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

The potential of naphthalenetrisulfonate as a powerful displacing anio nic eluent has been extended to the separation and detection of multiv alent inorganic polyphosphates and organic polycarboxylates using a lo w-capacity polystyrene-divinylbenzene ion-exchange column. Four polyph osphates (pyro-, trimeta-, tripoly- and tetrapolyphosphate) and three polycarboxylates (nitrilotriacetate, ethylenediaminetetraacetate and c itrate) can be separated in about 20 min with indirect photometric and conductivity detection. Indirect photometric detection was found to b e 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 ord er 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, resp ectively.