Optimal Separation Conditions Research Articles

HPLC with parallel ESI-MS and ICP-AES detection as a tool for the speciation studies of phosphovanadotungstates

The presence of different equilibrated chemical species in aqueous solutions of polyoxometalates represents a challenge for their identification, requiring the use of both separation and detection techniques. The use of reversed-phase ion-pair high-performance liquid chromatography (HPLC) in gradient elution mode resulted in optimal separation conditions. The detection was accomplished by parallel hyphenation of the inductively coupled plasma atomic emission spectrometry (ICP-AES) and electrospray ionization mass spectrometry (ESI-MS), which combined the advantages of element and molecule specific detectors. This hyphenation resulted in an unambiguous identification of the products of the synthesis of mixed-addendum Keggin-type phosphovanadotungstates of [PVxW12-xO40](3+x)- (x = 1 – 3) general formula without the isolation of the individual species.

Evaluation of ion pairing reversed-phase liquid chromatography for the separation of large RNA molecules

The rapid development of mRNA-based therapeutics, especially post-COVID-19, has necessitated the precise characterization of mRNA quality attributes, including sequence integrity. Ion-pairing reversed-phase liquid chromatography (IP-RPLC) has been widely accepted as a reference method for the characterization of small oligonucleotides. Some studies have already investigated the use of IP-RPLC for RNA, but no systematic approach has been developed to assess the impact of ion-pairing agents (IPAs) on the separation of large RNA molecules. This study addresses this gap by investigating the potential of IP-RPLC for the separation and characterization of large RNA molecules, with a specific focus on optimizing the use of IPAs to enhance retention and selectivity. Thirteen different IPAs, varying in hydrophobicity, were systematically tested using a polymeric column (divinylbenzene) with a very broad pore size range under various conditions, including different temperatures, pH, and IPA concentrations. The results demonstrate that moderately hydrophobic IPAs provide superior resolution for RNA species up to 6000 nucleotides. An optimized combination of 100 mM butylammonium acetate and 50 mM tripropylammonium acetate achieved the best overall separation, significantly improving resolution by 35% compared to individual IPAs. The study also identifies optimal conditions for RNA separation, including a mobile phase pH of 7.0, acetonitrile as the organic solvent, and a column temperature of 65°C. In a second step, a solution to increase the retention of small nucleotides and thereby separate nucleic acids ranging from 1 to 6000 nucleotides allowing to characterize IVT-mRNA differing in length and study their integrity and fragmentation or monitor the presence of in-process impurities (nucleotides) was investigated by combining two different HPLC columns. These findings enhance the analytical toolbox for evaluating the critical quality attributes of RNA, supporting the development of reliable and efficient RNA-based therapeutics.

A novel homologous acid ferric chloride/5-sulfosalicylic acid coordinated catalytic pretreatment for high-efficiency selective separation of poplar hemicellulose

The selective and efficient separation of hemicellulose is a challenge for utilizing lignocellulosic biomass for high-value purposes. This study reports the development of a novel homogeneous acid-catalyzed pretreatment technique based the homologous action of both FeCl3 and 5-sulfosalicylic acid (5-SAA). The optimal separation conditions (5-SAA concentration of 7.0 %, reaction temperature of 130 °C, FeCl3 concentration of 0.15 mol·L−1, and reaction time of 60 min) enabled a high hemicellulose separation efficiency of 90.68 %. The hemicellulose-derived total sugar yield was as high as 83.05 % which was increased by 30 %. Moreover, the xylose yield was increased by 10 %, and the content of oligosaccharides was triple higher than that in the single component treatment, up to 19.64 %. The depolymerization and recondensation of lignin were prevented using the 5-SAA hydrophobic structure (benzene ring structure) and hydrophilic end (−HSO3 and −COOH). The proposed strategy is a promising approach that can enable an efficient and selective separation of hemicellulose and consequently improve the quality of biomass materials.

