Trace-level analysis of phosphonates in environmental waters by ion chromatography and inductively coupled plasma mass spectrometry

Abstract

A novel analytical method for the trace-level determination of the organic phosphonates 1-hydroxyethane(1,1-diphosphonic acid) (HEDP), nitrilotris(methylene phosphonic acid) (NTMP), ethylenediaminetetra(methylene phosphonic acid) (EDTMP), hexamethylenediaminetetra(methylene phosphonic acid) (HDTMP) and diethylenetriaminepenta(methylene phosphonic acid) (DTPMP) in natural waters is described. Key-elements of the novel method are the destruction of the various metal complexes which are present in natural water samples by a strong cation exchange resin, the subsequent 50-fold pre-concentration of the analytes by a weak anion exchanger and their final determination by ion chromatography and inductively coupled plasma mass spectrometry. Addition of the complexing agent diethylenetriaminepentaacetic acid (DTPA) to the eluent of the anion exchanger leads to a significant improvement of the chromatographic performance for all phosphonates, but especially for EDTMP. Detection of the phosphorous species in ICP-MS is done via the molecular ion ⁴⁷PO⁺ which exhibits high sensitivity and which is only marginally affected by interferences. Validation of the method gives excellent performance parameters with recoveries close to 100%, limits of detection below 0.1 µg/L for each individual target compound and standard deviations for replicate analyses below 10%. Application of the novel method to environmental samples shows that trace amounts of HEDP and DTPMP may be found in river waters affected by discharges of municipal or industrial wastewater treatment plants.

Keywords:

• ICP-MS
• ion chromatography
• phosphonates
• water analysis