Screening of Chlorinated Paraffins and Unsaturated Analogues in

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Screening of Chlorinated Paraffins and Unsaturated Analogues in Commercial Mixtures: Confirmation of Their Occurrences in the Atmosphere Tong Li, Shixiong Gao, Yujie Ben, Hong Zhang, Qiyue Kang, and Yi Wan Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b04761 • Publication Date (Web): 25 Jan 2018 Downloaded from http://pubs.acs.org on January 25, 2018

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Screening of Chlorinated Paraffins and Unsaturated Analogues in Commercial

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Mixtures: Confirmation of Their Occurrences in the Atmosphere

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Tong Li, Shixiong Gao, Yujie Ben, Hong Zhang, Qiyue Kang, Yi Wan*

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Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences,

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Peking University, Beijing 100871, China

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(Received

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*Address for Correspondence:

)

8 9 10 11 12 13 14 15 16

Address for Correspondence

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Dr. Yi WAN

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College of Urban and Environmental Sciences

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Peking University

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Beijing 100871, China

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TEL & FAX: 86-10-62759126

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Email: [email protected] 1

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ABSTRACT

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Characterizing the detailed compositions of chlorinated paraffins (CPs) commercial

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mixtures is crucial to understand their environmental sources, fates, and potential risks. In

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this study, dichloromethane (DCM)-enhanced UPLC-ESI-QTOFMS analysis combined with

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characteristic isotope chlorine peaks is applied to screen all CPs and their structural analogues

28

in the three most commonly produced CP commercial mixtures (CP-42, CP-52, and CP-70).

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Mass fractions of total short-chain CPs (SCCPs), medium-chain CPs (MCCPs) and

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long-chain CPs (LCCPs) ranged from 0.64 to 31.8%, 0.64 to 21.8%, and 0.04 to 43.9%,

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respectively, in the three commercial mixtures. One hundred thirteen unsaturated SCCPs,

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MCCPs and LCCPs were identified in the commercial mixtures. The detailed mass

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percentages of saturated and unsaturated CPs with carbon numbers of 10-30, chlorine

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numbers of 5-28, and unsaturated degrees of 0 to 7 were characterized in all commercial

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mixtures. Occurrences of the predominant saturated and unsaturated CPs were further

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confirmed in air samples collected in Guangdong Province, one of the major CP production

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areas in China, over one year. The profiles of the detected compounds indicated that LCCPs

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in air samples might come mainly from the production and usage of CP-52, and unsaturated

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C24-29-LCCPs were specifically originated from CP-70 used in the area.

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Keywords:

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Nontargeted screening, By-products

Chlorinated

paraffins,

Unsaturated

analogues,

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mixtures,

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Introduction

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Chlorinated paraffins (CPs) are mixtures of commercially produced polychloroalkanes,

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with a general formula of CnH2n+2-zClz with n ranging from 10 to 30 and chlorine content

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ranging from 30 to 70%.1 CPs have emerged as a concerning group of pollutants due to their

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wide usage,2,

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Commercial mixtures of CPs are formed by chlorination of n-alkane feedstocks at high

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temperatures and/or in the presence of UV light/visible irradiation.20-21 Their reactions have

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low positional selectivity and produce complex mixtures containing thousands of isomers

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including CPs and degradation products.22 The currently known CPs are sub-classified into

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short-chain CPs (SCCPs; C10-C13), medium-chain CPs (MCCPs; C14−C17), and long-chain

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CPs (LCCPs; C>17).1 It is possible that more CP structure analogues could be generated

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during commercial preparation processes. Screening and identification of complex CP

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homologues is a challenge in environmental analysis of the compounds.

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ubiquitous environmental occurrence,4-13 and potential toxicity.14-19

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Commercial mixtures of CPs were produced at three chlorine content levels on a weight

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basis: 40% to 50%, 50% to 60%, and 60% to 70%. The most commonly produced and used

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commercial mixtures are CP-42, CP-52, and CP-70, which have chlorine contents of

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approximately 42%, 52%, and 70%, respectively.23 CP-42 and CP-52 account for more than

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80% of CP productions in China, and CP-52 accounts for 90% of CP output in China, the

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largest producer, consumer, and exporter of CPs in the world. Information about mass

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fractions of CPs in commercial mixtures is limited. 24, 6, 25 Only mass fractions of SCCPs in

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CP-42, CP-52 and CP-70 were reported as 3.7%, 24.9%, and 0.5%, respectively,6,

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suggesting that 75.1% to 99.5% of these mixtures might be contributed by MCCPs, LCCPs, 3

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and unknown CP structure analogues. Currently, MCCPs and LCCPs are produced as

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alternatives for SCCPs, which are included in the Stockholm Convention on Persistent

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Organic Pollutants.6 However, the mass fractions of MCCPs and LCCPs in commercial

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mixtures remain unclear.