Experimental, modeling, and numerical simulation of ultrasonic assisted drilling of CFRP/Ti stacks

Carbon fiber reinforced polymer (CFRP) and Ti-6Al-4V alloy (Ti) stacks structures are increasingly utilized in aircraft load-bearing applications, where the quality of hole processing significantly impacts their connection performance. Conventional drilling (CD) methods for CFRP/Ti stacks often encounter challenges such as severe interface damage, high cutting forces, and excessive heat generation. This study investigates the application of ultrasonic-assisted drilling (UAD) on CFRP/Ti stacks by integrating finite element method (FEM) modeling with experimental approaches to analyze the machinability of these materials under different machining methods and parameters. A self-developed high-frequency vibration spindle was employed to process CFRP/Ti stacks using both CD and UAD techniques. The newly developed numerical model effectively elucidates the mechanical and thermal coupling involved in the machining process and the transfer behavior of temperature and stress at the laminate interface. The experimental results of cutting force, hole inlet and outlet surface morphology, inner wall condition, chips, tool wear, etc. under different machining parameters were studied and analyzed. To ensure the reliability of our findings, experimental data were validated against simulation results. The findings reveal that UAD, when optimal separation conditions are achieved, significantly reduces cutting forces and enhances the surface morphology of both the inner and outer hole surfaces. Specifically, UAD lowers cutting forces by 27.2 % and the damage coefficient (Fd) by 15.7 % compared to CD. Furthermore, the high-frequency vibration generated by UAD markedly extends tool life. The specially designed high-frequency vibration spindle successfully meets drilling requirements, thereby significantly improving the machining performance of CFRP/Ti stacks materials, and it provides a certain reference for practical industrial applications.

Iron separation from iron-rich manganese ore leachate: Comprehensive optimization of operating parameters and economic viability

In the current electrolytic manganese industry, iron separation and reuse from iron-rich manganese ore leachate (IRMOL) has become one of the most pressing challenges. This study aimed to investigate the optimal conditions for iron separation from IRMOL and to assess the economic and practical advantages of iron separation or removal in industrial manufacturing. To identify more cost-effective and technologically advanced production circumstances, we examined five key elements that weaken Fe(OH)3 colloidal production conditions in enterprises: reaction temperature, pH, crystal species, aging and reaction time. The screening results showed that when the conditions were optimized, the efficiency of reducing manganese loss decreased from 6.15% to 4.69%. Additionally, the generation of iron-rich electrolytic manganese residue (IREMR) was decreased by 44.32%, and the filtration velocity of IREMR increased from 0.0030 to 0.0220 mL/(s·cm2) compared to the production conditions before optimization at the enterprises. Through multiphase equilibria modeling with Visual MINTEQ, we have determined that raising the temperature and pH levels increases the expenses associated with chemicals and energy usage and results in an elevation of Fe(OH)2+ concentration. This can lead to the creation of Fe(OH)3 colloidal, causing a high water content in IREMR, inefficient filtration, and significant loss of manganese. This strategy is highly significant for the production of electrolytic manganese and the reduction of electrolytic manganese residue.

Reduction of the environmental impact of the determination of l-carnitine and acetyl-l-carnitine in milk products by microchip electrophoresis

A novel miniaturized analytical method for the simultaneous determination of l-carnitine and its ester, acetyl-l-carnitine in fresh milk and milk products by microchip electrophoresis (MCE) with conductivity detection was developed. Under optimized separation conditions, separation voltage of 4 kV and 50 mmol L−1 acetic acid and 0.1 % methylhydroxyethylcellulose at pH 3.0 as background electrolyte, carnitines were sufficiently separated in less than 10 min. An elimination of adsorption of the cationically migrated analytes on a poly(methyl methacrylate) microchip was achieved by addition of 1 mmol L−1 triethylenetetramine to all analyzed samples. The detector response was linear in the range 0.2–1.5 µg mL−1 for l-carnitine and 0.4–2.0 µg mL−1 for acetyl-l-carnitine. The LOQ values were 0.1 µg mL−1 and 0.4 µg mL−1 for l-carnitine and acetyl-l-carnitine, respectively. Recoveries of the analytes in the analyzed samples were in the range 87.5–97.8 %. The developed MCE method has been successfully applied to the analysis of carnitines in eight milk products after a sample pretreatment which included precipitation, centrifugation, and filtration. The developed MCE method has a low hazardous impact on human health and the environment.

