Determination of isocyanates on industrial sampling filters by MALDI-MS and associated studies

• Main Author: Warburton, Karen Elizabeth
• Other Authors: Clench, Malcolm ; White, John ; Rimmer, Duncan
• Published: Sheffield Hallam University 2006
• Subjects: 363.1791
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435347

The primary aim of the work presented in this thesis was to develop methodologies for the characterisation of isocyanate compound fragments by LC/MS/MS and MALDI/MS analysis of isocyanates (NCO) on workplace sampling devices. The secondary aim was to perform related studies of veterinary medicine and pesticide compounds for possible quantitation from crop samples. NCO are a group of highly reactive compounds widely used in the manufacture of polyurethane products such as flexible and rigid foams, fibres, elastomers and coatings such as paints and varnishes. NCO are known respiratory sensitisers and are the most common cause of occupationally induced asthma, bronchitis and emphysema. The determination of NCO functionality and any contributions to understanding more about NCO chemistry is of significant value to occupational hygiene bodies globally. Here we demonstrate the application of MALDI-TOF-MS and tandem MS to the analysis of derivatised isocyanate monomers and prepolymers. NCO as 1-(2-methoxy) piperazine (MP) derivatives are analysed using MALDI-TOF-MS. The work was carried out to gauge the selectivity obtainable from the analysis of NCO mixtures without prior separation. Derivatised monomers and prepolymer mixtures are analysed and the potential of MALDI-TOF-MS for an NCO monitoring program is assessed. The results obtained show the possibility for mixture separation by this method, enabling the resolution of monomeric and prepolymeric species in spectra. Tandem MS is used for primary elucidation of fragment structures in the prepolymer samples and to designate proposed structures for unknown molecular parts. Quantitation of MDI-MP was performed on spot samples, deuterated MDI-MP (d6 MDI-MP) and MDI derivatized with the novel derivatizing reagent 1-(2-ethoxyphenyl) piperazine (EP) to give MDI-EP were used as internal standards. Quantitation of MDI-MP on filters was also performed using a direct filter calibration with d6 MDI-MP as the internal standard. Veterinary medicines are widely used to treat farm animals whether as a preventative measure (prophylactic use) or on a remedy basis. Treatment includes curing disease, improving feed conversion and promoting growth. A mixture of drug and its subsequent metabolites is excreted from the animal and the manure slurry is used as a fertiliser to treat crops destined for human consumption. The leaching of these substances into water/soil systems and consequently the human food chain is therefore of great concern. The work presented shows the preliminary analysis of a range of compounds to attempt quantitation and determine the content from a number of crop samples. Ionic Liquid Matrices are employed to reduce background noise and improve the appearance of sample spectra.