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The mass percentages of individual SCCP, MCCP, and LCCP congeners have been

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detailed in the standard technical CP mixtures, which were produced by Ehrenstorfer

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(Augsburg, Germany) and widely applied as calibration standards for quantifying total

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concentrations of SCCPs, MCCPs, and LCCPs.26-28 In comparison, detailed mass percentages

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have only been reported for SCCPs in commonly produced commercial mixtures.6,

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addition, SCCPs have been profiled in commercial mixtures of SCCP-49, SCCP-60, and

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SCCP-70 (number shows the chlorine content), MCCPs have been profiled in commercial

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mixtures of MCCP-45, MCCP-50, MCCP-52, MCCP-53, and MCCP-56, and LCCPs have

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been profiled in LCCP-40, LCCP-49, and LCCP-70, of which the chlorine content and

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carbon chain length were specified by the manufacturers in Germany, the United Kingdom,

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and the United States.21,

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contained the CPs with carbon numbers specified by the producer; for example, only SCCPs

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were profiled in Witaclor 149 because the German manufacturer’s specifications were SCCP

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C10 to C13 49%Cl.21, 26, 29 However, it has been reported that SCCPs were detected in all the

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three most commonly produced commercial mixtures (CP-42, CP-52 and CP-70), and our

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recent study found high MCCP contents (up to 20%) even in the LCCP standard technical

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mixtures.6, 28 Characterizing the detailed compositions of these complex CPs in commercial

26, 29

25

In

The reports assumed that the commercial mixtures only

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mixtures is crucial to understand the occurrences, sources and fates of the compounds in the

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environment.

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Tentative high throughput screening techniques have been shown to be superior for

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identifying organo-bromine and organo-iodine compounds based on chemical features

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containing bromine and iodine atoms in environmental samples.30,

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dichloromethane

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characteristic isotope peaks of chlorine is applied to screen CPs and their structure analogues

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in CP-42, CP-52 and CP-70 commercial mixtures. Unsaturated SCCPs, MCCPs and LCCPs

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were firstly identified in the commercial mixtures. The detailed mass percentages of saturated

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and unsaturated CPs with carbon numbers of 10 to 30 and chlorine numbers of 5 to 28 were

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clarified for all commercial mixtures. Occurrences of saturated and unsaturated CPs were

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further confirmed in air samples collected in Guangdong Province, one of the major CP

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production areas in China, over one year. The results suggest that future work is necessary to

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investigate the predominant saturated and unsaturated CPs identified in commercial mixtures

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and environmental samples.

(DCM)-enhanced

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Materials and methods

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Sample collection.

UPLC-ESI-QTOFMS

analysis

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In this study,

combined

with

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Air samples were collected from six sites (A1-A6) every 4 months over 1 year

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(September 2013 to August 2014) in Shenzhen, Guangzhou (Figure S1). At each sampling

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site, a total of 1200 to1500 m3 of air was sampled using an HV-1000 sampler purchased from

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SIBATA Scientific Technologies, Ltd. (Saitama, Japan), drawing 500 L/min of air through the

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sampling train for 48 hours. The sampling train was fitted with a glass fiber filter (Whatman 5

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GF/F, 70 mm diameter, Merck-Eurolabs, Spånga, Sweden) pre-baked at 450°C for 4 hours,

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and two polyurethane foam (PUF) plugs (75 × 85 mm) pre-cleaned by Soxhlet extraction in

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acetone and dichloromethane (24 hours each) before sampling commenced. Quarterly field

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blanks of the air samples were also taken by loading the filter and PUF plugs in the air

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sampler for 10 seconds. The samples were extracted as combined sets of glass fiber filter and

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two PUF plugs. Thus, a total of 24 air samples and 4 field blank samples were collected.

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Sample preparation.

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About 0.5 g or 100 uL commercial mixture samples were directly dissolved in 10 mL

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hexane, diluted with acetonitrile to 5-70 ng/uL and spiked with 100 ng of an internal standard

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(13C10-anti-Dechlorane Plus) for analysis of ultra-high-pressure liquid chromatography

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coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOFMS). Air samples

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were spiked with 100 ng of internal standard (13C10-anti-Dechlorane Plus), and Soxhlet

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extracted with toluene for 24 hours. The extract was concentrated to about 1 mL, and then

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passed through a glass column containing 8 g of 5% H2O-deactivated active Al2O3, which

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was baked at 600°C for 4 hours. The column was pre-cleaned with 30 mL DCM and 30 mL

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hexane. After loading the sample extracts, the column was eluted with 30 mL hexane and a 30

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mL mixture of hexane and DCM (3:1). The eluent was concentrated to about 1 mL using a

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rotary evaporator and evaporated to dryness under a gentle nitrogen stream. The samples

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were finally redissolved in 100 µL acetonitrile for UPLC-QTOFMS analysis.

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UPLC-QTOFMS analysis.

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CPs were analyzed by an ACQUITY UPLC system (Waters, Milford, MA) coupled with

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a Xevo QTOF-MS (G2, Waters). Instrument control was performed using MassLynx 6

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Software (version V4.1, Waters). All standards and samples were separated on a Waters

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ACQUITY UPLC BEH C18 column (1.7 µm, 2.1 × 50 mm). The flow rate was set as 0.1 mL

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min−1, the column temperature was 40°C, and 3 µL of samples was injected. Ultrapure water

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(A) and methanol (B) were used as the mobile phases for gradient elution. The initial

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conditions were 10% B for 1 minute, ramped to 30% by 1.5 minute, ramped to 60% by 2

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minute, ramped to 80% by 3 minute, ramped to 90% by 3.5 minute, ramped to 100% by 4

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minute, held from 4.5 to 8.5 minute, ramped to 30% by 9 minute, and held for 1 minute

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before returning to the initial conditions, which were equilibrated for 1 minute before the next

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injection. DCM was added to the sample, separated by the column between the UPLC and the

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ion source, with a syringe pump at a flow of 10 µL min-1 using a T-connection in the period of

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5.5 to 8.5 minute.