Evaluating the potential of hydrophilic interaction liquid chromatography for collagen peptide mapping analysis

This study presents a systematic approach for developing an innovative hydrophilic interaction liquid chromatography (HILIC) method for collagen peptide mapping analysis. The predominant post-translational modification (PTM) of collagen, proline hydroxylation, introduces polar hydroxyl groups throughout the collagen sequence, making HILIC a promising alternative to classical reversed-phase liquid chromatography (RPLC) approaches. This study employs sixteen model peptides, selected from in silico predicted tryptic peptides with zero missed cleavages and representing diverse physicochemical properties and structural motifs of collagen. The peptides were used as standards to conduct detailed chromatographic evaluation. Various HILIC stationary phases and mobile phases were systematically examined to identify optimal separation conditions for collagen peptides, contributing to a better understanding of peptide behavior in HILIC. The study also explores the effects of sample diluent and injection mode, comparing classical injection with the Performance Optimizing Injection Sequence (POISe), to determine their impact on HILIC performance. Introducing a plug of weak solvent (acetonitrile) prior to sample injection, effectively mitigates the mismatch in eluent strength between the fully aqueous sample diluent (resulting from tryptic digestion) and the mobile phase, addressing issues of peak distortion. Different injection volumes (from 0.5 to 8 µL) and acetonitrile ratios (1:1, 1:2, 1:5 and 1:10) were tested to optimize sample injection and increase sensitivity of collagen tryptic peptides.Following method optimization, HILIC was coupled with mass spectrometry (MS) to evaluate its effectiveness in analyzing collagen-digested samples. This evaluation included the assessment of peptide sequence coverage and the method ability to identify hydroxylation patterns, thereby demonstrating its potential for detailed peptide analysis.

Laser enrichment of the 62Ni isotope for betavoltaic devices

We have studied the laser isotope separation of the 62Ni isotope using a three-step ladder type photoionization scheme. Using density matrix formalism, optimum conditions for the efficient separation of the 62Ni isotope have been derived. The optimum bandwidth of the excitation lasers has been found to be 200 MHz, 1200 MHz, and 1200 MHz for the enrichment of the 62Ni isotope. It has also been shown that it is possible to produce 75 mg/day of 90% enriched 62Ni using the optimized experimental operating parameters derived in this work. Upon irradiation of this enriched 62Ni isotopic mixture, it is possible to produce ∼19mg/day of the 63Ni isotope, which is sufficient to manufacture a 100 µW betavoltaic device each day.

Quantitative Analysis of Chondroitin Sulfate and Dermatan Sulfate Using Capillary Electrophoresis With Gaussian Distribution‐Based Peak Fitting for Improved Peak Resolution

ABSTRACTIn this work, capillary electrophoresis with Gaussian distribution‐based peak fitting for improved peak resolution for simultaneous quantitative analysis of chondroitin sulfate (CS) and dermatan sulfate (DS) was developed for the first time. The effects of different pH, voltage, and peak shapes on the peak fitting were investigated. The results indicate that separation conditions that affect peak shape have a significant impact on peak fitting. Under optimized separation conditions, the peak fitting achieves high accuracy and precision, the relative standard deviation (n = 5) of peak area and migration time of CS and DS were 1.1%, 1.8% and 0.94%, 0.84%, respectively. Furthermore, the results obtained by peak fitting were close to real values. The developed method was used to analyze the purity of CS. The results had a high consistency with the labeled value; furthermore, the peak fitting could point out the number of possible impurities. The developed method has good potential for the analysis of other glycosaminoglycans with peak overlap.

