Determination of chlorinated paraffins in PM_2.5 by QuEChERS combined with ultra-high performance liquid chromatography-quadrupole/orbitrap high resolution mass spectrometry

Background Previous research on chlorinated paraffins (CPs) in fine particulate matter (PM_2.5) has predominantly focused on short- and medium-chain chlorinated paraffins (SCCPs and MCCPs), and few studies could simultaneously determine short-, medium-, and long-chain chlorinated paraffins (LCCPs). Simultaneous extraction and determination of SCCPs, MCCPs, and LCCPs in PM_2.5 could provide technical support for their environmental monitoring and human health risk assessment.

Objective To establish a method based on QUEChERS pretreatment method in conjunction with ultra-performance liquid chromatography-quadrupole/orbitrap high resolution mass spectrometry for simultaneously determining the levels of SCCPs, MCCPs, and LCCPs in PM_2.5.

Methods The extraction solvents, extraction salts, and extraction steps of a QuEChERS method were optimized. The extraction efficiencies of the target substances were compared under 4 extraction solvents acetonitrile, dichloromethane, and n-hexane solvents in sequence; acetonitrile: dichloromethane: n-hexane = 1: 1: 2 (v/v/v) mixed solvent; 1% acetic acid-acetonitrile: dichloromethane: n-hexane = 1: 1: 1 (v/v/v) mixed solvent; acetonitrile: dichloromethane: n-hexane = 1: 1: 1 (v/v/v) mixed solvent, 2 dehydrated salts (anhydrous MgSO₄+NaCl and anhydrous Na₂SO₄+NaCl), 2 purification salts (C18 and PSA), and 4 vortex time (5, 7.5, 10, and 12.5 min) conditions. Then internal standard was utilized to estimate linear range and detection limit of the refined QuEChERS approach.

Results The linearities of SCCPs, MCCPs, and LCCPs were good in the range of 10~1000 ng·mL⁻¹ with the correlation coefficients all greater than 0.96. The method detection limits (MDLs) ranged from 0.01 to 0.29 ng·m⁻³. The spiked recoveries of SCCPs, MCCPs, and LCCPs at the low, medium, and high concentrations were 77.38%-81.64%, 93.11%-99.78%, and 87.41%-101.39%, respectively, and the relative standard deviations (RSDs) were 2.90%-12.84%. This method was used to determine the CPs levels in 11 PM_2.5 samples from Shijiazhuang. The positive rates of ∑SCCPs, ∑MCCPs, and ∑LCCPs were all 100%, the concentration ranges were 0.24-2.18 ng·m⁻³ (mean 0.84 ng·m⁻³), 0.17-1.67 ng·m⁻³ (mean 0.70 ng·m⁻³), and 0.01-0.16 ng·m⁻³ (mean 0.04 ng·m⁻³), respectively, and the percentages to ΣCPs were 52.95%, 44.39%, and 2.66%, respectively.

Conclusion The method established in this study is simple, time-saving, solvent saving, and can simultaneously detect SCCPs, MCCPs, and LCCPs in PM_2.5, which is suitable for the determination of PM_2.5 samples in large quantities, and can also provide a reference for the detection methods of other halogenated organic compounds in PM_2.5.