Ultraviolet-visible Detection Research Articles

Characterization and Quantitation of Anthocyanins of the Pigmented Tea Cultivar TRI 2043 (Camellia sinensis L.) from Sri Lanka

Tea leaves are rich in diverse bioactive compounds. The tea accession TRI 2043 is unique due to its pigmented leaves caused by anthocyanins, clonal origin, resistance to blister blight disease, and high pubescence density. Because of its peculiarity, TRI 2043 is used to produce high-quality silver tip tea, a premium type of tea that commands high prices. This study was carried out to clarify and elucidate the types of anthocyanins in this particular accession. Four different anthocyanin species were identified and quantitated as cyanidin-3-O-β-d-galactoside and delphinidin-3-O-β-d-galactoside equivalents for leaf blades and stems of the cultivar TRI 2043. The characterization was performed by comparison with commercially available reference substances and further confirmed using ion mobility high-resolution time-of-flight-mass spectrometry (IMS-HRTOF-MS). Quantitation was carried out using ultra-high-performance liquid chromatography ultraviolet–visible detection (UHPLC-UV-vis) with cyanidin-3-O-β-d-glucoside as an internal standard. E- and Z-geometric isomers of 6-p-coumaroyl derivates of delphinidin and cyanidin-3-O-β-d-galactopyranosides were observed, and collision cross section (CCS) values were determined for all four different anthocyanidin species. The content of anthocyanins in leaf blades of cultivar TRI 2043 was 856.32 ± 41.56 µg/g dry weight, with cyanidin being the more abundant anthocyanin (69.8%). Conversely, the stem material contained an anthocyanin amount of 459.5 ± 44.7 µg/g dry weight, with a higher content of delphinidin (69.6%). In summary, an enrichment strategy using analytical membrane chromatography was established to fully elucidate and quantify the anthocyanin profile of plant samples such as the special tea variety TRI 2043.

Evaluation of Iron Chlorin e6 disappearance and hydrolysis in soil and garlic using salting-out assisted liquid-liquid extraction coupled with high-performance liquid chromatography and ultraviolet-visible detection

Iron Chlorin e6 (ICE6), a star plant growth regulator (PGR) with independent intellectual property rights in China, has demonstrated its efficacy through numerous field experiments. We innovatively employed salting-out assisted liquid-liquid extraction (SALLE) with HPLC-UV/Vis to detect ICE6 residues in water, soil, garlic seeds, and sprouts. Using methanol and a C18 column with acetonitrile: 0.1% phosphoric acid mobile phase (55:45, v:v), we achieved a low LOQ of 0.43 to 0.77 μg kg−1. Calibration curves showed strong linearity (R2 > 0.992) within 0.01 to 5.00 mg kg−1. Inter-day and intra-day recoveries (0.05 to 0.50 mg kg−1) demonstrated high sensitivity and accuracy (recoveries: 75.36% to 107.86%; RSD: 1.03% to 8.78%). Additionally, density functional theory (DFT) analysis aligned UV/Vis spectra and indicated ICE6's first-order degradation (2.03 to 4.94 days) under various environmental conditions, mainly driven by abiotic degradation. This study enhances understanding of ICE6's environmental behavior, aids in risk assessment, and guides responsible use in agroecosystems.

Comparison of extraction processes, characterization and intestinal protection activity of Bletilla striata polysaccharides

We optimized the extraction process of Bletilla striata polysaccharides using orthogonal design, Box-Behnken design (BBD), and genetic algorithm-back propagation (GA-BP), then compared and evaluated them to confirm that the combination of BBD and GA-BP neural networks was capable of increasing polysaccharide yields and antioxidant activity. The optimal extraction parameters were as follows: liquid-to-solid ratio of 15 mL/g, extraction power of 450 W, and extraction time of 34 min. Under these conditions, the polysaccharide yield and antioxidant activity were 8.29 ± 0.50 % and 26.20 ± 0.28 (mM FE/mg). Subsequently, the polysaccharide was purified to obtain purified Bletilla striata polysaccharides 1 (pBSP1) with a Mw of 255.172 kDa. Scanning electron microscope (SEM), ultraviolet-visible detector (UV), fourier transform infrared spectrometer (FTIR), high performance liquid chromatography (HPLC), X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and periodate oxidation were used to analyze the structure of pBSP1. The results showed pBSP1 had a smooth surface and a rough interior, with a composition of α-D conformation glucose (18.23 %) and β-D conformation mannose (53.77 %), and an amorphous crystal structure. According to the results of thermogravimetric and rheological tests, pBSP1 exhibits good thermal stability and viscoelastic behavior. Furthermore, pBSP1 protected lipopolysaccharide (LPS)-induced GES − 1 and Caco2 cells, the results showed pBSP1(400 μg/mL) lowered TEER synthesis in Caco2 cells as well as apoptosis and reactive oxygen species (ROS) production in both cells, indicating that pBSP1 may have an intestine protective effect.

