Article pubs.acs.org/JAFC
Organochlorine Pesticides and Pyrethroids in Chinese Tea by Screening and Confirmatory Detection Using GC-NCI-MS and GC-MS/MS Pan 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 were screened and confirmed for the contamination of 31 organochlorine pesticides (OCPs) and 19 pyrethroids (PYs) by gas chromatography−negative chemical ionization−mass spectrometry (GC-NCI-MS) and gas chromatography−tandem mass spectrometry (GC-MS/MS). 50 pesticides, 3 deuterium-labeled PYs, and 24 13C-labeled OCPs were separated well with the limits of detection (LODs) ranging from 0.02 to 4.5 μg/kg for GC-NCI-MS, and the positive samples were verified by GC-MS/MS with LODs 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), and 15.8% (ND−0.100 mg/kg), respectively. KEYWORDS: organochlorine pesticides, pyrethroids, Chinese tea, screening and confirmation, GC-NCI-MS, GC-MS/MS
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residues of pesticides in tea,10 especially for PYs and OCPs. Therefore, establishment of a method for detecting all of the OCPs and PYs in tea samples and a comprehensive survey of OCPs and PYs in Chinese tea samples were necessary and important for human health and tea exportation. Tea matrix is very complex as it contains pigments, caffeine, sugars, organic acids, and other interferences.11 For the pretreatment of tea samples, a number of solvents have been used for multiresidue pesticide extraction, and the most common ones included acetone, ethyl acetate, and acetonitrile. The most commonly employed cleanup techniques comprise liquid− liquid extraction (LLE),12 solid-phase extraction (SPE),13 gel permeation chromatography (GPC), solid-phase microextration (SPME),14 and matrix solid-phase dispersion (MSPD).15 Among these techniques, SPE is being increasingly used in food analysis, especially for tea sample cleanup. The detection techniques include gas chromatography−electron capture detection (GC-ECD),16−18 gas chromatography−mass spectrometry (GC-MS),13,14 and gas chromatography−tandem mass spectrometry (GC-MS/MS) in the EI mode.19
INTRODUCTION Organochlorine pesticides (OCPs) and pyrethroids (PYs) are two kinds of widely used pesticides for the effective control of pests and diseases of plants and animals.1 Due to their low biodegradability 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 shown to have potentially harmful effects on human beings. Some OCPs, including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), aldrin, dieldrin, endrin, chlordane, heptachlor, and hexachlorobenzene, are listed in the Stockholm Convention as persistent organic pollutants (POPs) and have been banned by the United Nations Environment Program (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 also very popular in other foreign countries for its characteristic aroma, flavor, and health benefits.8 China has the largest tea plantation area in the world and is the second largest tea producer.9 PYs are the most commonly used pesticides in tea plantations in China, as the use of OCPs and some organophosphate pesticides with acute toxicity have been gradually banned or restricted. Importing countries, such as the European Union and Japan, have established stringent limits on maximum © 2014 American Chemical Society
Received: Revised: Accepted: Published: 7092
March 13, 2014 June 14, 2014 June 25, 2014 June 25, 2014 dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−7100
Journal of Agricultural and Food Chemistry
Article
Table 1. GC-NCI-MS and GC-MS/MS Parameters for OCPs and PYs GC-NCI-MS no.
pesticide
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
pentachlorobenzene pentachlorobenzene (13C6) α-BHC α-BHC (13C6) hexachlorobenzene hexachlorobenzene (13C6) empenthrin β-BHC β-BHC (13C6) lindane lindane (13C6) tefluthrin δ-BHC δ-BHC (13C6) vinclozolin transfluthrin heptachlor heptachlor (13C10) o′,p-dicofol aldrin aldrin (13C12) dicofol fenson oxychlordane oxychlordane (13C10) cis-heptachlorepoxide cis-heptachlorepoxide (13C10) trans-heptachlorepoxide trans-chlordane trans-chlordane (13C10) allethrin prallethrin 2,4′-DDE 2,4′-DDE (13C12) cis-chlordane endosulfan I endosulfan I (13C9) trans-nonachor trans-nonachor(13C10) chlorfenson dieldrin dieldrin (13C12) 4,4′-DDE 4,4′-DDE (13C12) 2,4′-DDD 2,4′-DDD (13C12) endosulfan II endosulfan II (13C9) cis-nonachor cis-nonachor (13C10) 4,4′-DDD 4,4′-DDD (13C12) 2,4′-DDT 2,4′-DDT (13C12) endrin endrin (13C12) endosulfan sulfate endosulfan sulfate (13C9)
