Organochlorine Pesticides and Pyrethroids in Chinese Teaby Screening and Confirmatory Detection Using GC-NCI-MSand GC-MS/MSPan Zhu,†,§,# Hong Miao,*,† Juan Du,⊥ Jian-hong Zou,⊗ Guo-wen Zhang,# Yun-Feng Zhao,†

and Yong-Ning Wu*,†,§

†Key Laboratory of Food Safety Risk Assessment of Ministry of Health, China National Center for Food Safety Risk Assessment,Beijing, China§Center for Disease Prevention and Control of Guangdong Province, Guangzhou, China#State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, Jiang Xi, China⊥China National Food Quality and Safety Supervision and Inspection Center, Beijing, China⊗General Hospital of the Second Artillery, Chinese People’s Liberation Army, Beijing, China

*S Supporting Information

ABSTRACT: One hundred and one tea samples including green tea, dark tea, scented tea, black tea, and oolong tea werescreened and confirmed for the contamination of 31 organochlorine pesticides (OCPs) and 19 pyrethroids (PYs) by gas chro-matography−negative chemical ionization−mass spectrometry (GC-NCI-MS) and gas chromatography−tandem mass spec-trometry (GC-MS/MS). 50 pesticides, 3 deuterium-labeled PYs, and 24 13C-labeled OCPs were separated well with the limits ofdetection (LODs) ranging from 0.02 to 4.5 μg/kg for GC-NCI-MS, and the positive samples were verified by GC-MS/MS withLODs of 0.1−5.0 μg/kg. High detection rates for some PYs, such as 63.4% for bifenthrin (not detected (ND)−3.848 mg/kg),55.4% for λ-cyhalothrin (ND−3.244 mg/kg), 46.5% for cypermethrin (ND−0.499 mg/kg), and 24.8% for fenvalerate(ND−0.217 mg/kg), were found in the 101 tea samples. Endosulfan, DDTs, HCHs, and heptachlor, the persistent OCPs,were frequently detected with rates of 63.4% (ND−1.802 mg/kg), 56.4% (ND−0.411 mg/kg), 24.8% (ND−0.377 mg/kg), and15.8% (ND−0.100 mg/kg), respectively.

KEYWORDS: organochlorine pesticides, pyrethroids, Chinese tea, screening and confirmation, GC-NCI-MS, GC-MS/MS

■ INTRODUCTION

Organochlorine pesticides (OCPs) and pyrethroids (PYs) aretwo kinds of widely used pesticides for the effective control ofpests and diseases of plants and animals.1 Due to their lowbiodegradability and high persistence in the natural environment,OCPs and PYs are ubiquitous among samples of air, water, soil,sediments, food, and biological tissues2−5 and have been shownto have potentially harmful effects on human beings. SomeOCPs, including hexachlorocyclohexanes (HCHs), dichlorodi-phenyltrichloroethanes (DDTs), aldrin, dieldrin, endrin, chlor-dane, heptachlor, and hexachlorobenzene, are listed in theStockholm Convention as persistent organic pollutants (POPs)and have been banned by the United Nations EnvironmentProgram (UNEP)6 for their link to reproductive disorders,disruption of the cellular immune system, cancer predisposition,and nervous system damage of humans.7

Tea is a popular and traditional drink in China. It has been alsovery popular in other foreign countries for its characteristicaroma, flavor, and health benefits.8 China has the largest teaplantation area in the world and is the second largest teaproducer.9 PYs are the most commonly used pesticides intea plantations in China, as the use of OCPs and some organo-phosphate pesticides with acute toxicity have been graduallybanned or restricted. Importing countries, such as the EuropeanUnion and Japan, have established stringent limits on maximum

residues of pesticides in tea,10 especially for PYs and OCPs.Therefore, establishment of a method for detecting all of theOCPs and PYs in tea samples and a comprehensive survey ofOCPs and PYs in Chinese tea samples were necessary andimportant for human health and tea exportation.Tea matrix is very complex as it contains pigments, caffeine,

sugars, organic acids, and other interferences.11 For thepretreatment of tea samples, a number of solvents have beenused for multiresidue pesticide extraction, and the most commonones included acetone, ethyl acetate, and acetonitrile. Themost commonly employed cleanup techniques comprise liquid−liquid extraction (LLE),12 solid-phase extraction (SPE),13 gelpermeation chromatography (GPC), solid-phase microextra-tion (SPME),14 and matrix solid-phase dispersion (MSPD).15

Among these techniques, SPE is being increasingly used in foodanalysis, especially for tea sample cleanup. The detectiontechniques include gas chromatography−electron capture detec-tion (GC-ECD),16−18 gas chromatography−mass spectrometry(GC-MS),13,14 and gas chromatography−tandem mass spectro-metry (GC-MS/MS) in the EI mode.19

Received: March 13, 2014Revised: June 14, 2014Accepted: June 25, 2014Published: June 25, 2014

Article

pubs.acs.org/JAFC

© 2014 American Chemical Society 7092 dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−7100

Table 1. GC-NCI-MS and GC-MS/MS Parameters for OCPs and PYs

GC-NCI-MS GC-MS/MS

no. pesticidemol wt(Mw) retention time (min)

quantitationion (mau) qualitative ions (mau)

parent ion(mau)

daughter ions(mau)

collisionenergy (eV)

