Adsorbent SPME fibers with Carboxen® or divinylbenzene (DVB) coatings on a Nitinol core have been introduced. In the provided study, the Nitinol core fibers show an improved reproducibility and mechanical stability vs. their predecessors on fused silica cores while maintaining inertness and analyte recovery, enabling direct implementation into existing methods. Read this article from Issue 9 of the Analytix Reporter, produced by Merck, to find out more.
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Introduction
Late 2019, saw the introduction of Supelco® adsorbent fibers with a Nitinol core. Compared to absorbent (“film”) type coatings, adsorbent (“particle”) type coatings for SPME fibers facilitate multiple interaction/mechanisms between sample analytes and the coating, often improving analyte retention/sensitivity. However due to multiple materials used in particle type SPME fiber coatings, such as adsorbent and binder/adherent, variability between fibers can increase. Nitinol core coated fibers, contained in standard stainless steel (SS) assemblies, are not only more durable but also highly reproducible. In this article, the various factors likely to cause variability such as the coating process, testing process, inertness, raw materials, and durability are discussed by comparing coatings on fused silica cores and Nitinol cores.
Results of Study
Coating process
Nitinol core fibers are produced using new state-of-the art coating equipment. The equipment allows reliable and reproducible application of coatings to the Nitinol core and monitors the entire process.
The new proprietary coating process also results in an even distribution of a highly bonded coating around the Nitinol core, further contributing to the improvement of fiber reproducibility. Further, the reproducibility of performance of newly made fibers with a Nitinol core was tested against historically available fibers with a fused silica core.
Conclusion
The adsorbent fiber coatings on the Nitinol core have been shown to be highly reproducible due to the following reasons:
- New state-of-the-art coating technology – variability in coated fiber diameter under 1% RSD
- Improved intra-lot reproducibility for Nitinol cores, as compared to the fused silica cores. 43.8% lesser variability for Carboxen® coatings and 81.3% lesser for DVB coatings
- Improved inter-lot reproducibility for Nitinol cores compared to the fused silica cores. 68.1% lesser variability for Carboxen® coatings and 71.7% lesser for DVB coatings
- New QC testing process
- Repeatable extractions with fibers having less than 2% RSD
- Testing probes that measure different adsorption mechanisms - Good fiber inertness – similar or better than fused silica fiber cores
- Highly controlled raw materials – in-house made materials with additional specifications to have more tight control on variability between material lots
- High durability - nearly unbreakable flexible fibers with well bonded smooth coatings
The analyte recoveries between core types for the same coating are similar.
These results suggest that users of adsorbent fibers on fused silica cores can easily transfer their methods for the same coatings onto the Nitinol core versions and take advantage of the improvements.
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