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A Novel Miniaturised Dynamic Hollow-Fibre Liquid-Phase Micro-Extraction Method for Xenobiotics in Human Plasma Samples
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bioanalytical chemistry is a challenging field, often involving complex samples, such as blood, plasma, serum or urine. In many applications, sample cleanup is the most demanding and time-consuming step.

In the work underlying this thesis a novel dynamic miniature extractor, known as a hollow-fibre liquid-phase microextractor (HF-LPME), was designed, evaluated and studied closely when used to clean plasma samples. Aqueous-organic-aqueous liquid extraction, in which the organic liquid is immobilised in a porous polypropylene membrane, was the principle upon which the extractor was based, and this is discussed in all the papers associated with this thesis. This type of extraction is known as supported-liquid membrane extraction (SLM). The aim of this work was the development of a dynamic system for SLM. It was essential that the system could handle small sample volumes and had the potential for hyphenations and on-line connections to, for instance, LC/electrospray-MS. The design of a miniaturised HF-LPME device is presented in Paper I. The extraction method was developed for some weakly acidic pesticides and these were also used for evaluation. In the work described in Paper II, the method was optimised on the basis of an experimental design using spiked human plasma samples. Paper III presents a detailed study of the mass-transfer over the liquid membrane. The diffusion through the membrane pores was illustrated by a computer-simulation. Not surprisingly, the more lipophilic, the greater the retention of the compounds, as a result of dispersive forces. The main focus of the work described in Paper IV was to make the HF/LPME system more versatile and user-friendly; therefore, the extractor was automated by hyphenation to a SIA system.

Place, publisher, year, edition, pages
Stockholm: Department of Analytical Chemistry, Stockholm University , 2010. , 97 p.
Keyword [en]
sample clean-up, human blood plasma, hollow-fibre liquid phase microextraction, supported liquid membrane extraction, SLM, HF-LPME, sample preparation, bioanalysis, liquid-liquid extraction
National Category
Other Basic Medicine
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-41742ISBN: 978-91-7447-128-1 (print)OAI: oai:DiVA.org:su-41742DiVA: diva2:337869
Public defence
2010-09-29, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Available from: 2010-09-07 Created: 2010-08-05 Last updated: 2011-05-02Bibliographically approved
List of papers
1. Assessment of a dynamic hollow-fibre liquid phase microextraction system forhuman blood plasma samples
Open this publication in new window or tab >>Assessment of a dynamic hollow-fibre liquid phase microextraction system forhuman blood plasma samples
2009 (English)In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 77, no 4, 1309-1314 p.Article in journal (Refereed) Published
Abstract [en]

A dynamic liquid phase microextraction (LPME) system, based on hollow-fibre supported liquid membrane(SLM) extraction, was developed for extracting ionisable xenobiotics from human plasma, andits performance was evaluated (in terms of extraction efficiency, reproducibility, durability and carryover)using nitrophenolic compounds as model analytes at concentrations of 0.1–0.5gmL−1 in aqueousstandards. The efficiency and repeatability were tested also on spiked human plasma. The system isnon-expensive, convenient, requires minimal manual handling and enables samples with volumes assmall as 0.2mL to be extracted. For plasma samples extraction efficiencies of between 30 and 58% wereachieved within 20 min, including washing steps. The limit of detection (LOD) values were in the range0.02–0.03gmL−1. The developed system can provide enrichment factors up to eight, based on theinjection-to-acceptor volume ratio (in this case 0.2–0.025 mL). The same hollow-fibre membrane wasused up to 8 days with no loss of efficiency. Carry-over was lower than detection limit.

Place, publisher, year, edition, pages
Elsevier, 2009
Keyword
Supported liquid membrane
National Category
Other Basic Medicine
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-38145 (URN)10.1016/j.talanta.2008.09.005 (DOI)000262761500009 ()
Available from: 2010-03-30 Created: 2010-03-29 Last updated: 2010-08-10Bibliographically approved
2. Dynamic hollow-fibre liquid phase microextraction of dinitrophenols from human plasma: Optimization of an extraction flow system using experimental design methodology
Open this publication in new window or tab >>Dynamic hollow-fibre liquid phase microextraction of dinitrophenols from human plasma: Optimization of an extraction flow system using experimental design methodology
2009 (English)In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 79, no 3, 633-638 p.Article in journal (Refereed) Published
Abstract [en]

