Tammy L. Jones

Validation of liquid chromatography—mass spectrometry methods: interlaboratory studies

Abstract Developments over the last 15 years have led to widespread acceptance and commercialization of two liquid chromatography—mass spectrometry (LC-MS)interfaces: thermospray (TSP) and particle beam (PB). Very few LC-MS methods have been developed and formally adopted, however, by the U.S. Environmental Protection Agency (EPA). This article addresses the difficulties encountered with current LC-MS instrumentation in validating the methods and discusses some of the results of three interlaboratory EPA studies, including a thermospray-LC-MS (TSP-LC-MS) study for chlorinated herbicides, a TSP-LC-MS study for carbamate pesticides, and a particle beam-LC-MS (PB-LC-MS) study for benzidines. Differences in features among the various LC-MS interfaces made it impractical to impose strict guidelines to the participants in conducting these analyses. Consequently, difficulties were encountered in analyzing the data; nonetheless, interesting and useful data, as outlined in this article, were obtained.

Particle beam liquid chromatography—electron impact mass spectrometry of dyes☆

Abstract A liquid chromatograph was interfaced with a triple quadrupole mass spectrometer by means of a particle beam-type interface. The system was used for the analysis and characterization by electron impact mass spectra of a series of commercial dyes. The pure dyes were separated from their impurities with a reversed-phase C18 column using methanol—water as the mobile phase. Detection limits were determined using the system as a single quadrupole mass spectrometer. Sensitivity for dyes was found to be two to three orders of magnitude worse than with thermospray ionization using a wire repeller. Characterization of the azo dyes could be achieved by observing typical fragment ions formed by cleavage of the N—C and C—N bond on either side of the azo linkage and/or cleavage of the N  N double bond with transfer of two hydrogen atoms to form an amine.