Sol–gel niobia sorbent with a positively charged octadecyl ligand providing enhanced enrichment of nucleotides and organophosphorus pesticides in capillary microextraction for online HPLC analysis

Abstract

A niobia-based sol-gel organic-inorganic hybrid sorbent carrying a positively charged C ligand (Nb O -C (+ve)) was synthesized to achieve enhanced enrichment capability in capillary microextraction of organophosphorus compounds (which include organophosphorus pesticides and nucleotides) before their online analysis by high-performance liquid chromatography. The sorbent was designed to simultaneously provide three different types of molecular level interactions: electrostatic, Lewis acid-base, and van der Waals interactions. To understand relative contributions of various molecular level analyte-sorbent interactions in the extraction process, two other sol-gel niobia sorbents were also created: (a) a purely inorganic sol-gel niobia sorbent (Nb O ) and (b) an organic-inorganic hybrid sol-gel niobia sorbent carrying an electrically neutral-bonded octadecyl ligand (Nb O -C ). The extraction efficiency of the created sol-gel niobia sorbent (Nb O -C (+ve)) was compared with that of analogously designed and synthesized titania-based sol-gel sorbent (TiO -C (+ve)), taking into consideration that titania-based sorbents present state-of-the-art extraction media for organophosphorus compounds. In capillary microextraction with high-performance liquid chromatography analysis, Nb O -C (+ve) had shown 40-50% higher specific extraction values (a measure of extraction efficiency) over that of TiO -C (+ve). Compared to TiO -C (+ve), Nb O -C (+ve) also provided superior analyte desorption efficiency (96 vs. 90%) during the online release of the extracted organophosphorus pesticides from the sorbent coating in the capillary microextraction capillary to the chromatographic column using reversed-phase high-performance liquid chromatography mobile phase.

Yttria‐based sol–gel coating for capillary microextraction online coupled to high‐performance liquid chromatography

“…This is because the sol–gel chemistry involves the chemical bonding of the polymer coating inside the fused silica capillary. Utilization of sol–gel chemistry has helped to introduce different types of functional groups into the growing sol–gel network that resultantly form a polymeric coating to the inner surface of fused silica capillary and enhances the extraction and sensitivity. Right after the introduction of sol–gel chemistry for CME, many silica‐based and without silica‐based polymeric coatings were introduced for improved characteristics and better extraction.…”