Desorption electrospray ionisation mass spectrometry reveals in situ modification of a hindered amine light stabiliser resulting from direct N–OR bond cleavage
Paine, M.R.L., Barker, P.J., & Blanksby, S.J. (2011) Desorption electrospray ionisation mass spectrometry reveals in situ modification of a hindered amine light stabiliser resulting from direct N–OR bond cleavage. The Analyst, 136(5), pp. 904-912.
Detection and characterisation of structural modifications of a hindered amine light stabiliser (HALS) directly from a polyester-based coil coating have been achieved by desorption electrospray ionisation mass spectrometry (DESI-MS) for the first time. In situ detection is made possible by exposing the coating to an acetone vapour atmosphere prior to analysis. This is a gentle and non-destructive treatment that allows diffusion of analyte to the surface without promoting lateral migration. Using this approach a major structural modification of the HALS TINUVIN®123 (bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate) was discovered where one N-ether piperidine moiety (N-OC8H17) is converted to a secondary piperidine (N–H). With the use of 2-dimensional DESI-MS imaging the modification was observed to arise during high curing temperatures (ca. 260 °C) and under simulated physiological conditions (80 °C, full solar spectrum). It is proposed that the secondary piperidine derivative is a result of a highly reactive aminyl radical intermediate produced by N–O homolytic bond cleavage. The nature of the bond cleavage is also suggested by ESR spin-trapping experiments employing α-phenyl-N-tert-butyl nitrone (PBN) in toluene at 80 °C. The presence of a secondary piperidine derivative in situ and the implication of N–OR competing with NO–R bond cleavage suggest an alternative pathway for generation of the nitroxyl radical—an essential requirement in anti-oxidant activity that has not previously been described for the N-ether sub-class of HALS.
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|Item Type:||Journal Article|
|Additional Information:||Paine, Martin R. L. Barker, Philip J. Blanksby, Stephen J. Australian Research Council; BlueScope Steel [LP0775032]; ARC Centre of Excellence For Free Radical Chemistry and Biotechnology; Australian Postgraduate Award (Industry) The authors would like to thank Assoc. Prof. Michelle Coote and her research group for their helpful discussions. S.J.B. and M. R. L. P. acknowledge funding from the Australian Research Council and BlueScope Steel (LP0775032) and additional support from the ARC Centre of Excellence For Free Radical Chemistry and Biotechnology. M. R. L. P. is the holder of an Australian Postgraduate Award (Industry). Royal soc chemistry Cambridge|
|Keywords:||solid sampling technique, gas chromatography, organic coatings, scattering detection, nitroxyl radicals, hals, photostabilization, polypropylene, mechanisms, photodegradation|
|Divisions:||Current > QUT Faculties and Divisions > Science & Engineering Faculty|
|Deposited On:||29 Apr 2014 04:11|
|Last Modified:||16 May 2014 06:32|
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