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A capillary gas chromatographic method with flame ionisation detection (FID) has been developed for the analysis of Tamoxifen, Anastrozole, and Letrozole in their pharmaceutical preparations, using Clomipramine as the internal standard in order to achieve quantification. Optimal conditions were investigated: column head pressure (110 kPa), injector and detector (FID) temperatures (both 3258C), time and temperature for the splitless step (0.75 min and 708C), volume injected (2 lL), and an oven temperature program providing analysis times shorter than 8 minutes. The principal aspects of the validation method are examined and discussed. A test of the ruggedness of this method was carried out using the Plackett-Burman fractional factorial model with a matrix of fifteen experiments. Detection limits of 17.0, 9.6, and 30.6 lg L -1 were obtained for Tamoxifen, Anastrozole, and Letrozole, respectively. This method is simple, rapid, and sensitive; it was tested on the analysis of pharmaceutical preparations, achieving recoveries between 98.8% and 100.3%.

A sensitive and reliable method based on MEKC has been developed and validated for trace determination of neonicotinoid insecticides (thiamethoxam, acetamiprid, and imidacloprid) and the metabolite 6-chloronicotinic acid in water and soil matrices. Optimum separation of the neonicotinoid insecticides was obtained on a 58 cm long capillary (75 μm id) using as the running electrolyte 40 mM SDS, 5 mM borate (pH 10.4), and 5% (v/v) methanol at a temperature of 25°C, a voltage of 25 kV and with hydrodynamic injection (10 s). The analysis time was less than 7 min. Prior to MEKC determination, the samples were purified and enriched by carrying out extraction-preconcentration steps. For aqueous samples, off-line SPE with a sorptive material such as Strata-X (polymeric hydrophobic sorbent) and octadecylsilane (C₁₈) was carried out to clean up and preconcentrate the insecticides. However, for soil samples, matrix solid-phase dispersion (MSPD) was applied with C₁₈ used as the dispersant. Good linearity, accuracy, and precision were obtained and the detection limits were in the range between 0.01 and 0.07 μg mL⁻¹ for river water and 0.17 and 0.37 μg g⁻¹ for soil samples. Recovery levels reached greater than 92% for all of the assayed neonicotinoids in river water samples with Strata-X. In soil matrices, the best recoveries (63-99%) were obtained with MSPD.

SummaryAn easy, rapid, and sensitive high-performance liquid chromatographic (HPLC) method is proposed for simultaneous determination of five antidepressants (trazodone, citalopram, fluoxetine, fluvoxamine and clomipramine) and norfluoxetine, a major metabohte of fluoxetine. Optimum conditions for the quantitative separation were investigated. The compounds were separated on a Nova Pack Cls column with acetonitrile-pH 2.5 phosphate buffer, 40:60 (v/v), as mobile phase at a flow rate of 1.5 mL min 1.. Stability of solutions, hnearity, repeatability and reproducibility, accuracy, specificity, and detection and quantification limits were examined to validate the method. The method is rapid and sensitive and can be applied to the analysis of antidepressants in pharmaceutical formulations and biological fluids; norfluoxetine can also be determined in these matrices. We have tested the method by analysis of several pharmaceutical formulations; recoveries obtained were bef,,veen 102.7% and 98.2% of the labelled values.

A voltammetric analytical assay for the selective quantification of vanillin is described. It is based on the use of a gold nanoparticle-modified screen-printed carbon electrode (SPCE) modified with graphene quantum dots (GQD) in a Nafion matrix. The GQD were synthesized by an acidic thermal method and characterized by UV-Vis, photoluminescence, and FTIR spectroscopy. The modified SPCE displays a strongly enhanced response to vanillin. Linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) were applied to optimize the methods. The analytical assay has linear responses in the 13 to 660 μM and 0.66 to 33 μM vanillin concentration ranges. The detection limits are 3.9 μM and 0.32 μM when using LSV and DPV, respectively. The analytical assay is selective and stable. It was applied to the determination of vanillin in several food samples with satisfactory results. Recoveries from spiked samples ranged between 92.1 and 113.0%. Graphical abstract The selective and sensitive quantification of vanillin is carried out by the use of a gold nanoparticle-modified screen-printed carbon electrode modified with graphene quantum dots in a Nafion matrix.

SummaryA simple and rapid method was developed for the analysis of Sildenafil Citrate (Viagra) in its pharmaceutical formulations (Viagra 25, 50 and 100 mg) in the presence of excipients, using its metabohte UK-103, 320 as internal standard for quantification. The optimal separation conditions were established in presence of all compounds in the pharmaceutical formulations and provided analysis times of less than 12 minutes. The conditions were: column head pressure (110 KPa), injector and flame ionisation detector (FID), temperatures (325 and 300 ~ time and temperature for the sphtless step (0.75 min and 70 ~ sample size (2 gL) and an oven temperature program.Aspects such as stability of the solutions, hnearity, accuracy, reproducibihty, specificity, limits of detection (LODs) and of quantification (LOQs) are examined in order to validate the method in presence of all excipients. Some of these aspects such as specificity were also assessed by mass spectrometric detection in the SCAN mode. A ruggedness test of this method was made using the fractional factorial model of Plackett-Burman. In our case, this involved designing a matrix of 15 experiments in which the influence of the seven factors mentioned above was tested at three different levels on different chromatographic results such as resolution, efficiency, relative peak areas, etc. The chromatographic results were evaluated statistically by the method of Youden and Steiner. The highly satisfactory results obtained in both the validation and ruggedness tests show that the CG method could be a very valuable option as an official method for the determination of Sildenafil Citrate in its pharmaceutical formulations.