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

Abstract

The total amount of residual free monomeric methylene diphenyl diisocyanate, fmMDI, in polyurethane foams and prepolymers has been lowered by EU and US EPA legislation due to their harmful effects on human health. A new HPLC method using either UV or mass spectrometry detection has been developed for quantitative analysis of fmMDI. The isocyanate group is stabilized with a new derivatizating amine, N-benzylmethylamine (NBMA), resulting in analytes that are considerably more soluble in solvents routinely used in HPLC than previous methods. The naphthyl isocyanate-NBMA derivative is used as an internal standard, either in the calibration curve method or the standard addition method. Mass spectra of the three compounds of interest (NBMA, fmMDI NBMA derivative, and naphthyl isocyanate NBMA derivative) have been obtained and structural assignment of the major fragment peaks has been accomplished, thus establishing relevant parent-daughter mass transitions in ESI + -MS/MS mode that made the quantitation process highly specific for NBMA derivatives of fmMDI isomers. UV detection uses a wavelength of 254 nm. The HPLC separation is accomplished by columns packed with 5 mm reversephase C18 particles. Intra-and inter-day precision for both methods are below the limits established by the Horwitz equation, and the accuracy was measured at 108-111% recovery for both methods. The method does not use toluene, xylene, DMF, DMSO or chlorinated compounds. The use of MS/MS detection considerably reduces the possibility of false or grossly inflated results, avoiding errors that are common in GPC-UV underivatized measurements.

A novel treatment and derivatization for quantification of residual aromatic diisocyanates in polyamide resins

“…The goal can be reached by choosing the right strategy or more than one can be adopted at the same time, and the results strongly depends on the matrix composition. The LOQs of MDI reported in literature 24 are 33.5 mg/l for HPLC–UV and 1.65 mg/l for HPLC–MS/MS when it is present in polyurethane foams and prepolymers. According to our results, we reached a lower sensitivity with values of 0.2 and 0.7 mg/l for MDI and TDI respectively.…”

“…Suitable techniques for very complex matrices, which allow determining such a low concentration of analytes, are chromatographic ones 23 . In the most suitable scientific paper found for the case under study, the authors used two techniques to determine MDI in a polyurethane foam matrix 24 : reversed-phase high performance-liquid chromatography coupled with ultraviolet detector (HPLC–UV) and reversed-phase high-performance liquid chromatography coupled with mass spectrometry triple quadrupole detector (HPLC–ESI–MS/MS). The first is widespread and easy to use technique, the latter gives a more specific response, but it is more expensive and complex.…”

Polyurethane one-component foam formulation optimization for low free isocianate monomer content

“…The sample's compartment is kept at room temperature. 15 The flame resistance of the foam is determined using a certified burning chamber, following the German norm DIN 4102. The samples for this test are sprayed between plasterboards, two to three weeks in advance to let the material stabilize at a standard atmosphere (DIN 50014 -23/50-2).…”

2,4-Toluene diisocyanate detection in liquid and gas environments through electrochemical oxidation in an ionic liquid

“…Both instrumental and continuous monitoring methods have been developed in this regard as reviewed by Guglya. 2 As shown in Table S1, for the instrumental methods, 7 such as high performance liquid chromatography (HPLC), 8, 9 capillary gas chromatography (CGC) with flame ionization 10, 11 and ion chromatography with UV detection, 12, 13 the derivatization and extraction steps are quite time-consuming. Moreover, such offline strategies provide significant statistical differences as compared to online protocols.…”