2D CuInP2Se6 in High‐Sensitivity UV‐vis And X‐Ray Detection

AbstractMetal thio(seleno)phosphates are renowned for their multifaceted physical characteristics and versatile applications, particularly in optoelectronics. In detection applications, a low and stable dark current is crucial, enhancing the sensitivity and signal‐to‐noise ratio of detectors. Herein, a van der Waals layered material has synthesized, CuInP2Se6. Despite its nanometric scale, 2D CuInP2Se6 detector transcends the conventional absorption inefficiencies tied to ultrathin materials. It delivers exceptional ultraviolet–visible detection, characterized by an ultralow, stable dark current of 150 fA, and a noise power density of 27.7 fA Hz−1/2 at room temperature. The in‐depth investigation reveals a responsivity of 4.47 A W−1, an external quantum efficiency of 1369%, a special detectivity of 1.44 × 1013 Jones, and a rapid response speed of 280 µs, positioning it at the pinnacle of 2D photodetector performance. The CuInP2Se6’s ultralow, stable dark current paves the way for X‐ray detection, achieving an unprecedented sensitivity of 1.32 × 105 µC Gyair−1 cm−2 and a low detection limit of 0.15 µGyair s−1. Furthermore, 2D CuInP2Se6 detector exhibits a remarkable image‐sensing capability, adeptly capturing intricate patterns with high resolution. This discovery indicates its promise in revolutionizing integrated micro/nano optoelectronic devices, opening avenues for advancements in light and X‐ray detection and imaging technologies.

Validation of a method for measuring rifampicin plasma drug concentration in tuberculosis patients

Rifampicin is a first-line drug used in the management of tuberculosis (TB) due to its sterilizing effect that targets the bacteria responsible for the disease. This study modified and validated a method for quantitatively determining rifampicin plasma drug concentration of TB patients through High Performance Liquid Chromatography Ultraviolet Visible detection. The analytic method modified from a standard method was validated for linearity, coefficient of variation, intra-day and inter-day precision, and recovery rate. The retention time of rifampicin was reduced from 18.3 to 3.1 minutes after the method was modified. To validate the method, the coefficient of determination was determined for the linearity to be between 0.975 and 0.998, the coefficient of variation ranged between 2.8% to 15.5% for both intra-day and inter-day precision. Recovery rates ranged between 87% and 125%. The results indicated that the analytical method developed was valid, precise and feasible, and could be useful for quantitatively determining rifampicin plasma drug concentration in TB patients.

Cork by-products as a sustainable source of potential antioxidants

Cork harvesting process is considered sustainable, however, the potential of the waste that is generated in the cork transformation process, in the context of bio-circular economy, still needs more investigation. This work investigated three cork by-products, coarse powder (P0) and fine powder (P1), as well as cork boiling wastewater (CBW), as sustainable sources of value-added ingredients with antioxidant potential for pharmaceutical, food products and the cosmetic industry. The free radical scavenging effect and the metals content of P0 and P1 extracts and CBW was evaluated. A low content of metals was detected for P0 and P1 powders, while CBW showed high levels of the prohibited heavy metals As and Pb, among other metals, above the permissible trace amounts allowed in cosmetics, pharmaceuticals and food products. The extractive process was optimized by taking into account the effect of temperature, solvent, extraction time and number of extraction cycles on DPPH scavenging activity and process sustainability. Liquid chromatography coupled to the high-resolution mass spectrometry and ultraviolet–visible detection allowed the unequivocal identification and quantification of the target compounds, respectively. All extracts displayed promising DPPH scavenging effect, being P1 extract obtained with 30% ethanol (IC50 = 4.7 ± 0.2 μg/mL) the most active. The DPPH scavenging effect of cork powder extracts could be explained by the efficiency of extraction of phenolics. This work allied clean and environmentally friendly processes by the use of green solvents and low energy consumption in the extraction procedures. The relationship between chromatographic patterns and the antioxidant activities was also explored.

