Trifluoroacetic Acid Solution Research Articles

Determination of the Maillard reaction products in complementary rice, flour, and noodles by high performance liquid chromatography with a diode array detector

AbstractA method was established for the simultaneous determination of furosine, furanone, and four furfural compounds (5‐hydroxymethylfurfural, furfural, furyl methyl ketone, and methyl furfural) in complementary rice, flour, and noodles for infants and young children by high performance liquid chromatography with a diode array detector. The sample was extracted using oxalic acid aqueous solution as a solvent, and the protein was removed using trichloroacetic acid. Then the six Maillard reaction products were separated by an Eclipse XDB‐C18 column with a gradient elution at a flow rate of 0.6 mL/min using acetonitrile‐0.1% trifluoroacetic acid solution as the mobile phase, detected by a diode array detector and quantified by external standard method. The linear ranges of the six Maillard reaction products were 250–20000 μg/100 g with the correlation coefficients greater than 0.999, and the limits of quantification ranged from 250 to 1000 μg/100 g (S/N ≥ 10). The recoveries of the six Maillard reaction products ranged from 71.2% to 100% with a relative standard deviation of 0.9%–4.9%. The real sample analysis results showed that 5‐hydroxymethylfurfural was detected in two cookie samples, the contents of which were 335 μg/100 g and 436 μg/100 g, respectively. There are no studies on the detection of the six Maillard reaction products in rice, flour, and noodles in the previous reports. The established method provided reference for the quantification of expiration date in complementary rice, flour, and noodles for infants and young children.

Development and Validation of Analytical Method by HPLC-PDA and Seasonality from Gallic Acid, Catechin, and Epicatechin in Leaf Extracts from Campomanesia adamantium

Campomanesia adamantium is native of the Brazilian Cerrado, and its leaves are popularly used as anti-inflammatory, antidiarrheal, and antiseptic in the urinary tract. This study aimed to develop and validate an analytical method by high-performance liquid chromatography for the simultaneous quantification and evaluation of the seasonal variability of gallic acid, catechin, and epicatechin, during 12 months, in C. adamantium leaf extracts. Chromatographic separations were performed with a mobile phase gradient of acetonitrile and 0.05% (v/v) trifluoroacetic acid solution, flow rate of 1.0 mL min-1, detection at 210 nm, C18 column (150 × 4.6 mm, 5 μm) and column oven temperature of 35 °C. The analytical method developed was selective, linear, precise, accurate, robust, and without matrix effect. The parameters obtained in the present study meet the requirements established by national and international guidelines. The best time for leaves harvesting, with the highest levels reached, was in September (0.0626%, m/v) and August (0.044%, m/v) for gallic acid, in June (0.3953%, m/v) and July (0.3804%, m/v) for catechin, and from May (0.1622%, m/v) and June (0.1415%, m/v) for epicatechin, in the dry season. Therefore, this study contributes by providing parameters for quality control of the raw material C. adamantium.

Design and validation of analytical methods for quantitative determination of active ingredients in extemporal combined medicine in spray form

The aim of the work was the development and study of the validation characteristics of the method of quantitative determination of phenylephrine hydrochloride, nitrofural and diphenhydramine hydrochloride when they are simultaneously present in an extemporaneous combined medicinal product in the form of a spray using liquid chromatography method.
 Materials and methods. Agilent 1260 liquid chromatographs, equipped with a diode-matrix and UV detector from the company "Agilent technologies", USA. Chromatographic columns 250×4.6 mm filled with octadecylsilyl silica gel for chromatography (Zorbax StableBond SB-Aq, Agilent company), mobile phase - 0.1 % aqueous solution of trifluoroacetic acid R - methanol R, elution mode - gradient; mobile phase speed – 1.2 ml/min; the detection wavelength is 220 nm.
 Results. The determined chromatographic conditions ensure proper separation of the peaks of the substances to be determined: phenylephrine hydrochloride, nitrofural and diphenhydramine hydrochloride in their joint presence, and do not have a negative effect on the quantitative assessment of their content. Validation tests were conducted to confirm the suitability of the analytical method for the performance of the task - control of the quantitative content of active substances in the combined medicinal product in the form of a spray. The determined validation characteristics indicate that the method is characterized by appropriate specificity, linearity, correctness and convergence in the range of application for phenylephrine hydrochloride (range 0.499-0.749 mg/ml, ΔZ=0.44 ≤ max ΔZ=3.20, d=0.22 ≤ max d=1.02, a=0.01 max a=5.1, r = 0.9997 min r= 0.9924), nitrofural (range 0.154-0.231 mg/ml, ΔZ=0.44 ≤ max ΔZ=3.20, d=0.62 ≤ max d=1.02, a=0.0006 max a=5.1, r = 0.9996 min r= 0.9924) and diphenhydramine hydrochloride (range 0.499-0.749 mg/ml, ΔZ=0.50 ≤ max ΔZ=3.20, d=0.05 ≤ max d=1.02, a=0.076 max a=5.1, r = 0.9999 min r= 0.9924).
 Conclusions. An analytical technique for the quantitative determination of phenylephrine hydrochloride, nitrofural and diphenhydramine hydrochloride when simultaneously present in an extemporaneous combined medicinal product in the form of a spray by the method of high-performance liquid chromatography was developed. The determined validation parameters confirm the correctness of the methodology. The proposed HPLC technique was used to study the chemical stability of the spray for the treatment of allergic rhinitis

