| Popis: |
Cyano bonded phases from six solid-phase extraction cartridge vendors (identified as A to F) have been characterized by elemental analysis, chromatography of probe molecules, and infrared and solid-state nuclear magnetic resonance spectroscopy. The results indicate that cyano solid-phase extraction cartridges from different vendors possess diverse surface properties presumably arising from differences in bonding chemistry and manufacturing methods. For example, nuclear magnetic resonance and infrared spectra indicate that vendors E and F use mono- and difunctional cyanopropyl silane, respectively, while all others use trifunctional. A wide range of hydrophobicities (determined using the alkylarylketone retention index scale) was observed among these bonded phases, determined primarily by degree of cyano group loading, whether the product has been endcapped or not and ratio of cyano functional group to endcapping reagent. Products from vendors A and D showed the presence of carboxyl groups, possibly arising from hydrolysis of cyano groups during silane bonding, thus imparting them with ion-exchange character. One would expect that extraction properties of cyano cartridges from different vendors may be very different. These results help explain the difficulty in transfer of procedures from cyano cartridges of one vendor to another and lend insight into the possible origin of lot-to-lot variability of cyano bonded phase from a single vendor. |