A stable core-shell metal-organic framework@covalent organic framework composite as solid-phase extraction adsorbent for selective enrichment and determination of flavonoids

Hydrophobization and stability is crucial for the practical application of most metal-organic frameworks (MOFs) in extraction technique. In this study, a stable core-shell MOF@COF composite (NH2-MIL-101(Fe)@TAPB-FPBA-COF) was successfully prepared by Schiff base reaction and applied to solid-phase extraction (SPE) of hydrophobic flavonoids. Notably, the TAPB-FPBA-COF shell acts as a hydrophobic "shield", which not only improves the hydrophobicity and stability of hydrophilic NH2-MIL-101(Fe), but also makes the extraction efficiency of flavonoids from MOF@COF composite significantly higher than that of pure NH2-MIL-101(Fe) and TAPB-FPBA-COF. In addition, a sensitive analytical method with excellent linearities (0.1–500 ng mL−1, R2 ≥ 0.9967), low limits of detection (0.02–0.04 ng mL−1 for water; 0.04–0.07 ng mL−1 for grape juice; 0.06–0.08 ng mL−1 for honey), good repeatability (intra-day/inter-day precision are 1.86–5.37%/1.82–7.79%, respectively) and only 5 mg of adsorbent per cartridge was established by optimizing the SPE process combined with high performance liquid chromatography with ultraviolet-visible detector (HPLC-UV). Meanwhile, selectivity study and comparative experiments with the commercial C18 adsorbent showed that the MOF@COF adsorbent exhibited satisfactory extraction efficiency for flavonoids due to multiple interactions such as hydrogen bonding, hydrophobic, and π-π interactions. Finally, the good recoveries in grape juice (84.5–102.5%) and honey (87.5–104.6%) samples further validated the applicability of the proposed method in complex samples.

A portable liquid chromatography system based on a separation/detection chip module consisting of a replaceable ultraviolet-visible absorbance or contactless conductivity detection unit

Recently, there has been a growing demand for miniaturized analytical instruments, including portable HPLC systems, that can enable rapid analysis in the field. This study aimed to develop chip-based separation/detection modules with replaceable detection units for constructing compact HPLC systems to minimize the dead volume. This module provides a tubing-free connection between the column and the detection unit. This study also built detection units for conductivity detection and ultraviolet-visible (UV–Vis) detection to cover a wide variety of inorganic and organic compounds. Furthermore, UV- and Vis-light-emitting diodes were employed for the absorbance detection unit. In addition, portable all-in-one HPLC systems and a handy HPLC system were constructed for ion chromatography and reversed-phase chromatography, demonstrating the successful separation and detection of inorganic ions and several organic compounds.

Validated method for polystyrene nanoplastic separation in aqueous matrices by asymmetric-flow field flow fraction coupled to MALS and UV–Vis detectors

Plastics with nanosize (nanoplastics, NPLs) must be characterized, since they can be toxic or act as carriers of organic and inorganic pollutants, but there is a lack of reference materials and validated methods in the nanosize range. Therefore, this study has focused on the development and validation of a separation and size characterization methodology of polystyrene latex nanospheres, by using an asymmetric-flow field flow fraction system coupled to multi-angle light scattering and ultraviolet–visible detectors (AF4-MALS-UV). Hence, this work presents a fully validated methodology in the particle size range 30 to 490 nm, with bias between 95 and 109%, precision between 1 and 18%, LOD and LOQ below 0.2 and 0.3 µg respectively, except for 30-nm standard, for both detectors, and showing stable results for 100 analyses.Graphical

Sensitivity enhancement of capillary electrophoresis-frontal analysis-based method for characterization of drug-protein interactions using on-line sample preconcentration.