The potential of three different adsorbents in solid‐phase extraction of antihistaminic and antimigraine drugs from water samples using ultra‐high‐performance liquid chromatography‐ultraviolet analysis

AbstractIn this study, eight pharmaceuticals belonging to two classes, antihistaminic and antimigraine, were considered. Ultra‐performance liquid chromatography‐diode array detection was set up and gradient elution was used. The mobile phase was composed of acetonitrile and trifluoroacetic acid solution. Chromatographic separation was carried out with a run time of 9 min. The preconcentration of eight studied solutes was realized by micro solid‐phase extraction. Multiwalled carbon nanotubes, cetyltrimethylammonium bromide‐titanium dioxide nanotubes, and C‐18 bonded silica solid‐phase extraction (SPE) sorbents were evaluated and compared concerning recoveries. The results of the optimization of factors affecting the extraction efficiency including sample volume, the elution solvent type, and its volume are reported. For validation of the analytical procedure, specificity, linearity, precision, accuracy, limit of detection, and limit of quantification were evaluated. The developed method was successfully applied to the analysis of wastewater treatment samples. The extraction recoveries of pharmaceutical substances were above 81.23% for the three SPE sorbents. The extraction method was selective and the detection and quantification limits were between 0.004–0.02 and 0.01–0.06 μg/L, respectively. All the results indicated the potential application of the three studied SPE sorbents for the extraction of selected pharmaceuticals from wastewater.

Kinetic model-aided process optimization via integrated in-situ FTIR and real-time oscillatory shear rheometry: A case study on impurity control and gelation mitigation for a solid phase peptide cleavage process

Solid phase peptide synthesis is a widely used technique for the production of medicinal peptides, particularly when using unnatural amino acids. In such processes, when the synthesis is complete and the designed peptide sequence is obtained, a subsequent peptide isolation technique is often employed using a trifluoroacetic acid (TFA)/dichloromethane (DCM) solution mixture to promote the cleavage of the peptide from the resin while retaining the protecting groups on the peptide (soft cleavage). The peptide is then isolated via distillation, precipitation/crystallization, and drying unit operations. Throughout these processes, the reaction conditions must be optimized to minimize peptide degradation in the acidic cleavage solution. Furthermore, any peptide network formation during cleavage can dramatically increase the solution viscosity which poses significant operating risks in manufacturing. In this study, a systematic model-aided kinetics and rheology analysis is performed to rapidly identify optimal reaction conditions using the minimum number of screening experiments. The reaction kinetics investigation was conducted with the aid of a mid-FTIR probe to track peptide and TFA solution concentrations during the reaction in real-time. A detailed kinetics model of peptide cleavage and impurity formation is proposed and the adsorption isotherm of TFA is also considered. To confirm that an acceptable solution viscosity can be maintained at the specified reaction conditions over the duration of the projected process time, in-situ oscillatory rheometry was conducted to monitor any viscosity and modulus increase in the soft-cleavage reaction medium. The novel combination of reaction kinetics modeling, impurity control techniques, and the development of a peptide network phase diagram provides a layered approach that can be utilized in the rapid rational design of any solid phase peptide isolation processes.