1 pentachlorobenzene 250.3 6.71 249.9 251.9 247.9 253.82 pentachlorobenzene (13C6) 256.3 6.77 255.9 257.9 254 259.93 α-BHC 290.8 9.076 254.9 256.9 253 71.64 α-BHC (13C6) 296.8 9.076 260.9 259 262.9 187.15 hexachlorobenzene 284.8 9.164 283.9 285.9 249.9 287.86 hexachlorobenzene (13C6) 290.8 9.164 289.9 291.8 293.9 287.97 empenthrin 274.4 9.33 167.3 168.4 169.5 121.4 167.3 165.5 163 358 β-BHC 290.8 9.776 254.9 256.9 71.6 70.69 β-BHC (13C6) 296.8 9.776 261 263 259.1 187.110 lindane 290.8 10.055 254.9 256.9 71.6 73.211 lindane (13C6) 296.8 10.055 261 262.9 187.2 25912 tefluthrin 418.7 10.79 241.1 243 205.2 244.4 241.1 204.9 204.8 4513 δ-BHC 290.8 10.92 254.9 256.9 71.6 73.214 δ-BHC (13C6) 296.8 10.92 261 259 263 189.115 vinclozolin 286.1 12.07 241.2 243.1 244.9 246.4 241.1 204.9 240.2 2516 transfluthrin 371.2 12.35 207.1 209.1 137.3 210.9 207.1 205.5 204 4517 heptachlor 373.3 12.459 299.8 236.8 265.9 301.918 heptachlor (13C10) 383.3 12.459 309.9 307.9 311.9 27619 o′,p-dicofol 370.5 13.17 214.2 216 250.1 252 214.1 211.6 35.3 2520 aldrin 364.9 13.998 236.9 329.9 234.9 331.921 aldrin (13C12) 376.9 13.998 342 242 239.9 24422 dicofol 370.5 14.71 250.1 252 253.8 216.3 250.1 35.5 233.8 2523 fenson 268.5 14.99 141.2 142.4 143.4 127.4 141.3 77.2 140.2 2524 oxychlordane 423.8 16.105 236.1 349.9 351.9 423.925 oxychlordane (13C10) 433.8 16.105 431.9 361.8 359.9 24226 cis-heptachlorepoxide 389.3 16.105 316.1 351.7 281.827 cis-heptachlorepoxide

(13C10)399.3 16.105 399.8 327.9 290 325.9

28 trans-heptachlorepoxide 389.3 16.331 236.9 353.8 281.8 234.929 trans-chlordane 409.8 17.353 409.7 265.9 301.8 238.930 trans-chlordane (13C10) 419.8 17.353 419.8 417.8 385.9 27631 allethrin 301.4 16.680, 16.753 167.3 168.5 134.4 169.6 167.3 165.9 164.7 3532 prallethrin 300.4 17.207, 17.436 167.3 132.4 168.5 133.5 167.3 165.6 163.9 3533 2,4′-DDE 318 17.565 246.2 318 248 21234 2,4′-DDE (13C12) 330 17.565 330 328 260 258.135 cis-chlordane 409.8 17.841 266 264 236.9 409.836 endosulfan I 406.9 17.959 407.7 241.9 373.7 301.837 endosulfan I (13C9) 415.9 17.969 414.7 250 380.8 24238 trans-nonachor 444.2 18.092 443.6 299.9 236.9 335.839 trans-nonachor(13C10) 454.2 18.092 453.8 309.9 451.9 455.940 chlorfenson 303.2 18.625 176.5 175.1 177.8 191.3 175.1 111 173.1 1541 dieldrin 380.9 19.146 345.8 236.9 238.9 379.742 dieldrin (13C12) 392.9 19.146 391.7 395.8 358 241.943 4,4′-DDE 318 19.057 319.7 262 315.9 317.944 4,4′-DDE (13C12) 330 19.057 329.9 322 326.245 2,4′-DDD 320 19.301 248.1 212.4 246.1 73.546 2,4′-DDD (13C12) 332 19.301 260.2 262.1 258 264.247 endosulfan II 406.9 20.398 405.7 241.9 335.8 369.748 endosulfan II (13C9) 415.9 20.408 414.7 344.8 378.8 25049 cis-nonachor 444.2 20.55 443.6 333.8 299.9 236.950 cis-nonachor (13C10) 454.2 20.55 453.8 451.8 455.8 343.951 4,4′-DDD 320 20.678 248.1 71.5 250 251.852 4,4′-DDD (13C12) 332 20.678 260.1 262.153 2,4′-DDT 354.5 20.733 246.1 212.1 71.5 281.154 2,4′-DDT (13C12) 355.6 20.733 295.8 293.9 238.255 endrin 380.9 20.932 272 236.1 306 381.856 endrin (13C12) 392.9 20.932 282 284 358 39257 endosulfan sulfate 422.9 21.799 385.7 351.7 97.5 185.258 endosulfan sulfate (13C9) 431.9 21.786 394.8 360.7 97.5 250

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In this study, a rapid, efficient, and sensitive method for thesimultaneous determination of 31 OCPs and 19 PYs in Chineseteas by GC-NCI-MS and GC-MS/MS were developed. Theestablished methods were validated according to the criteriaby EU Commission Decision 2002/657/EC,20 and a survey of101 tea samples was conducted by the established method.

