QUANTITATION OF ALKYLTRIMETHYLAMMONIUM BROMIDES IN BAYER PROCESS LIQUORS BY GAS-CHROMATOGRAPHY AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A sensitive and specific capillary gas chromatographic (GC) assay has been developed for the quantitation of the series of quaternary ammoni um (QA) compounds, dodecyltrimethylammonium bromide (C12QA), tetradecy ltrimethylammonium bromide (C14QA) and hexadecyltrimethylammonium brom ide (C16QA) in high ionic strength, highly alkaline solutions. The pro cedure employed a single dichloromethane extraction of the iodide ion- pairs of the QA compounds from pH-adjusted Bayer liquor, followed by i njection (in methanol) onto the gas chromatography-mass spectrometry ( GC-MS) system. Detection was based upon thermal dequarternisation of t he QA-iodide complex in the injection port, with the corresponding ter tiary amine (TA) analogue resolved by the GC system. Optimal extractio n and GC conditions, as well as limits of detection and preliminary re coveries of these compounds, are reported. GC-MS combined with injecti on of the pure TA analogues, was used to confirm the identities of the compounds eluted from the column.