Calix[3]Pyrrole and Related Macrocycles: Synthesis and Properties

Calix[4]pyrrole is a porphyrinogen-like macrocycle in which four pyrrole units are linked by four sp3-hybridized carbon atoms at the α-positions. While such tetrapyrrolic macrocycles are readily synthesized by acid-catalyzed condensation reactions of pyrrole monomer and carbonyl compound, analogous macrocycles composed of three pyrrole units are always not observed. Calix[3]pyrrole is a ring-contracted analogue of calix[4]pyrrole, and has been missing in porphyrin-related chemistry. In this presentation, the first synthesis of calix[3]pyrrole and its furan-embedded analogues is reported, and their unique reactivity derived from their macrocyclic ring strain will be discussed.Synthesis of calix[3]pyrrole started with a linear trimer of 3,3-dimethylpentane-2,5-dione. Intramolecular cyclization of the linear hexaketone was accomplished in 5 steps to give a cyclic hexaketone precursor. Paal–Knorr type pyrrole formation reaction of cyclic hexaketone gave calix[3]pyrrole in 41% yield (Scheme 1). Using similar strategies, analogous calix[3]-type macrocycles, namely, calix[1]furan[2]pyrrole, calix[2]furan[1]pyrrole, and calix[3]furan, were successfully synthesized. Single crystal X-ray diffraction analysis of calix[3]pyrrole revealed its strained structure, and the theoretical calculations showed the strain energy of calix[3]pyrrole is 22.1 kcal/mol per unit higher than that of calix[4]pyrrole. Such strain energy tends to decrease as the number of pyrrole unit decreased.Calix[3]pyrrole exhibited unique reactivity derived from macrocyclic ring strain under acidic (Rothemund–Lindsey) conditions that are frequently used for porphyrin synthesis. When calix[3]pyrrole was dissolved in 10 mM solution of trifluoroacetic acid in dichloromethane, calix[6]pyrrole was quantitatively formed within 30 seconds (Scheme 1). Similar strain-induced ring expansion was observed for calix[1]furan[2]pyrrole, but full conversion took approximately 5 minutes. On the other hand, calix[2]furan[1]pyrrole and calix[3]furan did not show ring expansion. Detailed mechanistic analysis revealed that protonation at a pyrrole unit in calix[3]pyrrole triggers irreversible ring-cleavage to give a linear tripyrrane moiety which undergoes cyclodimerization under acidic conditions.The strain-induced ring expansion reaction of calix[3]pyrrole solved a long-standing question in porphyrin-related chemistry. Tripyrrolic macrocycles such as calix[3]pyrrole are, even formed, not isolable from pyrrole condensation reaction using acid, because the strain-induced conversion to calix[6]pyrrole is too fast. Besides, this reaction provided a novel approach to ring-expanded calix-type macrocycles. Figure 1

A green HPLC method for the determination of apixaban in pharmaceutical products: Development and validation

Abstract Apixaban (APX) is a novel anticoagulant drug used in the treatment of ischemic stroke and venous thromboembolism. In this study, two different chromatographic methods were developed for the determination of APX in pharmaceutical products. In the first method, an Agilent C18 column (250 mm × 4.6 mm, 5 μm) was used, and the temperature was kept constant at 30°C. The mobile phase was chosen to be 0.1% trifluoroacetic acid solution and acetonitrile (65:35, v/v), and isocratic elution was applied. The flow rate of the mobile phase was found to be 1.0 mL·min−1 and the injection volume was 20 µL. The detection was carried out at a wavelength of 276 nm using a UV detector. In the second method, ethanol was used as an organic modifier. The only difference between these methods was the organic modifier. All other conditions of the methods were the same. Both chromatographic methods were validated in accordance with ICH guidelines for various parameters such as selectivity, linearity, accuracy, precision, detection and quantification limit, and robustness. The determination coefficients of chromatographic methods were greater than 0.999 in the concentration range of 5–30 mg·mL−1 of APX. Later, these chromatographic methods were applied to tablet formulations. Comparison of the obtained results in terms of mean was made using Student’s (t) test, and comparisons in terms of standard deviations were made using the Fisher (F) test. It was observed that there was no significant difference between these methods. These two methods were then evaluated using AGREE-Analytical greenness metric software. The chromatographic method using ethanol as an organic modifier has been proposed as an excellent eco-friendly and analyst-friendly alternative for the determination of APX in pharmaceutical formulations.

