Comprehensive IC-ICP-MS analysis of polyphosphonates and their transformation products

Abstract

Polyphosphonates (PPs) are increasingly used in detergents and as antiscalants in Europe, with an estimated 18,600 tons annually entering surface waters. Aminopolyphosphonates (APPs) can be readily transformed by environmental processes, contrary to previous beliefs about PP stability during wastewater treatment. Together with the identification of glyphosate as a minor transformation product (TP) of the widely used diethylenetriamine penta(methylenephosphonate) (DTPMP), this necessitates further detailed APP transformation studies. A novel speciation analysis method for phosphonates and several potential phosphorus-containing TPs was developed using a rapid ion chromatographic (IC) separation and element-specific detection by inductively coupled plasma-triple quadrupole-mass spectrometry (ICP-TQ-MS). Chromatographic separation was optimised with a five-step gradient, allowing the simultaneous analysis of a wide range of analytes with varying sizes and numbers of negative charges within a single chromatographic run. Nine phosphorus species including APPs, PPs, glyphosate, aminomethylphosphonic acid (AMPA) and phosphate can be analysed within a run time of 205 seconds. Excellent species-specific detection limits in the range of 0.06 to 0.73 µg/L of phosphorus were reached. Unidentified TPs could also be quantified by using a species-unspecific calibration approach to close the phosphorus mass balance (PMB). The method's applicability was successfully demonstrated by monitoring DTPMP transformation with MnO₂ under environmentally relevant conditions. DTPMP and its TPs were identified and quantified over the course of the transformation experiment with PMB values ≥73 %. This rapid, straightforward, robust and highly sensitive approach offers an effective means of quantifying (aminopoly)phosphonates and their TPs, contributing to a better understanding of their environmental fate and impact.