Capillary electrophoresis-frontal analysis is one of the most frequently used approaches for the study of plasma protein-drug interactions as a substantial part of new drug development. However, the capillary electrophoresis-frontal analysis typically combined with ultraviolet-visible detection suffers from insufficient concentration sensitivity, particularly for substances with limited solubility and low molar absorption coefficient. The sensitivity problem has been solved in this work by its combination with an on-line sample preconcentration. According to the knowledge of the authors this combination has never been used to characterize plasma protein-drug binding. It resulted in a fully automated and versatile methodology for the characterization of binding interactions. Further, the validated method minimalizes the experimental errors due to a reduction in the manipulation of samples. Moreover, employing an on-line preconcentration strategy with capillary electrophoresis-frontal analysis using human serum albumin-salicylic acid as a model system improves the drug concentration sensitivity 17-fold compared to the conventional method. The value of binding constant (1.51±0.63) ·104 L/mol obtained by this new capillary electrophoresis-frontal analysis modification is in agreement with the value (1.13±0.28) ·104 L/mol estimated by a conventional variant of capillary electrophoresis-frontal analysis without the preconcentration step, as well as with literature data obtained using different techniques.

Pharmacokinetic interaction of voriconazole and clarithromycin in Pakistani healthy male volunteers: a single dose, randomized, crossover, open-label study.

Background: Voriconazole an antifungal drug, has a potential for drug-drug interactions (DDIs) with administered drugs. Clarithromycin is a Cytochromes P450 CYP (3A4 and 2C19) enzyme inhibitor, and voriconazole is a substrate and inhibitor of these two enzymes. Being a substrate of the same enzyme for metabolism and transport, the chemical nature and pKa of both interacting drugs make these drugs better candidates for potential pharmacokinetic drug-drug interactions (PK-DDIs). This study aimed to evaluate the effect of clarithromycin on the pharmacokinetic profile of voriconazole in healthy volunteers. Methods: A single oral dose, open-label, randomized, crossover study was designed for assessing PK-DDI in healthy volunteers, consisting of 2weeks washout period. Voriconazole, either alone (2mg × 200mg, tablet, P/O) or along with clarithromycin (voriconazole 2mg × 200mg, tablet + clarithromycin 500mg, tablet, P/O), was administered to enrolled volunteers in two sequences. The blood samples (approximately 3 cc) were collected from volunteers for up to 24h. Plasma concentrations of voriconazole were analyzed by an isocratic, reversed-phase high-performance-liquid chromatography ultraviolet-visible detector (RP HPLC UV-Vis) and a non-compartmental method. Results: In the present study, when voriconazole was administered with clarithromycin versus administered alone, a significant increase in peak plasma concentration (Cmax) of voriconazole by 52% (geometric mean ratio GMR: 1.52; 90% CI 1.04, 1.55; p = 0.000) was observed. Similarly, the area under the curve from time zero to infinity (AUC0-∞) and the area under the concentration-time curve from time zero to time-t (AUC0-t) of voriconazole also significantly increased by 21% (GMR: 1.14; 90% CI 9.09, 10.02; p = 0.013), and 16% (GMR: 1.15; 90% CI 8.08, 10.02; p = 0.007), respectively. In addition, the results also showed a reduction in the apparent volume of distribution (Vd) by 23% (GMR: 0.76; 90% CI 5.00, 6.20; p = 0.051), and apparent clearance (CL) by 13% (GMR: 0.87; 90% CI 41.95, 45.73; p = 0.019) of voriconazole. Conclusion: The alterations in PK parameters of voriconazole after concomitant administration of clarithromycin are of clinical significance. Therefore, adjustments in dosage regimens are warranted. In addition, extreme caution and therapeutic drug monitoring are necessary while co-prescribing both drugs. Clinical Trial Registration: clinicalTrials.gov, Identifier NCT05380245.

