Seyed Sadjadi (Presenter)
Phenomenex, Inc.
Authorship: Seyed Sadjadi, Shahana Huq, Laura Snow and Sean Orlowicz
Phenomenex, Inc, Torrance, CA
| Short Abstract Oral fluids present a convenient sample to collect and generally a non-invasive method of sample collection. Furthermore, OF is becoming increasingly popular in clinical and forensic laboratories. To address the demand, there are also increasing number of sample collection devices and some are offered with a preservative solution. These solutions may contain varying degree of excipients to maintain constant pH, stabilize the analytes and/or prevent bacterial growth in the samples. The nature and concentration of these excipients may pose difficulties with LC/MS detection of the analytes. We investigated multi-mode SPE media to substantially reduce or eliminate the preservative solution excipients. |
Long Abstract
We qualitatively examined several popular OF collection buffer to determine the nature of the compounds in the preservative solution. The chromatography was accomplished by a Kinetex C18 50x2.1 mm, 2.6 um and simple 0.1% formic acid in water and MeOH. A Shimadzu Nexera LC system equipped with two LC pump , A/S, column oven and a 25 uL MP mixer. The entire run time was 7 min including the equilibration step. The MS detection was carried out on a Sciex 4000 QTRAP with ESI source. We ran two sets of Q1 scan from 100 to 2000 Da in positive and negative polarity modes. Nothing significant was observed in negative polarity. However, in positive polarity mode, these solutions contained a mixture of overlapping homologues and polymeric species ranging in MW from 500 to 1800 m/z.
These buffers were then subjected to extraction through two separate SPE media, one with strong cation exchange retention mechanism (Strata-X-C) and another with strong anion exchange retention mechanism (Strata-X-A). It should be pointed out that both aforementioned SPE media are polymeric beads capable off retaining compounds through strong hydrophobic and π-π interaction mechanisms. Preservative solutions were first diluted with the appropriate extraction buffer. Afterward, they were loaded onto the SPE bed and subjected to was step from weak to strong solvents, in concentrated and diluted form (with DI water). A solvent mixture appropriate for each ion-exchange mechanism was used for the final elution step and afterward evaporated to dryness. The residue from final extracts was then analyzed by LC/MS and the resulting data compared against those obtained from blank and the unextracted preservative solution.
Surprisingly, strong washes containing 100% acetonitrile or methanol were ineffective in removing the polymeric species or the homologues. Traditionally, strong wash steps with aforementioned solvents are recommended and encouraged. The extracts with the lowest polymeric species were obtained from diluted acetone and isopropanol washes. Furthermore, strong cation exchange resin was more effective in reducing the polymeric species as compared against anion exchange resin.
References & Acknowledgements:
| Description | Y/N | Source |
| Grants | no | |
| Salary | yes | Phenomenex, Inc. |
| Board Member | no | |
| Stock | no | |
| Expenses | no |
IP Royalty: no
| Planning to mention or discuss specific products or technology of the company(ies) listed above: | yes |