Biomedical Engineering Reference
In-Depth Information
Highly Sensitive Pharmaceutical and Clinical
Analysis Using Selective Solid-Phase Extraction
Coupled to Microflow Liquid Chromatography
and Isotope-Dilution Mass Spectrometry
Haoying Yu , Xiaotao Duan , and Jun Qu
Abstract
The capacity of ultrasensitive quantification is highly desirable in many
clinical and pharmaceutical applications, such as the PK study of low-dose admin-
istration and quantification of low-abundance markers in circulating systems.
Nonetheless, this task is highly challenging even for a LC-MS/MS approach, due to
the extremely low levels of analytes and the highly complex matrices. Here we
describe a robust method for the ultrasensitive quantification of therapeutic agents
or clinical markers in highly complex biological systems. This is achieved by the
combination of a selective solid-phase extraction (SPE) with a highly sensitive cap-
illary LC (mLC)-MS/MS analysis. Comparing to a conventional LC-MS/MS, a
mLC-MS/MS provides much higher sensitivity due to the lower peak dilution. SPE
washing and elution conditions were optimized so that target drugs are selectively
extracted from the biological matrix. By eliminating most undesirable matrix com-
ponents, this selective SPE procedure enabled a high sample loading volume on the
mLC column without compromising chromatographic performance and operational
robustness, and helped to achieve ultralow detection limits. Sufficient m LC separa-
tion was employed in order to further improve analytical sensitivity and to decrease
matrix effects. To show the application of this strategy, three paradigms, respec-
tively, the quantifications of (1) corticosteroids after an intravitreous injection, (2)
an anticancer agent after a low-dose treatment, and (3) several vitamin D (VitD)
metabolites in plasma, are introduced in this chapter. Typically, low pg/mL LOQ
were achieved, and the linearity, accuracy, and precision of these developed
methods were excellent.
Collectively, this strategy enables the ultrasensitive, accurate, and robust
LC-MS-based quantification of extremely low levels of drug/markers in biological
samples, which were previously approachable only by ELISA or RIA methods.
H. Yu • X. Duan • J. Qu , Ph.D. (
*
)
Department of Pharmaceutical Sciences, University at Buffalo, State University of New York,
Cooke Hall 544 , Amherst , NY 14260 , USA
e-mail: junqu@buffalo.edu
