Determination of ethyltriphenylphosphonium bromide and butyltriphenylphosphomium chloride in saturated polyester resins by LC-MS

Abstract

Powder Coatings are a type of paintings fully applied in the form of dry powder. Thermosseting Polyester Powder Coatings, one of the most used in industry, are based in a saturated polyester resin (with –COOH or –OH functionality group) as binder and crosslinker. In certain cases small amount of catalyst is added in order to the resin to try to achieve an acceptable curing time in baking temperatures. In Arkema Química S.A.U. (Sant Celoni) two specific types of catalyst, TRAP and BTPC (phosphonium salts), are added to the polyester that they synthesizes. The R&D laboratory of the industry requires the analysis of these two catalysts in the resins. The present work aims at developing a method that allows an estimation of the proportion of TRAP and BTPC present in the resins. Several tests have been performed to find the optimal working conditions to analyze the target catalysts by LC-MS. The chromatographic parameters have been optimized, finding the proportions of the appropriate eluents in a gradient method and the best parameters for mass detection using ES ion source. Two blank injections between every single sample analysis were determined as the best way to prevent the carry-over effect of TRAP. The extraction conditions of the catalysts in the resin have also been optimized, obtaining an approximate recovery of 90% for different sets of resin containing TRAP. This study is the basis for future validation of the quantitative method