Structural analyses of silk fibroins based on the structures of oligoalanine, and periodic oligopeptides of L‐alanine and glycine using x‐ray diffraction and 13C solid‐state NMR methods

AbstractThe structures of (A)12, (AAAG)7, (AAG)10, (AG)15, and (AGG)10 were determined using x‐ray diffraction and 13C sold‐state NMR methods after different solvent treatments to obtain knowledge about the structural changes of silk fibroins (SFs) from Samia cynthia ricini (S.c.ricini) and Bombyx mori (B. mori). Three solvent treatments were performed: precipitation from dialysis of LiSCN (LiSCN/Dialysis) or LiBr (LiBr/Dialysis) aqueous solutions, and drying from formic acid (FA) or trifluoroacetic acid (TFA) solutions. (AAAG)7 and (AAG)10 as models of S.c.ricini SF, formed antiparallel β‐sheet structure with staggered packing configuration and did not change after LiSCN/Dialysis or LiBr/Dialysis and FA treatments. (AGG)10 formed 31 helix structure and did not change with these solvent treatments either. On the other hand, (AG)15 as model of B. mori SF formed Silk I (type II β‐turn) structure after LiBr/Dialysis treatment and Silk II (lamellar packing) structure after FA treatment. Especially, B. mori SF seems useful for biomaterials.

Development, transfer and validation of a HPLC-DAD method for analysis of six herbal medicines marketed in D.R. Congo: Fingerprinting and stability study

ContextPhytomedicines, also known as improved traditional medicines (ITMs), are increasingly used in the management of diseases throughout the world. While quality control widely known to be an essential tool that can ensure the efficacy and safety of health products, most ITMs lack appropriate analytical methods for their control. The aim of this study was to develop a reliable analytical method for the quality control of ITMs commonly used in the Democratic Republic of the Congo (D.R. Congo). For this purpose the method needs to be validated and transferred. ObjectivesThe objective of this research was to develop, transfer, and validate an affordable, rapid and easily implementable analytical method by HPLC-DAD for the quality control of herbal medicines marketed in the Democratic Republic of the Congo. Also, to determine these drugs fingerprint and their stability under accelerated conditions. MethodsChromatographic separation was achieved using two chromatographic columns, an XBridge C18 (250 × 4.6 mm i.d.; 5 μm particle size) and an XBridge C18 (100 × 4.6 mm i.d.; 3.5 μm particle size), column maintained at 30 °C. The mobile phase consisted of a gradient mixture of mobile phases A (acetonitrile) and B (aqueous solution of trifluoroacetic acid 0.05%) pumped at 1.0 mL/min. UV detection was performed at 280 nm. The method using the short column was validated using the total extracts as references. The strategy of total error was used to decide on the reliability of the method taking into account the acceptance limits fixed at ± 10%. ResultsThe validation results show that the developed HPLC-DAD method presented an adequate trueness, linearity, precision and accuracy. Two extra peaks found in the finish products did not interfere with phytomarkers, thus confirming the selectivity of the developed method as appropriate chromatographic profiles. The method was successfully used to determine the content of the phytomarkers in six ITMs. Furthermore, we could notice that the ITMs submitted to the accelerated degradation studies remained chemically stable over six months of harsh treatments. ConclusionA generic method of analysis of herbal medicines was developed using HPLC-DAD, and subsequently validated before being applied in a stability study of these drugs. The proposed method holds the promise of providing a new tool for quality product development in the field of traditional herbal medicines.

PET/Graphene Nanocomposite Fibers Obtained by Dry-Jet Wet-Spinning for Conductive Textiles.

The combination of polyethylene terephthalate (PET), one of the most used polymers in the textile industry, with graphene, one of the most outstanding conductive materials in recent years, represents a promising strategy for the preparation of conductive textiles. This study focuses on the preparation of mechanically stable and conductive polymer textiles and describes the preparation of PET/graphene fibers by the dry-jet wet-spinning method from nanocomposite solutions in trifluoroacetic acid. Nanoindentation results show that the addition of a small amount of graphene (2 wt.%) to the glassy PET fibers produces a significant modulus and hardness enhancement (≈10%) that can be partly attributed to the intrinsic mechanical properties of graphene but also to the promotion of crystallinity. Higher graphene loadings up to 5 wt.% are found to produce additional mechanical improvements up to ≈20% that can be merely attributed to the superior properties of the filler. Moreover, the nanocomposite fibers display an electrical conductivity percolation threshold over 2 wt.% approaching ≈0.2 S/cm for the largest graphene loading. Finally, bending tests on the nanocomposite fibers show that the good electrical conductivity can be preserved under cyclic mechanical loading.