Performance of global retention models in the optimisation of the liquid chromatographic separation (II): Complex multi-analyte samples

BackgroundEnhancing the quality control of medicinal plants is a complex challenge due to their rich variety of chemical compounds present at varying and extreme concentrations. Chromatographic fingerprints, which have become essential for characterising these complex natural materials, require achieving optimal separation conditions to effectively maximise the number of detected peaks. The challenges in optimising fingerprints and other complex multi-analyte samples include the unavailability of standards, the presence of unknown constituents and the substantial workload that would require conventional optimisation methods based on models. ResultsThis work introduces an interpretive optimisation approach which operates on the premise of predicting chromatograms using global models. Initially, a multi-linear gradient experimental design is sequentially executed to accommodate all peaks in the chromatogram in an adequate time window. Following this, a small set of sample peaks (reference peaks) is selected based on their consistent traceability across all chromatograms in the design. Using this reference dataset, a global model is constructed, initially focused solely on the reference peaks and later extended to encompass all detected peaks in the sample. The aim is to find gradients that maximise resolution while minimising analysis time. These optimised gradients are applied successfully to enhance the separation of medicinal plant extracts, with particular emphasis on peppermint and pennyroyal extracts. SignificanceThe proposed optimisation relying on global models can be applied to highly complex samples even in the absence of standards, or in cases where standards are available but their use is impractical due to workload constraints. Moreover, in discerning the most promising gradients for highly complex samples, peak purity has demonstrated superior reliability and competitiveness compared to peak capacity as chromatographic objective function.

Predictions of Chromatography Methods by Chemical Structure Similarity to Accelerate High-Throughput Medicinal Chemistry.

We introduce a new workflow that relies heavily on chemical quantitative structure-retention relationship (QSRR) models to accelerate method development for micro/mini-scale high-throughput purification (HTP). This provides faster access to new active pharmaceutical ingredients (APIs) through high-throughput experimentation (HTE). By comparing fingerprint structural similarity (e.g., Tanimoto index) with small training data sets containing a few hundred diverse small molecule antagonists of a lipid metabolizing enzyme, we can predict retention time (RT) of new compounds. Machine learning (ML) helps to identify optimal separation conditions for purification without performing the traditional crude QC step involving ultrahigh performance liquid chromatography (UHPLC) analyses of each compound. This green-chemistry approach with the use of predictive tools reduces cost and significantly shortens the design-make-test (DMT) cycle of new drugs by way of HTE.

Aqueous Two-Phase Flotation Combined with Gold Nanoparticle Colorimetry for Determination of Thiocyanate in Raw Milk

Thiocyanates are effective in inhibiting the growth of microorganisms in raw milk to extend shelf life, but excessive addition can cause human health problems. Currently, ion chromatography and spectrophotometry are the main methods used in industry to determine SCN, but the pre-treatment process is cumbersome and time-consuming and has low sensitivity. Aqueous two-phase flotation (ATPF) technology has the advantages of simplicity, rapidity and economy. In this study, an acetonitrile/ammonium sulfate ATPF–gold nanoparticle (AuNP) colorimetric method was developed for the determination of SCN− in raw milk, and ATPF was used to separate and concentrate SCN− in raw milk to improve the detection sensitivity under convenient and economical conditions. The separation conditions were optimized by single-factor experiments and RSM, while the detection conditions, effects of CTAB concentration, pH and reaction time, were investigated. The “aggregation–anti-aggregation” mechanism of the gold-nano colorimetric method for the determination of SCN− was investigated by UV-vis absorption spectroscopy (UV-vis) and transmission electron microscopy (TEM). Under the optimal separation and detection conditions, the SCN− concentration showed a linear relationship with A630/A520 values in the concentration range of 0–2.5 mg/L with R2 of 0.9933, limit of detection (LOD) of 0.0919 mg/L, limit of quantitation (LOQ) of 0.306 mg/L, intra-day precision of 5.3% and spiked recoveries of 80.91–101.25%. In addition, the ATPF-AuNP colorimetric method demonstrated high selectivity and stability.

Tailoring polishing steps for effective removal of polysorbate-degrading host cell proteins in antibody purification.

