6 research outputs found
Modular Nucleic Acid Surrogates. Solid Phase Synthesis of α-Helical Peptide Nucleic Acids (αPNAs)
LC-ESI-MS/MS Analysis of Testosterone at Sub-Picogram Levels Using a Novel Derivatization Reagent
Testosterone analysis by LC-MS/MS is becoming the analytical
method
of choice over immunoassays due to its specificity and accuracy. However,
neutral steroid hormones possess poor ionization efficiency in MS/MS,
resulting in insufficient sensitivity for analyzing samples with trace
concentrations of the hormones. The method presented here utilizes
a derivatization step involving a novel, permanently charged, quaternary
aminooxy (QAO) reagent or MS-tag that reacts to the ketone functionality
of testosterone and significantly enhances its ESI-MS/MS sensitivity.
This derivatization method enabled quantitation of total testosterone
in human serum (200 μL) with a lower limit of quantitation (LLOQ)
of 1 pg/mL (3.47 pmol/L), total testosterone in dried blood spots
(8–10 μL) with a LLOQ of 40 pg/mL, and free testosterone
in serum ultrafiltrate (400 μL) with a LLOQ of 0.5 pg/mL. The
linearity of each of the high sensitivity applications was maintained
over a broad dynamic range of 1–5000 pg/mL for the serum samples
and 40–10 000 pg/mL for the dried blood spots (DBS)
with <i>R</i><sup>2</sup> >0.998. The %CV at the LLOQ
was
<15 for all applications. The QAO derivatization and sample preparation
workflows are quick, simple, and robust. Comparison of the derivatization
method with an LC-ESI-MS/MS nonderivatization method yielded high
correlation and agreement. The derivatization reagent is universal
and reacts with other compounds containing ketone or aldehyde functionality