■ MATERIALS AND METHODSMaterials and Reagents. The Florisil cartridges (2 mg, 12 mL)

were purchased from Agilent (Santa Clara, CA, USA); primary−secondary amine (PSA) powder with the size of 40−60 μm was alsoobtained from Agilent.Acetone, hexane, and ethyl acetate (P.R. grade) were purchased from

J. T. Baker (Deventer, The Netherlands); anhydrous sodium sulfate(P.R. grade) purchased from Sigma Co. (Beijing, China) was heated at250 °C for 4 h and kept in a desiccator; sodium chloride (analyticalreagent grade) was purchased from Beijing Chemical Industry (Beijing,China); deionized water was obtained from a Milli-Q water purificationsystem (Millipore, Bedford, MA, USA).Analytical Standards. Analytical reference standards of PYs and

OCPs (listed in Table 1), d6-trans-cypermethrin, d6-trans-permethrin,d5-bifenthrin, and 24 13C-labeled OCPs were all purchased fromDr. Ehrenstorfer GmbH (Augsburg, Germany), with purity of not lessthan 96.0%.Standard Solution. The stock solution for all of the standards

and the internal standards (IS) were prepared by accurately weighinga certain amount of the standard powder and then quantitativelydissolving by ethyl acetate at the concentration of 1000 mg/L, respec-tively. The mixed intermediate standard and internal standard solutionwere quantitatively diluted from the stock standard solutions withhexane, and the final concentrations of all the individual standardsand the internal standards were 2 and 1 mg/L, respectively. All of thestandard solutions were stored at −20 °C in amber glass bottles.Tea Samples and Pretreatment. All 101 tea samples were

purchased from local supermarkets (Beijing, China) in 2013, includinggreen tea (n = 44), scented tea (n = 23), dark tea (n = 8), black tea(n = 13), and oolong tea (n = 13). The tea samples were groundby a homogenizer and filtered through a 40 mesh sieve. The grinding

program was conducted as follows: ground for 3 s and halted for 5 s;5−10 cycles were enough for each sample.

A negative green tea sample was selected as the blank for the recoverystudies.

Sample Extraction. 2.0 g of ground tea powder was weighed bya balance with the precision of 1 mg; 40 μL of the mixed IS solution(1 mg/L) was spiked, and then the mixture was soaked by 10 mL of hotwater (90−100 °C) for 30 min. 20 mL of acetone was added, and themixture was vortexed for 1 min and then ultrasonicated for 30 min, andthen centrifugation was performed at 7000 rpm for 5 min at 4 °C. Theextracted solution was transferred and partitioned by 20 mL of hexanewith the addition of 1.0 g of NaCl. Two partitions were performed, andthe organic solutions were combined and evaporated to near drynessat 30 °C by rotary evaporation. The residues were redissolved with 3 mLof hexane.

Sample Cleanup. The Florisil cartridge (2 mg, 12 mL) with a layer(ca. 1 cm) of PSA on the sieve plate was prepared and preconditionedwith 5.0 mL of acetone/hexane (1:9, v/v) and 5.0 mL of hexane. Theextract was applied to the conditioned cartridge and eluted with 10 mLof acetone/hexane (1:9, v/v). The loading and eluting fluid were bothcollected and evaporated to dryness by a gentle nitrogen stream in awater bath at 30 °C. The residue was redissolved with 200 μL of hexaneand filtered through a 0.22 μm PTFE filter for GC-NCI-MS analysis.

GC-NCI-MS Analysis. The analysis of the target analytes wasperformed on a DB-5 ms column (30 m × 0.25 mm i.d. × 0.25 μm) byBruker 450 GC and 320 MS (triple-quadrupole mass spectrometry, MSworkstation version 7.0 software) with the 8400 autosampler (Bruker,USA), operated under NCI for screening. Helium with a purity of notless than 99.999%was used as carrier gas at a constant flow of 1mL/min.Methane gas was used as the reaction gas for NCI analysis, and thefilament current was set to the default value. The GC oven temperatureprogramwas as follows: 80 °Ckept for 1min, raised to 200 °C at a rate of20 °C/min, then raised to 240 °C at a rate of 15 °C/min, then raised to286 °C at a rate of 5 °C/min, held for 5 min, and finally raised to 300 °Cat a rate of 20 °C/min and held for 5 min. The temperature of theinjection port and transform line were 250 °C. The splitless injectionvolume was 1 μL with a solvent delay time of 5 min.

The ion source temperature of 230 °C, MS quadrupole temperatureof 40 °C, electron multiplier voltage of 1400 V, and ion source energy of70 eV were used. Analysis was performed in the selected ion monitoring

Table 1. continued

GC-NCI-MS GC-MS/MS

no. pesticidemol wt(Mw) retention time (min)

quantitationion (mau) qualitative ions (mau)

parent ion(mau)

daughter ions(mau)

collisionenergy (eV)

59 4,4′-DDT 354.5 22.008 248.1 262.1 71.6 282.860 4,4′-DDT (13C12) 355.6 22.008 274 275.8 73.561 tetramethrin 331.4 23.659, 23.993 165.3 331.2 167.3 133.5 331.2 167.2 163.1 562 bifenthrin 422.9 23.69 205.2 386.1 241.1 243 386.2 205.4 204.3 4563 d5-bifenthrin 427.9 23.65 391.3 241.1 205.2 242.964 fenpropathrin 349.4 24.19 141.4 142.6 221.3 322.2 141.4 139.5 137.9 3565 phenothrin 350.4 24.701, 24.940 167.3 168.5 169.5 181.3 167.3 165.3 162.9 1566 λ-cyhalothrin 449.9 25.403, 25.738 205.2 241.1 243 206.4 241.1 240.4 204.6 4567 acrinathrin 541.4 26.15 333.1 167.2 305.1 334.5 333.1 166.8 164.7 2568 cyphenothrin 375.5 26.511, 26.686,

26.744167.3 168.5 348.2 169.5 167.3 165.8 168.6 35

69 permethrin 391.3 27.226, 27.472 207.2 209.1 171.2 354.1 207.1 205.9 203.7 2570 d6-cis-permethrin 397.3 27.4 213.2 215 217 179.271 cyfluthrin 434.3 28.258, 28.462,

