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Sorption of amitriptyline and amphetamine to mixed-mode solid-phase microextraction in different test conditions.
J Chromatogr A. 2015 Apr 17; 1390:28-38.JC

Abstract

A solid-phase microextraction (SPME) method based on a sampler coating that includes strong cation groups (C18/SCX) is explored as a rapid direct sampling tool to detect and quantify freely dissolved basic drugs. Sampling kinetics, sorption isotherms and competitive effects on extraction yields in mixtures were tested for amphetamine and the relatively large/hydrophobic tricyclic antidepressant amitriptyline. Both compounds are >99% ionized at pH 7.4 but their affinity for the C18/SCX fiber is markedly different with distribution coefficients (Dfw values) of 2.49±0.02 for amphetamine and 4.72±0.10 for amitriptyline. Typical changes in electrolyte homeostasis that may occur in biomedical samples were simulated by altering pH and ionic composition (Na(+) and K(+) concentrations). These changes were shown to affect C18/SCX sorption affinities of the tested drugs with less than 0.2log units. At relatively low fiber loadings (<10mmol/L coating) and at all tested exposure times, linear sorption isotherms were obtained for both compounds but at aqueous concentrations of the individual drugs corresponding to concentrations in blood that are lethal, sorption isotherms became strongly nonlinear. Competition effects within binary mixtures occurred only if combinations of aqueous concentrations resulted in total fiber loadings that were in the nonlinear range of the SPME sorption isotherm for the individual compounds. We also compared sorption to the (prototype) C18/SCX SPME coating with analogue (biocompatible) C18 coated SPME fibers. C18/SCX fibers show increased sorption affinity for cationic compounds compared to C18 fibers, as tested using amitriptyline, amphetamine and trimethoprim. Surprisingly, sorption affinity of these ionized compounds for the C18 SPME fibers were within 1log unit of the C18/SCX SPME fibers. This shows that the strong cation exchange groups within the C18/SCX coating only has a relatively small contribution to the total sorption affinity of cationic compounds. Also the role of negatively charged silanol groups in both the C18 and C18/SCX coating seems small, as anionic diclofenac species sorbed strongly to the C18 fiber. Ionized organic species seem to be substantially adsorbed to the high surface area of C18 in SPME types using porous silica based coatings.

Authors+Show Affiliations

Institute for Risk Assessment Sciences, Utrecht University, P.O. Box 80177, 3508 TD Utrecht, The Netherlands. Electronic address: H.Peltenburg@uu.nl.Institute for Risk Assessment Sciences, Utrecht University, P.O. Box 80177, 3508 TD Utrecht, The Netherlands.Institute for Risk Assessment Sciences, Utrecht University, P.O. Box 80177, 3508 TD Utrecht, The Netherlands.Netherlands Forensic Institute, P.O. Box 24044, 2490 AA The Hague, The Netherlands.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

25747669

Citation

Peltenburg, Hester, et al. "Sorption of Amitriptyline and Amphetamine to Mixed-mode Solid-phase Microextraction in Different Test Conditions." Journal of Chromatography. A, vol. 1390, 2015, pp. 28-38.
Peltenburg H, Droge ST, Hermens JL, et al. Sorption of amitriptyline and amphetamine to mixed-mode solid-phase microextraction in different test conditions. J Chromatogr A. 2015;1390:28-38.
Peltenburg, H., Droge, S. T., Hermens, J. L., & Bosman, I. J. (2015). Sorption of amitriptyline and amphetamine to mixed-mode solid-phase microextraction in different test conditions. Journal of Chromatography. A, 1390, 28-38. https://doi.org/10.1016/j.chroma.2015.02.065
Peltenburg H, et al. Sorption of Amitriptyline and Amphetamine to Mixed-mode Solid-phase Microextraction in Different Test Conditions. J Chromatogr A. 2015 Apr 17;1390:28-38. PubMed PMID: 25747669.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Sorption of amitriptyline and amphetamine to mixed-mode solid-phase microextraction in different test conditions. AU - Peltenburg,Hester, AU - Droge,Steven T J, AU - Hermens,Joop L M, AU - Bosman,Ingrid J, Y1 - 2015/02/28/ PY - 2014/10/03/received PY - 2015/01/17/revised PY - 2015/02/20/accepted PY - 2015/3/10/entrez PY - 2015/3/10/pubmed PY - 2015/7/15/medline KW - Bio-analysis KW - C18/SCX KW - Cation-exchange KW - Cationic drugs KW - Mixed-mode fiber KW - Solid-phase microextraction SP - 28 EP - 38 JF - Journal of chromatography. A JO - J Chromatogr A VL - 1390 N2 - A solid-phase microextraction (SPME) method based on a sampler coating that includes strong cation groups (C18/SCX) is explored as a rapid direct sampling tool to detect and quantify freely dissolved basic drugs. Sampling kinetics, sorption isotherms and competitive effects on extraction yields in mixtures were tested for amphetamine and the relatively large/hydrophobic tricyclic antidepressant amitriptyline. Both compounds are >99% ionized at pH 7.4 but their affinity for the C18/SCX fiber is markedly different with distribution coefficients (Dfw values) of 2.49±0.02 for amphetamine and 4.72±0.10 for amitriptyline. Typical changes in electrolyte homeostasis that may occur in biomedical samples were simulated by altering pH and ionic composition (Na(+) and K(+) concentrations). These changes were shown to affect C18/SCX sorption affinities of the tested drugs with less than 0.2log units. At relatively low fiber loadings (<10mmol/L coating) and at all tested exposure times, linear sorption isotherms were obtained for both compounds but at aqueous concentrations of the individual drugs corresponding to concentrations in blood that are lethal, sorption isotherms became strongly nonlinear. Competition effects within binary mixtures occurred only if combinations of aqueous concentrations resulted in total fiber loadings that were in the nonlinear range of the SPME sorption isotherm for the individual compounds. We also compared sorption to the (prototype) C18/SCX SPME coating with analogue (biocompatible) C18 coated SPME fibers. C18/SCX fibers show increased sorption affinity for cationic compounds compared to C18 fibers, as tested using amitriptyline, amphetamine and trimethoprim. Surprisingly, sorption affinity of these ionized compounds for the C18 SPME fibers were within 1log unit of the C18/SCX SPME fibers. This shows that the strong cation exchange groups within the C18/SCX coating only has a relatively small contribution to the total sorption affinity of cationic compounds. Also the role of negatively charged silanol groups in both the C18 and C18/SCX coating seems small, as anionic diclofenac species sorbed strongly to the C18 fiber. Ionized organic species seem to be substantially adsorbed to the high surface area of C18 in SPME types using porous silica based coatings. SN - 1873-3778 UR - https://www.unboundmedicine.com/medline/citation/25747669/Sorption_of_amitriptyline_and_amphetamine_to_mixed_mode_solid_phase_microextraction_in_different_test_conditions_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0021-9673(15)00338-6 DB - PRIME DP - Unbound Medicine ER -