Simple Method For Determination Research Articles

A methylene blue assay for the quantification of fucoidan – A specific application for seaweed extracts

AbstractFucoidan is a fucose-rich sulfated polysaccharide found mainly in brown seaweeds. Fucoidan has recently gained much attention due to its bioactive and medicinal properties, hence its high potential to be utilized in the pharmaceutical industry. Therefore, an accurate, reliable, and simple method for the specific determination of fucoidan would be a useful tool when looking to recover this valuable polysaccharide. This research focused on developing an assay utilizing the thiazine dye, methylene blue, for the quantification of fucoidan, with a specific application for fucoidan found in algal extracts. Fucoidan could be specifically determined at pH 1, to maximum concentrations of 4 g L-1 in solution without the interference of alginate and other seaweed extract contaminants. At pH 7 and 11, quantification of fucoidan led to interference from alginate and gallic acid. A conversion factor of 1.8 allowed the quantification of fucoidan from Ecklonia maxima extracts using a commercial standard from Fucus vesiculosis. An Ecklonia maxima extract was found to contain 5.47 ± 0.061 g L-1 of fucoidan. Measuring the fucoidan and L-fucose concentration in crude seaweed extract through the methylene blue assay and modified Dische and Shettles J Biol Chem 175:595–603, (1948) method, respectively, confirmed the accuracy and specificity of the method. The limit of quantification of the methylene blue assay at pH 1 was 0.62 g L-1 of fucoidan.

Simultaneous Quantification of Vancomycin, Linezolid and Voriconazole in Human Plasma by UHPLC–MS/MS: Application in Therapeutic Drug Monitoring

Abstract Objective Individual differences challenge the treatment of vancomycin, linezolid and voriconazole in severe infections. This study aimed to build a simple and economical method for simultaneous determination of the three antibiotics in human plasma by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) and provided a reference for therapeutic drug monitoring (TDM) of infected patients. Methods The plasma samples were precipitated by acetonitrile and detected and separated on a shim-pack GIST C18 column following the gradient elution within 5 min. Mass quantification was performed on multiple reaction monitoring mode under positive electrospray ionization. Results The linear ranges of vancomycin, linezolid and voriconazole were 1.00–100.00, 0.10–15.00 and 0.10–20.00 μg·mL−1, respectively, with good linearity (R2 > 0.99). The accuracy and precision, matrix effect, extraction recovery and stability were validated, and the results all meet the acceptance criteria of China Food and Drug Administration (CFDA) guidelines. Conclusion The UHPLC–MS/MS method was established and validated for the simultaneous determination of vancomycin, linezolid and voriconazole in human plasma and successfully applied to routine TDM for individualized treatment.

A simple, rapid, and green method for determination of three cholic acids in bio-transformed Jindanfen by HPLC-MS

AbstractA simple, rapid, and green high-performance liquid chromatography-mass spectrometry (HPLC-MS) method was developed for determination of tauroursodeoxycholic acid (TUDCA), taurocholic acid (TCA), and taurochenodeoxycholic acid (TCDCA) in bio-transformed Jindanfen (BTJDF), which is obtained from chicken bile through a bioconversion process. The sample was prepared using water. The HPLC separation was operated on a poroshell 120 EC-C18 column with a 2.0 min gradient elution procedure. Detection was performed on a single quadrupole mass spectrometer in negative mode with selected ion monitoring mode (SIM). This developed HPLC-MS method presented good linearity (r > 0.997) and sensitivity (limit of quantification, 30.0–80.0 pg) for three analytes. The relative standard deviations (RSDs) for precision, repeatability, and stability were all below 3.00%. The matrix effects and average recoveries of three analytes were 91.2–97.9% (RSDs < 1.50%) and 95.4–103% (RSDs < 3.00%), respectively. The average contents of TUDCA, TCA, and TCDCA in ten batches of samples were 33.8, 13.2, and 20.5%, respectively. Finally, the greenness of the developed method was validated by Analytical Eco-Scale and Complex-GAPI. The developed method was proved to be an eco-friendly, effective, and reliable approach for assaying the three cholic acids in BTJDF, which is help to improve the quality evaluation level of the BTJDF industry.