Forecasting the Degradation of Vitamin C Concentration in Commonly Consumed Vegetable Cabbage (Brassica oleracea) dipped in Different Pre-treatment Solutions

Vitamin C is considered an essential vitamin that is commonly found in most fruits and vegetables. It is susceptible to easy degradation, especially during pre-treatment and storage. This study aimed at forecasting the degradation of vitamin C in commonly consumed vegetable (cabbage) dipped in different pre-treatment solutions at different time intervals. The samples after dipping at different time intervals were prepared for analysis. Evaluation of the ascorbic acid content of the vegetable was determined using High-Performance Liquid Chromatography (HPLC). This consists of an isocratic elution procedure with ultraviolet-visible detection at 245 nm. The half-lives and rate constants were calculated using the integrated law method. Forecasts were determined using time series analysis. Degradation of vitamin C in this study followed a first-order kinetic model, and the average coefficient of determination (R2-value) was greater than 0.9413. The rate constants of vitamin C degradation for the vegetable dipped in different pretreatment solutions (sodium chloride, sodium benzoate, sodium metabisulfite and vinegar) at different time intervals were 0.0804, 0.1049, 0.0706 and 0.0553 minutes-1; half-lives were 8.2322, 7.3896, 10.9675, and 12.1086 minutes, respectively. The vegetable dipped in different pretreatments for 90 minutes exhibited ln(C) forecast of -2.2057, -4.6307, -1.1746, and 0.0789, respectively. The coefficient of correlation for sodium chloride, sodium benzoate, sodium metabisulfite, and vinegar are 0.084, 0.093, 0.063 and 0.059 respectively. The kinetic models were formulated using predicted initial contents, processing time, and measured contents. The vegetable dipped in vinegar pretreatment solution using ln(C) =ln(C0) - 0.0553t gave the best model. From the results, the most appropriate pretreatment solution for enhancing the shelf life of cabbage is synthetic vinegar (prepared from acetic acid) because it has a lower rate constant, lower coefficient of correlation, and the longest half-life.

Method development, validation, and impurity measurement of β-estradiol from radiolabeled [131I]β-estradiol using radio-high-performance liquid chromatography for radioligand of saturation binding assay.

β-estradiol is an estrogen steroid hormone and acts as an estrogen receptor agonist. Radiolabeled β-estradiol is widely used as a radioligand for binding assays. In this present study, the synthesis of [131I]β-estradiol has been successfully carried out. Accordingly, the measurement of the radiochemical purity (RCP) value and the presence of chemical impurities are needed. To validate the method for identifying the RCP and chemical impurities from [131I]β-estradiol using high-performance liquid chromatography (HPLC). The synthesis of [131I]β-estradiol was accomplished by a radioiodination reaction, and the RCP was determined by radio-HPLC. The method for β-estradiol measurement was validated by reversed-phase HPLC radio-analytical employing ultraviolet-visible (UV-Vis) and radioactive detector. The method for radio-HPLC analysis was validated and established using a C-18 column and MeCN: H2O (55:45 v/v) as the mobile phase. The following conditions were applied: a flow rate of 1.2 mL/min, isocratic, and a UV-Vis detector at 280 nm. The RCP of [131I]β-estradiol measured by thin-layer chromatography and radio-HPLC was 99.27% ± 1.25% and 95.75% ± 2.41%, respectively. The validation parameters were appropriate and met the requirements for acceptance. HPLC analysis was able to identify the presence of unlabeled estradiol (24.51%-27.29%) in the mixture of [131I]β-estradiol. As a result, purification using preparative HPLC or other methods will be required in future studies.

Modified matrix solid phase dispersion-HPLC method for determination of pesticide residue in vegetables and their impact on human health: A risk assessment.