Analytical Quality by Design-Assisted HPLC Method for Quantification of Canagliflozin and Stability Studies.

The present study is intended to develop the high-performance liquid chromatography (HPLC) method for the analysis of Canagliflozin using the analytical quality by design (AQbD) approach. The key parameters were methodically optimized with the help of factorial experimental design, and contours were plotted when investigated using Design Expert software. A stability-indicating HPLC technique was developed and validated for the quantitative estimation of Canagliflozin, and its stability was assessed using various forced degradation conditions. Successful separation of Canagliflozin was accomplished using a Waters HPLC system with a photo diode array (PDA) detector and Supelcosil C18 column (250 × 4.6 mm, 5 μm) and 0.2% v/v solution of trifluoroacetic acid in water/acetonitrile (80:20% v/v) as the mobile phase maintaining the flow rate at 1.0 mL/min. The detection wavelength was 290 nm, and Canagliflozin got eluted at 6.9 min with a run time of 15 min. Canagliflozin peak purity values in all degradation conditions indicated that the peak is homogeneous, and therefore this method can be considered stability-indicating. The proposed technique was found to be specific, precise (% RSD about 0.66%), linear (12.6-37.9 μg/mL), rugged (overall % RSD about 0.50%), and robust. The standard and sample solutions were stable after 48 h (cumulative % RSD about 0.61%). The developed AQbD-based HPLC method can be used for the assay of Canagliflozin in Canagliflozin tablets of regular production batches and stability samples.

Bio-Based Electrospun Fibers from Chitosan Schiff Base and Polylactide and Their Cu2+ and Fe3+ Complexes: Preparation and Antibacterial and Anticancer Activities.

The Schiff base derivative (Ch-8Q) of chitosan (Ch) and 8-hydroxyquinoline-2-carboxaldehyde (8QCHO) was prepared and fibrous mats were obtained by the electrospinning of Ch-8Q/polylactide (PLA) blend solutions in trifluoroacetic acid (TFA). Complexes of the mats were prepared by immersing them in a solution of CuCl2 or FeCl3. Electron paramagnetic resonance (EPR) analysis was performed to examine the complexation of Cu2+(Fe3+) in the Ch-8Q/PLA mats complexes. The morphology of the novel materials and their surface chemical composition were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The performed microbiological screening demonstrated that in contrast to the neat PLA mats, the Ch-8Q-containing mats and their complexes were able to kill all S. aureus bacteria within 3 h of contact. These fibrous materials had efficiency in suppressing the adhesion of pathogenic bacteria S. aureus. In addition, Ch-8Q/PLA mats and their complexes exerted good anticancer efficacy in vitro against human cervical HeLa cells and human breast MCF-7 cells. The Ch-8Q-containing fibrous materials had no cytotoxicity against non-cancer BALB/c 3T3 mouse fibroblast cells. These properties render the prepared materials promising as wound dressings as well as for application in local cancer treatment.

Solution electrospinning and properties of poly(ethylene 2,5-furandicarboxylate) fibers

Poly(ethylene 2,5-furandicarboxylate) (PEF) is an attractive bio-based alternative to petroleum-based polymers. In this work, novel PEF-based nonwovens were obtained by the solution electrospinning, using as solvents: trifluoroacetic acid, its mixtures with dichloromethane and dichloroethane, and also 1,1,1,3,3,3-hexafluoro-2-propanol. The effect of the solvent type and PEF concentration on the fiber thickness and the properties of nonwovens was studied. The average thickness of nonwoven fibers ranged from 180 nm to 2.3 μm. The fibers were amorphous with the glass transition temperature of 85–87 °C. The nonwovens were strongly hydrophobic, with water contact angles of 144–146° although they exhibited the rose petal effect. The mechanical properties of the materials were influenced by their porosity and fiber thickness. The nonwoven electrospun from 20 wt% PEF solution in trifluoroacetic acid, with an average fiber diameter of 2.13 μm and a porosity of 74%, exhibited the highest tensile strength and elongation at break, 10.8 MPa and 190%, respectively.