A simple and green offline-online capillary electrophoresis stacking strategy for the simultaneous determination of hydrophobic compounds in complicated samples using sodium dodecyl sulfate as the solubilizer and pseudophase

BackgroundCapillary electrophoresis is a powerful analytical method featured with high separation efficiency, minimal sample requirements, and reduced organic solvents consumption. However, its low sensitivity hinders its wide application in determination of trace analytes especially for the weakly ionized hydrophobic compounds. Offline and Online capillary electrophoresis stacking methods are more favored to enhance detection sensitivity of analytes. The determination of two sesquiterpenes and an alkaloid from the dried root of Lindera aggregata merged as an example for developing a simple, sensitive and green method for the simultaneous determination of two hydrophobic compounds in complicated matrix samples. ResultsAn offline-online capillary electrophoresis stacking strategy by integrating micro matrix solid phase dispersion with field-amplified sample stacking and micelle to cyclodextrin stacking has been developed for the simultaneous determination of dehydrocostus lactone, linderane, norisoboldine in complex matrices. The optimized parameters were set at 65 mM sodium dihydrogen phosphate, 35% methanol, 180 s for sample injection and 210 s for cyclodextrin injection, 20 mM sodium dodecyl sulfate of sample matrix for online stacking; 1:1 sample to MCM-48, 180 s grinding time, and 1,000 μL of 20 mM sodium dodecyl sulfate elution for offline procedure. Under the optimum conditions, the method showed good linearity with correlation coefficients (R2≥0.9927), low limits of detection within the range of 25-50 ng mL-1, satisfactory repeatability and reproducibility below 3.98%, and acceptable recoveries between 94% and 97%. The developed method was successfully applied to two real samples, the root of L. aggregata and rat feces. SignificanceSodium dodecyl sulfate is firstly used as an eluent in micro matrix solid phase dispersion and plays a dual role throughout the analytical procedure, including extraction solvent in sample preparation and micelle pseudophase during online stacking. It brings great procedure convenience to the method. The sensitivity of this method can improve up to 1283-folds compared with the normal mode. Moreover, the overall strategy indicates satisfied green potential evaluated by greenness assessment tools

RBFNN-based angles-only orbit determination method for non-cooperative space targets

Angles-only orbit determination during space situational awareness missions for non-cooperative targets such as space debris is subject to the well-known observability problem, that is, the orbital state is weakly observable or even unobservable because of missing range measurements. The key point to solve this problem is how to quickly capture the nonlinearity of orbit dynamics if only one space-based passive sensor is available to observe the target and translational maneuvers are not executed. To solve the short-arc angles-only problem, this study develops a simple and fast orbit determination method by exploiting the advantages of radial basis function neural network (RBFNN). Emphasis was placed on the design of the RBFNN, which was trained to construct a mapping network model from line-of-sight (LOS) measurements to the relative orbit. First, the perturbed relative orbit dynamics considering the Earth's non-spherical J2 term and air drag was established with the LOS measurement model. Second, a RBFNN-based angles-only orbit determination frame was developed, in which the generator of the training dataset, data preprocessing algorithm, and RBF network structure were designed. Finally, the proposed method was verified and tested using a set of numerical simulations of low-Earth orbit cases. The anti-noise and generalization performance of the designed network and the sensitivity of the solution accuracy to the measurement frequency and span were presented and discussed. Additionally, the advantages of the RBFNN-based method were confirmed by comparison with the results obtained using the BPNN (Back Propagation Neural Network)-based method. The simulation results show that the average orbit prediction error for LEO scenarios is approximately 0.08% using the index of initial relative distance, where only three sets of LOS angles are measured within a span of 24 s.

Rapid determination of hippuric acid as an exposure biomarker of toluene using a colorimetric assay and comparison with high-performance liquid chromatography

Occupational exposure to toluene is associated with health risks that require reliable monitoring methods. Hippuric acid (HA), a urinary metabolite of toluene, serves as a valuable biomarker for such exposure. Colorimetric methods for the quantitative determination of HA have gained prominence due to their simplicity, cost-effectiveness, and suitability for field application. In the present study, a simple colorimetric technique was optimized for the determination of HA in the urine sample, and compared with a usual HPLC technique. The central composite design (CCD) was applied to examine the effective parameters on the colorimetric determination of HA. The calibration curve for HA was established within the concentration range of 6 to 100 mg L−1 with R2 = 0.97. The detection limit (LOD) and quantification limit (LOQ) were determined to be 1.8 mg L−1 and 6 mg L−1 respectively. The relative standard deviation (RSD%) was less than 5%, and the recovery% (R%) was 90.5–100.1. The overall results showed good agreement between the colorimetric and HPLC results. There was a significant relationship between the results obtained from HPLC and colorimetric methods especially for higher concentration levels of HA (≥ 500 mg/g creatinine). In conclusion, our optimized colorimetric method is a simple, cost-effective, and rapid method for determination of HA in occupational exposure, which is comparable with the HPLC technique.

