Time-of-flight Secondary-ion-mass Spectrometric (ToF-SIMS) and X-ray Photoelectron Spectroscopic (XPS) Analyses of the Surface Lipids of Wool

Characterisation of the bound lipids at the wool fibre surface by time of flight secondary ion mass spectrometry (ToF-SIMS)

“…The assignment of many ToF-SIMS peaks to acyl species confirms previous assignments (Peet et al, 1995;Shao et al, 1997;Volooj et al, 2000;Ward et al, 1993) and confirms fatty acids are bound to the fibre surface by both acyl and thioester linkages (Evans et al, 1985;Peet, 1994). Relative amounts of the different species were calculated by subtracting the signal at each respective mass for the 2 h KOH-treated fabric from the respective signals for the different fabric samples to yield a 'corrected' estimate of the relative peak intensity for each respective species.…”

“…The dominant peaks at m/z = 325 À , 327 À , 339 À , 341 À (and peaks related to 341 À at 342 À , 343 À and 344 À ; see later text) in untreated wool fabric 1 and fabric 2 were assigned to aC 20 H 41 COO À , C 19 H 39 -COS À , an unknown thiolate ion, and aC 20 H 41 COS À ions, respectively, largely in agreement with previous reports (Peet et al, 1995;Shao et al, 1997;Volooj et al, 2000;Ward et al, 1993). In contrast, for fabric given a 2 h KOH treatment, all the surface bound lipids were expected to be removed (Negri et al, 1993), and as expected none of these peaks were detected experimentally, Table 1 and Figure 1.…”

“…Negative ion ToF-SIMS analyses of wool Positive and negative ion ToF-SIMS spectra of both untreated wool fabrics were similar to one another and those reported previously (Peet, Wettenhall, Rivett, & Allen, 1992;Shao et al, 1997;Volooj et al, 2000;Ward et al, 1993). However, unless samples were exhaustively extracted with solvent and appropriately handled prior to ToF-SIMS measurement (Vickerman & Briggs, 2001), PDMS and detergent residues were visible in both positive and negative ion spectra of all untreated and treated fabrics.…”

“…ToF-SIMS has been used in the past to identify lipids at the untreated wool fibre surface (Peet, Wettenhall, & Rivett, 1995;Shao, Jones, Mitchell, Vickerman, & Carr, 1997;Volooj, Carr, Mitchell, & Vickerman, 2000;Ward et al, 1993) and to reveal information about protein surfaces (Batts & Paul, 1994;Mantus, Ratner, Carlson, & Moulder, 1993) and it was hoped in this study that it could confirm the presence of cysteine residues at the fibre surface after hydroxylamine treatments and potentially exploit this selective route to functionalise the wool surface. Meade, Dyer, et al (2008) have suggested on the basis of atomic force microscopy (AFM) measurements that significant degradation of the wool fibre surface occurs during hydroxylamine treatment, raising doubts about the production of a cysteine rich surface following lipid removal with this treatment.…”

New insights into the nature of the wool fibre surface

“…This model explains the high carbon content obtained by x-ray photoelectron spectroscopy (Carr et al, 1986;Körner et al, 1990;Ward et al, 1993) and the predominant hydrocarbon fragments observed by secondary ion mass spectrometry (Natio et al, 1995;Shao et al, 1997;Ward et al, 1993). It also explains the change from a hydrophobic to a hydrophilic surface on treatment of wool with alkali, oxidants and reductants (Evans and Lanczki, 1997;Jones and Rivett, 1997;Leeder et al, 1985;Negri et al, 1993b;Shao et al, 1997). This model, however, does not explain the surprising stability of the thioester linkage (Bizzozero, 1995) or the surface properties of wool in an aqueous environment that indicates a solid with an ionisable surface (Evans et al, 2002).…”