Chitosan-graphene quantum dot-based molecular imprinted polymer for oxaliplatin release.

Molecularly imprinted polymers (MIPs) have garnered the interest of researchers in the drug delivery due to their advantages, such as exceptional durability, stability, and selectivity. In this study, a biocompatible MIP drug adsorption and delivery system with high loading capacity and controlled release, was prepared based on chitosan (CS) and graphene quantum dots (GQDs) as the matrix, and the anticancer drug oxaliplatin (OXAL) as the template. Additionally, samples without the drug (non-imprinted polymers, NIPs) were created for comparison. GQDs were produced using the hydrothermal method, and samples underwent characterization through FTIR, XRD, FESEM, and TGA. Various experiments were conducted to determine the optimal pH for drug adsorption, along with kinetic and isotherm studies, selectivity assessments, in vitro drug release and kinetic evaluations. The highest drug binding capacity was observed at pH 6.5. The results indicated the Lagergren-first-order kinetic model (with rate constant of 0.038 min-1) and the Langmuir isotherm (with maximum adsorption capacity of 17.15 mg g-1) exhibited better alignment with the experimental data. The developed MIPs displayed significant selectivity towards OXAL, by an imprinting factor of 2.88, in comparison to two similar drugs (cisplatin and carboplatin). Furthermore, the analysis of the drug release profile showed a burst release for CS-Drug (87% within 3 h) at pH 7.4, where the release from the CS-GQD-Drug did not occur at pH 7.4 and 10; instead, the release was observed at pH 1.2 in a controlled manner (100% within 28 h). Consequently, this specific OXAL adsorption and delivery system holds promise for cancer treatment.

Extraction and preconcentration of residual solvents in pharmaceuticals using dynamic headspace-liquid phase microextraction and their determination by gas chromatography-flame ionization detection.

The present study describes a microextraction and determination method for analyzing residual solvents in pharmaceutical products using dynamic headspace-liquid phase microextraction technique followed by gas chromatography-flame ionization detection. In this method dimethyl sulfoxide (µL level) placed into a GC liner-shaped extraction vessel is used as a collection/extraction solvent. Then the liner is exposed to the headspace of a vial containing the sample solution. The effect of different parameters influencing the microextraction procedure including collection/extraction solvent type and its volume, ionic strength, extraction time, extraction temperature and concentration of NaOH solution used in dissolving the studied pharmaceuticals are investigated and optimized. Under the optimum extraction conditions, the method showed wide linear ranges between 0.5 and 5000 mg L-1 . The other analytical parameters were obtained in the following ranges: enrichment factors 240-327, extraction recoveries 72-98% and limits of detection 0.1-0.8 mg L-1 in solution and 0.6-3.2 µg g-1 in solid. Relative standard deviations for the extraction of 100 mg L-1 of each analyte were obtained in the ranges of 4-7 and 5-8% for intra-day (n = 6) and inter-day (n = 4) respectively. Finally the target analytes were determined in different samples such as erythromycin, azithromycin, cefalexin, amoxicillin and co-amoxiclav by the proposed method.

Gas chromatographic determination of some phenolic compounds in fuels and engine oil after simultaneous derivatization and microextraction.

In this study, a simultaneous derivatization/air-assisted liquid-liquid microextraction method has been developed for sample preparation of some phenolic compounds in fuels and engine oil. Analytes are transferred by back liquid-liquid extraction into NaOH solution and then are derivatized with butyl chloroformate and extracted simultaneously into carbon tetrachloride. The extracted derivatized analytes are analyzed using gas chromatography with flame ionization detection. The effect of extracting solvent type, derivatization agent and extraction solvent volumes, ionic strength of the aqueous solution, number of extraction cycles, etc., on the extraction efficiency is investigated. The calibration graphs are linear in the range of 3-10,000 µg/L. Enhancement factors, enrichment factors, and extraction recoveries are in the ranges of 497 to 1471, 571 to 991, and 60 to 109%, respectively. Detection limits are obtained in the range of 0.8 to 2.0 µg/L. Relative standard deviations for the extraction of each selected phenols are in the ranges of 2-4% for intraday (n = 6) and 3-6% (n = 5) for interday precisions for 200 µg/L. This technique is successfully applied for the extraction, preconcentration, and determination of the selected phenols in gasoline, kerosene, gas oil, and engine oil.

Air-assisted liquid-liquid microextraction-gas chromatography-flame ionisation detection: a fast and simple method for the assessment of triazole pesticides residues in surface water, cucumber, tomato and grape juices samples.

A recently reported microextraction technique namely air-assisted liquid-liquid microextraction (AALLME) has been described for the extraction/preconcentration of some triazole pesticides from different samples prior to gas chromatography-flame ionisation detection (GC-FID). This technique is similar to dispersive liquid-liquid microextraction (DLLME) but in this method there is no need to use a disperser solvent and also volume of the used extraction solvent is less than DLLME. In this study, toluene with a density lower than that of water was used as an extraction solvent. Under the optimum extraction conditions, the method showed wide linear ranges with R(2)>0.996 and low limits of detection and quantification between 0.53-1.13 and 1.76-3.77 ng mL(-1), respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 713-808 and 100-113%, respectively. Relative standard deviations (RSDs) for the extraction of 25 and 250 ng mL(-1) of each selected triazole pesticide were less than 7% for intra-day (n=6) and inter-days (n=5) precision. The method was successfully used for analytes determination in different surface water, grape juice, cucumber, and tomato samples.

Combination of solid-phase extraction-hollow fiber for ultra-preconcentration of some triazole pesticides followed by gas chromatography-flame ionization detection.

In this study, an extraction and preconcentration technique using solid-phase extraction (SPE) along with hollow fiber (HF) has been developed as an ultra-preconcentration technique for some triazole pesticides in aqueous samples. Triazole pesticides were employed as model compounds to assess the method and were monitored by gas chromatography-flame ionization detection (GC-FID). Initially, an aqueous solution of target analytes was passed through an RP-8 SPE cartridge and then the adsorbed analytes were eluted with µL amounts of toluene. The collected elute was slowly introduced into an HF that had one end blocked. This allowed precipitation inside the lumen and pores of the HF. Finally, the obtained HF was mounted on a home-made solid-phase microextraction syringe and entered into the GC injection port for thermal desorption-GC analysis. The effect of various experimental parameters including injection port temperature, desorption time, state of HF, washing solvent, elution solvent and its volume, sample volume, etc. were investigated for finding the optimum conditions. The calibration graphs were linear in the ranges of 2-1000 ng/mL (penconazole and hexaconazole), 5-1000 ng/mL (tebuconazole), 15-1000 ng/mL (triticonazole) and the detection limits (LODs) ranged from 0.6 to 4.5 ng/mL. The enhancement factors were in the range of 870-950. The relative standard deviations (RSD%) for five repeated experiments (C=250 ng/mL of each pesticide) varied from 4.5 to 8.7%. The relative recoveries obtained for analytes in grape juice samples, spiked with different levels of each pesticide, were in the range of 87-119%.