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17Vortex-assisted liquid-liquid microextraction (VALLME) coupled with high-performance liquid 18 chromatography (HPLC) is proposed here for the rapid determination of octanol-water partitioning 19 coefficients (K ow ). VALLME uses vortex agitation, a mild emulsification procedure, to disperse 20 microvolumes of octanol in the aqueous phase thus increasing the interfacial contact area and 21 ensuring faster partitioning rates. With VALLME, 2 min were enough to achieve equilibrium 22 conditions between the octanolic and aqueous phases. Upon equilibration, separation was achieved 23 using centrifugation and the octanolic microdrop was collected and analyzed in a HPLC system. Six 24 model compounds with log K ow values ranging between ~0.5 and 3.5 were used during the present 25 investigations. The proposed method produced log K ow values that were consistent with previously 26 published values and the recorded uncertainty was well within the acceptable log unit range. Overall, 27 the key features of the proposed K ow determination procedure comprised speed, reliability, 28 simplicity, low cost and minimal solvent consumption. 29

The applicability of MnFe 2 O 4 nanoparticles as a new sorbent for group pre-concentration of V, Co, Ni, Cu, Zn, As, Se, Cd and Pb was investigated and compared with that of magnetite nanoparticles. A solid-phase extraction (SPE) of target analytes based on sorption of their hydrophobic complexes with ammonium pyrrolidine dithiocarbamate (APDC) on the surface of unmodified nanoparticles (NPs) was optimized. Magnetic NPs with retained metal complexes were easily separated from the bulk solution by a permanent magnet applied for 5 min. Analyte restoration in the final solution was accomplished by heating with 0.5 mL of 7 mol L À1 nitric acid. The obtained solutions were suitable for continuous nebulization in ICP-MS. Spectral and non-spectral matrix effects for urine analysis (direct and after SPE) were studied and adequate calibration strategies are suggested. Under optimized conditions the magnetically assisted SPE procedure enables enrichment of target analytes by factors of between 7.4 and 10, with linear dynamic ranges of 1-100 mg L À1 for V, Co, Ni, Cd, Pb and 10-1000 mg L À1 for Zn, As, Se and method detection limits in the interval 0.01-0.7 mg L À1 . The relative standard deviations (RSD%, for 10 mg L À1 V, Co, Ni, Cd, Pb and for 100 mg L À1 Zn, As, Se, n ¼ 6) were less than 5.5%. The accuracy of the method was evaluated by analysing urine certified reference material SeronormÔ Trace Elements Urine 201205 and obtained recoveries were in the range 85-109%. For correct determination of As and Se in urine, a preliminary microwave sample treatment with a mixture HNO 3 + H 2 O 2 was needed, but it led to a worsening of method detection limits. The developed method was successfully applied for analysis of human urine.