Spectroscopic analysis of bosentan in biological samples after a liquid-liquid microextraction

Optimisation of dispersive liquid-liquid microextraction for plasma sample preparation in bioanalysis of CDK4/6 inhibitors in therapeutic combinations for breast cancer treatment

Cyclin D dependent kinase 4 and 6 (CDK 4/6) inhibitors are novel anticancer drugs used in therapeutic combinations with endocrine therapy for breast cancer treatment. Their determination in patient plasma is of high interest as a prerequisite for possible therapeutic drug monitoring. Dispersive liquid-liquid microextraction (DLLME) shows great potential in bioanalytical sample preparation. Its simplicity and speed, along with the suitability for using small amounts of sample and hazardous solvents are some of its main advantages. However, its application on plasma samples is scarce and requires further development. The aim of this work was to explore the applicability of DLLME in the simultaneous extraction of six drugs of interest from human plasma, with an emphasis placed on achieving high extraction recoveries with low sample and solvent consumption. To tackle the low availability and amount of the plasma sample, as well as the complexity of the biological matrix, three novel DLLME modes are proposed: organic sample DLLME (OrS-DLLME), aqueous sample DLLME (AqS-DLLME), and a modified air-assisted DLLME (AA-DLLME). The extractant and disperser type and volume, volume ratios of all the components in the ternary system, effect of pH and salting out were optimised for all three proposed modes of DLLME. Optimised representative DLLME-HPLC-DAD-FLD method was validated and shown to be linear (R > 0.994), precise (RSD ≤13.8%, interday), accurate (bias -13.1-13.1%, interday) and robust (relative effect -3.34-6.08%). Simultaneous extraction of all six drugs with high recoveries (81.65-95.58%) was achieved. Sample volumes used were as low as 50-100 μL, with necessary organic solvent volumes in μL ranges. Greenness scores obtained using the AGREE software were between 0.63 and 0.66, demonstrating compliance with green analytical chemistry principles. Finally, the validated method was successfully applied on breast cancer patient plasma samples.

Solvent-terminated dispersive liquid-liquid microextraction: a tutorial

Solvent-terminated dispersive liquid-liquid microextraction (ST-DLLME) is a special mode of DLLME in which a demulsifying solvent is injected into the cloudy mixture of sample/extractant to break the emulsion and induce phase separation. The demulsification process starts by flocculation of the dispersed microdroplets by Ostwald ripening or coalescence to form larger droplets. Then, the extractant either floats or sinks depending on its density as compared with that for the aqueous sample. The demulsifier should have high surface activity and low surface tension in order to be capable of inducing phase separation. The extraction efficiency in ST-DLLME is controlled by the same experimental variables of normal DLLME (n-DLLME) such as the type and volume of the extractant as well as the disperser. Other parameters such as pH and the temperature of the sample, the stirring rate, the time of extraction and the addition of salt are also important to consider. Along with these factors, the demulsifier type and volume and the demulsification time have to be optimized. By using solvents to terminate the dispersion step in DLLME, the centrifugation process is not necessary. This in turn improves precision, increases throughput, decreases the risk of contamination through human intervention and minimizes the overall analysis time. ST-DLLME has been successfully applied for determination of both inorganic and organic analytes including pesticides and pharmaceuticals in water and biological fluids. Demulsification via solvent injection rather than centrifugation saves energy and makes ST-DLLME easier to automate. These characteristics in addition to the low solvent consumption, the reduced organic waste and the possibility of using water in demulsification bestow green features on ST-DLLME. This tutorial discusses the principle, the practical aspects and the different applications of ST-DLLME.