Search

The recently introduced gadolinium-based magnetic ionic liquid (Gd-MIL) has been exploited as an extractant in dispersive liquid-liquid microextraction (DLLME) for preconcentration of ivermectin (IVR) from water samples followed by analysis using reversed-phase HPLC with UV detection at 245 nm. The utilized Gd-MIL extractant is hydrophobic with markedly high magnetic susceptibility. These features result in an efficient extraction of the lipophilic analyte and facilitate the phase separation under the influence of a strong magnetic field, thus promoting the method sensitivity and increasing the potential for automation. To maximize the IVR enrichment by DLLME, the procedure was optimized for extractant mass, dispersive solvent type/volume, salt addition and diluent pH. At optimized conditions, an enrichment factor approaching 70 was obtained with 4.0-mL sample sizes. The method was validated in terms of accuracy, precision, specificity and limit of quantitation. The method was successfully applied to the determination of IVR in river water samples with a mean relative recovery of 97.3% at a spiked concentration of 400 ng/mL. Compared with other reported methods, this approach used a simpler procedure with improved precision, lower amounts of safer solvents and a short analysis time., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Google Trends has been extensively used in different sectors from finance to tourism, the economy, fashion, the fun industry, the oil trade, and healthcare. This scoping review aims to summarize the role of Google Trends as a monitoring and a predicting tool in the COVID-19 pandemic. Inclusion criteria for this scoping review were original English-language peer-reviewed research articles on the COVID-19 pandemic conducted in 2020 using Google Trends as a search tool. Articles that were in a language other than English, were only in abstract form, or did not discuss the role of Google Trends during the COVID-19 pandemic were excluded. According to these criteria, a total of 81 studies were included to cover the period of the first year after the emergence of the crisis. Google Trends can potentially help health authorities to plan and control pandemics earlier and to decrease the risk of infection among people., (© The Author(s) 2023. Published by Oxford University Press on behalf of Postgraduate Medical Journal. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Ascorbic acid (ASC; vitamin C) is a weak chromophore, so its presence cannot be determined directly by spectrophotometry., Objective: This work aims to develop and validate a simple and ecofriendly analytical method for the determination of ASC concentration based on the reaction of ASC with the metal complex, ferric salicylate., Methods: The visible absorbance of ferric salicylate was found to be inversely proportional to the concentration of ASC. The possible mechanism of the reaction between ASC and ferric salicylate was investigated: ferric salicylate was found to be reduced by ASC under the applied experimental conditions. Different parameters that may affect the reaction were also investigated: ferric salicylate concentration, pH, ionic strength, and the time of reaction. The optimum concentration of ferric salicylate was found to be 1000 µM and the optimum pH was 5.5. The developed method was validated according to International Conference on Harmonization (ICH) guidelines., Results: The linearity range of the developed method was 5-70 µg/mL and the correlation coefficient was 0.9994. The limits of detection and quantitation were 0.38 µg/mL and 1.16 µg/mL, respectively. The method was successfully applied to the determination of ASC concentration in commercial Ruta-C60® tablets. The mean recovery ± standard deviation was found to be 101.10 ± 0.70%. The results were statistically compared to those obtained by a reported HPLC method. Good agreement was observed., Conclusion: The developed method is simple, fast, cost-effective, and suitable for routine pharmaceutical analysis of ASC., Highlights: The developed method is more sensitive than the other spectrophotometric methods reported for determination of ASC., (© The Author(s) 2022. Published by Oxford University Press on behalf of AOAC INTERNATIONAL. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

A validated method for preconcentration and determination of nateglinide in plasma was developed using vortex-assisted dispersive liquid-liquid microextraction. Different variables that affect extraction efficiency were studied and optimized, including type and volume of extractant, type and volume of disperser, pH of diluent, salt addition effect, centrifugation and vortex time. Nateglinide was extracted using 30 μL of 1-octanol as an extractant and 200 μL of methanol as a disperser. The enrichment factor reached 330 under the optimum conditions. High-performance liquid chromatography/ultraviolet was used for detection using phosphate buffer (pH 2.5, 10 mM): acetonitrile (45:55, v/v) as a mobile phase at a flow rate of 1 mL/min. The method was linear over the range of 50-20,000 ng/mL with a limit of detection of 15 ng/mL (signal-to-noise ratio = 3). Intra- and inter-day precision had %relative standard deviation <6% (n = 3) and the %recoveries were found to be between 102.5 and 105.9%. The proposed method is simple, sensitive, eco-friendly, cost-effective and powerful for microextraction of nateglinide from human plasma samples., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