The utility of a dynamic hollow-fibre liquid phase microextraction method (optimized using a four-variable experimental design and response surface modelling) for extracting dinitrophenolic compounds from human plasma samples was evaluated. The investigated variables were donor phase salt concentration (10–400 mM), donor phase pH (2–6), acceptor phase pH (7–12), and donor/acceptor phase flow rates (30/7.5 to 70/17.5 μL min−1). Four dinitrophenol pesticides were used as model substances at concentrations of 0.1 μg mL−1 in spiked human plasma samples. Extraction efficiencies ranging from 42 to 77% with RSDs below 9 were achieved with the optimized method. The flow rate and acceptor pH were shown to strongly affect the extraction efficiency for all compounds, while the donor phase pH and salt concentration had minor effects. With a well-defined acceptor phase pH and flow rate the system exhibited high robustness. The limits of quantification for the investigated compounds, using the presented extraction method followed by liquid chromatography/electrospray ionization mass spectrometry in selected ion monitoring mode, ranged from 0.05 to 0.1 μg mL−1 plasma.

Place, publisher, year, edition, pages
Elsevier, 2009
Keyword
Supported liquid membrane; Hollow-fibre liquid phase microextraction; Nitrophenols; Human blood plasma; Optimization
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-34670 (URN)10.1016/j.talanta.2009.04.051 (DOI)000268346800012 ()
Available from: 2010-01-11 Created: 2010-01-11 Last updated: 2011-03-04Bibliographically approved
3. Study of mass transfer in a dynamic hollow-fibreliquid phase microextraction system
Open this publication in new window or tab >>Study of mass transfer in a dynamic hollow-fibreliquid phase microextraction system
2010 (English)In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 33, no 1, 112-119 p.Article in journal (Refereed) Published
Abstract [en]

The extraction characteristics of a dynamic hollow-fibre liquid phase microextractionsystem were investigated by studying the mass transfer and diffusion rates of dinitrophenolsfrom plasma samples over the liquid membrane (dihexylether). The measureddiffusion coefficients were compared with theoretical values calculated from Stokesdiameters. The diffusion mechanism was simulated by computer and the most polarcompounds, 2,4-dinitrophenol and 4,6-o-dinitrocresol, had associated diffusion coefficientsthat were close to the calculated theoretical values. 2-sec-Butyl-4,6 dinitrophenoland 2-tert-butyl-4,6-dinitrophenol, the compounds with the highest log P values, wereretained by the polypropylene membrane, which reduced the experimentally observeddiffusion rates to about half of the theoretical values. The retention was most likely due todispersive forces interacting with the pore inner walls. Extraction was linearly correlatedwith time for all compounds and the repeatability was high (RSDs 7–11%), even for theshortest extraction times. Method LOD as the amount injected ranged between 0.3 and3.1 ng for an extraction cycle of 213 s.

Place, publisher, year, edition, pages
Wiley Interscience, 2010
Keyword
dynamic hollowfibre liquid phase microextraction
National Category
Other Basic Medicine
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-38143 (URN)10.1002/jssc.200900539 (DOI)000274306800014 ()
Available from: 2010-03-30 Created: 2010-03-29 Last updated: 2011-11-23Bibliographically approved
4. Dynamic hollow-fibre liquid phase microextraction for human plasma samples automated by sequential injection analysis
Open this publication in new window or tab >>Dynamic hollow-fibre liquid phase microextraction for human plasma samples automated by sequential injection analysis
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This paper presents an easily handled, hollow-fibre liquid phase microextraction (HF-LPME) sample clean-up method, automated by the use of a programmable sequential injection analysis (SIA) system. Use of a SIA system significantly reduces the need for manual sample handling. This new type of clean-up system was assessed and compared with manual HF-LPME for the extraction of acidic compounds (dinitrophenols) from human plasma, in terms of human intervention requirements, efficiency, repeatability and carry-over. Its application to a SIA system for basic compounds (b-blockers) is also presented. The sample aliquots collected off-line from the SIA system were subsequently subjected to separation with LC and the various analytes were detected with ESI-MS.

Extraction efficiency values between 28 and 56% (RSD 5-10%, n = 7) were achieved for the dinitrophenol compounds after an extraction cycle of 58 min including a 30 min washing step. According to the MS analysis the SIA/HF-LPME method yielded clean chromatograms with no detectable interfering peaks. Ion suppression in positive ESI-MS was between 4 and 21% when tested on extracts with b-blockers.

National Category
Other Basic Medicine
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-40984 (URN)
Available from: 2010-06-30 Created: 2010-06-30 Last updated: 2010-08-10Bibliographically approved

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