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The atmospheric pressure ionization-electrospray ionization (API-ESI) source was

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operated in negative ion mode. The optimized analytical parameters were as follows. Source

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capillary voltage: 2.5 kV; sampling cone voltage: 40 V; extraction cone voltage: 4.0 V;

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source temperature: 100°C; desolvation temperature: 250°C; cone gas flow rate: 50 L/h;

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desolvation gas flow rate: 600 L/h. Full-scan mode in the mass range of 250 to 1600 Da with

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a 1-second scan time was performed at resolution R = 25000. Leucine-enkephalin was used

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as a reference lock mass (200 pg/µL infused at 5 µL/min, m/z 554.2615). The detector of

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QTOFMS was calibrated with a sodium formate solution. The achieved mass accuracy is

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lower than 3 ppm.

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Orbitrap MS analysis.

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CPs in the standard and commercial mixtures were analyzed by directly injecting into 7

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APCI/ESI-Orbitrap MS. The instrumental settings were: capillary temperature 150°C, Aux

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gas heater temperature: 50°C, resolution 140,000, maximum IT 250 ms, spray voltage 2.60 kv,

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AGC target 5e6, sheath gas flow rate 8 arb and Aux gas flow rate 1 arb.

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Screening of CPs and unsaturated CPs.

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Chemical profiling analysis was carried out on the UPLC-QTOFMS spectra obtained for

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the commercial mixture samples. The raw data were extracted and aligned in time and

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mass-direction using Waters MarkerLynx (version 4. Waters Corporation, Milford, MA) with

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the following parameters. The software worked by predefined parameters and the spectral

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peaks were collected combining chromatographic separation, mass abundance, and accuracies.

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The data collection tried to discover as many important peaks as possible. For ions with low

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mass differences, the spectral peaks can be identified through chromatographic separation

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even when they were not baseline separated by UPLC. Data collection parameters were set to

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intensity threshold 500 counts, mass window level at 250−1600 Da, retention time window of

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11 min, and noise elimination level (signal-to-noise ratio) at 6.00. Because the pattern of

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chlorine isotopic peaks is important to narrow the list of CP analogues, the detected chemical

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features containing chlorine atoms were identified based on peak height ratios of isotopic

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peaks through calculation by Matlab software (Mathworks, Natick, MA). The elemental

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compositions of identified chlorinated features were calculated using Waters MarkerLynx, in

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which chemical formulas were set to contain up to 40 C, 40 H and 40 Cl per molecule, and

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the mass tolerance was set to 5 ppm.

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Semi-quantifications of CPs and unsaturated CPs.

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The quantification methods of SCCPs, MCCPs and LCCPs have been reported in our 8

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previous study,28 and strict quality assurance and quality control (QA/QC) was applied to

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ensure the quantification of chemical concentration. The details were provided in the SI.

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Because unsaturated CPs were not commercially available and were undetected in the

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standard technical mixtures, unsaturated SCCPs, MCCPs, and LCCPs were semi-quantified

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by the response factors of saturated SCCPs, MCCPs, and LCCPs, respectively, assuming that

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the responses for unsaturated CPs were similar to those of the saturated CPs with similar

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chlorine contents and carbon numbers. 13C10-anti-DP was used as the surrogate standard, and

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the congener groups of unsaturated CPs were not detected in the blank samples.

181 182

Results and discussion

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Screening of commercial mixtures.

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The development of the chlorine-enhanced UPLC-QTOFMS method with superior

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sensitivity and selectivity has opened up new windows of opportunity for profiling CPs and

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their structural analogues in commercial mixtures and environmental samples.28 Using the

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UPLC separation and high resolution QTOFMS analysis (resolution: 25,000), 872 chemical

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features were extracted in the CP-42 and CP-52 commercial mixtures. The pattern of chlorine

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isotopic peaks was applied to narrow the list of CP analogues, and about 421 chemical

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features were identified as compounds containing chlorine atoms. Among the chlorinated

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chemicals, 318 chemical features were identified as 182 CPs based on their elemental

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composition. Element analysis of the remaining chlorinated chemicals showed that 41

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chemical features were suspected to be 11 unsaturated CPs.

