In this study, the mass transfer coefficient of two local anesthetics in liquid-phase
microextraction (LPME), which is performed in a single hollow fibre, was
investigated. Previously developed mathematical model has been applied for the
determination of the overall mass transfer coefficient based on the acceptor phase,
KA, in an unsteady-state LPMEPhysical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Ake-Jönsson, J.

Kumrić, Ksenija

Trtić-Petrović, Tatjana M.

Vladisavljević, T.

Đorđević, Jelena S.

Repository of the Vinča Nuclear Institute (VinaR)

        Pon HYSICAL11th InterFundamentPhyUnder UnivePThe ConfProfesSeptemBe CHEMISnational Coal and Appsical Chem the auspicersity of Beroceeding      erence is desor  Ivan Dr        ber 24-28lgrade, Ser  TRY 2012nference lied Aspectistry s of the lgrade s dicated to aganić , 2012  bia   s of       ISBN 978-86-82475-27-9 Volume 1 ISBN 978-86-82475-28-6 Volume II  Title: PHYSICAL CHEMISTRY 2012 (Proceedings) Editors: S. Anić and Ž. Čupić Published by: Society of Physical Chemists of Serbia, Studenski trg 12-16, 11158, Belgrade, Serbia Publisher: Society of Physical Chemists of Serbia For Publisher: S. Anić, President of Society of Physical Chemists of Serbia Printed by: “Jovan” Priting and Publishing Company; 200 Copies; Number of pages: 6+ 497; Format: B5; Printing finished in September 2012.  Text and Layout: “Jovan”  200- Coppy printing  III CONTENTS  Volume 1 Organizers V Committees VI Sponsors VIII Professor Ivan Draganić IX Plenary lectures 1 Chemical Thermodynamics 35 Spectroscopy, Molecular Structure,  Physical Chemistry of Plasma 65 Kinetics, Catalysis  137 Nonlinear Dynamics  225 Electrochemistry  301 Biophysical Chemistry, Photochemistry,  Radiation Chemistry  337 Radiochemistry, Nuclear Chemistry  Material Science 415  Volume II Solid State Physical Chemistry 505 Macromolecular Physical Chemistry  515 Environmental Protection  Forensic Sciences Pharmaceutical Physical Chemistry 557 Phase Boundaries 667 Complex Compounds 681 General Physical Chemistry 707 Geophysical Chemistry 719 Education, History 731 Food Physical Chemistry 743 Free Topic 783 Index 791  K-07-P 582 LIQUID-PHASE MICROEXTRACTION IN A SINGLE HOLLOW FIBRE - DETERMINATION OF MASS TRANSFER COEFFICIENT T. M. Trtić-Petrović1, K. R. Kumrić1,T. Vladisavljević2,  J. S. Đorđević1, J. Åke Jönsson3  1Laboratory of Physics, Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia, 2Loughborough University, Department of Chemical Engineering, Leicestershire UK, 3Center for Analysis and Synthesis, Department of Chemistry, Lund University, Sweden Abstract In this study, the mass transfer coefficient of two local anesthetics in liquid-phase microextraction (LPME), which is performed in a single hollow fibre, was investigated. Previously developed mathematical model has been applied for the determination of the overall mass transfer coefficient based on the acceptor phase, KA, in an unsteady-state LPME [1]. Introduction Miniaturized LPME has been developed using flat or hollow fibre membrane and applied to concentrate analytes prior to chromatographic analysis [2]. Recently, an alternative concept of unsteady-state LPME in a single hollow fibre (HF-LPME) has been introduced [3] and focused mainly on sample preparation and equilibrium sampling. The quantification of mass transport coefficients in LPME is important for a proper design and operation of the process and for the purpose of identification of rate limiting steps during mass transfer of solute(s) through the membrane. The overall mass transfer coefficient based on the acceptor phase, KA, in HF-LPME has been estimated from time-dependent concentration of extracted analyte in the acceptor phase while maintaining a constant analyte concentration in the donor phase: ⎥⎦⎤⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛ −∂∂−= **lnAAAAA CCCtAVK      (1) where VA is the volume of the acceptor phase, A is the area of the hollow fibre wall, and *AC  and CA is the equilibrium and actual concentration of the analyte in the acceptor phase in time t. The proposed conditions can be achieved either using a relatively large volume of the donor phase or tuning the extraction conditions in order to get a very low enrichment factor, so that the analyte concentration in the bulk of the donor phase can be regarded as a constant. The purpose of this work was to determinate the overall mass transfer coefficient of the selected drugs in an unsteady-state HF-LPME. K-07-P 583 Results and Discussion The investigated local anesthetics bupivacaine (Bup) and lidocaine (Lid) are amines with the values of the dissociation constants (pKa) of 8.9 and 8.5, respectively. The equilibrium extraction