28.557, 28.647207.2 209.1 171.2 173.1 207.1 206 204 25

72 cypermethrin 416.3 28.868, 29.082,29.186, 29.257

207.2 209.1 171.3 173.2 207.1 205.8 201.6 25

73 d6-cis-cypermethrin 422.6 29.021, 29.210 213.1 215.1 177.2 179.274 flucythrinate 451.4 29.186, 29.593 243.2 244.3 199.3 245.3 243.2 198.8 196.7 2575 τ-fluvalinate 502.9 30.782, 30.930 294.1 295.9 258.2 502 294.1 293 144.9 2576 fenvalerate 419.9 30.533, 30.930 211.2 213 167.4 214.3 211.2 166.8 164.8 577 deltamethrin 505.2 32.06 81.5 79.5 137.4 296.9 296.9 79.2 81.4 5

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mode (SIM). Pesticides were identified according to retention times,the quantitative ions and three qualitative ions (Table 1), and thechromatogram is shown in the Supporting Information. Four ions wereselected following the EU regulation (EEC657/2002). Pesticides weremonitored in different time segments, and the dwell time for each ionwas fixed by the instrument.Calibration and Quantification. Three deuterium PYs and

24 13C-labled OCPs were used as IS as shown in Table 1. For the

quantification of the OCPs, quantitative values were calculated usingisotope dilution technique through a relative response factor (RRF)calculation.

GC-NCI-MS/MS Identification.GC-MS/MS identification was alsoconducted on a 450GC-320MS under NCImode. The other parameterswere the same as for the GC-NCI-MS method except for the ion sourceenergy. With the ion source energy of 20 eV, ions with larger mass weremore easily acquired, which is helpful for MS/MS detection. The mass

Table 2. Linearity Curves, Limits of Detection (LODs), and Limits of Quantitation (LOQs) of 50 Standard Pesticides in Blank TeaMatrix

GC-MS GC-MS/MS

no. pesticide IS RRF r LOD (μg/kg) LOQ (μg/kg) LOD (μg/kg)

1 pentachlorobenzene pentachlorobenzene (13C6) 0.9975 0.03 0.12 α-BHC α-BHC (13C6) 0.92 0.9999 0.5 1.73 hexachlorobenzene hexachlorobenzene (13C6) 1 0.9982 0.03 0.14 empenthrin d5-bifenthrin 0.9971 0.03 0.1 0.35 β-BHC β-BHC (13C6) 0.85 0.9959 0.3 0.96 lindane lindane (13C6) 0.93 0.9975 0.1 0.47 tefluthrin d5-bifenthrin 0.9985 0.03 0.08 0.28 δ-BHC δ-BHC (13C6) 0.94 0.9969 1.1 3.69 vinclozolin endosulfan I (13C9) 0.9982 0.04 0.1 0.310 transfluthrin d5-bifenthrin 0.9986 0.03 0.09 0.311 heptachlor heptachlor (13C10) 1 0.9970 3 1012 o′,p-dicofol endosulfan I (13C9) 0.9987 0.07 0.3 0.413 aldrin aldrin (13C12) 0.95 0.9978 1.2 4.214 dicofol endosulfan I (13C9) 0.9968 0.07 0.3 0.415 fenson endosulfan I (13C9) 0.9983 0.01 0.02 0.116 Oxychlordane Oxychlordane(13C10) 0.95 0.9959 0.2 0.617 cis-heptachlorepoxide cis-heptachlorepoxide (13C10) 1 0.9997 0.2 0.618 trans-heptachlorepoxide cis-heptachlorepoxide (13C10) 1.4 0.9969 0.4 1.419 trans-chlordane trans-chlordane (13C10) 0.99 0.9993 0.5 1.820 allethrin d5-bifenthrin 0.9981 0.01 0.02 4.021 prallethrin d5-bifenthrin 0.9977 0.4 1.4 2.122 2,4′-DDE 2,4′-DDE (13C12) 0.97 0.9983 1.7 5.623 cis-chlordane endosulfan I (13C9) 0.89 0.9985 0.2 0.724 endosulfan I endosulfan I (13C9) 0.9977 0.2 0.725 trans-nonachor trans-nonachor (13C10) 1.12 0.9993 2.1 7.126 chlorfenson endosulfan I (13C9) 0.9959 0.05 0.2 0.427 dieldrin dieldrin (13C12) 1.18 0.9992 1.8 5.928 4,4′-DDE 4,4′-DDE (13C12) 1.03 0.9989 4.5 1529 2,4′-DDD 2,4′-DDD (13C12) 1.04 0.9993 3 1030 endosulfan II endosulfan II (13C9) 0.9998 0.1 0.331 cis-nonachor cis-nonachor (13C10) 0.94 0.9998 0.3 0.932 4,4′-DDD 4,4′-DDD (13C12) 1 0.9961 4.1 13.633 2,4′-DDT 2,4′-DDT (13C12) 1.19 0.9926 4.1 13.634 endrin endrin (13C12) 0.92 0.9982 3.2 10.735 endosulfan sulfate endosulfan sulfate (13C9) 0.9981 0.03 0.0836 4,4′-DDT 4,4′-DDT (13C12) 1.1 0.9663 0.6 237 tetramethrin (I, II) d5-bifenthrin 0.9973 0.3 0.9 2.138 bifenthrin d5-bifenthrin 0.9974 0.1 0.3 0.739 fenpropathrin d5-bifenthrin 0.9979 0.06 0.2 0.440 phenothrin (I, II) d5-bifenthrin 0.9969 0.7 2.3 4.041 λ-cyhalothrin (I, II) d5-bifenthrin 0.9967 0.02 0.06 0.242 acrinathrin d5-bifenthrin 0.9981 0.05 0.2 0.543 cyphenothrin (I, II, III) d6-cis-permethrin 0.9996 0.1 0.4 0.644 permethrin (I, II) d6-cis-permethrin 0.9968 0.7 2.4 5.045 cyfluthrin (I, II, III, IV) d6-cis-cypermethrin 0.9981 0.08 0.3 0.646 cypermethrin (I, II, III, IV) d6-cis-cypermethrin 0.9974 0.06 0.2 0.547 flucythrinate (I, II) d6-cis-cypermethrin 0.9946 0.03 0.1 0.348 τ-fluvalinate (I, II) d6-cis-cypermethrin 0.9993 0.04 0.1 0.349 fenvalerate (I, II) d6-cis-cypermethrin 0.9991 0.02 0.08 0.350 deltamethrin d6-cis-cypermethrin 0.9954 0.02 0.05 0.2