Ensuring the quality and safety of biopharmaceutical products requires the effective separation of monoclonal antibodies (mAbs) from host cell proteins (HCPs). A major challenge in this field is the enzymatic hydrolysis of polysorbates (PS) in drug products. This study addresses this issue by investigating the removal of polysorbate-degrading HCPs during the polishing steps of downstream purification, an area where knowledge about individual HCP behavior is still limited. We investigated the separation of different mAb formats from four individual polysorbate degrading hydrolases (CES1F, CES2C, LPLA2, and PAF-AH) using cation exchange (CEX) and mixed-mode chromatography (MMC) polishing steps. Our research identified a key challenge: The similar elution behavior of mAbs and HCPs during chromatographic separation. To investigate this phenomenon, we performed high-throughput binding screenings for recombinant polysorbate degrading hydrolases and representative mAb candidates on CEX and MMC chromatography resins. We then employed a three-step strategy that also served as a scale-up process, optimizing separation conditions and leading to the successful removal of specific HCPs while maintaining high mAb recovery rates (>96%). This strategy involved the use of surface response models and miniature columns for screening, followed by validation on larger columns using a chromatography system. Our results highlight the critical role of the inherent properties of mAbs for successful separation from HCPs. These results underscore the need to tailor the purification process to leverage the slight differences in binding behavior and elution profiles between mAbs and specific HCPs. This approach lays the foundation for developing more effective strategies for overcoming the challenge of enzymatic polysorbate degradation, paving the way for improved quality and safety in biopharmaceutical products.

Influences of fractional separation on the structure and reactivity of wheat straw cellulose for producing 5-hydroxymethylfurfural

High-efficient production of 5-hydroxymethylfurfural (HMF), a “sleeping giant” in sustainable chemistry, from cellulose depends significantly on the effective separation of cellulose from lignocellulosic biomass. Herein, we report the fractional separation of wheat straw cellulose (WSC) from wheat straw under solvothermal conditions using a mixed solvent of γ-valerolactone (GVL) and H2O as the separating solvent, wherein the impacts of fractional separation parameters (solvent composition, temperature, and time) on removals of lignin and hemicellulose as well as purity and recovery of cellulose were studied by a Box-Behnken Design of response surface method. The optimization of the solvothermal parameters enabled an optimal fractional separation condition (VGVL: ∼ 60.0 vol%, T: 205 oC, t: ∼1.7 h) that led to a higher purity (89.4%) and recovery (86.7%) of cellulose in WSC. A further correlation of the removals of lignin and hemicellulose as well as purity and recovery of cellulose with the yield of HMF excluded an independent influence of the above factors. Instead, a comprehensive contribution of high fractional separation efficiency (defined as the product of cellulose purity and recovery) and low crystallinity of WSC was found to improve the HMF yield. However, the heat- and freeze-dryings of WSC after the solvothermal separation were found to lower the HMF yield because it re-improved the crystallinity of WSC. A high HMF yield of 58.6 mol% was achieved after reacting wet-WSC in a mixed solvent of 1,4-dioxane and H2O at 180 oC for 20 min, which was 1.5 fold higher than that from microcrystalline cellulose. This work highlights the importance of enhancing the fractional separation efficiency of cellulose from lignocellulosic biomass whereas avoiding drying process for future HMF biorefinery.

Compliant mechanism design of combined aircraft wing for stable separation

Abstract Stable separation is a crucial condition that must be met in order for combined aircraft to successfully engage in cooperative flight. In order to achieve the desired fast and controlled separation, this paper proposes a novel design for a torque-driven compliant separation mechanism. By taking into account the compliance characteristics of a sinusoidal acceleration function curve, a mechanical model for the separation mechanism is developed. By utilising the Coulomb friction law, an accurate determination of the aerodynamic load distribution under various conditions is achieved. Subsequently, the relationship between the unlocking moment and the aerodynamic load is derived based on these findings. Through the utilisation of the finite element method, a model of the separation mechanism is generated. To ensure the safety and reliability of the compliant separation mechanism, the mechanical properties of the structural materials are thoroughly analysed under the maximum aerodynamic load. Subsequently, the separation mechanism structure is constructed and subjected to testing in order to showcase the compliance characteristics. In addition, this paper conducts a simulation to analyse the impact of flight speed and angle-of-attack on the separation process. By doing so, the optimal conditions for separation are determined. The methods and findings presented in this study have the potential to contribute valuable insights to the design of combined aircraft.

