Analysis and classification of tea varieties using high-performance liquid chromatography and global retention models.

As a result of their metabolic processes, medicinal plants produce bioactive molecules with significant implications for human health, used directly for treatment or for pharmaceutical development. Chromatographic fingerprints with solvent gradients authenticate and categorise medicinal plants by capturing chemical diversity. This work focuses on optimising tea sample analysis in HPLC, using a model-based approach without requiring standards. Predicting the gradient profile effects on full signals was the basis to identify optimal separation conditions. Global models characterised retention and bandwidth for 14 peaks in the chromatograms across varied elution conditions, facilitating resolution optimisation of 63 peaks, covering 99.95 % of total peak area. The identified optimal gradient was applied to classify 40 samples representing six tea varieties. Matrices of baseline-corrected signals, elution bands, and band ratios, were evaluated to select the best dataset. Principal Component Analysis (PCA), k-means clustering, and Partial Least Squares-Discriminant Analysis (PLS-DA) assessed classification feasibility. Classification limitations were found reasonable due to tea processing complexities, involving drying and fermentation influenced by environmental conditions.

Evaluation of the in vitro activity of ampicillin-sulbactam and cefoperazone-sulbactam against A. Baumannii by the broth disk elution test.

To evaluate the in vitro activity of ampicillin-sulbactam and cefoperazone-sulbactam against A. baumannii using the broth disk elution testing, a total of 150 A. baumannii isolates were collected from across China between January 2019 and January 2021, including 51 carbapenem-susceptible and 99 carbapenem-resistant isolates. Broth disk elution (BDE) and the broth microdilution (BMD) method were performed for all strains. The concentration range of the BDE was 10/10 µg/mL, 20/20 µg/mL, and 30/30 µg/mL for ampicillin-sulbactam, and 37.5/15 µg/mL, 75/30 µg/mL, 112.5/45 µg/mL, and 150/60 µg/mL for cefoperazone-sulbactam, respectively. Compared with BMD, the BDE results of ampicillin-sulbactam and cefoperazone-sulbactam showed a categorical agreement of 83.3% (125/150) and 95.3% (143/150), with minor errors of 16.7% (25/150) and 4.7% (7/150), respectively. No major error or very major errors were detected. The sensitivity differences by BDE of carbapenem-resistant A. baumannii (CRAb) to different concentrations of ampicillin-sulbactam showed statistically significant (p < 0.017), while those to cefoperazone-sulbactam at 37.5/15 µg/mL, 75/30 µg/mL, and 112.5/45 µg/mL were significant (p < 0.008). However, no significant difference in sensitivity was observed between 112.5/45 µg/mL and 150/60 µg/mL (p > 0.008). In conclusion, the BDE is a reliable and convenient method to detect the in vitro activity of cefoperazone-sulbactam against A. baumannii, and the results could serve as a clinical reference value when deciding whether or not to use high-dose sulbactam for the treatment of A. baumannii infections.

Application of ion-exchange dynamic conditions in the recovery of precious metals from refining waste.

The objective of this study was to assess the potential for recovering precious metals from technological solutions using an ion-exchange dynamic method. Precious metals like platinum, palladium, rhodium, and gold are essential materials in various industries such as: automotive, electronics, pharmaceuticals, and jewellery. Due to their limited occurrence in primary sources, there is a growing trend in the market to extract these metals from secondary sources. The research involved conducting sorption and elution tests under different parameters to investigate their impact on the process in dynamic conditions. Additionally, an attempt was made to calculate the operational and total capacity of the resins, which has not been done previously for industrial solutions. The results showed that using Puromet MTS9200, Puromet MTS9850, and Lewatit MonoPlus MP600 resins, the sorption process could be effectively carried out in dynamic conditions with a contact time of 5 min between the technological solution and the resin bed. For optimal elution, the contact time between the eluent solution and the bed should range between 10 and 30 min. To improve rhodium sorption efficiency, it was found that neutralizing the technological solution to a pH of approximately 7 and using Lewatit MonoPlus MP600 resin could be beneficial.

Development and optimization of high-performance extraction chromatography method for separation of rare earth elements.