28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58
mol wt (Mw)
retention time (min)
quantitation ion (mau)
GC-MS/MS
qualitative ions (mau)
250.3 256.3 290.8 296.8 284.8 290.8 274.4 290.8 296.8 290.8 296.8 418.7 290.8 296.8 286.1 371.2 373.3 383.3 370.5 364.9 376.9 370.5 268.5 423.8 433.8 389.3 399.3
6.71 6.77 9.076 9.076 9.164 9.164 9.33 9.776 9.776 10.055 10.055 10.79 10.92 10.92 12.07 12.35 12.459 12.459 13.17 13.998 13.998 14.71 14.99 16.105 16.105 16.105 16.105
249.9 255.9 254.9 260.9 283.9 289.9 167.3 254.9 261 254.9 261 241.1 254.9 261 241.2 207.1 299.8 309.9 214.2 236.9 342 250.1 141.2 236.1 431.9 316.1 399.8
251.9 257.9 256.9 259 285.9 291.8 168.4 256.9 263 256.9 262.9 243 256.9 259 243.1 209.1 236.8 307.9 216 329.9 242 252 142.4 349.9 361.8 351.7 327.9
247.9 254 253 262.9 249.9 293.9 169.5 71.6 259.1 71.6 187.2 205.2 71.6 263 244.9 137.3 265.9 311.9 250.1 234.9 239.9 253.8 143.4 351.9 359.9 281.8 290
253.8 259.9 71.6 187.1 287.8 287.9 121.4 70.6 187.1 73.2 259 244.4 73.2 189.1 246.4 210.9 301.9 276 252 331.9 244 216.3 127.4 423.9 242
389.3 409.8 419.8 301.4 300.4 318 330 409.8 406.9 415.9 444.2 454.2 303.2 380.9 392.9 318 330 320 332 406.9 415.9 444.2 454.2 320 332 354.5 355.6 380.9 392.9 422.9 431.9
16.331 17.353 17.353 16.680, 16.753 17.207, 17.436 17.565 17.565 17.841 17.959 17.969 18.092 18.092 18.625 19.146 19.146 19.057 19.057 19.301 19.301 20.398 20.408 20.55 20.55 20.678 20.678 20.733 20.733 20.932 20.932 21.799 21.786
236.9 409.7 419.8 167.3 167.3 246.2 330 266 407.7 414.7 443.6 453.8 176.5 345.8 391.7 319.7 329.9 248.1 260.2 405.7 414.7 443.6 453.8 248.1 260.1 246.1 295.8 272 282 385.7 394.8
353.8 265.9 417.8 168.5 132.4 318 328 264 241.9 250 299.9 309.9 175.1 236.9 395.8 262 322 212.4 262.1 241.9 344.8 333.8 451.8 71.5 262.1 212.1 293.9 236.1 284 351.7 360.7
281.8 301.8 385.9 134.4 168.5 248 260 236.9 373.7 380.8 236.9 451.9 177.8 238.9 358 315.9 326.2 246.1 258 335.8 378.8 299.9 455.8 250
234.9 238.9 276 169.6 133.5 212 258.1 409.8 301.8 242 335.8 455.9 191.3 379.7 241.9 317.9
71.5 238.2 306 358 97.5 97.5
281.1
7093
parent ion (mau)
daughter ions (mau)
collision energy (eV)
167.3
165.5
163
35
241.1
204.9
204.8
45
241.1 207.1
204.9 205.5
240.2 204
25 45
214.1
211.6
35.3
25
250.1 141.3
35.5 77.2
233.8 140.2
25 25
167.3 167.3
165.9 165.6
164.7 163.9
35 35
175.1
111
173.1
15
325.9
73.5 264.2 369.7 250 236.9 343.9 251.8
381.8 392 185.2 250 dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−7100
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Table 1. continued GC-NCI-MS mol wt (Mw)
no.
pesticide
59 60 61 62 63 64 65 66 67 68
4,4′-DDT 4,4′-DDT (13C12) tetramethrin bifenthrin d5-bifenthrin fenpropathrin phenothrin λ-cyhalothrin acrinathrin cyphenothrin
354.5 355.6 331.4 422.9 427.9 349.4 350.4 449.9 541.4 375.5
69 70 71
permethrin d6-cis-permethrin cyfluthrin
391.3 397.3 434.3
72
cypermethrin
416.3
73 74 75 76 77
d6-cis-cypermethrin flucythrinate τ-fluvalinate fenvalerate deltamethrin
422.6 451.4 502.9 419.9 505.2
retention time (min) 22.008 22.008 23.659, 23.993 23.69 23.65 24.19 24.701, 24.940 25.403, 25.738 26.15 26.511, 26.686, 26.744 27.226, 27.472 27.4 28.258, 28.462, 28.557, 28.647 28.868, 29.082, 29.186, 29.257 29.021, 29.210 29.186, 29.593 30.782, 30.930 30.533, 30.930 32.06
quantitation ion (mau)
qualitative ions (mau)
248.1 274 165.3 205.2 391.3 141.4 167.3 205.2 333.1 167.3
262.1 275.8 331.2 386.1 241.1 142.6 168.5 241.1 167.2 168.5
71.6 73.5 167.3 241.1 205.2 221.3 169.5 243 305.1 348.2
133.5 243 242.9 322.2 181.3 206.4 334.5 169.5
207.2 213.2 207.2
209.1 215 209.1
171.2 217 171.2
207.2
209.1
213.1 243.2 294.1 211.2 81.5
215.1 244.3 295.9 213 79.5
daughter ions (mau)
collision energy (eV)
282.8 331.2 386.2
167.2 205.4
163.1 204.3
5 45
141.4 167.3 241.1 333.1 167.3
139.5 165.3 240.4 166.8 165.8
137.9 162.9 204.6 164.7 168.6
35 15 45 25 35
354.1 179.2 173.1
207.1
205.9
203.7
25
207.1
206
204
25
171.3
173.2
207.1
205.8
201.6
25
177.2 199.3 258.2 167.4 137.4
179.2 245.3 502 214.3 296.9
243.2 294.1 211.2 296.9
198.8 293 166.8 79.2
196.7 144.9 164.8 81.4
25 25 5 5