The use of pesticides is unavoidable in agricultural practices. This class of chemicals is highly toxic for the environment as well as for humans. The present work was carried out to assess the presence of some pesticides (diafenthiuron, lufenuron, azoxystrobin, difenoconazole, and chlorothalonil) residues in five of the very commonly used vegetables (eggplant, capsicum, apple gourd, cauliflower, and sponge gourd). Matrix solid phase dispersion (MSPD) technique was used to extract the pesticides and subsequently their quantification was performed through high performance liquid chromatography (HPLC) coupled to ultraviolet-visible (UV-Vis) detector. The elution was accomplished at wavelength of 254nm by injecting 20µL of standards or samples into chromatographic system. The mobile phase consisted of acetonitrile and water (80:20 v/v), where the flow rate was adjusted at 1.0ml/min. The linearity was good (R 2 ≥ 0.994) over a concentration range from 20 to 100μg/ml for the investigated pesticides. The low detection limits showed a quite appreciable potential of the method to detect (1.12-1.61μg/L) and quantify (3.73-5.36μg/ml) the pesticides under study. The accuracy was demonstrated in terms of percent recovery which ranged between 88.5% and 116.9% for all the pesticides under investigation. These results justify the suitability of the technique for the intended purpose. The concentration of difenoconazole in apple gourd (20.97mg/kg), cauliflower (10.28mg/kg), and sponge gourd (40.32mg/kg) whereas diafenthiuron in cauliflower (0.66mg/kg) exceeded the maximum residue level (MRLs) as defined by Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO). Target hazard quotient (THQ) values of difenoconazole and diafenthiuron (except for adults) were more than one which indicates the significant effect on human health on consumption of apple gourd, cauliflower, and sponge gourd.

Long-term profound investigation of Fenoxaprop-p-ethyl and indirect pesticide pollution in jute-cropped environmental ecosystem for dietary and ecological risk assessment.

Jute is a healthy vegetable due to its high content of carotenoids, vitamins, and minerals, in addition to its industrial utility. The purpose of this study was to look into the dissipation of fenoxaprop-p-ethyl and to track indirect sources of pesticide accumulation in jute ecosystems for three years in a row during tropical monsoon seasons. To avoid the intake of residues over approved limits, a rapid extraction technique was developed to evaluate the residues of this herbicide (Whip-Super 9% EC) in jute leaves, fiber, cropped soil, and water. A modified QuEChERS approach based on liquid chromatography and ultraviolet-visible (UV-VIS) detection was developed and successfully validated in accordance with SANCO requirements. Gas chromatography mass spectrometer (GC-MS) was used to examine fish and water samples from jute fields and retting pond for twenty widely-used multi-class pesticide contaminations from indirect sources. Relative standard deviations (RSD) (≤ 20) and recoveries (100-115%) are observed to be within acceptable ranges. In edible jute leaves, independent of season, first-order kinetics of dissipation was recorded, with half-lives ranging from 0.61 to 0.68days. Based on the findings of the risk assessment, it is feasible to conclude that the consumer health risks of ingesting jute leaves are insignificant, even on day zero, when used at the recommended amount, and that using jute bags for food packaging and storage is safe. But jute field water was found to be less polluted with indirect pesticides than water from a nearby jute retted pond. Fish samples from this jute retted pond were also analyzed and found to be 26% contaminated. The presence of quinalphos and chlorpyriphos in jute retting water and fish might pose a concern to consumer health and environmental ecosystems.

Occurrence and risk assessment of fullerene colloidal nanoparticles by ultrasonic-assisted dispersive liquid-liquid extraction and high-performance liquid chromatography in surface waters

This paper presents a developed analytical technique for risk assessment of colloidal fullerene in surface waters by ultrasonic-assisted dispersive liquid-liquid extraction (UADLLE) and high-performance liquid chromatography ultraviolet-visible detector (HPLC-UV). Fullerene colloidal nanoparticles were synthesised and characterized by high-resolution transmission electron microscopy (HRTEM) and ultraviolet-visible spectroscopy (UV-Vis). Ultrasonication step, disperser solvent, and sodium chloride salt enhance the surface area of fullerene derivative aggregates for better contact and lowers the solubility of fullerene derivative to the aqueous solution, respectively promoting mass transfer of fullerene from aqueous into the organic phase. Several extraction parameters were optimized, and the optimal conditions were established: 5 mL toluene as extraction solvent (2 cycles); 200 mL water sample; 1% sodium chloride salt; 15 min ultrasonication, and 400 μL methanol as disperser solvent. The mean absolute recoveries established in drinking water, wastewater, and river water were 117%, 103%, and 93%, respectively. The proposed analytical technique was linear in the ranges between 0.25 μg L−1 – 250 μg L−1 with an r-squared of 0.9958. The limit of detection (LOD) determined from the signal-to-noise ratio of 3 was 0.11 μg L−1 and the limit of quantification (LOQ) from a signal-to-noise ratio of 10 was 0.38 μg L−1. The precision ranges from 2% to 11% and accuracy percent error ranged from 7%–14% for spiked concentration levels of 0.25 μg L−1, 50 μg L−1, and 250 μg L−1. The measured environmental concentration (MECs) for the fullerene in water samples ranged from not detected to 10.54 μg L−1 and ecological assessment showed the concentration level of the fullerene can pose risk. Overall, according to the author's knowledge, this is the earlier work on the occurrence and risk assessment of fullerene colloidal nanoparticles (C61-PCBM) in potable and wastewater on the African continent.

