Amino-Modified Diamond as a Durable Stationary Phase for Solid-Phase Extraction
Gaurav Saini, Li Yang, Milton L. Lee, Andrew Dadson, Michael A. Vail, and Matthew R. Linford
We report the formation of a highly stable amino stationary
phase on diamond and demonstrate its use in solid-phase
extraction (SPE). This process consists of spontaneous
and self-limiting adsorption of polyallylamine (PAAm)
from aqueous solution onto oxidized diamond. Thermal
curing under reduced pressure or chemical cross-linking
with a diepoxide was shown to ﬁx the polymer to the
particles. The resulting adsorbents are stable under even
extreme pH conditions (from at least pH 0-14) and
signiﬁcantly more stable than a commercially available
amino SPE adsorbent. Coated diamond particles were
characterized by X-ray photoelectron spectroscopy (XPS)
and diffuse reﬂectance Fourier transform-infrared spectroscopy (DRIFT). Model silicon surfaces were characterized by spectroscopic ellipsometry and wetting. Solidphase extraction was demonstrated using cholesterol,
hexadecanedioic acid, and palmitoyloleoylphosphatidylcholine as analytes, and these results were compared to
those obtained with commercially available materials.
Breakthrough curves indicate that, as expected, porous
diamond particles have higher analyte capacity than
nonporous solid particles.
Solid-phase extraction (SPE) is a much-used technique for
sample preparation, puriﬁcation, concentration, and cleanup.1,2 It
has, in many cases, replaced liquid-liquid extraction and it often
precedes high-performance liquid chromatography (HPLC) in
analytical analyses. SPE has been referred to as on/off chromatography because ideally it is designed to either perfectly retain
or completely release (not retain) analytes of interest.
Diamond is an extraordinary material because of its chemical
inertness, hardness, high thermal conductivity, and optical transparency. Diamond’s chemical inertness and hardness make it an
ideal material in a number of applications. Indeed, there is
increasing recognition (vide infra) that synthetic diamond, which
has become relatively inexpensive, might function well as a
stationary phase for HPLC and SPE.
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