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In the CP-70 mixtures, the number of chemical features (4762) extracted were five folds

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that found in the CP-42 and CP-52 mixtures. Two kinds of mass spectrum patterns were

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found in the signals extracted with retention time of 6.5-9.0 min in CP-70 commercial

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mixtures. The first pattern exhibited two cluster peaks centering around 700 to 800 and 1100

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to 1300 Da with mass ranges of about 500 to 1500 (Figure S2a). The other pattern showed a

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mass range of about 800 to 1200 only centering around 950 to 1050 Da (Figure S2b). In

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previous studies, detected LCCP congener groups comprised compounds with carbon

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numbers ranging from 18 to 28.26, 32 In this study, screening of CP-70 commercial mixtures

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detected LCCPs with carbon numbers of about 29 to 30 possible due to the relatively high

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sensitivities of chlorine enhance ESI ionizations, and LCCPs with carbon number >30 were

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not detected in any of the commercial mixtures. Among the 4762 chemical features extracted

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in CP-70 commercial mixtures, about 1993 chemical features were identified as compounds

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that contained chlorine atoms with the aid of chlorine isotopic patterns, and 1305 chemical

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features were identified as 242 CPs. Element analysis of the remaining chlorinated chemicals

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showed that 415 chemical features were suspected to be 102 unsaturated CPs.

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The potential in-source fragmentations of CPs have been reported in ECNI and APCI

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sources, and deprotonated [M-H]- ([M-HCl+Cl]-) can be found when injecting the CP

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standard mixtures into the sources.33 The molecular weight of deprotonated ion was same

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with that of unsaturated CP. But a recent study indicated that chlorine enhanced APCI

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method was optimized to favor adduct formation ([M+Cl]-) rather than fragmentation, and the

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spectra obtained for pure CP material also did not indicate substantial in-source

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deprotonation.22 Similar phenomenon was also reported by a previous study, which found 10

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that chlorine enhanced APCI provided exclusively [M+Cl]- adducts, resulting in an increased

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selectivity and reduced mass interferences for CP analysis.34 In this study, the signals of

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suspected unsaturated CPs, observed in the commercial mixtures, were not detected in the

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standard CP mixtures. As shown in Figure 1, the chorine adduct ions of the parent SCCPs,

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MCCPs and LCCPs were obtained with similar responses in both commercial and standard

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CP mixtures, but the ions of [M-H]- were only found in the commercial mixtures, suggesting

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that in-source deprotonation was extremely weak or almost not observed in the chlorine

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enhanced ionizations and [M-H]- ions were not the in-source fragmentations.

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Mass difference between CPs and their unsaturated analogues is an important issue for

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identifications of the signals of suspected unsaturated CPs. Especially for unsaturated CPs

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with unsaturation degrees (Ω) of 1, the mass differences of ionization ions between CPs and

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corresponding unsaturated CPs were only 0.0186. The separation of the two groups of ions

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requires a mass resolution of R >50,000 when molecular weights of CPs were about 1000.

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The direct injection of CP mixtures to the QTOFMS used in this study can identify

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unsaturated CPs with molecular weight less than 465 and/or Ω high than 1. For identification

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of other unsaturated CPs, chromatographic separation prior QTOMS gives significant

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quantitative and qualitative advantages. The incorporation of UPLC helped separate the ions

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which cannot be resolved by direct MS injection analysis, since the spectral peaks can be

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identified through chromatographic separation even when they were not baseline separated.

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As shown in Figure S3, distinct peaks were observed for the two ions with mass difference of

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0.0186, and their retention time differences ranged from 0.11 to 1.14 min. The chemical

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features were identified only when the chromatogram peaks were good separated and the 11

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height ratios of all the extracted chlorine isotopic peaks match the pattern of chlorinated

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compounds. The above results indicated that the identified chlorinated signals other than CP

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ions were unsaturated CPs. Furthermore, the commercial mixtures of CP-42, CP-52 and

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CP-70 were directly injected to the chlorine enhanced APCI-Orbitrap MS with resolution of

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140,000. As shown in Figure 2, the existence of unsaturated SCCPs, MCCPs and LCCPs as

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exemplified by C12H18Cl6, C14H15Cl13, and C25H27Cl23, respectively, were confirmed in

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commercial mixtures, and these compounds were not detected in the standard mixtures. The

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responses and number of detected unsaturated LCCPs were much higher than those of the

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unsaturated SCCPs and MCCPs (Figure 2), which is consistent with the results obtained by

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UPLC-QTOFMS analysis.

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The dominant peaks of unsaturated SCCPs, MCCPs and LCCPs were compounds with

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unsaturation degrees (Ω) of 1-2. As we known, Cl2 and alkanes reacted at high temperatures

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(95°C to 100°C) to synthesize CP commercial mixtures.35, 36 It has been reported that high

251

temperatures

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dechlorohydrogenation and subsequent generation of chlorinated alkenes.22 In addition, Fe3+

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can be derived from the transmission pipeline of Cl2 and/or packages of CP mixtures, and

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iron is the catalyst to form the unsaturated double bonds.35, 36 The results are consistent with

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the identification of unsaturated CPs in commercial mixtures in this study.

