Trace-level determination of phosphonates in liquid and solid phase of wastewater and environmental samples by IC-ESI-MS/MS

Abstract

Phosphonates are increasingly used as water-softening agents in detergents, care products, and industrial processes. Despite poor biodegradability, high removal rates during wastewater treatment (WWT) have been observed, owing to strong adsorption affinity to activated sludge and mineral surfaces. Due to phosphonates representing challenging analytes, no method for the compound-specific quantification of phosphonates from solid samples has hitherto been published. In order to improve the data foundation on the environmental fate of phosphonates, an analytical method based on anion exchange chromatography and detection by electrospray ionization coupled to tandem mass spectrometry (IC-ESI-MS/MS) was developed, allowing the trace quantification of phosphonates from surface water (LOQs between 0.04 and 0.16 μg/L), wastewater (LOQs between 0.6 and 2.3 μg/L), sediment and suspended matter of rivers (LOQ < 0.1 mg/kg), and suspended matter of wastewater (LOQ < 1 mg/kg). Specificity and selectivity were enhanced by the implementation of isotope-labeled internal phosphonate standards derived through synthesis. This study describes the development of a comprehensive tool set for the determination of aminotris(methylenephosphonic acid) (ATMP), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP), ethylenediaminetetra(methylenephosphonic acid) (EDTMP), 1-hydroxyethanediphosphonic acid (HEDP), and 2phosphonobutane-1,2,4-tricarboxylic acid (PBTC) during WWT and in the aqueous environment. In the investigated matrices, HEDP and PBTC were generally present in highest and EDTMP in lowest abundance. The phosphonate contents detected in river water were in the sub to low μg/L range, depending on the wastewater burden, whereas contents in the low to medium μg/L range were found in untreated wastewater. The loads of the solid phases exceeded the contents of the corresponding liquid phases by roughly three orders of magnitude. Current data imply that phosphonates undergo significant partitioning to the solid phase during WWT and in natural water bodies.

Behavior of PBTC, HEDP, and Aminophosphonates in the Process of Wastewater Treatment

“…The background and validation of the sample preparation techniques used for this study have already been presented in detail by Armbruster et al [18] in another publication. In this paragraph, this preparation technique is described briefly.…”

“…The analysis was carried out via anion exchange chromatography in accordance with Armbruster et al [18]. The method involves a ten-minute washing step with dilute eluent (18 mmol/L sodium hydroxide) immediately after injection for the chromatographic separation of interfering anions with low charge and NTA (present in the extracts of solid samples), followed by a sodium hydroxide gradient with a constant proportion of 20% methanol and detection via ESI-MS/MS.…”

“…However, the method did not involve internal phosphonate standards and none of the previously described methods allowed the quantification of phosphonates in the solid fraction of wastewater. For the current study, the method by Armbruster et al [18] was used, which allows the quantification Phosphorus in wastewater can essentially be divided into three fractions using the molybdenum blue method and different sample pretreatment techniques. The concentration (c in mg/L) of the particulate P fraction (PP) corresponds to the difference between total P (sample digestion with persulfate and sulfuric acid) and dissolved P (total P of the membrane-filtered sample).…”

“…However, the method did not involve internal phosphonate standards and none of the previously described methods allowed the quantification of phosphonates in the solid fraction of wastewater. For the current study, the method by Armbruster et al [18] was used, which allows the quantification of phosphonates from liquid and solid matrices. In combination with adapted sample preparation techniques, the method based on ion exchange chromatography coupled to tandem mass spectrometry with electrospray ionization (IC-ESI-MS/MS) involves isotope-labeled internal phosphonate standards and achieves low LOQs (surface water: 0.04-0.16 µg/L, wastewater: 0.6-2.3 µg/L, river sediment and suspended matter: <0.1 mg/kg, and solids of wastewater: <1 mg/kg).…”

Influence of Wastewater Discharge on the Occurrence of PBTC, HEDP, and Aminophosphonates in Sediment, Suspended Matter, and the Aqueous Phase of Rivers

“…For this purpose, a newly developed analytical method based on ion exchange chromatography coupled to tandem mass spectrometry with electrospray ionization (IC-ESI-MS/MS) applying isotope-labeled internal standards was used [13]. This method allows the extraction of >95% phosphonates from solid samples and their quantification down to 0.1 mg/kg on SM and sediment.…”