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Omamogho, Jesse O; Stack, Elaine M; Santalad, Apichai; Srijaranai, Supalax; Glennon, Jeremy D; Yamen, Helen; Albert, Klaus;
Analytical and Bioanalytical Chemistry
Retention and selectivity properties of carbamate pesticides on novel polar-embedded stationary phases
Scopus: 13 ()
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This study describes the use of stationary phases with polar functionality suitable for the chemical analysis of carbamates pesticides and comparing with conventional alkyl C8 and C18 phases. The emphasis of this study was to compare the selectivity and retention of the pesticides on different stationary phases, bonded onto 1.7 mu m partially porous silica particles under isocratic separation condition. Four stationary phases including: phenylaminopropyl (PAP) phase, bidentate propylurea-C18 (BPUC18), C8 and C18, were successfully bonded on the partially porous silica spheres as evidenced by Si-29 and C-13 solid-state NMR analysis. The phenylaminopropyl phase exhibited smaller retentivity and enhanced selectivity compared to the alkyl C8 phase; the analysis time to run separation of the six carbamate pesticides (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) on the PAP phase was threefold faster than alkyl C8 phase. In a similar manner, the BPUC18 phase shows similar selectivity to that of the PAP phase, but with longer retentivity; although the BPUC18 phase is characterized with a lesser degree of retentivity for the carbamate pesticides than the conventional alkyl C18 phase. We propose that pi-pi and weak polar interactions between the carbamate pesticides and the PAP phase dominates the separation mechanism and providing a superior selectivity; faster separation time was also achieved as a result of smaller retentivity. Whereas the C8 and C18 bonded phases exhibits only hydrophobic interactions with the pesticides, leading to larger retentivity. The BPUC18 phase is shown to interact via polar-polar interactions in addition to hydrophobic interactions with the pesticides, providing similar selectivity with the PAP phase but with larger retentivity.

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