Determination of levodopa by chromatography-based methods in biological samples: a review

Levodopa (L-DOPA) is the most effective drug for Parkinson's disease; however, various side effects occur during therapy. L-DOPA metabolites and the high cumulative dose of L-DOPA were responsible for its side effects. It is necessary to monitor the concentration of L-DOPA and its metabolites for individualized therapy. This review focuses on L-DOPA analysis by chromatography-based methods in biological matrices. Literature published up to September 2021 was collected in the PubMed, Web of Science, and Embase by using search strategy ("levodopa" OR "L-DOPA") AND ("chromatography"). A total of 1249 articles were identified and 32 articles were included. The contents for method development and validation were summarized and analyzed. Due to the instability of catecholamines (L-DOPA, dopamine, and 3-O-methyldopa) and carbidopa, antioxidation (0.5 mg sodium metabisulfite for 100 μL sample) and environment temperature control were used alone or in combination to enhance stability. Sample was mainly pretreated by protein precipitation (0.4-0.7 M perchloric acid). Separation was usually achieved using methanol or acetonitrile:water (with formic acid) on C18 columns. Mass spectrometry, electrochemical detector, ultraviolet-visible detector and fluorescence detector were used for detection. For L-DOPA, the calibration range was 2.5-10,000 ng/mL, the matrix effect and its coefficient of variation was 85-115 and -9.0-8.5%, and the recovery was 66.8-127.0%. Without stabilization strategy, L-DOPA was stable in plasma at room temperature for 1-7 h (4-6 h for most studies), at - 70 °C to - 80 °C for 10-20 days and after 3-5 freeze-thaw cycles. With stabilization strategies, the stability of L-DOPA in plasma was significantly improved. Metabolites of L-DOPA and enzyme inhibitors (carbidopa, entacapone, tolcapone and benserazide) were all stable in biological matrix. This study might be useful for researchers to develop their methods for individualized therapy of patients with Parkinson.

Three-dimensional acanthosphere-like hierarchical Co@graphitic carbon for dispersive magnetic solid-phase extraction of nitroimidazole

Herein, a magnetic three-dimensional acanthosphere-like hierarchical Co@graphitic carbon (3D Co@GC) is introduced as an efficient adsorbent for extraction of three nitroimidazoles (NMZs: metronidazole (MNZ), ornidazole (ONZ) and tinidazole (TNZ)) from environmental water and food samples. The proposed 3D Co@GC was synthesized by a simple template-free method, which consisted of plentiful freely arranged one-dimensional nanowires. The adsorption properties of 3D Co@GC for three NMZs were investigated systematically by adsorption kinetic and isotherm studies. 3D Co@GC exhibits good adsorption capacity and fast adsorption kinetics toward three NMZs by virtue of its unique hierarchical structure. In addition, it was also found that a bit of methanol can effectively elute the adsorbed NMZs, eliminating the need for other dangerous strong acid or base solutions. Thus, 3D Co@GC as adsorbent to extraction three trace NMZs followed by direct quantification detection of targets with high-performance liquid chromatography with ultraviolet–visible detector (HPLC-UV) was developed. The parameters of dispersed magnetic solid-phase extraction (d-MSPE) were optimized by univariate and multivariate methods (Box-Behnken design). This established method revealed wide linear range and low limits of detection. Furthermore, the satisfactory recoveries of NMZs (86.7–106.7%) were acquired in spiked river water, honey, milk, and muscle samples. This study might provide a potential strategy for the efficient extraction and sensitive analysis of trace NMZs in river water, honey, milk, and muscle samples.