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Mass Fractions in Commercial Mixtures.

can

lead

to

the

dechlorohydrogenation

of

CPs

and

result

in

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The mass fractions of the identified SCCP, MCCP, and LCCP congeners were calculated

258

in the CP-42, CP-52, and CP-70 commercial mixtures. Previous studies only focused on the

259

mass fractions of SCCPs in commercial mixtures,6, 25 and no information is available about 12

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MCCPs and LCCPs, even though these compounds are used as alternatives for SCCPs with

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production volumes increasing every year.3 As shown in Figure 3, mass factions of CPs were

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very constant in CP-42 mixtures from various manufacturers and the previous reported

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proportions of SCCPs (3.1% to 3.7%) were within the range of this study.6, 25 It should be

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noted that MCCPs were detected in all three CP-42 mixtures with mass fractions higher than

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those of SCCPs. MCCPs and LCCPs were detected with constant mass fractions in all of the

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CP-52 mixtures, whereas high variations of SCCP mass fractions were found in the CP-52

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mixtures. Significantly different CP mass fractions were also observed in CP-70 mixtures,

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possibly due to the different feedstock and production processes used by various

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manufacturers.23 For unsaturated CPs, the mass fraction ratios (MFRs) between unsaturated

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CPs and CPs were applied to assess the percentages of unsaturated analogues. Relatively low

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MFRs of SCCPs (0.08 ± 0.07) and MCCPs (0.1 ± 0.1) were found in the commercial

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mixtures, but were as high as 0.4 ± 0.3 for LCCPs. The significantly different profiles of

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LCCPs and the high proportions of unsaturated LCCPs in the commercial mixtures suggest

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the complexity of the long-chained compounds, whose occurrences in the environment

275

deserve more attention.

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Profiles in Commercial Mixtures.

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To accurate profile the CPs, a recent study presented an interesting approach to quantify

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SCCPs by introducing specific response factors for each SCCP congener groups, and the

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response factors were estimated by analyzing the binary mixtures of standard SCCP mixtures

280

with different chain length.37 But the standard mixtures of MCCPs and LCCPs with different

281

chain length were not commercial available, and no standard mixtures can be found for 13

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unsaturated CPs. Thus, the generally used profiling method was used in this study, and the

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method was based on the assumption that the response factors were identical for individual

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congener groups of SCCPs, MCCPs and LCCPs.4-6, 9, 25, 27 While the obtained profiles would

285

be affected by the difference responses of CP congener groups, the predominant compounds

286

in the commercial mixtures could be clarified, and pattern comparisons between commercial

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mixtures and environmental samples were able to provide source and discharging information.

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As shown in Figure 4, Table S1, S2, and S3, the profiles of CPs were constant in all of the

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CP-42 commercial mixtures, and the abundance of CP congener groups was in the order of

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C13-SCCPs > C14-MCCPs > C15-MCCPs > C16-MCCPs > C12-SCCPs with chlorine numbers

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of 6-9. The profiles of SCCPs were reported in the CP-42, CP-49, CP-52, CP-60, and CP-70

292

commercial mixtures.6, 21, 25, 26 The profiles of SCCPs obtained in this study were consistent

293

with those reported in CP-49, CP-60, and CP-70 mixtures by APCI-QTOFMS with high

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abundance of C13-SCCPs,26 but different from those observed in CP-42, CP-52, CP-60, and

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CP-70 mixtures by GC/ECNI−HRMS and GC/ECNI−LRMS analysis with C10-SCCPs and

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C11-SCCPs as the predominant compounds.6,

297

response factors for each congener groups of SCCPs with various ion sources.37 Ionization

298

efficiencies of APCI-QTOFMS increased with the carbon number, and reached maximum for

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C13-SCCPs, but those of ECNI sources showed a decreasing trend with the carbon number,

300

and highest responses were observed for C10-SCCPs and C11-SCCPs.37 The results well

301

explained the different patterns of SCCPs reported in studies using various ion sources. In the

302

CP-52 commercial mixtures, C13Cl7-8-CPs, C17Cl7-9-CPs, and C23Cl9-10-CPs were the

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predominant SCCPs, MCCPs, and LCCPs respectively. The profiles of MCCPs in CP-52

21, 25

A recent study reported the specific

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commercial mixtures in this study were different from those reported in the CP-52

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commercial mixtures provided by Dover Chemical Corp (Dover, OH) with C14Cl5-8-CPs as

306

predominant congeners,29 but similar to those reported in the CP-50 and CP-56 mixtures

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purchased from Hoechst AG (Germany) and Dynamit Nobel AG.26 It is interesting to note

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that the concentration ratios of ∑SCCPs/∑MCCPs (0.04 to 1.4) and ∑MCCPs/∑LCCPs (0.9

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to 29) had wide ranges in the CP-52 mixtures from various manufacturers. In the CP-70

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commercial mixtures, the profiles of SCCPs, MCCPs, and LCCPs, with C13Cl12-14-CPs,

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C17Cl15-17-CPs, and C23Cl19-22-CPs as the predominant compounds, respectively, were

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individually similar to those of the three groups of compounds in the CP-52 commercial

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mixtures. It should be noted that all the congener groups in CP-70 commercial mixtures

314

contained more Cl atoms (SCCPs: 11-14, MCCPs: 14-17, and LCCPs: 19-24) compared with

315

those with same carbon atoms in CP-42 and CP-52 commercial mixtures. Especially for one

316

mixture as shown in Figure 4(c1), even the carbon numbers of predominant congener groups

317

were low, percentages of the congener groups with 11-17 chlorines and 12-17 carbon were

318

80.1%. The predominant LCCP congeners in this study were similar to those in CP-70

319

mixtures from Oxychem Co. USA.26 High variations of concentration ratios of

320

∑SCCPs/∑MCCPs (1.3 to 2.2) and ∑MCCPs/∑LCCPs (0.01 to 3.6) were obtained in CP-70

321

mixtures, suggesting significantly different homologue patterns in the mixtures from various

322

producers. The different percentages and profiles of SCCPs, MCCPs, and LCCPs in CP-42,

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CP-52, and CP-70 could result in different pollutant patterns in areas adjacent to their

324

manufacture or usage locations.

