Use of ion chromatography–electrospray mass spectrometry for the determination of ionic compounds in agricultural chemicals

This paper reports the use of ion chromatography–electrospray mass spectrometry for the separation and structure elucidation of anionic compounds in a complex organophosphate matrix. Conventional HPLC with ion pairing reagents, pH adjustments or use of buffer solutions have limited compatibility with mass spectrometry, as the ion pairing reagents or buffers have to be volatile to be introduced into the mass spectrometer. The choice of volatile additives is limited, resulting in poor chromatography. This paper demonstrates the use of ion-exchange chromatography (IC) for the separation of ionic compounds, followed by mass spectrometry (MS) for the structure elucidation of unknowns. The anionic impurities are separated using an anion-exchange column with aqueous sodium hydroxide as the eluent. Electrospray in the negative ion mode is used to obtain the mass spectra. The elemental composition of an unknown component in the sample is determined by high-resolution mass spectrometry. The coupling of IC to MS provides a new analytical tool to chemists faced with the challenge of separating and analyzing ionic compounds in complex matrices.