Electromembrane extraction of gonadotropin-releasing hormone agonists from plasma and wastewater samples.

In the present study, for the first time electromembrane extraction followed by high performance liquid chromatography coupled with ultraviolet detection was optimized and validated for quantification of four gonadotropin-releasing hormone agonist anticancer peptides (alarelin, leuprolide, buserelin and triptorelin) in biological and aqueous samples. The parameters influencing electromigration were investigated and optimized. The membrane consists 95% of 1-octanol and 5% di-(2-ethylhexyl)-phosphate immobilized in the pores of a hollow fiber. A 20 V electrical field was applied to make the analytes migrate from sample solution with pH 7.0, through the supported liquid membrane into an acidic acceptor solution with pH 1.0 which was located inside the lumen of hollow fiber. Extraction recoveries in the range of 49 and 71% within 15 min extraction time were obtained in different biological matrices which resulted in preconcentration factors in the range of 82-118 and satisfactory repeatability (7.1 < RSD% < 19.8). The method offers good linearity (2.0-1000 ng/mL) with estimation of regression coefficient higher than 0.998. The procedure allows very low detection and quantitation limits of 0.2 and 0.6 ng/mL, respectively. Finally, it was applied to determination and quantification of peptides in human plasma and wastewater samples and satisfactory results were yielded.

Application of magnetic dispersive solid phase extraction combined with solidification of floating organic droplet-based dispersive liquid-liquid microextraction and GC-MS in the extraction and determination of polycyclic aromatic hydrocarbons in honey.

A magnetic dispersive solid phase extraction method combined with solidification of floating organic droplet-based dispersive liquid-liquid microextraction has been validated for the extraction of polycyclic aromatic hydrocarbons from honey samples. For this purpose, a carbonised cellulose-ferromagnetic nanocomposite was used as a sorbent through the magnetic dispersive solid phase extraction. For preparation of the sorbent, first, carbonised cellulose nanoparticles were created by treating cellulose filter paper with concentrated solution of sulfuric acid. Then, the prepared nanoparticles were loaded onto Fe3O4 nanoparticles through coprecipitation. In the extraction process, first, a few mg of the sorbent was added to the diluted honey solution and dispersed in it using vortex agitation. The particles were then separated and the adsorbed analytes were eluted with an organic solvent. The eluent was taken and after mixing with a water-immiscible extraction solvent was used in the following solidification of floating organic droplet-based dispersive liquid-liquid microextraction procedure. By performing the extraction process under the obtained optimum conditions, low limits of detection (0.08-0.17 ng g-1) and quantification (0.27-0.57 ng g-1), satisfactory precision (relative standard deviations ≤ 5.0%), and wide linear range (0.57-500 ng g-1) with great coefficients of determination (r2≥ 0.9986) were obtained.