Characterisation of Derivatised Monomeric and Prepolymeric Isocyanates by Matrix-Assisted Laser Desorption/Ionisation Time-of-Flight Mass Spectrometry and Structural Elucidation by Tandem Mass Spectrometry

Abstract

Isocyanates are an important class of compounds in occupational hygiene monitoring due mainly to their behaviour as respiratory sensitisers. Here, we demonstrate the application of matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) and MALDI tandem mass spectrometry (MS-MS) to the analysis of derivatised isocyanate monomers and prepolymers. The aim of the work has been to gauge the selectivity obtainable from the direct analysis of isocyanate mixtures without prior separation. Monomeric and prepolymeric isocyanate mixtures were analysed as their 1-(2-methoxyphenyl) piperazine derivatives and the potential of MALDI time-of-flight (ToF)-MS for an NCO monitoring program was assessed. The results obtained demonstrated the possibility of direct mixture analysis by this method. MALDI-MS-MS was used for the elucidation of fragment structures in the prepolymer samples. The developed methodology was then applied to the analysis of swabs from an occupational hygiene monitoring scheme and enabled the identification of the isocyanate species detected.

HPLC-UV and HPLC-ESI+-MS/MS analysis of free monomeric methylene diphenyl diisocyanate in polyurethane foams and prepolymers after stabilization with NBMA a new derivatizating agent

“…Nowadays, the analyses of isocyanates, either from airborne samples, insulating and adhesive foams, sealing waxes, hardeners, primers or surface coatings, are based mainly on the derivatization of the isocyanates with different nucleophiles (secondary amines and alcohols), followed by chromatographic separation and quantication using a specic detector. Examples of amine-based derivatization agents are n-dibutylamine (DBA), 18,19 1-(anthracene-9-yl)-N-methylmethanamine (or 9-(methylaminomethyl)anthracene, MAMA), [20][21][22][23][24][25] 1-(2-pyridyl)piperazine (2-PP), [26][27][28] 1-(9-anthracenylmethyl)piperazine (MAP), 20,26 1-(2-methoxyphenyl)piperazine (2-MP), 20,26,[29][30][31][32][33] 4nitro-7-piperazino-2,1,3-benzoxadiazole (NBDPZ) [34][35][36] and Nbenzylmethylamine (NBMA, rst introduced in this paper). Alcohols used include methanol and ethanol.…”

“…Gel Permeation Chromatography (GPC) separates the isocyanates directly (without formation of derivatives). 40 The quantitation is done using different types of specic detection: ultraviolet absorption (UV), [20][21][22][23][24][25][26][28][29][30]33,34,[37][38][39]41 electrochemical (EC), 29,30,37,42,43 uorescence (Fl) 20,23,26,27,34,[44][45][46][47] or mass spectrometric (MS) 18,19,26,29,31,32,35,36,[48][49][50][51] detection.…”

Characterization of Low-Molecular Weight Iodine-Terminated Polyethylenes by Gas Chromatography/Mass Spectrometry and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry with the Use of Derivatization

“…47 It has also been shown that, for the analysis of monomeric and pre-polymeric isocyanates by MALDI mass spectrometry, their 1-(2-methoxyphenyl) piperazine derivatives were suitable. 48 Among the most interesting derivatization agents are those allowing the introduction of a group already containing covalently-bonded charge or promoting the formation of a charge. 38 This is the principle used in the present study for investigation with the aid of MALDI-ToF mass spectrometry.…”

A laboratory comparison of analytical methods used for isocyanates

“…26 Recent efforts also include the use of matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) and MALDI/MS/MS. 27 Methodological improvements have focused on improving sensitivity and measuring oligomers with greater specificity. Much of the challenge associated with measuring oligomers is that there are no commercial oligomer standards.…”