Statistical optimization of two-phase hollow fiber liquid-phase microextraction for preconcentration of strychnine in the clinical and postmortem biological fluids prior to gas chromatography-mass spectroscopy detection

Strychnine is a herbal alkaloid whose role in military and doping applications as well as the nervous system stimulation and cancer therapy has been confirmed. Because of its lethal nature, even at low dosages, developing a rapid, sensitive, and accurate method for determination of this alkaloid in the clinical and postmortem samples is of great importance. In this study, a green analytical method based on the two-phase hollow fiber liquid-phase microextraction (HF-LPME) combined with gas chromatography-mass spectrometry (GC–MS) was presented for preconcentration and determination of strychnine in biological fluids. A Box-Behnken design (BBD) with three variables, including extraction time (30–90 min), solution pH (9.0–11.0), and ionic strength (1.0–3.0 mol/L) was employed to maximize the extraction efficiency of strychnine by 1-octanol. The results were satisfactorily fitted to a quadratic response surface model (R2 = 0.979, F = 34.4) which predicted the optimum conditions of operation (extraction time of 89 min, pH = 11.0, and ionic strength of 3.0 mol/L). Based on the results, the studied variables and the interaction between pH and extraction time showed highly significant effects on the process efficiency. The calibration curve was linear in the concentration range of 2.7–1000.0 µg/L (R2 = 0.9978) and the limits of detection and quantitation were found to be 0.8 and 2.7 µg/L, respectively. Moreover, the method was successfully applied to different real samples, including urine (clinical sample), bile and stomach contents, blood, and vitreous humor (postmortem samples), and relative recoveries were obtained in the range of 93.8 % to 99.8 %. The findings of this study suggest that the environmentally friendly HF-LPME method which uses a small amount of a chlorine-free solvent, is a sensitive, cost-effective, simple, and efficient preconcentration method for trace determination of strychnine in biological fluids.

Liquid chromatography with tandem mass spectrometric method for determination of 52 antibiotics in human whole blood and urine and application to forensic cases.

A rapid and reliable method was developed and validated for the simultaneous analysis of 52 antibiotics (cephalosporins, penicillins, carbapenems, lincosamides, quinolones, nitroimidazoles, macrolides, sulfonamides, tetracyclines, glycopeptide) in urine and whole blood by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Analytes were extracted by dilution or protein precipitation and analyzed on an Agilent 1260 HPLC system coupled to an Agilent 6470 Triple Quadrupole Mass Spectrometer. The method attended method validation criteria. The limits of detection were equal or lower than 2.0ng/mL, whereas the limits of quantification ranged from 0.1 to 10.0ng/mL, from 0.1 to 5.0ng/mL, in urine and whole blood, respectively. For all analytes, the bias and intra- and inter-day precision values were less than 14.7%. The ranges of recovery values of all antibiotics were 76.5-124.5% in whole blood and 76.3-121.8% in urine, values of the effects were lower than 25% in two matrices. No evidence of carryover was observed. The study of sample stability showed that almost all analytes were stable at 24°C for 24h, all analytes were stable at -20°C for 14 days and at -80°C for 30 days. Freeze-thaw cycles stability showed that antibiotics were stable except for imipenem. Autosampler stability study showed that all analytes were stable for 24h, except for imipenem and amoxicillin. Applicability was proven by analyzing authentic whole blood (n = 86) and urine (n = 79) samples from patients under antibiotics treatment. Therefore, this method was applied to the analysis 3 forensic allergy cases, which were positive for at least one analyte. A simple, sensitive and high-throughput method for the simultaneous determination of different classes of antibiotics in urine and whole blood samples was developed and applied. This sensitive method was successfully applied to forensic cases.