UHPLC-PAD Protocol for the Simultaneous Identification of Polyphenols and Bitter Acids: Organoleptic and Nutraceutical Fingerprinting of Bergamot-Flavored Craft Beer.

In this study, a UHPLC-PDA method for the simultaneous identification of polyphenols and bitter acids (alpha, beta, and isoalpha) in beer was developed. The resulting chemical profiles were leveraged to distinguish the characteristics of four (IPA, Lager, Blanche, ALE) bergamot-flavored beers, produced on a pilot-scale plant. In a streamlined 29 min analysis, thirty polyphenols and fourteen bitter acids were successfully identified under optimized separation conditions. Validation, encompassing parameters such as LOD (from 0.028 ppm for isorhamnetin to 0.106 for narirutin), LOQ (from 0.077 ppm for naringenin to 0.355 for narirutin), R2 (always more than 0.9992), repeatability (from 0.67% for tangeretin to 6.38% for myricetin), and reproducibility (from 0.99% for sinensetin to 6% for naringin), was conducted for polyphenol quantification using constructed calibration curves with seven levels. Exploring polyphenolic components as potential discriminators among different beer styles, a total of thirty-two polyphenolic compounds were identified and quantified, including characteristic bergamot peel polyphenols like neoeriocitrin (from 7.85 ppm for CBS2 to 11.95 ppm in CBS1); naringin (from 4.56 ppm for CBS4 to 10.96 in CBS1), and neohesperidin (from 5.93 in CBS3 to 15.95 for CBS2). The multivariate analysis provided additional insights into variations among specific beer styles, revealing discrepancies in the presence or relative concentrations of specific compounds linked to brewing ingredients and processes. This research enhances the fingerprinting of the chemistry governing beer quality through a straightforward and cost-effective analytical approach.

Determination of antibiotics of the tetracycline group in water by high-performance liquid chromatography on a diode matrix detector with preliminary concentration by solid-phase extraction

Introduction. Antibiotic contamination of the environment is a serious environmental threat that poses a hazard to human health. To monitor the content of tetracycline antibiotics in environmental objects and control technological processes aimed at their disposal, accessible analytical methods are needed. 
 Purpose of the study. Development of a method for determining antibiotics of the tetracycline group in water using a diode array detector with preliminary solid-phase concentration.
 Material and methods. The objects of the study were model solutions of minocycline, tetracycline, oxytetracycline, demeclocycline, metacycline, and doxycycline in deionized, tap, natural, and treated wastewater. For solid-phase extraction, Diapak P and Diapak PG cartridges were used. SPE was performed using a VacMaster-10 manifold (Biotage). Chromatographic separation was carried out on Diasphere C10CN and Kromasil Eternity 250 × 4.6 mm 5 µm columns on an Agilent 1100 liquid chromatograph (Agilent Technology).
 Results. Optimal conditions for the chromatographic separation of minocycline, tetracycline, oxytetracycline, demeclocycline, metacycline, and doxycycline were selected: isocratic mode, wavelength of 350 nm, mobile phase – acetonitrile: aqueous solution of phosphoric acid (pH = 3.0). The analysis time on Diasphere C10CN and Kromasil Eternity columns was 12 and 14 minutes, respectively. The reliability of the linear approximation in both cases was more than 0.99, however, the slopes on the Kromasil Eternity column were 1.35 –1.65 times higher than on Diasphere C10CN. The degree of extraction of tetracyclines from deionized water on Diapak P and Diapak PG cartridges was 90–95%, from tap water 61–89%, from purified waste water: 51–87%.
 Limitations. The method is not suitable for water bodies with tetracycline contents less than 2 µg/dm3.
 Conclusion. An HPLC method has been developed for the determination of minocycline, tetracycline, oxytetracycline, demeclocycline, metacycline, and doxycycline in water with preliminary SPE concentration on Diapak P and Diapak PG cartridges. The lower limit of determination for the sorption of target compounds from 0,1 dm3 of sample was 2 μg/dm3.

