specified conditions. Our work illustrates the advantage of multivariate experimental design as a powerful tool for accelerating control and optimization in nanocrystal syntheses.

Doehlert design in the optimization of procedures aiming food analysis - A review

In the present paper is presented a review on the application of Doehlert design in the optimization of some of the steps of analytical procedures aimed the analysis of food samples. The theoretical principles and the main characteristics of this type of design are described. In addition, the main advantages and limitations of Doehlert design over other designs (Central Composite Design and Box-Behnken) and its application in the area of food analysis are discussed. Finally, to illustrate its potential, some examples of Doehlert design application in other areas of food chemistry without the purpose of analytical determination will be briefly presented.

Degradation of pesticides present in tomato rinse water by direct photolysis and UVC/H2O2: optimization of process conditions through sequential Doehlert design

The degradation of three pesticides, azoxystrobin (AZO), difenoconazole (DFZ), and imidacloprid (IMD), commonly found in the tomato rinse water, was studied through UVC (251-257 nm) and UVC/H₂O₂ photolysis. The results showed that direct photolysis follows pseudo-first-order kinetics, with total AZO and IMD removals within 15 min, using 21.8 and 28.6 W m^-2, respectively, while the highest percentage of DFZ degradation was 51.7% at 28.6 W m^-2 UVC. The estimated quantum yields were 0.572, 0.028, and 0.061 mol Einstein^-1 for AZO, DFZ, and IMD, respectively. With regard to UVC/H₂O₂, total pesticide removal was achieved after 10 min, while optimal treatment conditions in relation to the pesticide removal rates, estimated through the sequential Doehlert design, were about [H₂O₂]₀ = 130 mg L^-1 and 26 W m^-2. Cytotoxicity and genotoxicity assays carried out with Allium cepa, for real industrial tomato rinse water sampled from washing belts did not show abnormalities during cell division, with total pesticides degradation after 15 min, demonstrating the potential application of the UVC/H₂O₂ process as a viable localized treatment with a focus on the possible reuse of treated water.

Integration of Response Surface Methodology (RSM) and Principal Component Analysis (PCA) as an Optimization Tool for Polymer Inclusion Membrane Based-Optodes Designed for Hg(II), Cd(II), and Pb(II)

An optimization of the composition of polymer inclusion membrane (PIM)-based optodes, and their exposure times to metal ion solutions (Hg(II), Cd(II), and Pb(II)) was performed using two different chromophores, diphenylthiocarbazone (dithizone) and 1-(2-pyridylazo)-2-naphthol (PAN). Four factors were evaluated (chromophore (0.06-1 mg), cellulose triacetate (25-100 mg) and plasticizer amounts (25-100 mg), and exposure time (20-80 min)). Derringer's desirability functions values were employed as response variables to perform the optimization obtained from the results of three different processes of spectral data treatment: two full-spectrum methods (M1 and M3) and one band-based method (M2). The three different methods were compared using a heatmap of the coefficients and dendrograms of the Principal Component Analysis (PCA)reductions of their desirability functions. The final recommended M3 processing method, i.e., using the scores values of the first two principal components in PCA after subtraction of the normalized spectra of the membranes before and after complexation, gave more discernable differences between the PIMs in the Design of Experiments (DoE), as the nodes among samples appeared at longer distances and varyingly distributed in the dendrogram analysis. The optimal values were time of 35-65 min, 0.53 mg-1.0 mg of chromophores, plasticizers 34.4-71.9 of chromophores, and 62.5-100 mg of CTA, depending on the metal ion. In addition, the method yielded the best outcomes in terms of interpretability and an easily discernable color change so that it is recommended as a novel optimization method for this kind of PIM optode.