Identification of dental sexual dimorphism in deciduous teeth: A cross sectional study

The study of sex diagnosis is essential to reconstruct the biological profile of an unknown individual. Two approaches are often used: morphometric and scopic. This three-dimensional morphometric study aimed to assess sexual dimorphism in temporary dentition.: A total of 200 dental impressions digitized in 3D using the Revopoint® POP2 3D scanner were used for this odontometric analysis. Discriminant statistical analysis (Student's t-test) revealed that boys had higher mean values than girls for all distances measured. A highly significant sexual dimorphism was observed in the temporary second molars. The distance between the mandibular canines was slightly greater in boys, although this difference was not statistically significant. In conclusion, odontometric parameters are a simple, reliable, and inexpensive method of sex determination. The temporary canines and second molars are the most dimorphic.

Patient's Healthy-Limb Motion Characteristic-Based Assist-As-Needed Control Strategy for Upper-Limb Rehabilitation Robots.

The implementation of a progressive rehabilitation training model to promote patients' motivation efforts can greatly restore damaged central nervous system function in patients. Patients' active engagement can be effectively stimulated by assist-as-needed (AAN) robot rehabilitation training. However, its application in robotic therapy has been hindered by a simple determination method of robot-assisted torque which focuses on the evaluation of only the affected limb's movement ability. Moreover, the expected effect of assistance depends on the designer and deviates from the patient's expectations, and its applicability to different patients is deficient. In this study, we propose a control method with personalized treatment features based on the idea of estimating and mapping the stiffness of the patient's healthy limb. This control method comprises an interactive control module in the task-oriented space based on the quantitative evaluation of motion needs and an inner-loop position control module for the pneumatic swing cylinder in the joint space. An upper-limb endpoint stiffness estimation model was constructed, and a parameter identification algorithm was designed. The upper limb endpoint stiffness which characterizes the patient's ability to complete training movements was obtained by collecting surface electromyographic (sEMG) signals and human-robot interaction forces during patient movement. Then, the motor needs of the affected limb when completing the same movement were quantified based on the performance of the healthy limb. A stiffness-mapping algorithm was designed to dynamically adjust the rehabilitation training trajectory and auxiliary force of the robot based on the actual movement ability of the affected limb, achieving AAN control. Experimental studies were conducted on a self-developed pneumatic upper limb rehabilitation robot, and the results showed that the proposed AAN control method could effectively estimate the patient's movement needs and achieve progressive rehabilitation training. This rehabilitation training robot that simulates the movement characteristics of the patient's healthy limb drives the affected limb, making the intensity of the rehabilitation training task more in line with the patient's pre-morbid limb-use habits and also beneficial for the consistency of bilateral limb movements.

A simple, fast and green method for API gravity, density, sulfur and nitrogen determination in crude oil by ATR-FTIR

In this work, the combination of multivariate data analysis and Fourier-transformed infrared (FTIR) for the characterization of crude oil samples based on the determination of API gravity (°API), density, sulfur and nitrogen contents is proposed. Reference values for density and °API were determined according to ASTM D7042-04, while nitrogen was determined according to ASTM D4629. For sulfur determination, a miniaturized MAD-SRC method was used to obtain reference values. The best model for density and °API was obtained applying a partial least squares with two response variables (PLS2) calibration. Multiplicative scattering correction (MSC) and mean centering pre-treatments were applied for this model (R2 of 0.936 and 0.944 for density and °API, respectively). For N content, the best PLS model consisted in using selected variables and first derivative with Savitsky-Golay smoothing (R2 = 0.983). The PLS model for S content prediction was built using selected variables and applying first derivative with Savitsky-Golay smoothing and mean-centering data pre-treatment (R2 = 0.982). The environmental impact and greenness of crude oil characterization applying both the alternative (using multivariate calibration) and the official methods was evaluated using the White Analytical Chemistry (WAC) tool. WAC analysis resulted in relatively low scores for conventional methods (76.8 for ASTM D4629, 75.8 for ASTM D7042-04 and 70.7 for MAD-SRC) while the ATR-FTIR method was considered the greener method (low impact, WAC score of 98.3). The proposed method combining FTIR with multivariate calibration enabled the use of a very low sample volume (about 0.01 mL), minimum waste generation, and suitable results were achieved, saving time and reagents.

