Development of an ammonium chloride-enhanced thermal-assisted-ESI LC-HRMS method for the characterization of chlorinated paraffins

Identification of ∼200 transformation products of polyhalogenated compounds to characterize their transformation pathways in sludges

Sewage sludge adsorbs a large amount of harmful organic pollutants, particularly the persistent and hydrophobic polyhalogenated compounds (PHCs). PHCs have been subjected to biological and chemical oxidation treatments during wastewater treatment processes; however, the species and concentrations of their transformation products (TPs) in sludge remain unknown, and the transformation pathways are unclear. In this study, 234 TPs of PHCs, including 77 TPs of chlorinated paraffins (CPs-TPs), 102 TPs of organochlorine pesticides (OCPs-TPs), 45 TPs of dechlorane plus (DPs-TPs), and 10 TPs of brominated flame retardants (BFRs-TPs), were identified in sludge through Ph4PCl-enhanced ionization coupled with ultra-performance liquid chromatography-Orbitrap-mass spectrometry. Based on the chemical structures of the identified TPs, we identified three major transformation pathways: dehalogenation-hydroxylation, carbon chain decomposition, and desulfurization. Approximately 97 TPs were newly discovered through the pathways. Carbon chain decomposition products of OCPs and DPs were detected for the first time at relatively high abundances. More hydroxylation products of DPs and hexabromocyclododecane (HBCD) and multi-dehalogenation products of heptachlor, toxaphene, DPs and HBCDs were detected at relative intensities higher than those of the known TPs. The oxidation treatment of sludge achieved up to 13 %-94 % of PHCs to be removed, with dehalogenation-hydroxylation as the main transformation pathway. Advanced treatment technologies are needed for degradation of both PHCs and their TPs.

Quantification of chlorinated paraffins by chromatography coupled to high-resolution mass spectrometry - Part B: Influence of liquid chromatography separation

The analysis of chlorinated paraffins (CPs) is today an analytical challenge. Indeed, it is still impractical to describe their real composition in terms of polychlorinated alkanes (PCAs) homologue groups, which dominate technical mixtures. The co-elution of PCA congeners generates interferences due to the competition phenomena which occur during the ionisation process as well as to the dependence of the ionisation sources on the PCA chemistry. Therefore, the aim of this study was to investigate the influence of chromatographic separation, by LC-ESI-HRMS coupling, on the PCA homologue group pattern and, eventually, on their determination in food samples from interlaboratory studies. For this, three different mobile phases and six LC chromatographic columns were studied in order to optimise the analysis of CP mixtures. The first results showed that the use of a MeOH/H2O mobile phase reveals more appropriately the higher chlorinated PCAs. However, using ACN/H2O led to less ion species, with almost exclusively [M + Cl]- adducts, formed using post-column dichloromethane addition. Regarding the choice of the stationary phases, Hypercarb column provided a completely different homologue group pattern from the other chromatographic columns, in relation with the stronger retention of PCAs. Among the other columns, the C30 column better highlighted the short-chain PCAs compared to the C18 column conventionally used. Because the regulations now concern short-chain CPs, the quantification of food samples was then carried out on the C30 column. The optimised LC-ESI-HRMS conditions using C30 column and MeOH/H2O solvent mixture led to a quantification of PCAs in samples from interlaboratory studies with satisfactory accuracy (|Z-score| ≤ 2) and precision (<15%).

Interlaboratory trial of short-chain chlorinated paraffin: comparison of mass fractions and homolog profiles in a simulation environmental sample

Short-chain chlorinated paraffins (SCCPs) are listed in the Stockholm Convention. Therefore, selecting suitable methods for their accurate quantification is essential. Nowadays, the quality of commercial reagents employed as quantification standards is not guaranteed. As a solution, we adopted an SCCP formulation reference material with known homolog composition ratios as the quantification standard to evaluate the appropriateness of the methods. By mixing the SCCP formulation and interferences, an analytical sample was independently prepared and used as the simulation environmental sample. The homolog compositional profiles of the SCCPs resembled those of the quantification standard and the analytical sample. The mass fractions and the homolog profiles, including the carbon chain length and chlorine homolog profiles, of the SCCPs were reported by 14 different laboratories. For the mass fraction, the results reported by participants were consistent, except for the participants that employed low-resolution gas chromatography (GC). The results generated from liquid chromatography (LC) and GC were slightly different, despite of the similar homolog composition ratios between the quantification standard and the analytical sample. Although there were discreet discrepancies in the overall chlorine homolog profiles, the carbon chain length profiles acquired from GC and LC were similar. The differences depended on the method employed. Additionally, compared with the low-resolution data, the high-resolution data displayed less fluctuation since the effect of the interferences on the analytical sample was reduced because of the mass accuracy of high-resolution instruments. Accordingly, the interlaboratory trial employing the similar homolog compositional profiles of the quantification standard and the analytical sample proved valuable in elucidating the differences among methods, considering equipment, resolution specification, and ionization.

