Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume
38, Number 10, October 2000, pp. 458-464
Evaluation
of Solid-Phase Microextraction for the Study of Protein Binding in Human Plasma
SamplesMohamed
Abdel-Rehim1,*, Gunilla Carlsson2, Margareta Bielenstein1, Torbörn
Arvidsson1, and Lars G. Blomberg2
1AstraZeneca R&D Södertälje, Preclinical Development
DMPK and Bioanalytical Chemistry Development, SE-151 85 Södertälje,
Sweden and 2Karlstad University, SE-651 88 Karlstad, Sweden
Solid-phase
microextraction (SPME) in combination with capillary gas chromatography and
a nitrogenŠphosphorous detector is used to study protein binding in human plasma
samples. Local anesthetics of the amide-type (ropivacaine, bupivacaine, mepivacaine,
prilocaine, and lidocaine) are used as model compounds in this evaluation. Carbowax/divinylbenzene
(CW/DVB), polyacrylate, and polydimethylsiloxane fibers are tested. Sampling
on CW/DVB fibers give the highest recovery in plasma samples compared with other
fibers. Ultrafiltrate spiked with each of the substances is used for the construction
of calibration curves. The protein binding is investigated at four different
total concentrations from 0.5 to 15.0µM. The degree of protein binding increases
when the solute concentration decreases. Protein binding of the five solutes
is investigated at four pH levels (6.4, 7.4, 8.4, and 9.4). It is found that
protein binding increased with increasing pH. The influence of temperature variation
(from 32”C to 40”C) on protein binding is also investigated. The protein binding
decreases when the temperature increases. The methodology is validated and good
correlation and precision are obtained. Back-calculated quality control samples
give accuracy within 20% of theoretical values for all five substances. This
study shows that SPME as a sample-preparation method gives the same protein
binding for the studied local anesthetics as that achieved using earlier presented
methods.
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