Ferrocenoyl piperazide as derivatizing agent for the analysis of isocyanates and related compounds using liquid chromatography/electrochemistry/mass spectrometry (LC/EC/MS)

Abstract

Ferrocenoyl piperazide is introduced as a new pre-column derivatizing agent for the analysis of various isocyanates in air samples using reversed-phase liquid chromatographic separation, electrochemical oxidation/ionization, and mass spectrometry. The nonpolar derivatives can be separated well using a phenyl-modified stationary phase and a formic acid/ammonium formate buffer of pH 3, which yields excellent separations, especially for one problematic group of isocyanates consisting of 2,4-and 2,6-toluylenediisocyanate (2,4-and 2,6-TDI) and hexamethylenediisocyanate (HDI). Electrochemical oxidation at low potentials (0.5 V versus Pd/H 2 ) leads to formation of charged products, which are nebulized in a commercial atmospheric pressure chemical ionization (APCI) source, with the corona discharge operated only at low voltage. Limits of detection between 6 and 20 nmol/L are obtained for the isocyanate derivatives, and calibration is linear over at least two decades of concentration. The method is applied for the analysis of air after thermal degradation of a polyurethane foam, and it is demonstrated that it is suitable as well for the analysis of carboxylic acid chlorides and of

Probing Cysteine Reactivity in Proteins by Mass Spectrometric EC-Tagging

“…Then, the inherent electrochemical aspect of electrospray [6][7][8] has opened the way to the study of electrochemically induced reactions [9][10][11][12] like rearrangements of biological molecules. [13][14][15] Moreover, electro-active probes have been developed to chemically derivatize weakly ionisable compounds, [16][17][18][19][20][21] and to label specific amino acids. 22 Recently, we have developed a polymer micro-ESI emitter comprised of a microband electrode.…”

Mass spectrometric methods for monitoring redox processes in electrochemical cells

“…The ferrocene derivatives were separated by LC, and detected by ESI‐MS after oxidation in the electrochemical cell. Ferrocene‐based reagents were developed for specific conjugation to alcohols, phenols, isocyanates, and cysteine‐containing proteins (Diehl, Liesener, & Karst, ; Diehl & Karst, ; Diehl et al, ; Seiwert, Henneken, & Karst, ; Seiwert & Karst, ).…”

An electrochemical device generating metal ion adducts of organic compounds for electrospray mass spectrometry

“…LC-EC-MS. This approach was used in the determination of isocyanates and related nonpolar compounds where the electrochemical activation by ferrocenoyl piperazide was performed after LC separation [9].…”