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A plot was designed to show unsaturated CPs together with saturated CPs in one figure. 15

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As shown in Figure 5 and S4, the x-axis represents the carbon number, the y-axis represents

327

the Log [(Ω+1)×Cl percentage], and the color represents the concentrations of CPs. The

328

saturated SCCPs, MCCPs and LCCPs are aligned at the bottom of the figure, and the

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corresponding unsaturated CPs with different unsaturated degrees (Ω) are dispersed in the top

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of the figure (Figure 5a). The distributions of all the CP conger groups were clearly observed

331

in the scatter plots. The detailed mass percentages of unsaturated CPs in the commercial

332

mixtures are shown in Table S1, S2, and S3. The predominant compounds of unsaturated CPs

333

in CP-42 commercial mixtures were C13-15 CPs with chlorine numbers of 5 to 6 and Ω of 1 to

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2, of which the carbon number was similar to those of the predominant saturated CPs in the

335

commercial mixtures (Figure 5b, S4a, and S4b). The major unsaturated CPs in certain CP-52

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commercial mixtures were C20 CPs with chlorine numbers of 6 to 7 and Ω of 1, while the

337

dominant congener groups in another CP-52 commercial mixture was C13-15 CPs, which were

338

centered around Cl = 5 to 6 and Ω = 1 to 2 (Figure 5c, S4c, and S4d). The unsaturated CPs

339

showed high profile variations in the CP-70 commercial mixtures. The CP-70 commercial

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mixture with higher SCCP contents, as described above, was also dominated by unsaturated

341

C13-SCCPs with chlorine numbers of 12 to 13 and Ω of 1, and the CP-70 commercial

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mixtures with high LCCP mass fractions contained a higher abundance of unsaturated

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long-chained groups (C23-25-LCCPs, Cl = 19 to 21, Ω = 1 to 2) (Figure 5d, S4e, and S4f). It

344

should be highlighted that the unsaturated CPs identified in CP-70 commercial mixtures had

345

more chlorine atoms than those found in CP-42 and CP-52 commercial mixtures.

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As we known, there are about 150 CP producers in China,38 and it is possibly that high

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variations of the CP profiles exist among different producers. This study is a pilot study to 16

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characterize the CP homologue pattern in the commercial mixtures. The analyzed CP

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products were obtained from the major producer in provinces with high CP production

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capacities in China. Profiles of CPs were found to be constant in CP-40 from various

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producers. Relatively high variations were observed in CP-52 and CP-70 mixtures. Two kinds

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of homologue patterns are discovered for the high chlorine content CPs: one is dominated by

353

compounds with carbon length of 12-17, and anther dominated by CPs with carbon length

354

17-28.

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Occurrences in Atmosphere.

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The chlorine-enhanced UPLC-QTOFMS method was applied to 28 air samples collected

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over the four seasons from September 2013 to August 2014 in an urban area of Shenzhen,

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Guangzhou Province, for the analysis of CPs and unsaturated analogues identified in this

359

study. Concentrations of ∑SCCPs, ∑MCCPs, and ∑LCCPs were estimated to be 1.11 to 39.8,

360

0.70 to 12.2, 0.25 to 8.38 ng/m3, with mean values of 5.06±7.59, 3.53±2.93, and 2.32±1.91

361

ng/m3, respectively. The concentrations of ∑SCCPs in this study are comparable to those

362

reported in Japan (0.28 to 14.2 ng/m3), South Korea (0.60 to 8.96ng/m3) and Switzerland (1.1

363

to 42).39, 40 Concentrations of ∑SCCPs and ∑MCCPs were comparable to those reported in

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winter in the Pearl River Delta geographically close to our sampling sites (∑SCCPs: 0.95 to

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26.5 ng/m3, ∑MCCPs: 0.10 to 22.9 ng/m3), but lower than those reported during summer time

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(∑SCCPs: 2.01 to 106 ng/m3, ∑MCCPs: 0.78 to 230.9 ng/m3).11 To the best of our knowledge,

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only one study has attempted to determine the concentrations of ∑LCCPs in air samples

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using the direct APCI-QTOF analytical method, and the LCCPs were not detected.26 In this

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study, using the sensitive chlorine enhanced UPLC-ESI-QTOF method, LCCPs with carbon 17

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numbers ranging from 18 to 30 were detected in air samples, with detection frequencies of 38%

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to 75%. The concentration variations of CPs in four month of a year were shown in Figure 6a.

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Similar trends were observed for both the CPs and unsaturated analogues, and relatively low

373

concentrations were found in air samples collected in June. The possible reason could be that

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the temperature of four seasons are not distinct in the study area due to the influence of

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subtropical oceanic monsoons,41 and the clear wet period in June with an average

376

precipitation of 239 mm may be the predominate factor resulting in the relatively lower

377

concentrations.