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parameters are provided in Table 1. The positive samples of pyrethroidswere verified by the established GC-NCI-MS/MS method for thelimited isotope-labeled IS. For OCPs, one-to-one IS were used leadingto more reliable quantitation and qualitative analysis by GC-NCI-MS.Identification of the target compounds in the tea matrix was based oncriteria set by Commission Decision 2002/657/EC.20

Quality Control. A positive sample containing bifenthrin andcypermethrin and a positive sample with 4,4′-DDE and dicfol werechosen as quality control samples. The quality control samples wereboth tested and quantified in every batch. A procedural blank, a matrixblank, and QC samples must be run in each batch to check forcontamination, peak identification, and accurate quantification.

Table 3. Experimental Results of Accuracy and Precision in Blank Tea Matrix (n = 6)

average recoveries (%)

low spiked level, 0.010 mg/kg middle spiked level, 0.020 mg/kg high spiked level, 0.100 mg/kg

no. pesticide recovery RSDa RSDb recovery RSDa RSDb recovery RSDa RSDb

1 pentachlorobenzene 94.9 2.4 7.5 103.7 12.1 8.8 90.8 0.9 5.92 α-BHC 121.7 3.2 10.7 111.8 22.3 14.2 104.0 3.5 3.33 hexachlorobenzene 120.6 1.5 1.5 114.9 8.8 14.8 109.7 5.5 8.34 empenthrin 85.2 1.3 1.3 91.6 1.2 16.9 71.4 3.0 3.05 β-BHC 98.0 2.0 4.0 107.0 10.0 12.0 79.0 3.1 10.06 lindane 99.4 2.7 26.1 110.1 10.7 23.2 84.7 2.0 16.77 tefluthrin 87.1 1.3 1.3 92.3 1.7 15.3 95.2 1.3 3.08 δ-BHC 115.8 2.9 17.6 113.0 13.7 19.3 105.1 7.9 27.39 vinclozolin 88.1 2.7 14.0 101.4 17.2 9.0 95.0 5.8 20.810 transfluthrin 92.6 2.2 2.2 89.9 2.0 13.8 101.0 2.2 12.111 heptachlor 94.4 4.9 17.3 114.1 10.8 23.5 87.2 2.1 15.612 o′,p-dicofol 94.9 2.4 14.0 101.4 17.2 9.0 95.0 5.8 20.813 aldrin 66.7 3.5 24.3 78.1 10.0 9.6 67.2 4.1 6.314 dicofol 85.9 3.7 5.5 102.2 10.4 14.3 80.6 10.3 18.915 fenson 98.1 4.1 4.1 77.0 20.3 11.4 76.0 1.6 9.216 oxychlordane 77.4 1.8 10.4 97.5 10.5 7.1 87.7 1.8 10.617 cis-heptachlorepoxide 76.6 3.7 7.5 99.9 15.9 12.6 91.5 2.1 7.818 trans-heptachlorepoxide 77.7 0.7 7.8 82.3 3.5 10.0 72.3 3.4 2.619 trans-chlordane 98.7 3.6 9.5 103.3 19.9 14.3 97.0 4.2 6.820 allethrin 105.3 1.6 3.6 93.6 1.9 9.7 116.6 0.7 9.321 prallethrin 100.1 1.5 19.2 93.5 2.6 8.5 114.5 0.7 20.022 2,4′-DDE 91.2 4.2 2.7 79.5 5.9 9.3 93.5 4.9 12.823 cis-chlordane 68.1 1.7 15.2 95.3 14.5 8.9 96.2 2.9 8.424 endosulfan I 80.0 2.5 13.2 98.8 21.9 12.4 101.4 4.2 8.625 trans-nonachor 89.1 2.9 19.7 90.6 14.9 13.4 88.9 2.6 7.626 chlorfenson 92.8 4.0 18.1 91.7 18.7 18.4 71.3 1.4 2.327 dieldrin 63.6 1.0 5.6 87.9 12.4 10.1 84.6 2.4 6.528 4,4′-DDE 90.2 11.1 22.9 80.3 10.9 10.1 103.1 7.7 5.729 2,4′-DDD 95.2 3.2 12.0 97.9 8.9 9.6 104.4 2.1 4.230 endosulfan II 88.1 0.5 6.8 95.3 13.8 7.8 95.2 2.3 6.631 cis-nonachor 68.3 2.1 3.1 76.8 11.6 9.7 74.9 1.7 2.532 4,4′-DDD 87.5 1.3 1.2 83.5 0.0 12.2 94.3 9.2 7.433 2,4′-DDT 62.5 3.1 10.4 60.1 2.6 3.6 68.7 2.1 2.134 endrin 78.2 8.2 8.2 97.4 7.9 21.6 80.4 0.6 9.335 endosulfan sulfate 88.1 2.2 4.9 86.7 10.0 8.3 90.6 1.5 2.936 4,4′-DDT 87.3 3.1 4.4 81.4 2.1 3.0 86.7 2.6 4.937 tetramethrin (I, II) 85.4 4.2 6.2 81.8 4.2 5.5 102.1 5.9 7.238 bifenthrin 107.3 1.5 8.9 100.3 2.1 1.3 96.8 0.8 1.339 fenpropathrin 113.7 7.8 15.1 96.1 2.4 14.5 103.1 8.8 1.340 phenothrin (I, II) 115.4 2.9 12.0 77.4 1.7 13.8 114.5 0.7 16.241 λ-cyhalothrin (I, II) 82.9 2.8 6.3 102.0 4.2 18.8 106.9 3.9 3.942 acrinathrin 93.2 7.4 13.1 78.6 11.7 17.1 85.3 1.8 11.043 cyphenothrin (I, II, III) 111.0 4.8 4.9 87.9 0.9 14.8 119.9 2.7 9.544 permethrin (I, II) 86.9 2.8 3.1 79.7 4.0 7.9 76.4 14.6 9.145 cyfluthrin (I, II, III, IV) 76.0 1.9 3.1 78.0 4.2 9.7 86.2 5.7 3.946 cypermethrin (I, II, III, IV) 92.4 10.4 18.5 80.7 10.5 9.1 96.4 6.1 7.947 flucythrinate (I, II) 70.4 3.3 20.6 95.5 8.9 13.6 90.9 17.6 10.648 τ-fluvalinate (I, II) 71.4 0.9 2.9 77.1 7.0 7.5 71.5 4.8 7.749 fenvalerate (I, II) 105.5 3.7 18.7 83.6 6.7 6.8 101.8 5.3 14.750 deltamethrin 103.0 3.6 15.9 92.1 8.0 17.6 87.1 6.7 5.8