Multiwalled carbon nanotubes decorated with molybdenum sulphide (MoS2@MWCNTs) for highly selective electrochemical picric acid (PA) determination

Nitrophenols are industrially versatile yet environmentally detrimental compounds. Herein, we have synthesised molybdenum sulphide based dichalcogenide supported multiwalled carbon nanotubes i.e. MoS2@MWCNTs electrocatalyst by simple wet chemical method for PA determination. The successful decoration of MoS2 over MWCNTs were confirmed by various characterizations techniques including scanning electron microscopy (SEM) shows MoS2 layers grown on MWCNTs and having average size is –80 nm. Energy dispersive X-ray analysis (EDAX) reveals elements are homogenously distributed in nanocomposite. High resolution-transmission electron microscopy (HR-TEM) shows increase in average diameter after decoration of MoS2 over MWCNTs from 30 nm to 70 nm. The Fourier transform infrared (FT-IR) analysis suggests the presence of Mo-S stretching frequency at 605 cm−1 in addition to hydroxyl, carbonyl, C–C, C–O stretching frequencies are also observed. In Raman spectrum from apart D and G bands, the characteristic intense bands E2g1 and A1g of MoS2 were pointed towards presence of molybdenum and sulphur. The X-ray diffraction (XRD) confirms synthesised electrocatalyst is in hexagonal crystal structure with P63/mmc space group. The X-ray photoelectron spectroscopy (XPS) reveals that for Mo 3d is found to be two characteristics peaks at 231.2 eV and 233.2 eV corresponds to Mo4+ 3d3/2 and 3d5/2 respectively. The peak at 229 eV corresponds to S 2s. Whereas, the signal appears at 162.7 eV, 165 eV, 169 eV and 170 eV shows sulphur is in 2S3/2 and 2S5/2 states. Electrochemical performance was examined by cyclic voltammetry (CV) tests. The Electrocatalyst is highly selective, having appreciable anti-interference property, lower limit of detection (LoD), i.e., 0.5 μM with wide linear range. The low Rct and high k⁰ pointed that MoS2@MWCNTs performed better towards electrochemical detection of PA.

Selective adsorption and identification of penicillin G sodium in milk by molecularly imprinted polymer doped carbon dot.

A carbon dot (CD) was prepared by o-phenylenediamine and water, which showed bright yellow fluorescence under ultraviolet light irradiation (λ = 580nm), and verified good fluorescence quenching effect on penicillin G sodium (Png-Na). Using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, and Png-Na as a template, a kind of composite microsphere combining CD and molecularly imprinted polymer (MIP) was synthesized by surface-initiated atomic transfer radical polymerization (SI-ATRP). For reasons ofcomparison, we also prepared MIP without CD and non-imprinted polymers (NIPs). Through static and dynamic adsorption experiments, the maximum adsorption capacity was 47.05mgg-1 and the equilibrium time was 30min. High-performance liquid chromatography (HPLC) was utilized to determine the content of Png-Na in the spiked milk samples. A sensitive, rapid, and simple method for determination of Png-Na in food samples was developed. The utilized approach enabled the quantification of Png-Na within theconcentration range 20-1000μg L-1 (with a limit of detection of 5μg L-1). The recoveries achieved were in the range 93.3-98.2%, with a relative standard deviation of 1.2-4.2%. The results demonstrated that CD@MIP possessed the capability of specific adsorption and fluorescence detection of Png-Na, enabling simultaneous detection and enrichment of Png-Na in real samples.

Determination of the Absolute Configuration of Secondary Alcohols in a Compound Mixture via the Application of Competing Enantioselective Acylation Coupled with LC/MS Analysis.

The determination of natural product stereochemistry plays a significant role in drug discovery and development. Understanding the stereochemistry of natural products is essential for predicting and optimizing their interactions with biological targets, which, in turn, influences their therapeutic efficacy, safety, and overall impact on living organisms. Here, we present the first application of competitive enantioselective acylation (CEA) reactions in conjunction with LC/MS analysis for determining the absolute configuration of secondary alcohols in natural products which were purified as a mixture. This approach utilizes the enantiomeric pair of HBTM (homobenzotetramisole) catalysts, demonstrating sufficient kinetic resolution for the acylation of secondary alcohols. The rapid reaction kinetics were quantitatively estimated with LC/MS analysis as the characterization technique for the enantioselective transformations. Our study has expanded the application of the CEA reaction coupled with LC/MS analysis to mixtures. Utilizing LC/MS analysis, the CEA reaction offers a sensitive and simple method for stereochemistry determination. Additionally, the application of the CEA reaction is cost/time-effective since only small quantities of substrates and a short reaction time are required for characterizing the absolute configuration of secondary alcohols in natural products compared to other conventional methods.