A reversed-phase HPLC method was developed for the simultaneous determination of ursodeoxycholic acid (UDCA) and the epimeric isomer, chenodeoxycholic acid (CDCA), in their synthetic mixtures and in tablet dosage form. The proposed HPLC method uses a C18 column and mobile phase consisting of an acetonitrile-phosphate buffer mixture (pH 2.3, 100 mM; 50 + 50, v/v) at a flow rate of 2.0 mL/min with UV detection at 210 nm. The method was validated according to the International Conference on Harmonization guidelines; and linearity, range, accuracy, precision, robustness, and system suitability were studied. The LOD and LOQ were also calculated and found to be 1.23 and 3.73 μg/mL for UDCA and 0.83 and 2.52 μg/mL for CDCA, respectively. The method was adapted for UHPLC, in which baseline separation was achieved in <2.5 min. The assay results of Ursomix tablets by the developed method were statistically compared with those obtained by the reference method using t- and F-tests, and no significant differences were observed.

The present work describes new spectrophotometric methods for the simultaneous determination of phenylephrine hydrochloride and ketorolac tromethamine in their synthetic mixtures. The applied chemometric techniques are multivariate methods including classical least squares, principal component regression, and partial least squares. In these techniques, the concentration data matrix was prepared by using the synthetic mixtures containing these drugs dissolved in distilled water. The absorbance data matrix corresponding to the concentration data was obtained by measuring the absorbances at 16 wavelengths in the range 244-274 nm at 2 nm intervals in the zero-order spectra. The spectrophotometric procedures do not require any separation steps. The accuracy, precision, and linearity ranges of the methods have been determined, and analyzing synthetic mixtures containing the studied drugs has validated them. The developed methods were successfully applied to the synthetic mixtures and the results were compared to those obtained by a reported HPLC method.

Ion exclusion chromatography (IELC) of short chain aliphatic carboxylic acids is normally done using a cation exchange column under standard HPLC conditions but not in the ultra-HPLC (UHPLC) mode. A novel IELC method for the separation of this class of carboxylic acids by either HPLC or UHPLC utilizing a C18 column dynamically modified with sodium dodecyl sulfate has been developed. The sample capacity is estimated to be near 10 mM for a 20 µL injection or 0.2 µmol using a 150 × 4.6 mm column. The optimum mobile phase determined for three standard mixtures of organic acids is 1.84 mM sulfuric acid at pH 2.43 and a flow rate of 0.6 mL/min. Under optimized conditions, a HPLC separation of four aliphatic carboxylic acids such as tartaric, malonic, lactic and acetic can be achieved in under 4 min and in <2 min in the UHPLC mode at 2.1 mL/min. A variety of fruit juice and soft drink samples are analyzed. Stability of the column as measured by the retention order of maleic and fumaric acid is estimated to be ∼4,000 column volumes using HPLC and 600 by UHPLC. Reproducible chromatograms are achieved over at least a 2-month period. This study shows that the utility of a C18 column can be easily extended when needed to IELC under either standard or UHPLC conditions., (© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The determination of aromatic acids by ion exclusion chromatography is challenging due to peak tailing and the long retention time of hydrophobic solutes. This review discusses the retention mechanisms and the factors affecting retention, eluents and detection methods used in ion exclusion chromatography of aromatic acids such as mono-, di-, tri- and tetra-carboxylic acids, amino acids, sulfonates and phenol. In addition, the different approaches used to improve the chromatographic separation of these compounds are also discussed. These approaches include introducing an internal gradient of the ionic strength, using vacancy ion exclusion chromatography, employing a hydrophilic cation exchange resin or adding a modifier such as heptanol to the dilute sulfuric acid mobile phase. The applications of these methods in the analysis of aromatic acids are provided with a table summarizing the stationary phases, the mobile phases and the detection methods.