Design of Experiment on Concrete Mechanical Properties Prediction: A Critical Review

Concrete mix design and the determination of concrete performance are not merely engineering studies, but also mathematical and statistical endeavors. The study of concrete mechanical properties involves a myriad of factors, including, but not limited to, the amount of each constituent material and its proportion, the type and dosage of chemical additives, and the inclusion of different waste materials. The number of factors and combinations make it difficult, or outright impossible, to formulate an expression of concrete performance through sheer experimentation. Hence, design of experiment has become a part of studies, involving concrete with material addition or replacement. This paper reviewed common design of experimental methods, implemented by past studies, which looked into the analysis of concrete performance. Several analysis methods were employed to optimize data collection and data analysis, such as analysis of variance (ANOVA), regression, Taguchi method, Response Surface Methodology, and Artificial Neural Network. It can be concluded that the use of statistical analysis is helpful for concrete material research, and all the reviewed designs of experimental methods are helpful in simplifying the work and saving time, while providing accurate prediction of concrete mechanical performance.

Combination of supramolecular solvent-based microextraction and ultrasound-assisted extraction for cadmium determination in flaxseed flour by thermospray flame furnace atomic absorption spectrometry

This study describes the development of a new analytical method for cadmium determination in flaxseed flour based on ultrasound-assisted extraction combined with supramolecular preconcentration followed by thermospray flame furnace atomic absorption spectrometry. Cadmium from flaxseed flour was extracted by ultrasound-assisted radiation in acid medium (1.5 mol L-1HNO3) followed by liquid-liquid microextraction of the acid extractwith dodecanoic acid/THF supramolecular solvent using diethyl dithiophosphate as a chelating agent. The limit of detection and the analytical curve range were found to be 0.10 μg L-1 and 0.35 to 20.0 μg L-1, respectively. The cadmium concentration in the flaxseed flours was ranged from 0.11 ± 0.04 to 0.79 ± 0.03 µg g-1. The proposed methodis considered simpler, faster, low-cost, and environmentally friendly compared to procedures currently used for the determination of cadmium based on acid digestion and using graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

Enhancement of Iron-Based Photo-Driven Processes by the Presence of Catechol Moieties

Photo-induced Advanced Oxidation Processes (AOPs) using H2O2 or S2O82− as radical precursors were assessed for the abatement of six different contaminants of emerging concern (CECs). In order to increase the efficiency of these AOPs at a wider pH range, the catechol organic functional compound was studied as a potential assistant in photo-driven iron-based processes. Different salinity regimes were also studied (in terms of Cl− concentration), namely low salt water (1 g·L−1) or a salt–water (30 g·L−1) matrix. Results obtained revealed that the presence of catechol could efficiently assist the photo-Fenton system and partly promote the photo-induced S2O82− system, which was highly dependent on salinity. Regarding the behavior of individual CECs, the photo-Fenton reaction was able to enhance the degradation of all six CECs, meanwhile the S2O82−-based process showed a moderate enhancement for acetaminophen, amoxicillin or clofibric acid. Finally, a response-surface methodology was employed to determine the effect of pH and catechol concentration on the different photo-driven processes. Catechol was removed during the degradation process. According to the results obtained, the presence of catechol in organic macromolecules can bring some advantages in water treatment for either freshwater (wastewater) or seawater (maritime or aquaculture industry).

Clarification of tangerine juice using cellulases from Pseudoyma sp

Tangerine juice was treated with crude extract containing cellulase from Pseudozyma sp. obtained by liquid fermentation. The thermal stability of cellulase was investigated by incubating crude extract at different temperatures and times. The pulp, obtained from tangerine, was pasteurized at 85 °C for 5 min and then used in a clarification process with a Doehlert experimental design. The results showed that the cellulase obtained from Pseudozyma sp. is thermostable at temperatures of 60, 70 and 90 °C and retained 98%, 88% and 80% of activity, respectively, after a 1-h incubation time. The optimum conditions for clarification were verified by varying the enzyme extract concentration (%, v v^-1) and the time (minutes) in a shaker at 150 rpm, at 50 °C. The optimum condition for clarification was obtained in the 80th min with a 1.25% enzymatic extract concentration (v v^-1), resulting in a reduction of tangerine juice viscosity by 65%. The analysis of physical and chemical parameters of tangerine juice after clarification showed that the enzyme extract improved the process responsible for the clarification of tangerine juice. The results are promising since this is a methodology that can be used in the citrus juice industry.