A Fast and Simple Solid Phase Extraction-Based Method for Glucosinolate Determination: An Alternative to the ISO-9167 Method.

Glucosinolates (GLSs) are a well-studied sulfur-containing compound found in Brassicaceae plants that play critical roles in plant resistance and human health. Correctly identifying and reliably quantifying the total and individual GLS content is of great importance. An improved method as an alternative to the ISO 9167-1 (ISO) method is developed in the present study. An efficient extraction and purification procedure is proposed with a commercially available dimethylaminopropyl (DEA)-based weak anion exchange solid-phase extraction (SPE) cartridge instead of using the self-prepared ion-exchange columns in the ISO method. The GLSs are identified and quantified by ultra high-performance liquid chromatography (UHPLC) high-resolution mass spectrometry (HRMS). The method demonstrates a comparable quantification of total and individual GLSs on certified rapeseeds and other Brassicaceae vegetables when compared to the ISO method. The developed SPE method is simpler and more efficient, thus allowing for applications to a large sample size with reduced analysis time, improved repeatability and accuracy, and possible automation.

Development and Validation of an HPLC-MS/MS Method for Quantification of Apixaban in Human Plasma

Introduction. Apixaban is an anticoagulant used in a number of thromboembolic diseases with an improved benefit-to-risk ratio, according to multiple clinical studies. Due to the prescription of apixaban as antithrombotic therapy in patients with COVID-19, an increase in its use has been observed. Thus, due to the widespread use of apixaban and the need to conduct pharmacokinetic and bioequivalence studies of the drug, it is important to develop and validate a simple and sensitive method for the quantitative determination of apixaban in human blood plasma.Aim. The aim of the study is to develop and validate a method for the determination of apixaban in human blood plasma using high-performance liquid chromatography with tandem mass selective detection (HPLC-MS/MS) for the subsequent bioanalytical study.Materials and methods. The determination of apixaban in human plasma was carried out by HPLC-MS/MS with rivaroxaban as an internal standard. The method of protein precipitation with acetonitrile was used as sample preparation. Mobile phase: 0.1 % solution of formic acid in water (eluent A); 0.1 % solution of formic acid in acetonitrile (eluent B). The total run time was 3.00 min. Column: Shim-pack Velox Biphenyl; 2.7 µm; 50 × 2.1 mm. Ionization source: electrospray with positive ionization mode. MRM transitions: 460.15 → 443.10 m/z (apixaban); 436.05 → 144.95 m/z (rivaroxaban).Results and discussion. The developed method was validated in accordance with the EAEU requirements for the following parameters: selectivity, calibration curve, accuracy and precision, lower limit of quantitation, suitability of standard samples, matrix effect, recovery, stability, carry-over, dilution effects. The parameters met the acceptance criteria.Conclusion. The confirmed analytical range of the developed and validated method was 1.00–300.00 ng/mL in blood plasma. The method for determining apixaban in blood plasma is simple and sensitive. This method was tested during the analytical part of the bioanalytical study and can be used to conduct other pharmacokinetic studies of apixaban drugs.

SIMULTANEOUS DETERMINATION OF CHLORHEXIDINE, р-CHLORANILINE, TRICLOSAN, DIBUTYL PHTHALATE, AND IONOL IN ANTIBACTERIAL LIQUID BY HPLC WITH SPECTROPHOTOMETRIC DETECTION

The article is devoted to the development of a simple chromatographic method for the simultaneous determination of the well-known antiseptics – chlorhexidine and triclosan – in new generation of antiseptic liquids. The dependences of the retention times of chlorhexidine and triclosan on the acetonitrile concentration in the mobile phase (from 30 to 60%) and pH (in the range of 3–8 units) for sorbents Luna C18, Nucleosil CN, Diaspher C4 were studied. A perfect separation of chlorhexidine, p-chloraniline (the most toxic product of chlorhexidine decomposition), dibutylphthalate (as a component of cosmetic alcohol), triclosan and ionol (butylhydroxytoluene, BHT, E321 – antioxidant agent) during 20 minutes in the gradient elution mode on the column with a domestic sorbent Diaspher C4 has been demonstrated.

Advancing Molecular Weight Determination of Lignin by Multi-Angle Light Scattering.