The effectiveness of commonly used extractants for chromatographic separation of rare earth elements (REEs) was compared. Columns loaded with similar molar concentrations of tributyl phosphate (TBP), di-(2-ethylhexyl) phosphoric acid (HDEHP), and N-Methyl-N, N, N-tri-octyl-ammonium chloride (Aliquat-336), with mineral acid as eluent were evaluated. Retention factors were determined, and separation efficiency was assessed based on the resolution data of the REEs acquired under the same elution conditions for each column. HDEHP demonstrated the best separation efficiency for the entire REE series (mean Rs = 2.76), followed by TBP (mean Rs = 1.52), while Aliquat-336 exhibited the lowest performance (mean Rs = 1.42). The HDEHP-coated column was then used to optimize the extraction chromatographic separation of the REEs. The primary challenge was to completely elute the heavy REEs (Tb - Lu) while maintaining adequate separation of the light REEs (La - Gd) within a reasonably short time. The stepwise gradient elution procedure improved the resolution between adjacent REEs, allowing the complete separation of the entire REE series within 25 minutes. Better separation efficiency for light REEs was achieved at higher column temperatures and a mobile phase flow rate of 1.5 mL/min in the tested domain of 20-60 °C, and 0.5-2.0 mL/min, respectively, resulting in plate heights (H) ranging from 0.011 to 0.027 mm.

Instrumental and theoretical advancements in pulsed elution-LC × LC: Investigation of pulse parameters and application to wastewater effluent.

Due to the decoupling of the first (1D) and second (2D) dimension in pulsed elution-LC × LC (PE-LC × LC), method development is more flexible and straightforward compared to fast comprehensive LC × LC where the dependencies of key parameters between the two dimensions limits its flexibility. In this study we present a method for pulse generation, which is based on a switching valve alternating between one pump that delivers the gradient and a second pump that delivers low eluotrophic strength for the pause state. Consequently, the dwell volume of the system was circumvented and 7.5, and 3.75 times shorter pulse widths could be generated at flow rates of 0.2, and 0.4 mL/min with satisfactory accuracies between programmed and observed mobile phase composition (relative deviation of 6.0 %). We investigated how key parameters including pulse width and step height, 2D gradient time and flow rate affected the peak capacity in PE-LC × LC. The conditions yielding the highest peak capacity for the PE-LC × LC- high-resolution mass spectrometry (HRMS) system were applied to a wastewater effluent sample. The results were compared to a one dimensional (1D)-LC-HRMS chromatogram. The peak capacity increased with a factor 34 from 112 for the 1D-LC run to 3770 for PE-LC × LC-HRMS after correction for undersampling. The analysis time for PE-LC × LC-HRMS was 12.1 h compared to 67.5 min for the 1D-LC-HRMS run. The purity of the mass spectra improved for PE-LC × LC-HRMS by a factor 2.6 (p-value 3.3 × 10-6) and 2.0 (p-value 2.5 × 10-3) for the low and high collision energy trace compared to the 1D-LC-HRMS analysis. Furthermore, the signal-to-noise ratio (S/N) was 4.2 times higher (range: 0.06-56.7, p-value 3.8 × 10-2) compared to the 1D-LC-HRMS separation based on 42 identified compounds. The improvements in S/N were explained by the lower peak volume obtained in the PE-LC × LC-HRMS.

Method for lysis and paper-based elution-free DNA extraction with colourimetric isothermal amplification.

Nucleic acid amplification testing has great potential for point-of-need diagnostic testing with high detection sensitivity and specificity. Current sample preparation is limited by a tedious workflow requiring multiple steps, reagents and instrumentation, hampering nucleic acid testing at point of need. In this study, we present the use of mixed cellulose ester (MCE) paper for DNA binding by ionic interaction under molecular crowding conditions and fluid transport by wicking. The poly(ethylene) glycol-based (PEG) reagent simultaneously provides the high pH for alkaline lysis and crowding effects for ionic binding of the DNA under high salt conditions. In this study, we introduce Paper-based Abridged Solid-Phase Extraction with Alkaline Poly(ethylene) Glycol Lysis (PASAP). The anionic mixed cellulose ester (MCE) paper is used as solid phase and allows for fluid transport by wicking, eliminating the need for pipetting skills and the use of a magnet to retain beads. Following the release of DNA from the cells due to the lytic activity of the PASAP solution, the DNA binds to the anionic surface of the MCE paper, concentrating at the bottom while the sample matrix is transported towards the top by wicking. The paper was washed by dipping it in 40% isopropanol for 10 s. After air-drying for 30 s, the bottom section of the paper (3 mm × 4 mm) was snapped off using the cap of a PCR tube and immersed in the colourimetric loop-mediated isothermal amplification (cLAMP) solution for direct amplification and colourimetric detection. The total sample processing was completed in 15 min and ready for amplification. cLAMP enabled the detection of 102 CFU/mL of Escherichia coli (E. coli) from culture media and the detection of E. coli in milk < 103 CFU/mL (10 CFU) after incubation at 68 °C for 60 min, demonstrating applicability of the method to complex biological samples.