Development and Validation of an HPLC-UV Method for the Dissolution Studies of 3D-Printed Paracetamol Formulations in Milk-Containing Simulated Gastrointestinal Media.

Herein, a simple and rapid HPLC method for the determination of paracetamol milk-containing biorelevant media is proposed. The separation of the analyte from the milk-containing biorelevant media was accomplished isocratically using a mobile phase containing 25 mM phosphate buffer (pH = 3.0) and methanol, 80:20, v/v at a flow rate of 1 mL min−1. Following a protein precipitation-based sample clean-up, a thorough investigation of the effect of the precipitation reagent (methanol, acetonitrile, 10% v/v trifluoroacetic acid solution) on the analyte recovery was performed. The matrix effect was assessed in each biorelevant medium by comparing the slopes of the calibration curves of aqueous and matrix-matched calibration curves. The method was comprehensively validated using the accuracy profiles. The β-expectation tolerance intervals did not exceed the acceptance criteria of ±15%, meaning that 95% of future results will be included in the defined bias limits. The relative bias ranged between −4.5 and +3.9% for all analytes, while the RSD values for repeatability and intermediate precision were less than 2.7% and 3.0%, respectively. The achieved limit of detection (LOD) was 0.02 μg mL−1 and the lower limits of quantitation (LLOQ) were established as 10 μg mL−1, which corresponded to 2% of the highest expected concentration of paracetamol. The proposed scheme was utilized for the determination of paracetamol in dissolution studies of its 3D-printed formulation in milk-containing biorelevant media.

Electromembrane Extraction of Posaconazole for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Detection.

A new mode of electromembrane extraction (EME) has been developed for detection via matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS). Posaconazole, extracted from 8 mL of a 10 mM trifluoroacetic acid solution onto a thin polyvinylidene difluoride (PVDF) membrane, was used as a model analyte. The transport was forced by an electrical potential difference between two electrodes inside the lumen of a hollow fiber and glass tube. Under an application of 80 V, cationic posaconazole in the sample solution moved toward the negative electrode inside the glass tube and was trapped by the PVDF membrane on the side. After 15 min of extraction, 3 μL of α-cyano-4-hydroxycinnamic acid (CHCA) solution was applied on top of the membrane, which was then analyzed by MALDI/MS. Under optimal extraction conditions, the calibration curve of posaconazole was linear over a concentration range of 0.10–100.00 nM. The limit of detection (LOD) at a signal-to-noise ratio of 3 was 0.03 nM with an enhancement factor of 138 for posaconazole. The application of this method to the determination of posaconazole in human serum samples was also successfully demonstrated.

Phosphorylated Protein Levels in Animal-Sourced Food Muscles Based on Fe3+ and UV/Vis Spectrometry.

Protein phosphorylation, a post-translational modification of proteins, is important in biological regulation. The quantity of phosphorylated proteins is a key requirement for the quality change of animal muscle foods. In the present study, a new approach to quantify phosphorylated proteins and/or peptides was developed based on ferric ions (Fe3+) and UV/vis spectrometry. This method is proved to be ultra-effective in discriminating phosphopeptides and non-phosphopeptides with the assistance of Fe3+. The protocol of extracting proteins with 0.1% trifluoroacetic acid (TFA) solution from animal muscle samples coupled with Fe3+ was verified by using an artificial mixture of peptides with different phosphorylation sites and was successfully used to characterize the phosphorylation quantity in the samples via UV/vis spectrometry. A peptide with one phosphorylated site was taken as a reference standard and successfully utilized for the absolute quantification of phosphorylated proteins in caprine muscles during frozen storage and in fish muscle food samples. This present study paves a new way for the evaluation of phosphorylated protein quantitative levels in bio-samples.

Antibacterial Hydrogels Derived from Poly(γ-glutamic acid) Nanofibers.

