An enhanced capillary electrophoresis method for characterizing natural organic matter

Abstract

Natural organic matter (NOM) is ubiquitous and is one of the most complex naturally occurring mixtures. NOM plays an essential role in the global carbon cycle; atmospheric and natural water photochemistry; and the long-range transport of trace compounds and contaminants. There is a dearth of separation techniques capable of resolving this highly complex mixture. To our knowledge, this is the first reported use of ultrahigh resolution counterbalance capillary electrophoresis to resolve natural organic matter. The new separation strategy uses a low pH, high concentration phosphate buffer to reduce the capillary electroosmotic flow (EOF). Changing the polarity of the electrodes reverses the EOF to counterbalance the electrophoretic mobility. Sample stacking further improves the counterbalance separation. The combination of these conditions results in an electropherogram comprised up to three hundred peaks superimposed on the characteristic “humic hump” of NOM. Fraction collection, followed by three-dimensional emission excitation spectroscopy (EEMs) and UV spectroscopy generated a distinct profile of fluorescent and UV absorbing components. This enhanced counterbalance capillary electrophoresis method is a potentially powerful technique for the characterization and separation of NOM and complex environmental mixtures in general.