Efficient and environmentally friendly separation and recycling of cathode materials and current collectors for lithium-ion batteries by fast Joule heating

Spent Li-ion batteries(LIBs) cathodes possess high recycling value. To improve subsequent recovery efficiency and product purity, separating the cathode materials from the aluminum foil is critical. However, traditional separation methods are characterized by high energy consumption, low recycling efficiency, and environmental pollution. This research presents a novel method that involves injecting Joule heat directly into the aluminum foil in the air, resulting in the melting and slight thermal decomposition of the PVDF binder, which reduces its adhesive properties. Owing to the difference in thermal expansion coefficients between the binder and aluminum foil, an instantaneous thermal stress was generated at the interface of the cathode materials and aluminum foil, resulting in a peeling force. This method enabled a rapid and efficient separation of lithium iron phosphate (LFP) and ternary Li-ion (NCM) battery cathode materials. The optimal separation conditions, separation mechanism, and properties of the recovered products were investigated thoroughly using high-speed camera imaging, temperature rise calculations, and microscopic characterization. This chemical-free method avoids the generation of wastewater and gas emissions. Under optimal experimental parameters, the separation efficiency and purity of cathode material reached 99 % and 99.7 %, respectively. Additionally, this method preserves both the structural integrity of the aluminum foil and the crystalline structure of the cathode materials, offering a new pathway for sustainable recycling of end-of-life LIBs.

Enhancing biodiesel yield and purification with a recently developed centrifuge machine: A response surface methodology approach

Biodiesel production processes, such as gravity settling, have limitations in terms of biodiesel yield, purification efficiency, operating time in the separation process, and more extensive equipment. Therefore, this study has focused on using a recently developed centrifuge machine for biodiesel separation to address these challenges due to its compact design, high efficiency, and simplicity. Additionally, this study aimed to optimize the separation efficiency of glycerol from biodiesel using a centrifuge machine, employing response surface methodology (RSM) with central composite design (CCD). The optimum conditions for separating glycerol from biodiesel via centrifuge machine are a rotation speed of 1800 rpm, a mixture flow rate of 192.25 ml/min, and a temperature of 55 °C, respectively. In optimum conditions, 94.52% separation efficiency was achieved. Biodiesel production can be improved, leading to higher yields and greater purity. The utilization of RSM proved valuable in determining the optimum conditions for separation. Furthermore, the machine successfully separated the biodiesel to meet ASTM D6751 and EN 14,214 standards. The results highlight the potential of the centrifuge machine for efficient and reliable biodiesel production, contributing to the advancement of the biodiesel industry.

Quantification of serine residue stereoinversion in a short peptide by reversed-phase high-performance liquid chromatography: analysis of mechanisms promoting serine stereoinversion.

Stereoinversion of Ser residues within proteins, which has been identified in long-lived proteins, influences protein function. To quantify the stereoinversion of Ser residues, we investigated the potential adaptation of our direct peptide analytical method originally established for analyzing the isomerization of asparaginyl/aspartyl residues. Peptide pairs containing L-Ser or D-Ser residues with lengths of four or five residues were synthesized. Separation conditions for these peptide pairs were systematically examined by precisely adjusting the pH of the elution solvent using reverse-phase high-performance liquid chromatography (HPLC). Optimal separation conditions were successfully developed for all peptide pairs, enabling the direct quantification of Ser residue stereoinversion through a single HPLC run. Subsequently, the degree of Ser stereoinversion within the model peptide, Gly-Ser-Gly-Tyr, was determined using the method established in this study. Surprisingly, the stereoinversion of Ser residues occurred only when the absolute configurations of Ser and Tyr residues of the peptide differed from each other, whereas no stereoinversion was observed when their absolute configurations were identical. The experiments using peptides similar to the model peptide reveal that both the N-terminal amino group and the hydroxyl group of the C-terminal Tyr residue are involved in the stereoinversion of the Ser residue. By applying a simple method to quantify the stereoinversion of Ser residues, valuable insights into the mechanisms governing these stereoinversions were obtained.