Diamond Technology


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

engineering solution

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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