378

The profiles of all of the CPs in the air samples are shown in Figure 6b. SCCPs were

379

dominated by C13-CPs (30.4%), followed by C12-CPs (6.25%), all of which were centered

380

around Cl = 6 to 9. These profiles were consistent with those of air samples by

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APCI-QTOFMS in Stockholm,26 but different from those analyzed by ECNI-MS in the Pearl

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River Delta and Zurich, Switzerland,11, 40 possibly due to different ionization efficiencies

383

between the ECNI and ESI sources described above. For MCCPs, C14-CPs (19.9%) centered

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around Cl = 6 to 9 were the predominant homologue groups, and their profiles were similar to

385

those of air samples in the Pearl River Delta and Stockholm.11, 26 While CPs are potentially

386

used in large quantities in the investigated area, it is difficult to clarify the major products

387

used only based on the generally investigated SCCPs. This is due to the relatively constant

388

profiles of SCCPs in the widely used CP-40 and CP-52 commercial mixtures. The profiles of

389

LCCPs were firstly reported in the air samples in this study, and C23-25Cl7-10 CPs were found

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to be the predominate congener groups. This congener patterns were similar to those of

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CP-52 commercial mixtures but different from those of CP-70 commercial mixtures. The 18

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results suggested that LCCPs in air samples in the area might be mainly from the production

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and usage of CP-52 mixtures.

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The unsaturated CPs identified in this study were also detected in the air samples.

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Concentrations of unsaturated ΣSCCPs, ΣMCCPs, and ΣLCCPs were estimated to be 0.01 to

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0.27 ng/m3, 0.02 to 0.56 ng/m3, and 0.01 to 0.55 ng/m3, with mean values of 0.07, 0.11, and

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0.12 ng/m3, respectively. It should be noted that the total concentrations of unsaturated

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LCCPs were higher than those of unsaturated SCCPs and MCCPs. This is consistent with the

399

abundance of unsaturated LCCPs identified in CP-52 and CP-70 commercial mixtures. The

400

predominant unsaturated CPs in air samples were unsaturated C13-SCCPs and C14-15-MCCPs

401

with chlorine numbers of 5 to 6 and Ω = 1, followed by unsaturated C20-LCCPs with chlorine

402

numbers of 6 to 7 and Ω = 1 (Table S4). The predominant unsaturated CPs in air samples

403

were consistent with those identified in the CP-42, CP-52, and CP-70 commercial mixtures.

404

Different from the saturated CPs, unsaturated CPs were specifically originated from the

405

commercial mixtrues, for examples, unsatrutaed SCCPs were from CP-40 mixture, and

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unsturated LCCPs with carbon nubmer of 24-29 were from CP-70 mixture.

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environmental occurences of unsaturated C24-29-LCCPs suggested the usage and production

408

of CP-70 in the investigated area.

In this study,

409

In summary, a high throughput screening method was applied to characterize the CPs in

410

CP42, CP-52 and CP-70 commercial mixtures. Three hundred and sixty-seven CPs with 10 to

411

30 carbons and 5 to 28 chlorines, and 113 unsaturated analogues with Ω of 1 to 7 were

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identified. Detailed compositions of all of the CPs and identified unsaturated analogues were

413

characterized in three common CP commercial mixtures. Occurrences of the identified CPs 19

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were confirmed in atmosphere samples collected from Shenzhan, Guangzhou over one year.

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The generally investigated SCCPs were very constant in the widely used commercial

416

mixtures. In comparison, simultaneous profiling of SCCPs, MCCPs, and LCCPs helped

417

clarify the major commercial mixtures used in the local area, and investigation of unsaturated

418

CPs could provide more source-specific information. Investigations of CPs with their

419

unsaturated analogues in other environmental matrices are urgently required.

420 421 422

Acknowledgments

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The research is supported by Key Program for International S&T Cooperation Projects of

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China (S2016G6417), National Basic Research Program of China (2015CB458900), and

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National Natural Science Foundation of China (201677003, 21422701).

426 427

Supplementary Data

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Text, figures, and tables addressing (1) chemicals and reagents; (2) analysis and

429

quantification of CPs; (3) detail mass percentages of saturated and unsaturated CPs in

430

commercial mixtures; (4) concentrations of individual detected unsaturated CPs in air

431

samples; (5) locations of the CP producers and collection sites of air samples; (6) mass

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spectrum patterns of CPs in the CP-70 commercial mixtures; (7) chromatograms of ions with

433

low mass difference; and (8) profiles of saturated and unsaturated CPs in some commercial

434

mixtures.

