Lena Marianne von Sydow oral presentation (OA3-Tue3-3-4)
ToF-SIMS and multivariate analysis of commercially available chromatographic resins.
1 AstraZeneca, Pepparedsleden 1, 431 83 Gothenburg, Sweden
2 Chalmers, Maskingränd 2, 412 58 Gothenburg, Sweden
Chromatographic separation is a cornerstone in modern drug discovery to analyse and purify synthetic compounds based on their physicochemical properties. High performance separations are typically performed using chemically modified silica particles where different organic ligands are chemically immobilised. The separations will not only depend on different partitioning processes, but also on interactions with surface ligand(s), non-derivatized silanols and the surface properties of the stationary phase . The surface sensitivity of ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry) therefore makes it a very attractive technique allowing in-depth studies of materials used as stationary phases . ToF-SIMS can provide information of both the ligand, the underlying particle and possible impurities from the manufacturing process, giving the researcher an in-depth understanding of commercially available phases.
Eleven chromatographic stationary phases were analyzed using ToF-SIMS. The phases analyzed were: BEH HILIC, BEH C18, Torus 2-PIC; Torus DEA, Torus 1-AA and Torus DIOL, all 130Å, 1.7 µm, from Waters Corporation (Boston MA USA) and SIL, C4, DIOL, CN and NH2, all 100Å, 2.5um, from Eka Kromasil (Bohus Sweden). The stationary phases were fixed on ScotchTM tape and replicate measurements were made using an ION-TOF V (IONTOF GmbH, Germany) instrument with a Bi32+ primary ion source at 25 keV and 0.3 pA, in both positive and negative mode. Mass resolution was 5000 m/∆m at FWHM. Multivariate statistical analysis, both principal component analysis (PCA) and hierarcial cluster analysis (HCA), were made in SIMCA 13.0 (MKS/Umetrics, Umeå, Sweden). All variables were log transformed to enhance normal distribution.
The positive ion ToF-SIMS mass spectra can be seen as characteristic finger prints for the individual stationary phase and not surprisingly a clear clustering of replicate measurements for each phase could be observed in the following principal component analysis (PCA) with a significant difference between phases. The analysis of the ToF-SIMS spectra was expanded to a hierarchical clustering analysis to also capture variance in all valid score vectors. In the resulting dendrogram (R2=0.99) all phases were well separated and no overlap of the replicates between phases could be observed. The major observed difference in the dendrogram can be related to the presence of ionizable nitrogen groups in different phases.
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