Method validation and comparison of quantification strategies for analysis of chlorinated paraffins in indoor dust by liquid chromatography and high-resolution mass spectrometry

Abstract

This paper describes the validation of a method for the simultaneous analysis of short-, medium-, and long-chained chlorinated paraffins (SCCPs, MCCPs, and LCCPs, respectively) in indoor dust by ultrasonic extraction and liquid chromatography quadrupole time-of-flight high-resolution mass spectrometry (LC-QTOF-HRMS). A series of spike and recovery experiments (n = 54) were conducted using CPs with varying carbon-chain lengths, chlorination degree, and concentrations. Technical standard mixtures of the SCCPs, MCCPs, and LCCPs were used to quantify spiking experiments by two commonly used calibration procedures: pattern deconvolution and chlorine-content calibration. The results quantified by pattern deconvolution meet the acceptability limits of the European Union Reference Laboratory (EURL) for all tests with trueness ranging from 72% to 141% and good precision represented by coefficients of variation (CVs) less than 15% in all experiments. The chlorine-content calibration also performed well overall, but on average overestimated concentrations for SCCPs and MCCPs by 32% and 25%, respectively, and did not meet the EURL’s trueness limits in all cases. CVs were below 18% for all results derived from the chlorine-content quantification. The final method was successfully applied to indoor dust samples from offices (n = 4), homes (n = 3), and a vehicle (n = 1) from Melbourne, Australia, with SCCPs (C10-13), MCCPs (C14-17), and LCCPs (C18-20) detected in all samples, up to 100, 240 and 190 μg/g, respectively. A preliminary human exposure assessment suggested that CP intake via dust may constitute a major pathway of exposure for populations in Melbourne, Australia.

Seasonal variation of short-, medium- and long-chain chlorinated paraffin distribution in Belgian indoor dust

“…CP analysis was performed on an Agilent 1290 Infinity II LC coupled to an Agilent 6560 QTOF-MS with electrospray ionization (ESI) operated in negative mode according to methods described by McGrath et al (2022). Partial separation of CP homologues was achieved by 5 µL injections to an Agilent Zorbax Eclipse Plus C18 Rapid Resolution HD column (2.1 × 50 mm, 1.8 µm pore size) fitted with a matched 5 mm length guard column maintained at a temperature of 40 C. The mobile phase consisted of (A) Milli-Q water and (B) methanol containing 25 µM ammonium chloride with a constant flow rate of 0.2 mL/min.…”

“…Limits of quantification (LOQs) were defined as the lowest ∑ SCCP, ∑ MCCP, and ∑ LCCPs (C 18-20 ) concentration at which at least half of the congener groups were detected in both the lowest and highest Cl% standard mixtures, equating to the equivalent of 200, 100, and 100 ng/g in dust, respectively. The LOQ derivation is described in detail by McGrath et al (2022).…”

“…The sample extraction, analysis and quantification procedure employed in this study have undergone comprehensive validation involving technical CP mixture spiking tests with a variety of chlorine degrees at two concentrations (McGrath et al, 2022). The prior evaluation demonstrated acceptable accuracy and precision of the method with respect to performance criteria described by the European Union Reference Laboratory (EURL) for analysis of CPs (EURL, 2018(EURL, , 2020 and illustrated the suitability of 13 C-β-HBCD for internal standard quantification and extraction efficiency assessment.…”

“…Typically, technical mixture standards with defined carbon range and chlorine content have been employed for quantification by applying unique strategies designed to account for homologue response variation such as linear chlorine content calibration described by Reth et al (2005) or deconvolution and pattern reconstruction calibration described by Bogdal et al (2015). These techniques have been shown to provide adequate semiquantitative measurements of ∑ SCCP, ∑ MCCP and ∑ LCCP (C 18-20 ) groups (McGrath et al, 2022;McGrath et al, 2021b), though a lack of adequately characterised CP standards of C ≥21 has contributed to a scarcity of LCCP data. The available isotopically labelled individual CP compounds have shown limited suitability as internal standards for CP quantification and alternative mass-labelled halogenated compounds have been successfully employed (McGrath et al, 2022;McGrath et al, 2021b;Yuan et al, 2019;van Mourik et al, 2019).…”

“…These techniques have been shown to provide adequate semiquantitative measurements of ∑ SCCP, ∑ MCCP and ∑ LCCP (C 18-20 ) groups (McGrath et al, 2022;McGrath et al, 2021b), though a lack of adequately characterised CP standards of C ≥21 has contributed to a scarcity of LCCP data. The available isotopically labelled individual CP compounds have shown limited suitability as internal standards for CP quantification and alternative mass-labelled halogenated compounds have been successfully employed (McGrath et al, 2022;McGrath et al, 2021b;Yuan et al, 2019;van Mourik et al, 2019). Although homologue specific quantification is also not possible at present, comparison of homologue instrumental responses may provide a comparative account of homologue distribution in dust samples (Yuan et al, 2021;Schinkel et al, 2018).…”