aInterday recovery RSDs. bIntraday recovery RSDs.

Journal of Agricultural and Food Chemistry Article

dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−71007096

Table4.ResultsforOCPsandPYsin

Chinese

Tea

Samples

MRL(m

g/kg)

total

greentea

scentedtea

no.

compound

EU

China

concn

median

DR%

ER%

concn

median

DR%

ER%

conn

median

DR%

ER%

1HCHs

0.02

0.20

ND−0.377

0.02

24.8

1.0

ND−0.002

0.00

39.5

0.0

ND−0.377

0.02

8.3

4.2

2heptachlor

ND−0.100

0.05

15.8

0.0

ND−0.322

0.01

16.3

0.0

ND−0.099

0.01

8.3

0.0

3dicfol

20ND−2.624

1.10

46.5

0.0

ND−1.872

0.21

39.5

0.0

ND−2.381

0.15

62.5

0.0

4endosulfan

3010

ND−1.802

0.45

63.4

0.0

ND−0.888

0.16

52.1

0.0

ND−1.073

0.14

79.2

0.0

5DDTs

0.02

0.20

ND−0.411

0.10

56.4

4.0

ND−0.159

0.04

46.5

0.0

ND−0.411

0.10

37.5

8.3

6bifenthrin

530

ND−3.848

1.00

63.4

0.0

ND−3.848

0.19

50.0

0.0

ND−2.671

0.18

54.2

0.0

7fenpropathrin

0.02

2ND−0.070

0.00

7.9

0.0

ND−0.070

0.00

11.4

0.0

ND−0.021

0.00

4.2

0.0

8phenothrin

0.1

ND−0.139

0.01

17.8

1.0

ND−0.006

0.01

9.1

0.0

ND−0.139

0.01

37.5

4.2

9λ-cyhalothrin

153

ND−3.244

0.11

55.4

1.0

ND−0.492

0.08

34.1

0.0

ND−3.244

0.06

70.8

4.2

10cyfluthrin

ND−0.055

0.00

6.9

0.0

ND−0.025

0.00

2.3

0.0

ND−0.055

0.00

12.5

0.0

11cyperm

ethrin

0.5

20ND−0.499

0.14

46.5

0.0

ND−0.496

0.04

20.5

0.0

ND−0.499

0.03

58.3

0.0

12τ-fluvalinate

ND−0.887

0.00

8.9

0.0

ND−0.040

0.00

0.0

0.0

ND−0.887

0.00

8.3

0.0

13fenvalerate

0.05

2ND−0.217

0.00

24.8

3.0

ND

0.00

27.3

2.3

ND−0.217

0.00

33.3

8.3

14deltamethrin

55

ND−0.045

0.00

6.9

0.0

ND−0.045

0.00

0.0

0.0

ND−0.010

0.00

12.5

0.0

Table5.ResultsforMultiplePesticidesin

DifferentTea

Samples

MRL(m

g/kg)

dark

tea

oolong

tea

blacktea

no.