Quantitative extraction of multiclass antibiotic residues in cow milk utilizing salting-out assisted liquid-liquid extraction followed by liquid chromatographic determination

ABSTRACT The salting-out assisted liquid–liquid extraction (SALLE) method with the liquid chromatography ultraviolet-visible detector (LC-UV) has been developed and validated for the simultaneous determination of seven antibiotic compounds of five different therapeutic classes (β-lactams), amoxycillin, ampicillin, penicillin G, (sulphonamides), sulfamethoxazole, (aminoglycosides) gentamicin, (fluoroquinolones) ciprofloxacin and (macrolide) erythromycin, in the cow milk samples. The LC conditions for separation of the selected antibiotic compounds were achieved with the reversed phase isocratic elution. The mobile phase consisted of 0.05 M Na2HPO4, acetonitrile and methanol (70:10:20 v/v/v). The mobile-phase flow rate was 1 mL min−1 with the injection volume of 20 μL and all the seven standard compounds were eluted within 14 min. The developed analytical method has been validated for the linearity, precision, sensitivity, accuracy, specificity, decision limit (CCα), and detection capability (CCβ). Experimental parameters influencing the extraction efficiency were evaluated and optimised. Under the optimum experimental conditions, good linearity over wide concentration ranges was obtained with the coefficient of determination R2 > 0.9989 for all the antibiotics. The limits of detection (LODs) and quantification (LOQs) ranged from 1.28 to 2.46 µg mL−1 and 3.87–7.46 µg mL−1, respectively. The relative standard deviations for the repeated analysis were below 8% indicating acceptable method precision. The accuracy study yielded satisfactory recoveries in the ranges 95.5–103% for the pure standard compounds and 83.8–112% for the spiked matrix-match milk samples. The results of the study revealed that the developed method is simple and fast and the SALLE method is appropriate for the simultaneous determination of targeted five multiclass antibiotic residues in the cow milk samples by LC-UV/Vis with a better efficiency.

Investigation of the Quality of the 12 Most-Used Antibiotics Available in Retail Private Pharmacies in Rwanda.

Using poor-quality antibiotics leads to increased risk of the development of microorganism-resistant strains, treatment failure, loss of confidence in health systems, and associated socio-economic impacts. The prevalence of poor-quality antibiotics has been found to be high in some of the Low and Middle-Income Countries (LMICs), but no data were available on the situation in Rwanda. This study was conducted to obtain data and inform health professionals on the quality of the 12 most-used selected antibiotics from private retail pharmacies in Rwanda. The investigation was conducted on 232 batches collected from randomly selected private retail pharmacies in all provinces of Rwanda, and concerned only with visual inspection and assay tests. Visual inspection was performed using a tool adopted by the International Pharmaceutical Federation (FIP) to identify manufacturing defects. An assay test quantified the Active Pharmaceutical Ingredient (API) in each collected batch using high-performance liquid chromatography (HPLC) coupled with an ultraviolet-visible (UV) detector, and the results were reported as the percentage content of the amount of APIs stated on the label. A total of 232 batches were analyzed, manufactured in 10 countries; the main country of manufacture was Kenya, with almost half of the batches (49.6%). The results of the visual inspection did not show the presence of counterfeit/ falsified antibiotics on the Rwandan market in this study but revealed weaknesses in labeling: more than 90% of the analyzed batches of the 12 antibiotics did not present the dosage statement on their label, and the complete list of excipients was missing in more than 20% of the analyzed batches. The assay test using HPLC confirmed the presence of APIs in 100% of the analyzed batches. However, moderate deviations from acceptable ranges of the API content defined by M. M. Nasr & C. M. Stanley in 2006 for erythromycin and the United States Pharmacopoeia 2018 for the other 11 molecules were found. The failure rate to meet the quality requirements in terms of the percentage content of active pharmaceutical ingredients declared on the labels was estimated at 8.2% in total, with 3.9% and 4.3% containing more and less than the amount of APIs stated on the labels respectively. The most-represented antibiotics on the Rwandan market were amoxicillin, co-trimoxazole and cloxacillin. No counterfeit antibiotics were found in this study. However, substandard batches with moderate deviations were found, suggesting that regular quality control of antibiotics is needed in Rwanda.