A prototype system for the removal of 137Cs from liquid radioactive waste using reverse osmosis membrane.

Cesium removal from aqueous solutions of radioactive waste streams is a challenge in the field of radioactive waste management; this is due to the small atomic radii of Cs+ metal ions and their high migration ability. So, the development of a withstand system for the removal of Cs+ is crucial. In the current study, the removal of radioactive cesium from aqueous solutions using an RO-TLC membrane was studied. Two modifications were conducted; the first is to enlarge the cesium metal ion radii by interacting with mono- and dibasic acids, namely, stearic acid, tartaric acid, citric acid, and EDTA, and the second is the modification of the RO membrane pore size via reaction with the same acids. The modification was confirmed using SEM, FTIR, and EDX analysis techniques. The Cs+ and K+ rejection capacities and water permeability across the membrane at 1.5 bars were evaluated. Along with using the above-mentioned acids, the Cs+ metal ion retention index (RCs) was also obtained. It was found that employing EDTA as a chelating agent in an amount of 1.5 g/L in conjunction with the variation of feed content since it provided the highest value of RCs ~ 98% when used. Moreover, the elution of Cs+ using water, EDTA, ammonia, and HCl is also investigated. The optimal value of the eluent concentration was (0.25 M) HCl. Finally, Langmuir and Freundlich isotherm models were applied for a better understanding of the sorption process. The results of the present work more closely match the Langmuir isotherm model to determine the dominance of the chemical sorption mechanism.

Multiple-component covalent organic frameworks for simultaneous extraction and determination of multitarget pollutants in sea foods.

Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have been raising global concerns due to their toxic effects on environment and human health. The monitoring of residues of POPs in seafood is crucial for assessing the accumulation of these contaminants in the study area and mitigating potential risks to human health. However, the diversity and complexity of POPs in seafood present significant challenges for their simultaneous detection. Here, a novel multi-component fluoro-functionalized covalent organic framework (OH-F-COF) was designed as SPE adsorbent for simultaneous extraction POPs. On this basis, the recognition and adsorption mechanisms were investigated by molecular simulation. Due to multiple interactions and large specific surface area, OH-F-COF displayed satisfactory coextraction performance for PFASs, PCBs, and BPs. Under optimized conditions, the OH-F-COF sorbent was employed in a strategy of simultaneous extraction and stepwise elution (SESE), in combination with HPLC-MS/MS and GC-MS method, to effectively determined POPs in seafood collected from coastal areas of China. The method obtained low detection limits for BPs (0.0037 -0.0089 ng/g), PFASs (0.0038 -0.0207 ng/g), and PCBs (0.2308 -0.2499 ng/g), respectively. This approach provided new research ideas for analyzing and controlling multitarget POPs in seafood. ENVIRONMENTAL IMPLICATIONS: Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have caused serious hazards to human health and ecosystems. Hence, there is a need to develop a quantitative method that can rapidly detect POPs in environmental and food samples. Herein, a novel multi-component fluorine-functionalized covalent organic skeletons (OH-F-COF) were prepared at room temperature, and served as adsorbent for POPs. The SESE-SPE strategy combined with chromatographic techniques was used to achieve a rapid detection of POPs in sea foods from the coastal provinces of China. This method provides a valuable tool for analyzing POPs in environmental and food samples.

The Severity of Direct Antiglobulin Test Negative ABO Hemolytic Disease of Newborn: A Retrospective Analysis at a Tertiary Children's Hospital.

