Evaluation of graphitized carbon black as a selective adsorbent for extracting acidic organic compounds from water

Abstract

By a simple and rapid treatment, graphitized carbon black (GCB) can be made to act as both a reversed phase and an anion exchanger. The base—neutral/acid fractionation of organic species extracted from water with a GCB cartridge can be easily achieved by differential elution, provided that the p K a values of the acidic species are not higher than about 7. A tetramethylammonium hyroxidebasified solvent mixture is the most effective eluent for the rapid elution from a GCB extraction cartridge of any kind of organic acid. The subfractionation of acidic species can be easily performed on the basis of their acidity strength by passing sequentially through a GCB cartridge various solvent mixtures containing suitable phase modifiers. The ability of a GCB extraction cartridge to retain organic acids was unaffected by the ionic strength of the water sample. The influence of fulvic acids dissolved in water on the capability of GCB to extract acidic compounds and isolate them from co-extracted base—neutral species was evaluated. The advantage of using a GCB cartridge over that containing a chemically bonded silica for accurately determining acidic compounds is demonstrated by two practical applications.