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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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Environmental Science & Technology

1

Screening of Chlorinated Paraffins and Unsaturated Analogues in Commercial

2

Mixtures: Confirmation of Their Occurrences in the Atmosphere

3

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

4

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

5

Peking University, Beijing 100871, China

6

(Received

7

*Address for Correspondence:

)

8 9 10 11 12 13 14 15 16

Address for Correspondence

17

Dr. Yi WAN

18

College of Urban and Environmental Sciences

19

Peking University

20

Beijing 100871, China

21

TEL & FAX: 86-10-62759126

22

Email: [email protected] 1

ACS Paragon Plus Environment


23

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ABSTRACT

24

Characterizing the detailed compositions of chlorinated paraffins (CPs) commercial

25

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

26

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

27

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).

29

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

30

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

31

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

32

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

33

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

34

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

35

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

36

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

37

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

38

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

39

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

40

Keywords:

41

Nontargeted screening, By-products

Chlorinated

paraffins,

Unsaturated

analogues,

2


Commercial

mixtures,

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Introduction

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

44

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

45

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

46

wide usage,2,

47

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

48

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

49

low positional selectivity and produce complex mixtures containing thousands of isomers

50

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

51

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

52

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

54

homologues is a challenge in environmental analysis of the compounds.

3

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

55

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

56

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

60

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

61

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

62

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


25


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

65

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

66

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

67

mixtures remain unclear.

68

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

69

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

70

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

71

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

74

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

83

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

84

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

4


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

86

environment.

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

88

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

94

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

98

investigate the predominant saturated and unsaturated CPs identified in commercial mixtures

99

and environmental samples.

(DCM)-enhanced

100

Materials and methods

101

Sample collection.

UPLC-ESI-QTOFMS

analysis

31

In this study,

combined

with

102

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

103

(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



107

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

108

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

109

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

110

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.

114

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

115

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

116

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

117

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

119

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

120

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

121

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

122

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

123

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

124

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

125

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

126

UPLC-QTOFMS analysis.

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

128

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

130

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

131

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

132

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

133

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

134

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

135

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

137

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

138

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

139

5.5 to 8.5 minute.

140

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

141

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

142

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

145

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

146

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

147

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

148

lower than 3 ppm.

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Orbitrap MS analysis.

150

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



151

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

152

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.

155

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

156

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

157

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

158

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

159

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

160

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

161

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

162

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

163

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

164

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

165

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

166

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

167

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

168

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

169

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

170

the mass tolerance was set to 5 ppm.

171

Semi-quantifications of CPs and unsaturated CPs.

172

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

174

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

176

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

177

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

178

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

179

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

180

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

181 182

Results and discussion

183

Screening of commercial mixtures.

184

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

185

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

186

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

187

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

188

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

189

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

190

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

191

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

192

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

193

chemical features were suspected to be 11 unsaturated CPs.

9



194

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

195

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

196

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

197

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

198

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

199

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

200

previous studies, detected LCCP congener groups comprised compounds with carbon

201

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

202

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

203

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

204

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

205

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

206

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

207

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

208

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

209

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

210

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

211

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

212

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

213

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

214

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

215

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

217

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

218

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

219

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

220

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

221

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

222

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

223

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

224

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

225

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

226

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

227

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

228

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

229

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

230

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

231

of other unsaturated CPs, chromatographic separation prior QTOMS gives significant

232

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

233

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

234

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

235

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

236

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

237

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

239

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

240

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

241

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

242

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

243

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

244

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

245

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

246

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

247

UPLC-QTOFMS analysis.

248

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

249

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

250

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

251

temperatures

252

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

253

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

254

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

255

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

256

Mass Fractions in Commercial Mixtures.

can

lead

to

the

dechlorohydrogenation

of

CPs

and

result

in

257

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

261

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

262

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

263

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

264

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

265

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

266

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

267

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

268

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

269

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

270

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

271

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

272

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

273

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

274

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

275

deserve more attention.

276

Profiles in Commercial Mixtures.

277

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

278

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

279

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



282

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

283

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

284

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

287

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

288

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

289

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

290

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

291

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

294

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

295

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

296

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

299

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

303

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

21, 25

A recent study reported the specific

14


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304

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

305

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

307

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

308

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

309

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

310

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

311

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

312

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

313

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,

323

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

324

manufacture or usage locations.

325

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



326

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

329

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

330

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

334

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

336

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

340

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

342

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

343

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.

346

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

347

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


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348

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

349

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

350

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

351

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

352

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.

355

Occurrences in Atmosphere.

356

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

357

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

358

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

364

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

365

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

366

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

367

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

368

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

369

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



370

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

371

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

372

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

374

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

375

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

381

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

382

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

384

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

390

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

391

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


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392

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

393

and usage of CP-52 mixtures.

394

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

395

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

396

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

397

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

398

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

406

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

407

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

412

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



414

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

415

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

423

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

424

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

425

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

426 427

Supplementary Data

428

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

432

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.

20


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567 568 569 570

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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571 572 573 574 575 576 577 578

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



579 580 581 582 583

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.

26


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584 585 586


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



587 588 589 590 591 592

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.

28


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593 594 595 596 597 598 599


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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Screening of Chlorinated Paraffins and ... - ACS Publications

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