This study aimed to evaluate the severity of ABO hemolytic disease of newborn (ABO-HDN) with negative direct antiglobulin test (DAT), which was identified by elution test. We retrospectively reviewed the clinical records of all neonates admitted with the diagnosis of neonatal hyperbilirubinemia requiring phototherapy or exchange transfusion. Neonates were divided into four groups according to their immunohematology test results. Then their essential laboratory results, magnetic resonance image (MRI), brainstem auditory evoked potential (BAEP) findings, and rate of exchange transfusion were compared between different groups. We found that neonates in ABO-HDN with negative DAT group developed jaundice faster and anaemia more severely than those in the non-HDN group. Although they might get less severe anaemia than neonates in ABO-HDN with positive DAT group and the Rh-HDN group, neonates in ABO HDN with negative DAT group might develop jaundice as quickly as the latter two groups. As to MRI and BAEP findings, there were no significant differences among the four groups. The rate of exchange transfusion in ABO-HDN with negative DAT group was higher than that in the non-HDN group but lower than that in ABO-HDN with positive DAT group, though without statistical significance. It suggested that in the presence of clinical suspicion of ABO-HDN with negative DAT result, the elution test should be added to rule out or confirm the diagnosis to help prevent the morbidity from hyperbilirubinemia.

In situ monitoring of loading and elution processes of cryoprotectants at the single-cell level with Raman spectroscopy.

BACKGROUND: The analysis of cell membrane permeability plays a crucial role in improving the procedures of cell cryopreservation, which will affect the specific parameter settings in loading, removal and cooling processes. However, existing studies have mostly focused on deriving permeability parameters through osmotic theoretical models and cell volume response analysis, and there is still a lack of the direct experimental evidence and analysis at the single-cell level regarding the migration of cryoprotectants. RESULTS: In this work, a side perfusion microfluidics chips combined with Raman spectroscopy system was built to monitor in situ the Raman spectroscopy of extracellular and intracellular solution during loading and elution process with different cryoprotectant solution systems (single and dual component). And it was found that loading a high concentration cryoprotectant solution system through a single elution cycle may result in significant residual protective agent, which can be mitigated by employing a multi-component formula but multiple elution operations are still necessary. Furthermore, the collected spectral signals were marked and analyzed to was perform preliminary relative quantitative analysis. The results showed that the intracellular concentration changes can be accurately quantified by the Raman spectrum and are closely related to the extracellular solution concentration changes. SIGNIFICANCE AND NOVELTY: By using the method of small flow perfusion (≤20 µL/min) in the side microfluidic chip after the gravity sedimentation of cells, the continuous loading and elution process of different cryoprotectants on chip and the spectral acquisition can be realized. The intracellular and extracellular concentrations can be quantified in situ based on the ratio of spectral peak intensities. These results indicate that spectroscopic analysis can be used to effectively monitor intracellular cryoprotectant residues.

Relation between characteristic temperature and elution temperature in temperature programmed gas chromatography - Part II: Influence of column properties.

The method development process in gas chromatography can be accelerated by suitable computer simulation tools using knowledge about the solute-column interactions described by thermodynamic retention parameters. Since retention parameters usually are determined under isothermal conditions, the presented work offers a step to estimate one of the most important retention parameters, the characteristic temperature Tchar by less laborious temperature programmed measurements. In the first part an empirical multivariate model was introduced describing the correlation between the elution temperature Telu of a solute and its characteristic temperature Tchar. Now in the second part a simulation model of GC and available retention data from a retention database was used to investigate the correlation between Telu and Tchar for an expanded range of heating rates and initial temperatures. In addition to part I, the simulation is used to investigate the influences of different properties of the separation column such as different phase ratios and column geometries like length and diameter or various stationary phases including SLB-5 ms, SPB-50, Stabilwax, Rtx-Dioxin2, Rxi-17Sil MS, Rxi-5Sil MS, ZB-PAH-CT, DB-5 ms, Rxi-5 ms, Rtx5 and FS5ms. The fit model is valid for all investigated stationary phases. The influence of the phase ratio to the correlation could be determined. Therefore, the model was expanded to this parameter. The expanded range of heating rates and the normalization for the system independent dimensionless heating rate required a further modification of the previously presented correlation model. The model now fits also under isothermal conditions. The results were used for estimation of the Tchar of an analyte from the elution temperature in the temperature program. The prediction performance was investigated and evaluated for 20 different temperature program conditions and at two phase ratios (ß=125 and ß=250). Under best conditions the estimated and the measured Tchar values show relative differences <0.5 %. With this novel model estimations for Tchar are possible at 20 °C above the initial temperature, which expands the prediction range even for low and medium retained analytes compared to earlier approaches.

Structural and functional characterization of avian influenza H9N2 virus neuraminidase with a combination of five novel mutations.