compound

EUChina

concn

median

DR%

ER%

concn

median

DR%

ER%

concn

median

DR%

ER%

1HCHsa

0.02

0.20

ND−0.002

0.00

50.0

0.0

ND−0.037

0.00

7.7

0.0

ND−0.010

0.00

7.7

0.0

2heptachlor

ND

0.00

0.0

0.0

ND−0.294

0.05

46.2

0.0

ND−0.054

0.00

7.1

0.0

3dicfol

20ND−0.035

0.02

50.0

0.0

ND−2.624

1.10

69.2

0.0

ND−0.113

0.01

15.4

0.0

4endosulfan

3010

ND−0.017

0.01

12.5

0.0

ND−1.802

0.45

84.6

0.0

ND−0.279

0.09

61.5

0.0

5DDTs

0.02

0.20

ND−0.072

0.05

100.0

0.0

ND−0.202

0.09

100.0

7.7

ND−0.023

0.02

53.8

0.0

6bifenthrin

530

ND−0.154

0.09

75.0

0.0

ND−3.848

1.00

100.0

0.0

ND−0.828

0.05

71.4

0.0

7fenpropathrin

0.02

2ND−0.007

0.00

0.0

0.0

ND−0.070

0.00

15.4

0.0

ND−0.004

0.00

0.0

0.0

8phenothrin

0.1

ND

0.00

0.0

0.0

ND−0.006

0.00

30.8

0.0

ND−0.006

0.00

7.1

0.0

9λ-cyhalothrin

b15

3ND−0.068

0.02

37.5

0.0

ND−0.492

0.11

100.0

0.0

ND−0.200

0.05

57.1

0.0

10cyfluthrin

ND−0.003

0.00

0.0

0.0

ND−0.025

0.00

7.7

0.0

ND−0.006

0.00

14.3

0.0

11cyperm

ethrin

0.5

20ND−0.037

0.02

50.0

0.0

ND−0.496

0.14

84.6

0.0

ND−0.089

0.04

64.3

0.0

12τ-fluvalinate

ND−0.020

0.00

37.5

0.0

ND−0.040

0.00

30.8

0.0

ND

0.00

0.0

0.0

13fenvalerate

0.05

2ND

0.00

0.0

0.0

ND

0.00

0.0

0.0

ND−0.038

0.00

35.7

0.0

14deltamethrin

55

ND

0.00

0.0

0.0

ND−0.045

0.00

30.8

0.0

ND

0.00

0.0

0.0

aThe

BHCs(including

α-BHC,β

-BHC,γ-BHC(lindane),δ-BHC),heptachlors(heptachlor,cis-heptachlorepoxide,trans-heptachlorepoxide),chlordanes(oxychlordane,trans-chlordane,cis-chlordane),

DDTs(2,4′-D

DE,

4,4′-DDE,

2,4′-DDD,4

,4′-D

DD,2

,4′-D

DT,4

,4′-D

DT),andendosulfans

(α-endosulfan,

β-endosulfan,

endosulfansulfate),werecalculated

individually

andthen

addedforthetotal

amounts.bThe

concentrations

ofthetwoor

morethan

twoenantio

mersof

allethrin

,prallethrin

,tetramethrin,phenothrin

,λ-cyhalothrin,cyphenothrin

,permetrin

,cyfulthrin

,cypermethrin,flucythrinate,

τ-fluvalinate,andfenvaleratewerecalculated

together.

Journal of Agricultural and Food Chemistry Article

dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−71007097

■ RESULTS AND DISCUSSION

Sample Preparation. In this research, tea samples weresoaked in hot water for 30 min and then extracted with acetoneand hexane, which can effectively extract the target compoundsand remove water-soluble impurities such as caffeine and teapolyphenols.18 Considering the nonpolar or semipolar proper-ties of OCPs and PYs, cartridges of Florisil, Carb-NH2, diatomite,and neutral aluminum oxide were used to check the cleanupeffect for tea extracts. The results showed that most of thepesticides could not be eluted from the neutral aluminum oxidecartridge, and the recoveries of some pesticides were not satisfiedwith the diatomite column. The Florisil and Carb-NH2 cartridgeswere much more preferred. Considering the low cleanup abilityto the lutein in tea matrix and the lower recoveries for o,p′-DDT(62.1%) and acrinathrin (65.8%) with Carb-NH2 cartridge,the Florisil cartridge was selected. To sufficiently remove thepigments and other impurities such as fatty acids, organic acids,sugars,11,21,22 and extra water from the matrix, the mixture of150 mg of PSA powder and 500 mg of anhydrous sodium sulfatewas placed on the sieve plate of the Florisil cartridge for bettercleanup.GC-NCI-MS and GC-NCI-MS/MS Detection. Although

GC-MS provides qualitative and quantitative information onpesticide residues in foods, there were still some potential dif-ficulties for the accurate qualitation because of the complicatedmatrix effect. For more accurate qualitation and highersensitivity, a GC-MS/MS method under NCI mode for PYs

analysis in tea samples was established for the first time. All of thepositive samples were verified by the GC-MS/MS method.

Method Validation. Validation parameters for quantifica-tion of 31 OCPs and 19 PYs were obtained under the optimalconditions. Good linearity regression for all of the pesticides werein the range of 0.05−1.00 mg/L with correlation coefficients (r)of not less than 0.995 as shown in Table 2.The LOD and LOQ are determined, following IUPAC

recommendation, as the minimum detectable amount of analytesfrom blank sample spiked extract with signal-to-noise ratios(S/N) of 3:1 and 10:1, respectively. The LODs and LOQs were0.02−4.5 and 0.1−15 μg/kg for GC-NCI-MS determination,respectively (Table 2). The LODs for GC-MS/MS determi-nation ranged from 0.1 to 5.0 μg/kg.The accuracy and precision of the method were examined by

the interday and intraday reproducibility of the spiked blanktea samples at levels of 10, 20, and 100 μg/kg. The recoveries,as shown in Table 3, ranged from 61.4 to 119.9% with relativestandard deviations (RSDs) of 0.5−17.7% for interday recoveryand 1.2−18.8% for intraday recovery.To evaluate the matrix effect, six-point (0.05, 0.1, 0.2, 0.4,

0.8, and 1.0 μg/mL with IS 0.2 μg/mL for each) neat solu-tion calibration curves and matrix-matched calibration curveswere constructed. The responses of most pesticides wereslightly enhanced compared with that in the solvent; however,with the internal standards calibration, the matrix enhancementdid not have much influence on the quantitation results.

