Pharmaceutical and biomedical applications of dispersive liquid-liquid microextraction.

Sample treatment is so crucial in pharmaceutical and biomedical analysis. Proper sample preparation protects the analytical instrument, increases the sensitivity, and enhances the selectivity by removing probable interfering substances. Dispersive liquid-liquid microextraction (DLLME) is one of the most important approaches in sample treatment. In normal DLLME, the organic droplet of the extractant is mixed with a dispersing solvent before being injected into the sample. After manual or mechanical shaking, the cloudy solution is centrifuged to break the formed emulsion. The organic phase is then separated and transferred to the analytical instrument. The dispersion process employed in DLLME dramatically increases the contact surface between the extractant and the sample, which enhances the extraction kinetics and efficiency. DLLME can be classified based on the dispersion technique or the density of the extractant. Accordingly, different modes of DLLME have evolved and been applied for drug analysis in biological fluids. This review discusses the principle of DLLME, the requirements of organic solvents used as extractants in each mode and the different factors affecting the extraction efficiency. Selected applications of the different DLLME modes in bio-pharmaceutical analysis have also been presented.