Widespread presence of chlorinated paraffins in consumer products

Short-chain chlorinated paraffins (SCCPs) were listed for elimination under the Stockholm Convention in 2017 due to their persistence and toxicity. Although Canada and other Stockholm signatories have prohibited the manufacture, usage and import of SCCPs since 2013, they can still be detected at high concentrations in indoor dust. To identify the sources of the SCCPs in the Canadian indoor environment, short-, medium- and long-chain chlorinated paraffins (SCCPs, MCCPs, LCCPs, respectively) were measured using a sensitive LC-ESI-orbitrap method. SCCPs were detected in 84 of the 96 products purchased in Canada after 2013 (87.5%) including electronic devices, clothing, plastics (toys), and paintings. Concentrations of SCCPs were up to 0.93% (9.34 mg g^-1). SCCPs were also detected in newly purchased toys at 0.005-2.02 mg g^-1, indicating the potential for children's exposure. Profiles of chlorinated paraffins differed among categories of products. For example, C₁₃-SCCPs were most common in toys, while electronic devices like headphones showed comparable concentrations of SCCPs and MCCPs. Additionally, four new carboxylate derivatives of CPs were detected in an electronic device sample. These are the first data to show the ubiquitous occurrences of SCCPs in a wide range of products currently marketed in Canada, suggesting continuing indoor exposure to SCCPs despite their prohibition.

Development of a Proton-Enhanced ESI UPLC-MS/MS Method for the Determination of Tetrodotoxin

Tetrodotoxin (TTX) is a kind of low-molecular-weight non-protein neurotoxin. It is one of the most potent neurotoxins found in nature, and it is found in puffer fish and various marine biota. The low sensitivity of previous analytical methods limited their application in puffer fish organ samples. This study established a method for the accurate and fast determination of TTX by reversed ultra-performance liquid chromatography coupled with proton-enhanced electron spray ionization-tandem mass spectrometry. The method yields good peak shapes, high sensitivity and low coeluted interferences. The method was successfully applied to determine TTX in puffer fish tissue samples of about 0.2 g.

Tetraphenylphosphonium Chloride-Enhanced Ionization Coupled to Orbitrap Mass Spectrometry for Sensitive and Non-targeted Screening of Polyhalogenated Alkyl Compounds from Limited Serum

Although many types of halogenated compounds are known to bioaccumulate in humans, few are routinely biomonitored and many have remained uncharacterized in human exposome studies due to a lack of high-sensitivity and high-resolution analytical methods. In this study, we discovered tetraphenylphosphonium chloride (Ph₄PCl, 10 μM) as a simple additive to the mobile phase, which enhanced the ionizations of polyhalogenated alkyl compounds (such as organochlorinated pesticides [OCPs], chlorinated paraffins [CPs], dechlorane plus [DPs], and some brominated flame retardants [BFRs]) in the form [M + Cl]^- and boosted mass spectrometry responses by an average of 1-3 orders of magnitude at a resolution of 140,000. Ph₄PCl-enhanced ionization coupled with a halogenation-guided screening process was used to establish a sensitive and non-targeted method that required only single-step sample preparation and identified Cl- and/or bromine-containing alkyl compounds. The method enabled the identification of ∼700 polyhalogenated compounds from 200 μL of human serum, 240 of which were known compounds: 33 short-chain CPs, 52 median-chain CPs, 97 long-chain CPs, 22 very short-chain CPs (vSCCPs), 19 OCPs, 13 DPs, and 4 BFRs. We also identified 325 emerging contaminants (34 unsaturated CPs, 285 chlorinated fatty acid methyl esters [CFAMEs], and 6 chloro-bromo alkenes) and 130 new contaminants (114 oxygen-containing CPs, 2 hexachlorocyclohexane structural analogs, and 11 amino-containing and 3 nitrate-containing chlorinated compounds). The full scan results highlighted the dominance of CPs, CFAMEs, vSCCPs, and dichlorodiphenyltrichloroethanes in the serum samples. Ph₄PCl-enhanced ionization enabled the sensitive and non-targeted identifications of polyhalogenated compounds in small volumes of biological fluid.

Determination of trace organic contaminants by a novel mixed-mode online solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry

In this study, a novel mixed-mode online solid-phase extraction (SPE) method was developed to recover miscellaneous trace organic contaminants (TrOCs) from environmental water samples. Six kinds of sorbents, including C₁₈ substances, hypercross-linked polymers (2), cation-exchange resins, anion-exchange resins, and graphitized nonporous carbons, were packed into a single online SPE cartridge. Furthermore, a fully automated analytic method was established by coupling this mixed-mode online SPE with liquid chromatography tandem mass spectrometry (online SPE-LC-MS/MS). Sixty-nine TrOCs with diverse properties were selected to examine the performance of this mixed-mode SPE cartridge in comparison with solo-mode online SPE cartridges. The method quantification limit (MQL) and the relative recovery coefficient of TrOCs in diverse water matrices, including groundwater, surface water and sewage effluent were evaluated. The MQL of most TrOCs was lower than 10 ng L^-1. The relative recovery coefficients for most TrOCs in the groundwater (50/69) and surface water (38/69) matrix fit in the satisfactory range. Moreover, mixed-mode online SPE coupled with LC-high-resolution MS was applied for a suspect screening of TrOCs in sewage effluents. A series of highly polar TrOCs that had scarcely been reported by previous studies were identified by this practical and easily accessible method. Finally, this novel mixed-mode online SPE with LC-MS/MS method was applied to quantify the TrOCs in the environmental water samples.

