Direct Analysis of an Oligomeric Hindered Amine Light Stabilizer in Polypropylene Materials by MALDI-MS Using a Solid Sampling Technique To Study Its Photostabilizing Action

Abstract

A novel method for the direct analysis of small amounts of an oligomeric hindered amine light stabilizer (HALS) occluded in polypropylene (PP) material was developed to study its photostabilizing action on the basis of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) using a solid sampling technique while avoiding troublesome solvent extraction. In this sampling protocol, the powdered mixture of PP composite sample containing trace amounts of an oligomeric HALS, Adekastab LA-68LD (MW = 1900), and the matrix reagent (dithranol) was spotted on the sample plate, then ion exchanged water was deposited onto the mixture to make a suspension, and finally, the dried mixture adhered on the plate was subjected to MALDI-MS measurement. On the mass spectrum thus obtained by the solid sampling MALDI, the molecular ions of the HALS desorbed from the PP composite were clearly observed as three major series of the HALS components in the range up to about m/z 7000 with little interference by the PP substrate and the other additives. Moreover, in the MALDI-MS spectra for the UV-exposed sample, the satellite peaks around the major HALS components proved to enhance significantly, reflecting the oxidized HALS species at the tetramethylpiperidine units to cause the photostabilizing action. In addition, hydrolyzed HALS species were also observed for the irradiated sample. These results suggest that not only the oxidation reaction but also the hydrolysis or decomposition of the oligomeric HALS components competitively proceed in the PP composites during UV exposure.

DNA methyltransferase expression in the mouse germ line during periods of de novo methylation

“…One limitation of typical MALDI is the need for solubilization of the sample and the matrix. This limitation can be circumvented by solvent‐free MALDI sample preparation (Taguchi et al, 2004; Hughes et al, 2009). In this case, the sample as well as the matrix are ground to very small particle size either in a mortar or in a ball mill, and intimately mixed before deposition on the MALDI target.…”

Lab‐on‐a‐plate: Extending the functionality of MALDI‐MS and LDI‐MS targets

“…One limitation of typical MALDI is the need for solubilization of the sample and the matrix. This limitation can be circumvented by solvent-free MALDI sample preparation (Taguchi et al, 2004;Hughes et al, 2009). In this case, the sample as well as the matrix are ground to very small particle size either in a mortar or in a ball mill, and intimately mixed before deposition on the MALDI target.…”

Quantitative Analysis of an Antioxidant Additive in Insoluble Plastics by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry (SALDI-MS) Using TiO2 Nanoparticles

“…It is generally di$cult to quantify the species observed in the MALDI mass spectra, because the absolute intensities of the observed peaks are strongly dependent on the laser power used and the conditions for sample preparation. 9) An oligomeric hindered amine light stabilizer (HALS) in polypropylene (PP) was directly determined by solid sampling MALDI-MS. 10), 11) The matrix and the HALS-containing PP were co-ground in liquid nitrogen using a freezer mill and the powdered mixture was directly spotted onto the sample plate for MALDI-MS.…”