ION CHROMATOGRAPHY OF POLYPHOSPHATES AND POLYCARBOXYLATES USING A NAPHTHALENETRISULFONATE ELUENT WITH INDIRECT PHOTOMETRIC AND CONDUCTIVITY DETECTION

The potential of naphthalenetrisulfonate as a powerful displacing anionic eluent has been extended to the separation and detection of multivalent inorganic polyphosphates and organic polycarboxylates using a low-capacity polystyrene-divinylbenzene ion-exchange column. Four polyphosphates (pyro-, trimeta-, tripoly- and tetrapolyphosphate) and three polycarboxylates (nitrilotriacetate, ethylenediaminetetraacetate and citrate) can be separated in about 20 min with indirect photometric and conductivity detection. Indirect photometric detection was found to be superior to conductivity detection because early-eluting anions are well resolved from the injection peak and flow programming can be done with a minimum disturbance of the baseline. Detection limits for the analytes investigated range from 2 to 100 ng which are at least an order of magnitude better than those previously reported using postcolumn derivatization methods. Linear response ranges from 500 or 75 mg/l to the limit of detection for longer and shorter retained analytes, respectively.