could be reached by adjusting the pH of the acceptor solution. The stripping of the investigated compounds was complete at the acceptor pH at least 3 pH units below the pKa value of the analyte. With increasing acceptor pH, the amount of nonextractable form of the amines in the acceptor decreased, the back extraction of the amine decreased and the resistance to the mass transfer in the acceptor phase increased. The investigated drugs were extracted in the three phase extraction system [4], from the donor phase (0.067 mol dm-3 phosphate buffer at pH 7.5 or blood plasma), through the organic phase placed in the hydrophobic membrane pores (5% TOPO in di-hexyl ether), and finally reextracted into the acceptor phase. The experimental conditions of the acceptor pH can be found in Ref. [3]. Fig. 1 shows the time dependence of the concentration of the investigated drugs in the donor and acceptor phase. Comparing the initial concentration of the drug in the donor phase (0.025 and 0.018 mmol dm-3 for Lid and Bup, respectively) and the concentration at certain extraction time, it can be seen that the depletion of the drug from the donor phase was less than 5%, and Eq. (1) can be applied for determination of KA. Fig. 2 is a plot of the ratio of concentration driving force (the difference between the equilibrium and actual concentration of the analyte in the acceptor phase) and equilibrium concentration in the acceptor phase versus time for the studied local anaesthetics. The similar dependence was obtained for the extraction 0 50 100 150 200 2500.000.010.020.030.040.050.06 C, mmol dm-3Time, minFigure 1. Time dependence of Lid and Bup in the acceptor (CA) and donor (CD) phases. Legend: Lid CD - ●, CA - ○; Bup CD - ■, and CA - □. 0 10 20 30 40 50 60-6-5-4-3-2-10ln((C* A-C)/C* A) Time, min  Figure 2. Semi-log plot of the local anesthetics concentration driving force versus time. Legend: ○ - Lid and □ - Bup. K-07-P 584 of the local anesthetics from plasma sample. The slope of ]/)ln[( ** AAA CCC −  vs. t line is equal to −KAA/VA and enables KA to be determined in a batch system under unsteady-state conditions. The calculated values of KA of the investigated drugs are given in Table 1. The mass transfer coefficient of the drug with higher protein binding (Bup) was higher for extraction from buffer solution than that from plasma solution i.e. KA was higher for the higher initial drug concentration.  Table 1. The overall mass transfer coefficient of studied local anesthetics. Compound Donor inDC , mmol dm-3 pHA KA × 104, cm min-1 Lidocaine buffer 0.024 7.2 5.0 Lidocaine plasma 0.024 (aPB 11%) 7.2 5.1 Bupivacaine buffer 0.017 7.4 3.4 Bupivacaine plasma 0.017 (aPB 69%) 7.4 3.0       aPB is protein binding defined and estimated in Ref. [4] Conclusion The determination of the overall mass transfer coefficient in HF-LPME under non steady-state conditions was demonstrated in this paper. The results show that the developed mathematical model was successfully applied for determination of KA. Acknowledgment We acknowledge the support to this work provided by the Ministry of Education and Science of Serbia through project No. III 45006. References [1] K.Kumrić, et al, J. Sep. Sci., 2012, in press. [2] J.Å. Jönsson, et al, J. Sep. Sci., 2001, 24, 495-507. [3] S. Pedersen-Bjergaard, et al, J. Chromatogr. A, 2008, 1184, 132-142. [4] Trtić-Petrović, et al, J. Chromatogr. B, 2005, 826, 169-176. CIP Volime II  CIP - Каталогизација у публикацији Народна библиотека Србије, Београд  544(082) 621.35(082) 66.017/.018(082)  MEĐUNARODNA konferencija iz fundamentalne i  primenjene fizičke hemije (11 ; 2012 ;        Beograd)    Physical Chemistry 2012 : proceedings.     #Vol. #2 / 11th International Conference on   Fundamental and Applied Aspects of Physical   Chemistry, September 24-28, 2012, Belgrade ;  [editors S.[Slobodan] Anić and Ž.[Željko]     Čupić ; organized by Society of Physical      Chemists of Serbia ... et al.]. - Belgrade :  Society of Physical Chemists of Serbia, 2012  (Belgrade : Jovan). - VI str., 499-782 str. : ilustr. ; 24 cm  "The Conference is dedicated to Professor     Ivan Draganić" --> nasl. str. - Tiraž 200. - Bibliografija uz svaki rad. - Registar.  ISBN 978-86-82475-28-6 1. Društvo fizikohemičara Srbije (Beograd) a) Физичка хемија - Зборници b)             Електрохемијско инжењерство - Зборници c)  Наука о материјалима - Зборници COBISS.SR-ID 193433356 

Liquid-phase microextraction in a single hollow fibre - determination of mass transfer coefficient

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Liquid-phase microextraction in a single hollow fibre - determination of mass transfer coefficient

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