Due to the complexity and recalcitrance of lignin, its chemical characterization is a key factor preventing the valorization of this abundant material. Multi-angle light scattering (MALS) is becoming a sought-after technique for absolute molecular weight (MW) determination of polymers and proteins. Lignin is a suitable candidate for MW determination via MALS, yet further investigation is required to confirm its absolute MW values and molecular size. Studies aiming to break down lignin into a variety of renewable products will benefit greatly from a simple and reliable determination method like MALS. Recent pioneering studies, discussed in this review, addressed several key challenges in lignin's MW characterization. Nevertheless, some lignin-specific issues still need to be considered for in-depth characterization. This study explores how MALS instrumentation manages the complexities of determining lignin's MW, e.g., with simultaneous fractionation and fluorescence interference mitigation. Additionally, we rationalize the importance of a more detailed light scattering analysis for lignin characterization, including aspects like the second virial coefficient and radius of gyration.

Development of the RP-HPLC Method for Simultaneous Determination and Quantification of Artemether and Lumefantrine in Fixed-Dose Combination Pharmaceutical Dosage Forms.

Developing countries face enormous challenges with substandard and falsified antimalarial drugs. One specific issue is the lack of a simple, cost-effective, and robust HPLC method to simultaneously determine and quantify the active pharmaceutical ingredients (APIs) in fixed-dose artemether-lumefantrine pharmaceutical dosage forms. The current study developed a novel, simple, sensitive, precise, accurate, and cost-effective RP-HPLC method for the simultaneous determination and quantification of artemether and lumefantrine in pharmaceutical dosage forms. The HPLC analysis was carried out on an Agilent 1260 Infinity Series HPLC system equipped with an ODS Intersil-C8 (150 × 4.6 mm) 5.0 µm column, by isocratic elution. The mobile phase composition consisted of acetonitrile and 0.05% orthophosphoric acid buffer of pH 3.5 in the ratio of 70 : 30 v/v. The analysis was performed at a 1 mL/min flow rate and a column temperature of 25°C. The total run time was 6 minutes. The detection was done with a variable wavelength detector (VWD) at an isosbestic point wavelength (λ) of 210 nm. The developed method was validated according to the ICH guidelines concerning system suitability, specificity, linearity, accuracy, precision, and robustness. The system suitability of the developed method revealed satisfactory theoretical plates and symmetry factors. The method proved to be specific, with no interference of mobile phase or excipients. The calibration plot exhibited linearity over the concentration range of 275-1925 μg/mL with R2 = 0.9992 for artemether and a range of 150-1050 μg/mL with R2 = 0.9985 for lumefantrine. The accuracy of the method, determined by the recovery study, was 99.79-100.16% for artemether and 99.04-99.50% for lumefantrine. The % RSD values for intraday precision were 0.175 and 0.203, while interday precision values were 0.340 and 0.554 for artemether and lumefantrine, respectively. The method demonstrated robustness when subjected to slight modifications in the flow rate, column temperature, and mobile phase composition. The developed analytical method proved satisfactory as per ICH guidelines and hence can be used for the determination and quantification of artemether and lumefantrine in bulk drug and pharmaceutical dosage forms.

Simultaneous determination of selected ionophoric coccidiostats and amino acids in feed premixes using high-performance liquid chromatography-ultraviolet detection method.

The combination of ionophoric coccidiostats and amino acids (AAs) is important in poultry feeding to enhance immunity and improve the growth and feed efficiency of birds suffering from coccidiosis. A simple, rapid, and economical high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method for the simultaneous determination of three ionophoric coccidiostats, namely salinomycin (SAL), maduramicin (MAD), and monensin (MON) in addition to three AAs; L-tryptophan (L-TRP), alpha-ketoleucin (KLEU), and L-valine (L-VAL) in feed premixes was developed and validated. Chromatographic separation was achieved in less than 12min using a phenyl hexyl column with a mobile phase consisting of acetonitrile/methanol/water (25:20:55, v/v/v) adjusted to pH 3 using phosphoric acid. Isocratic elution was performed at a flow rate of 1mL/min with UV detection at 210nm. The method showed good linearity in the ranges 0.50-5.0mg/mL for MON, 0.20-2.0mg/mL for MAD and SAL, 10.0-100.0μg/mL for L-TRP and KLEU, and 50.0-500.0μg/mL for VAL. The developed method was successfully applied to determine the studied analytes in feed premixes with good recoveries and precision. The good validation criteria of the proposed method allow its utilization in quality control laboratories.