Novel determination of polychlorinated naphthalenes in water by liquid chromatography–mass spectrometry with atmospheric pressure photoionization

Porous chlorine-functionalized covalent organic framework anchored graphene aerogel composite for synergically enhanced solid phase microextraction of polychlorinated naphthalene in environmental water

The residues of polychlorinated naphthalenes (PCNs) produced in multiple industrial production and life processes are continuously entering environmental waters through atmospheric deposition and land drainage, and the water pollution caused by PCNs is continuing public concern due to their potential threat to aquatic ecosystems and public health. Herein, a new chlorine-functionalized covalent organic framework anchored graphene aerogel (COF-GA) was synthesized by covalent modification technology and used as fiber coating of solid-phase microextraction for synergically enhanced extraction of PCNs in environmental water. The extraction efficiency of COF-GA coated fiber was superior to commercial fiber due to the multiple interactions (π-π, hydrophobic interaction, and halogen bonding interaction). The COF-GA coated fiber has good stability, can avoid water vapor interference at 80 °C for a long time (30 -50 min) to maintain adsorption equilibrium, and can be reused at least 96 times. Combined with gas chromatography-tandem mass spectrometry, a sensitive method for the high-efficient enrichment (enrichment factors were 501 -7453 folds) and ultra-sensitive detection (LODs were 0.001 -0.428 pg/mL) of PCNs in environmental water was established. The enrichment factor for PCNs is significantly higher than in previous studies. This proposed method provides new technical support for the daily monitoring and risk assessment of trace PCNs in environmental water.

Phototransformation of three polychlorinated naphthalenes on surface of atmospheric particulate matter

Polychlorinated naphthalenes (PCNs) are a new class of persistent organic pollutants. Photoconversion is an important pathway for their transformation in the environment. In this work, silica gel was used to simulate atmospheric mineral particles, and the photochemical reaction of three PCNs 1-chloronaphthalene (CN-1), 2-chloronaphthalene (CN-2) and 2,3-dichloronaphthalene (CN-10)) on silica gel surface was studied under the irradiation of high-pressure mercury lamp, the phototransformation intermediates and pathways of PCNs were investigated, effects of reactive oxygen species (ROS, ·OH, ¹O₂ and O₂^-·) were proved by free radical scavenging method and the effects of co-existing components (water, inorganic ions and fulvic acid) were examined. The results showed that all the three PCNs could be photochemical degraded on silica gel surface. The order of the apparent rate constants was CN-2 ≈ CN-1 > CN-10. ROS accelerated the photochemical reaction. The three PCNs didn't produce completely identical photoproducts, but all underwent a series of reactions such as reductive dechlorination, hydroxylation, oxidation, decarboxylation and ring opening. In addition, for the photoconversion of CN-1, the presence of water, NO₃^- or fulvic acid all promoted the photochemical transformation, while the presence of Cu²⁺ had an inhibitory effect.

Atmospheric pressure ionization for gas chromatography-high resolution mass spectrometry determination of polychlorinated naphthalenes in marine sediments

In this work, the performance of the atmospheric pressure chemical ionization (APCI) and photoionization (APPI) was assessed to develop a new selective and sensitive gas chromatography-high resolution mass spectrometry (GC-HRMS) method for the determination of polychlorinated naphthalenes (PCNs) in sediment samples. The capability of both APCI and APPI sources for the ionization of PCNs was investigated, showing the formation of the molecular ion and the [M‒Cl+O]^‒ ion in positive and negative ion modes, respectively. Positive ion APCI provided high responses using high corona ion current, while the use of high vapour pressure dopant-solvents, such as toluene in positive mode and diethyl ether in the negative mode, was required to achieve high ionization efficiencies in APPI. The performance of the two API sources in the PCN determination by GC-HRMS were compared and the best results were achieved using the GC-APPI(+)-HRMS (Orbitrap) system. The GC-APPI(+)-HRMS (Orbitrap) method was applied to the characterization of Halowax mixtures and the analysis of marine sediments collected near to the coastal area of Barcelona (NE, Spain), demonstrating a great detection capability with low method limits of detection (0.2-1.6 pg g^-1 dry weight), good precision (RSD <15%) and trueness (relative error <13%). Total PCN concentrations ranged from 0.35 to 5.0 ng g^-1 dry weight and the presence of related compounds, such as polychlorinated biphenyls (PCBs), was also detected by combining positive and negative ion modes, providing complementary information to better monitor of all PCN congener groups. The results presented here show the feasibility of the GC-APPI-HRMS method for the suitable determination of PCNs.