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chlorinated paraffins exposure on the viability and metabolism of human hepatoma HepG2 cells. Environ Sci Technol 2015, 49, (5), 3076-83. 15. Zhang, Q.; Wang, J.; Zhu, J.; Liu, J.; Zhang, J.; Zhao, M., Assessment of the endocrine-disrupting effects of short-chain chlorinated paraffins in in vitro models. Environ Int 2016, 94, 43-50. 16. Geng, N.; Zhang, H.; Xing, L.; Gao, Y.; Zhang, B.; Wang, F.; Ren, X.; Chen, J., Toxicokinetics of short-chain chlorinated paraffins in Sprague-Dawley rats following single oral administration. Chemosphere 2016, 145, 106-11. 17. Ashby, J.; Lefevre, P. A.; Elcombe, C. R., Cell replication and unscheduled DNA-syntheis (UDS) activity of low-molecular-weight chlorinated paraffins in the rat-liver in vivo. Mutagenesis 1990, 5, (5), 515-518. 18. Warnasuriya, G. D.; Elcombe, B. M.; Foster, J. R.; Elcombe, C. R., A Mechanism for the induction of renal tumours in male Fischer 344 rats by short-chain chlorinated paraffins. Archives of Toxicology 2010, 84, (3), 233-243. 19. Hallgren, S.; Darnerud, P. O., Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and chlorinated paraffins (CPs) in rats - testing interactions and mechanisms for thyroid hormone effects. Toxicology 2002, 177, (2-3), 227-243. 20. Shojania, S., The enumeration of isomeric structures for polychlorinated N-alkanes. Chemosphere 1999, 38, (9), 2125-2141. 21. Tomy, G. T.; Stern, G. A.; Muir, D. C. G.; Fisk, A. T.; Cymbalisty, C. D.; Westmore, J. B., Quantifying C10-C13 Polychloroalkanes in Environmental Samples by High-Resolution Gas Chromatography/Electron Capture Negative Ion High-Resolution Mass Spectrometry. Anal. Chem. 1997, 69, (14), 2762-2771. 22. Schinkel, L.; Lehner, S.; Heeb, N.V.; Lienemann, P.; McNeill, K.; Bogdal, C., Deconvolution of Mass Spectral Interferences of Chlorinated Alkanes and Their Thermal Degradation Products: Chlorinated Alkenes. Anal. Chem. 2017, 89, (11), 5923-5931. 23. Tong, X. C.; Hu, J. X.; Liu, J. G., Performance situation and preliminary evaluation of short chain chlorinated paraffin in China. In Proceedings of the 2008 Symposium on Persistent Organic Pollutants (POPs) and the Third National Symposium on POPs, Beijing, 2008. 24. Bayen, S.; Obbard, J. P.; Thomas, G. O., Chlorinated paraffins: a review of analysis and environmental occurrence. Environ. Int. 2006, 32, (7), 915-29. 25. Gao, Y.; Zhang, H.; Zou, L.; Wu, P.; Yu, Z.; Lu, X.; Chen, J., Quantification of Short-Chain Chlorinated Paraffins by Deuterodechlorination Combined with Gas Chromatography-Mass Spectrometry. Environ Sci Technol 2016, 50, (7), 3746-53. 26. Bogdal, C.; Alsberg, T.; Diefenbacher, P. S.; MacLeod, M.; Berger, U., Fast quantification of chlorinated paraffins in environmental samples by direct injection high-resolution mass spectrometry with pattern deconvolution. Anal. Chem. 2015, 87, (5), 2852-60. 27. Xia, D.; Gao, L. R.; Zheng, M. H.; Tian, Q. C.; Huang, H. T.; Qiao, L., A Novel Method Mammals for Profiling and Quantifying Short- and Medium-Chain Chlorinated Paraffins in Environmental Samples Using Comprehensive Two-Dimensional Gas Chromatography– Electron Capture Negative Ionization High-Resolution Time-of-Flight Mass Spectrometry. Environ. Sci. Technol. 2015, 50, 7601. 28. Li, T.; Wan, Y.; Gao, S.; Wang, B.; Hu, J., High-Throughput Determination and 22

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Figure 1. Mass spectra of CPs (black) and deprotonated [M-H]- ([M-HCl+Cl]-, blue) in the commercial (upper panel) and standard (lower panel) mixtures. Ions of SCCPs, MCCPs, and LCCPs were shown in a/b), c/d) and e/f), respectively. RT means retention time. 24

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Figure 2. Mass spectrum of saturated and unsaturated CPs by directly injecting CP commercial mixtures to the chlorine enhanced APCI-Orbitrap MS. Ions belongs to one congener group were shown in the same colors, and unsaturated CPs were colored as blue. a) unsaturated SCCP, saturated SCCP and MCCP; b) unsaturated and saturated MCCPs; c) unsaturated and saturated LCCPs.

25

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Figure 3. Mass fractions of saturated and unsaturated CPs in the CP-42 (a), CP-50 (b) and CP-70 (c) commercial mixtures produced in Shandong (SD), Jiangsu (JS) and Guangdong (GD) provinces.

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Figure 4. Profiles of SCCPs, MCCPs, and LCCPs in the CP-42 (a1, a2, a3), CP-50 (b1, b2, b3) and CP-70 (c1, c2, c3) commercial mixtures from different major producers in China. 27

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Figure 5. Distribution of saturated and unsaturated CPs in the plot (a), and profiles of all target CPs in some CP-42 (b), CP-50 (c), and CP-70 (d) commercial mixtures. Profiles of CPs in other commercial mixtures are shown in Figure S2.

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Figure 6. Concentrations of saturated and unsaturated CPs in air samples in four month over a year (a), and their average profiles in the samples (b).

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