The influenza virus neuraminidase (NA) protein is responsible for actively cleaving the sialic acid (SA) bound to the viral hemagglutinin. In the present study, we identified a combination of five novel amino acid substitutions in the NA, conferring increased substrate binding and altered surface characteristics to a low pathogenic avian influenza (LPAI) H9N2 virus strain. The H9N2 strain reported from India, A/Environmental/India/1726265/2017 (H9N2-1726265) showed the combination of amino acid substitutions T149I, R249W, G346A, W403R and G435R, which were in the vicinity of the enzyme active site cavity. The strain A/chicken/India/99321/2009 (H9N2-99321) did not show these substitutions and was used for comparison. Virus elution was studied using turkey red blood cells (tRBCs). NA enzyme kinetics assays were carried out using the MUNANA substrate, which is an SA analogue. Homology modelling and molecular docking were performed to determine alterations in the surface characteristics and substrate binding. H9N2-1726265 showed enhanced elution from tRBCs. Enzyme kinetics revealed a lower KM of H9N2-1726265 (111.5 µM) as compared to H9N2-99321 (135.2 µM), indicating higher substrate binding affinity of H9N2-1726265, due to which the NA enzyme cleaved the SA more efficiently, leading to faster elution. Molecular docking revealed a greater number of binding interactions of H9N2-1726265 to SA as compared to H9N2-99321 corroborating the greater substrate binding affinity. Changes in the surface charge, hydrophobicity, and contour, were observed in H9N2-1726265 NA due to the five substitutions. Thus, the novel combination of five amino acids near the sialic acid binding site of NA, resulted in altered surface characteristics, higher substrate binding affinity, and virus elution.

Mitigation of Silicon Contamination in Fuel Cell Gasket Materials through Silica Surface Treatment.

Gaskets and seals are essential components in the operation of proton exchange membrane (PEM) fuel cells and are required for keeping hydrogen and air/oxygen within their individual compartments. The durability of these gaskets and seals is necessary, as it influences not only the lifespan but also the electrochemical efficiency of the PEM fuel cell. In this study, the cause of silicon leaching from silicone gaskets under simulated fuel cell conditions was investigated. Additionally, to reduce silicon leaching, the silica surface was treated with methyltrimethoxysilane, vinyltriethoxysilane, and (3,3,3-trifluoropropyl)trimethoxysilane. Changes in the silica surface chemistry were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, elemental analysis, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. Inductively coupled plasma-optical emission spectroscopy analysis revealed that surface-treated silica was highly effective in reducing silicon leaching.

Detection of ABO Blood Groups From Dentin and Pulp by Using the Absorption-Elution Technique: A Forensic Cross-Sectional Study Among the Population of the Al Jouf Province, Saudi Arabia.

Background and objective Human teeth have a significant forensic importance. As they are the hardest of all human tissues, they are not just chemically stable but also their characteristics are maintained for a long time after death even in the most harsh environmental conditions. Despite the advances made in DNA analysis, fingerprinting, etc., ABO blood grouping still plays a significant role in the forensic practice in the field of personal identification, paternity disputes, and several other scenarios including the identification of mass disaster victims. The term blood groups refers to inherited antigens on the surface of red blood cells (RBCs) detected by specific antibodies. Since tooth pulp contains numerous blood vessels, blood group antigens are most certainly bound to be present in tooth pulp. Various studies have shown that blood group antigens in the pulp and dentin are preserved as long as up to two years after the demise of an individual. Absorption-elution technique has been proven to be the most sensitive, reliable, and consistent method to determine the ABO blood group from both the pulp and dentine. This study aimed to ascertain the ABO blood group from both the hard (dentin) as well as the soft tissue (pulp) of the tooth by using the absorption-elution (AE) technique and also to determine if there are any variations in identifying the blood groups from the teeth based on age and gender. Material and methods After obtaining due consent, we included patients of both genders aged between 16-60 years visiting the outpatient department (OPD) clinics at the College of Dentistry for periodontal or orthodontic extractions. One patient's blood type was determined by using the slide agglutination technique before any capillary blood extraction was performed; this patient served as a control. For this investigation, we used the pulp and powdered dentin samples taken from the dental extractions to test for the presence of ABO and Rhesus (Rh) factor antigens by using the AE method. The study samples were compared with the control for blood group determination. Statistical analysis was carried out using the chi-square test with Monte Carlo (MC) simulation to check for any correlation of blood grouping with age and gender. Results The dentin and pulp were shown to have positive blood group antigens for the ABO and Rh factors. While neither pulp nor dentin performed significantly differently in identifying the blood group antigens, pulp showed marginally higher accuracy. There was no discernible difference regarding gender or age in the dentin or pulp of any of the 45 samples studied. Conclusions For determining an individual's blood type and Rh factor, both the hard (dentin) and soft (pulp) tissues of a tooth are valid sources. This is particularly helpful in forensic medicine cases where teeth are the only remains that can be viably used to find out a person's identity.