Biocompatible hydrogels with antibacterial properties derived from γ-polyglutamic acid (γ-PGA) were prepared from bulk and electrospun nanofibers. The antibacterial drugs loaded in these hydrogels were triclosan (TCS), chlorhexidine (CHX) and polyhexamethylene biguanide (PHMB); furthermore, bacteriophages were loaded as an alternative antibacterial agent. Continuous and regular γ-PGA nanofibers were successfully obtained by the electrospinning of trifluoroacetic acid solutions in a narrow polymer concentration range and restricted parameter values of flow rate, voltage and needle-collector distance. Hydrogels were successfully obtained by using cystamine as a crosslinking agent following previous published procedures. A closed pore structure was characteristic of bulk hydrogels, whereas an open but structurally consistent structure was found in the electrospun hydrogels. In this case, the morphology of the electrospun nanofibers was drastically modified after the crosslinking reaction, increasing their diameter and surface roughness according to the amount of the added crosslinker. The release of TCS, CHX, PHMB and bacteriophages was evaluated for the different samples, being results dependent on the hydrophobicity of the selected medium and the percentage of the added cystamine. A high efficiency of hydrogels to load bacteriophages and preserve their bactericide activity was demonstrated too.

Rapid Identification between Two Fish Species Using UV-Vis Spectroscopy for Substitution Detection.

Fish species substitution and fraud has become a worldwide economic issue in the seafood industry. In this study, an ultraviolet-visible (UV-Vis) spectroscopy-based method was developed for the identification of fish samples. Sixty fish samples from twelve commonly consumed fish species in China were analyzed as models to testify the protocol. The obtained results show that UV-Vis spectroscopy combined with chemometric analysis, such as principal component analysis (PCA), can accurately distinguish two fish species by boiling fish tissue sample in trifluoroacetic acid (TFA) solution for 2 min and analyzing the resultant samples using a UV-Vis spectrometer. The developed strategy was successfully applied to the classification and identification of fish samples on the market. It is a promising strategy that can be applied to the classification and authenticity testing of closely related fish species in order to detect and recognize fish substitution.

Interfacial film conformation and its molecular arrangement of s-triazine derivatives containing three fluorocarbons without hydrophilic groups

A monolayer on the water surface or a Langmuir monolayer of fluorinated long-chain s-triazine derivatives with no hydrophilic groups was formed, and its interfacial conformation was verified. As a highly water-repellent monolayer-forming substance, s-triazine derivatives with fluorocarbon chains of different chain lengths were used. These derivatives were poorly soluble in organic solvents and were spread from a mixed solution of chloroform and trifluoroacetic acid supported by a clean glass rod. Although interaction with the water surface was weak owing to a lack of hydrophilic groups, all the molecules reflected the interfacial film behavior in the surface pressure-area isotherms. These derivatives formed orientation almost perpendicular to the water surface in the normal direction to minimize unstable contact between the water subphase and fluorocarbon in the monolayer on the water surface. Atomic force microscopy revealed that derivatives with long fluorocarbons exhibit a two-dimensional crystal morphology based on van der Waals interactions between fluorocarbons. The multilayers of this derivative were found to form a highly oriented structure by polarized infrared spectroscopy and out-of-plane X-ray diffraction. However, it was predicted that the in-plane molecular packing was not always dense. In addition, the results of the contact angle measurement of the monolayer confirmed a systematic difference based on the change in chain length.

Development of a Simple, Precise, and Validated HPLC Method for the Anticancer Drug, Regorafenib: Application to Pharmacokinetics in Rats and Stability Study

The goal of this study was to establish a simple, precise, and validated high‐performance liquid chromatography‐ultraviolet (HPLC‐UV) method to quantify the amount of regorafenib in rat plasma using revaprazan as an internal standard. The mobile phase composition was 0.1% aqueous trifluoroacetic acid solution and 0.1% trifluoroacetic acid in acetonitrile (50/50, v/v). The flow rate was 0.5 mL/min, and the eluent was monitored at 265 nm. The results showed that this novel chromatographic method achieved the criteria of the FDA validation guidelines and presented excellent linearity over 0.0488–50 μg/mL (r2 = 0.9999) concentration. Additionally, this method was validated for evaluating regorafenib stability in three different storage conditions and was effectively utilized to analyze the drug concentration in rat plasma after oral administration by calculating its pharmacokinetic parameters. Therefore, this HPLC method is appropriate for evaluating the pharmacokinetics of regorafenib in rats.