Speciation of poly-amino carboxylic compounds in seawater

Abstract

In this work quantitative data on the interaction of EDTA and EGTA with the major inorganic components of seawater are reported. Protonation constants and alkali and alkaline earth metal complex formation constants are reported at different ionic strengths (0< l/mol L−1≤1). These formation data were obtained from potentiometric measurements in several single and mixed electrolyte media (such as artificial seawater). Potentiometric measurements in artificial seawater (containing Na+, K+, Mg2+, Ca2+, Cl−and SO42−) were analysed by using the single salt approximation (the artificial seawater being considered as a single salt BA whose ions have fractional charge -zanion = zcation = 1.117). Several species BpHrL (L = EDTA or EGTA) are formed and their formation constants are reported at different salinities. Present results, together with similar data on the complexing capability of NTA, DTPA and TTHA towards inorganic components of natural fluids, allowed to find general conclusions on the important class of complexons.