In vitro dissolution equivalence of Jordanian sildenafil generics via validated, stability-indicating HPLC method.

This study was conducted to compare dissolution profiles of four Jordanian registered sildenafil (SDF) products to the originator. Dissolution samples were analyzed utilizing a validated and stability-indicating HPLC method in human plasma. Validation was performed for specificity, linearity, limit of detection, lower limit of quantification, precision, trueness and stability. SDF was extracted from plasma samples using liquid-liquid extraction. The analysis was performed utilizing isocratic elution on C18 column with 1.0 ml/min flow rate. The regression value was ∼0.999 over 3 days with drug recovery between 86.6 to 89.8%with 10 ng/ml lower limit of quantitation. This method displayed a good selectivity of SDF with improved stability under various conditions. The method was used for SDF quantification in dissolution medium. Similarity factors for local products varied according to the used mediums, but all SDF local products passed the dissolution in vitro test since all of them showed a released of >85% after 60 min at the dissolution mediums.

[Box: see text].

Switching Separation Migration Order by Switching Electrokinetic Regime in Electrokinetic Microsystems.

Analyte migration order is a major aspect in all migration-based analytical separations methods. Presented here is the manipulation of the migration order of microparticles in an insulator-based electrokinetic separation. Three distinct particle mixtures were studied: a binary mixture of particles with similar electrical charge and different sizes, and two tertiary mixtures of particles of distinct sizes. Each one of the particle mixtures was separated twice, the first separation was performed under low voltage (linear electrokinetic regime) and the second separation was performed under high voltage (nonlinear electrokinetic regime). Linear electrophoresis, which discriminates particles by charge, is the dominant electrokinetic effect in the linear regime; while nonlinear electrophoresis, which discriminates particles by size and shape, is the dominant electrokinetic effect in the nonlinear regime. The separation results obtained with the three particle mixtures illustrated that particle elution order can be changed by switching from the linear electrokinetic regime to the nonlinear electrokinetic regime. Also, in all cases, better separation performances in terms of separation resolution (Rs) were obtained by employing the nonlinear electrokinetic regime allowing nonlinear electrophoresis to be the discriminatory electrokinetic mechanism. These findings could be applied to analyze complex samples containing bioparticles of interest within the micron size range. This is the first report where particle elution order is altered in an iEK system.

[Translated article] In vitro elution of local anaesthetics from PMMA bone cement.

BACKGROUND AND AIM: Currently, we do not have a gold standard for pain management after total knee arthroplasty. We may use one of more drug delivery systems, none of which are ideal. An ideal depot delivery system would provide therapeutic, nontoxic, doses of drug at the surgical side, especially during 72h postoperatively. The bone cement used in arthroplasties has been used as a drug delivery system, especially antibiotics, since 1970. Based on this principle, we developed this study with the aim to characterize the elution profile of two local anaesthetics (lidocaine hydrochloride and bupivacaine hydrochloride) from PMMA (polymethilmethacrylate) bone cement. MATERIAL AND METHODS: Palacos® R+G bone cement and lidocaine hydrochloride or bupivacaine hydrochloride specimens were obtained depending on the study group. These specimens were immersed in PBS (phosphate buffered saline) and removed from the solution at different set times. Subsequently, the concentration of local anaesthetic in the liquid was analyzed by liquid chromatography. RESULTS: The percentage of lidocaine eluted from PMMA bone cement in this study was 9.74% of the total lidocaine content per specimen at 72h and 18.73% at 336h (14 days). In case of bupivacaine, the elution percentage was 2.71% of the total bupivacaine content per specimen at 72h and 2.70% at 336h (14 days). CONCLUSIONS: Local anaesthetics elute in vitro from PMMA bone cement, reaching doses at 72h close to the doses used in anaesthetic blocks.