Short- and medium-chain chlorinated paraffins in commercial complementary baby food produced in different European countries: Occurrence, congener group profiles, portion-based dietary intake, and risk assessment

This study was performed to evaluate the presence of chlorinated paraffins (CPs) in complementary baby food from different European countries, to assess portion-based dietary intake of CPs, and to characterize possible risks to children arising from CPs uptake. In total, 86 baby food samples from 22 countries were grouped into eight food-type categories considering the WHO classification. In six out of eight sample categories, predominance of medium-chain CPs (MCCPs) concentrations over short-chain CPs (SCCPs) was observed and, contrary to expectations, samples that contained ingredients of animal origin (e.g., meat or fish) did not display elevated CPs levels. The median ∑_CPs concentrations for selected sample categories ranged from 0.8 ng g^-1 for desert to 2.8 ng g^-1 found in dry cereal and porridge subgroups, while the highest CPs concentration of 387 ng g^-1 was observed in dry porridge. Among the selected groups of baby foods, portion-based intake of ∑_CPs varied from 1.0 to 43.6 ng kg^-1 body weight (b.w.) while exposure estimations indicated that portion-based dietary exposure through consumption of complementary baby food was the highest for infants aged 3-12 months due to the lower body weight. The risk characterization according to the European Food Safety Authority (EFSA) approach showed that the margin of exposure (MOE) figures higher than the critical value for ∑_CPs, indicating that the dietary exposures through consumption of complementary baby food are unlikely to be of significant health concern for children. However, it should be pointed out that the performed risk assessment covered only SCCPs and MCCPs, while the occurrence of other groups from CPs and CPs related compounds (e.g., very short-chain CPs, chlorinated alkenes, or long-chain CPs (LCCPs)) was not addressed.

Microheterogeneous Distribution of Hydroxyl Radicals in Illuminated Dissolved Organic Matter Solutions

Hydroxyl radicals (^•OH) are important reactive species that are photochemically generated through solar irradiation of chromophoric dissolved organic matter (CDOM) in surface waters. However, the spatial distribution within the complex three-dimensional structure of CDOM has not been examined. In this study, we used a series of hydrophobic chlorinated paraffins as chemical probes to elucidate the microheterogeneous distribution of ^•OH in illuminated CDOM solutions. The steady-state concentration of ^•OH inside the CDOM microphase is 210 ± 31-fold higher than the concentration in the aqueous phase. Our results suggest that the most photochemically generated ^•OH are confined into the CDOM microphase. Thus, illuminated CDOM behaves as a natural microreactor for ^•OH-based oxidations. By including intra-CDOM ^•OH, the quantum yield of ^•OH for CDOM solutions was estimated to be 2.2 ± 0.5 × 10^-3, which is 2 orders of magnitude greater than previously thought. The elevated concentrations of photogenerated ^•OH within the CDOM microphase may improve the understanding of hydrophobic pollutant degradation in aqueous environments. Moreover, our results also suggest that ^•OH oxidation may play more important roles in the phototransformation of CDOM than previously expected.

A simplified method for determination of short-, medium-, and long-chain chlorinated paraffins using tetramethyl ammonium chloride as mobile phase modifier

The formation of halide adducts ion is an important pathway to improve the sensitivity of analytes in liquid chromatography (LC) combined with negative electrospray ionization (ESI) mass spectrometry (MS). Although adding modifier in mobile phase is generally the simplest way to form anions adducts, the formation of halide adducts ion requires a complex post-column addition strategy since traditional halide ionization enhancement reagents are incompatible with LC systems. To solve this problem, the volatile organochlorine salt tetramethyl ammonium chloride (TMAC) was therefore investigated as a potentially non-corrosive mobile phase modifier that was confirmed to be compatible with both LC and MS systems in this study. When short-chain, medium-chain, and long-chain chlorinated paraffins (CPs) were determinated simultaneously by ultra-high performance LC combined with ESI high resolution MS (UPLC-ESI-HRMS), all of them tended to ionize by forming [M+Cl]^- ions and exhibited excellent sensitivity with the instrumental detection limits of 1-4 pg/μL. Meanwhile, their sensitivities towards CPs were less dependent on their Cl content with the total relative response factors of 0.8-3.5. The method's utility was demonstrated through determination of CPs in surface soil and chicken muscle samples. This was an effective and practical method to enhance the selectivity for [M + Cl]^- ions and improve sensitivity towards CPs with various carbon lengths. Importantly, post-column addition was not required, and thus the analytical procedure was simplified. The method has also improved sensitivity towards some other organohalides and may be generally useful in the determination of challenging organic analytes.