Table 6. Occurrence of OCPs and PYs in Chinese Tea Samples

DR% MRL VR%

compound concn (mg/kg)greentea

scentedtea

darktea

oolongtea

blacktea GB2763 EU GB EU year ref

HCHs ND−0.377 39.5 8.3 50.0 7.7 7.7 0.02 0.20 24.8 1.0 2013 this researchND−0.385 2.9 2012 26

DDTs ND−0.411 46.5 37.5 100.0 100.0 53.8 0.02 0.20 4.0 2013 this researchND−0.011 2007 1ND−0.044 2012 25ND−0.189 0 0 2012 26

endosulfan ND−1.802 52.1 79.2 12.5 84.6 61.5 30 10 0 0 2013 this researchND−0.115 0 2012 25

dicfol ND−2.624 39.5 62.5 50.0 69.2 15.4 20 0 2013 this researchND−0.992 2007 1

bifenthrin ND−3.848 50.0 54.2 75.0 100.0 71.4 30 5 0 0 2013 this researchND−0.203 2007 10.020−7.020 2006−2008 24

cyhalothrin ND−3.244 34.1 70.8 37.5 100.0 57.1 3 15 1.0 0 2013 this research0.010−0.490 2006−2008 24

cypermethrin ND−0.499 20.5 58.3 50.0 84.6 64.3 20 0.5 0 1.0 2013 this research0.020−1.370 2006−2008 240.010−0.050 2007 23ND−0.106 25

fenvalerate ND−0.217 27.3 33.3 0.0 0.0 35.7 2 0.05 0 3.0 2013 this researchND−0.317 2007 10.010−2.320 2006−2008 240.050−0.250 52.3 73.4 3.0 2007 23

Journal of Agricultural and Food Chemistry Article

dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−71007098

Therefore, considering easy performance, the calibration curveby solvent was preferred.Quality Control Results. The results of the quality control

samples were relatively stable with the RSD of less than 3% for12 batch analysis, indicating the reliable analysis results of all teasamples.Contamination Levels of PYs in Chinese Tea. As shown

in Tables 4 and 5, the most frequently detected PY in Chinesetea was bifenthrin, with the detection rate (DR) of 63.4% atconcentrations of ND−3.848 mg/kg, followed by λ-cyhalothrin(55.4%, ND−3.244 mg/kg), cypermethrin (46.5%, ND−0.499 mg/kg), and fenvalerate (24.8%, ND−0.217 mg/kg).It was reported (Table 6) that the residues of bifenthrin,cyhalothrin, cypermethrin, and fenvalerate in Chinese tea duringthe years of 2006−2008 were 0.020−7.020mg/kg (543 samples),0.010−0.490 mg/kg (423 samples), 0.020−1.370 mg/kg(2321 samples), and 0.010−2.320 mg/kg (7095 samples),respectively.23,24 It was obvious that PYs were still the majorpesticides commonly used in tea plantations in China.Interestingly, residues of PYs in teas differed with tea type.

For example, fenvalerate, a pesticide restricted on tea plantationin China from 1999, was detected only in green tea samplesand scented tea samples with a violation rate (VR) of 3.0%.A study in 200723 reported that the concentration of fenvaleratein Chinese tea samples was in the range of 0.050−0.250 mg/kg,with VR of 73.4% in oolong tea and 52.3% in scented tea.It could be inferred that the usage of fenvalerate on tea plantationwas decreased after strict management by the government.In addition, there were two scented tea samples containingphenothrin and λ-cyhalothrin with the VR of 1.0%.Contamination Levels of OCPs in Chinese Tea. Although

the use of most OCPs has been banned or restricted in China,someOCPs were still detected in Chinese tea, such as endosulfanwith a DR of 63.4% and the concentration range of ND−1.802mg/kg, DDTs (56.4%, ND−0.411 mg/kg), HCHs (24.8%,ND−0.377 mg/kg), and heptachlor (15.8%, ND−0.102 mg/kg).Only three scented tea samples with concentrations of 0.411,0.390, and 0.260 mg/kg, respectively, exceeded the MRL forDDTs (0.20 mg/kg). The major DDT residues in Chinese teawere 2,4′-DDD and 2,4′-DDE. As OCPs have been banned fordecades in China, it was presumed that the DDTs were mainlyfrom the soil or water through the ecological cycle. Moreover,DDTs were used as intermediates in the production of thepesticides dicofol and may occur as a major impurity in the finalproducts.In all, most of the OCPs and PYs were in compliance with the

MRLs established in China and Europe, and thus Chinese tea wassafe enough for human consumption and exportation in terms ofOCP and PY residues.

■ ASSOCIATED CONTENT

*S Supporting InformationFigure 1. This material is available free of charge via the Internetat http://pubs.acs.org.

■ AUTHOR INFORMATION

Corresponding Authors*(H.M.) Phone: +86-010-67770158. E-mail: miaoh@cfsa.net.cn.*(Y.-N.W.) Phone: +86-010-67779118. E-mail: wuyongning@cfsa.net.cn

FundingThe research presented and the preparation of the manuscriptwere supported financially by the National Nature ScienceFoundation of China (No. 30700664) and the NationalScience and Technology Support Program of China (No.2011BAK10B06).NotesThe authors declare no competing financial interest.

■ ABBREVIATIONS USEDSPE, solid phase extraction; GC-MS, gas chromatography−massspectrometry; OCPs, organochlorine pesticides; GC-MS/MS,gas chromatography−tandem mass spectrometry; NCI, negativechemical ionization; MRLs, maximum residue levels; IS, internalstandard; LODs, limits of detection; LOQs, limits ofquantification; RSDs, relative standard deviations; SIM, selectiveion monitoring; EI, electron impact; HCHs, hexachlorocyclo-hexanes; DDTs, dichlorodiphenyltrichloroethanes

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Journal of Agricultural and Food Chemistry Article

dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−71007100