A dye elution method for the quantification of insecticidal crystal proteins from Bacillus thuringiensis and its compatibility with the presence of agro-industrial raw materials and waste products.

The insecticidal crystal proteins produced by Bacillus thuringiensis during sporulation are active ingredients against lepidopteran, dipteran, and coleopteran insects. Several methods have been reported for their quantification, such as crystal counting, ELISA, and SDS-PAGE/densitometry. One of the major tasks in industrial processes is the analysis of raw material dependency and costs. Thus, the crystal protein quantification method is expected to be compatible with the presence of complex and inexpensive culture medium components. This work presents a revalidated elution-based method for the quantification of insecticidal crystal proteins produced by the native strain B. thuringiensis RT. To quantify proteins, a calibration curve was generated by varying the amount of BSA loaded into SDS-PAGE gels. First, SDS-PAGE was performed for quality control of the bioinsecticide. Then, the stained protein band was excised from 10% polyacrylamide gel and the protein-associated dye was eluted with an alcoholic solution of SDS (3% SDS in 50% isopropanol) during 45 min at 95°C. This protocol was a sensitive procedure to quantify proteins in the range of 2.0-10.0 µg. As proof of concept, proteins of samples obtained from a complex fermented broth were separated by SDS-PAGE. Then, Cry1 and Cry2 proteins were properly quantified.

Study of Heterogeneity of Ethylene/1-Octene Copolymers Synthesized with Zirconium and Titanium Complexes Bearing Diamine-bis(phenolate) Ligands.

A series of ethylene/1-octene copolymers synthesized with diamine-bis(phenolate) complexes activated with Al(iBu)3/[Ph3C][B(C6F5)4] were subjected to preparative temperature rising elution fractionation (TREF). The complexes used differed in the type of metallic center (Zr or Ti) or the amine donor in the pendant arm of the ligand (NMe2 or NiPr2). The obtained fractions were then characterized via FTIR, DSC and GPC methods. It was found that all the copolymers had very broad chemical composition distributions, and the most heterogeneous was the copolymer produced by the titanium complex bearing a ligand with the NiPr2 donor group. The difference in the comonomer incorporation into the macromolecules of the fractions was as high as 8.3 mol%. The melting temperature and molecular weight of the fractions changed nearly linearly with the increased elution temperature. Copolymers produced by zirconium catalysts were also fractionated by molecular weight using the solvent/non-solvent technique with subsequent analysis of the fractions. It was shown that the fractions have a similar composition, low molecular weight distribution and very broad comonomer distribution. Therefore, the comonomer content in the fractions was not a function of the molecular weight as was observed for the copolymers synthesized with the Ziegler-Natta catalysts.

A comparative study of the predictive performance of different descriptor calculation tools: Molecular-based elution order modeling and interpretation of retention mechanism for isomeric compounds from METLIN database.

In the pharmaceutical industry, the need for analytical standards is a bottleneck for comprehensive evaluation and quality control of intermediate and end products. These are complex mixtures containing structurally related molecules. In this regard, chromatographic peak annotation, especially for critical pairs of isomers and closest structural analogs, can be supported by using a Quantitative Structure Retention Relationship (QSRR) approach. In our study, we investigated the fundamental basis of the reversed-phase (RP) retention mechanism for 1141 isomeric compounds from the METLIN SMRT dataset. Nine different descriptor calculation tools combined with different feature selection methods (genetic algorithm (GA), stepwise, Boruta) and machine learning (ML) approaches (support vector machine (SVM), multiple linear regression (MLR), random forest (RF), XGBoost) were applied to provide a reliable molecular structure-based interpretation of RP retention behaviour of the isomeric compounds. Strict internal and external validation metrics were used to select models with the best predictive capabilities (rtest > 0.73, order of elution > 60 %). For the developed models, mean absolute errors were in the range of 60 to 110 s. Stepwise and GA showed the most suitable performance as descriptor selection methods, while SVM and XGBoost modeling gave satisfactory predictive characteristics in most cases. Validation performed on the published experimental data for structurally related pharmaceutical compounds confirmed the best accuracy of MLR modeling in combination with GA feature selection of general physico-chemical properties. The resulting models will be useful for the prediction of separation and identification of structurally related compounds in pharmaceutical analysis, providing a simultaneous understanding of the interaction mechanisms leading to their retention under RP conditions.