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 recovery studies. Sample Extraction. 2.0 g of ground tea powder was weighed by a 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 hot water (90−100 °C) for 30 min. 20 mL of acetone was added, and the mixture was vortexed for 1 min and then ultrasonicated for 30 min, and then centrifugation was performed at 7000 rpm for 5 min at 4 °C. The extracted solution was transferred and partitioned by 20 mL of hexane with the addition of 1.0 g of NaCl. Two partitions were performed, and the organic solutions were combined and evaporated to near dryness at 30 °C by rotary evaporation. The residues were redissolved with 3 mL of 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 preconditioned with 5.0 mL of acetone/hexane (1:9, v/v) and 5.0 mL of hexane. The extract was applied to the conditioned cartridge and eluted with 10 mL of acetone/hexane (1:9, v/v). The loading and eluting fluid were both collected and evaporated to dryness by a gentle nitrogen stream in a water bath at 30 °C. The residue was redissolved with 200 μL of hexane and filtered through a 0.22 μm PTFE filter for GC-NCI-MS analysis. GC-NCI-MS Analysis. The analysis of the target analytes was performed on a DB-5 ms column (30 m × 0.25 mm i.d. × 0.25 μm) by Bruker 450 GC and 320 MS (triple-quadrupole mass spectrometry, MS workstation version 7.0 software) with the 8400 autosampler (Bruker, USA), operated under NCI for screening. Helium with a purity of not less than 99.999% was used as carrier gas at a constant flow of 1 mL/min. Methane gas was used as the reaction gas for NCI analysis, and the filament current was set to the default value. The GC oven temperature program was as follows: 80 °C kept for 1 min, raised to 200 °C at a rate of 20 °C/min, then raised to 240 °C at a rate of 15 °C/min, then raised to 286 °C at a rate of 5 °C/min, held for 5 min, and finally raised to 300 °C at a rate of 20 °C/min and held for 5 min. The temperature of the injection port and transform line were 250 °C. The splitless injection volume was 1 μL with a solvent delay time of 5 min. The ion source temperature of 230 °C, MS quadrupole temperature of 40 °C, electron multiplier voltage of 1400 V, and ion source energy of 70 eV were used. Analysis was performed in the selected ion monitoring
In this study, a rapid, efficient, and sensitive method for the simultaneous determination of 31 OCPs and 19 PYs in Chinese teas by GC-NCI-MS and GC-MS/MS were developed. The established methods were validated according to the criteria by EU Commission Decision 2002/657/EC,20 and a survey of 101 tea samples was conducted by the established method.
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GC-MS/MS parent ion (mau)
MATERIALS AND METHODS
Materials 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 also obtained 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 at 250 °C for 4 h and kept in a desiccator; sodium chloride (analytical reagent grade) was purchased from Beijing Chemical Industry (Beijing, China); deionized water was obtained from a Milli-Q water purification system (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 from Dr. Ehrenstorfer GmbH (Augsburg, Germany), with purity of not less than 96.0%. Standard Solution. The stock solution for all of the standards and the internal standards (IS) were prepared by accurately weighing a certain amount of the standard powder and then quantitatively dissolving by ethyl acetate at the concentration of 1000 mg/L, respectively. The mixed intermediate standard and internal standard solution were quantitatively diluted from the stock standard solutions with hexane, and the final concentrations of all the individual standards and the internal standards were 2 and 1 mg/L, respectively. All of the standard 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, including green tea (n = 44), scented tea (n = 23), dark tea (n = 8), black tea (n = 13), and oolong tea (n = 13). The tea samples were ground by a homogenizer and filtered through a 40 mesh sieve. The grinding 7094
dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−7100
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Table 2. Linearity Curves, Limits of Detection (LODs), and Limits of Quantitation (LOQs) of 50 Standard Pesticides in Blank Tea Matrix GC-MS no.
pesticide
IS
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
pentachlorobenzene α-BHC hexachlorobenzene empenthrin β-BHC lindane tefluthrin δ-BHC vinclozolin transfluthrin heptachlor o′,p-dicofol aldrin dicofol fenson Oxychlordane cis-heptachlorepoxide trans-heptachlorepoxide trans-chlordane allethrin prallethrin 2,4′-DDE cis-chlordane endosulfan I trans-nonachor chlorfenson dieldrin 4,4′-DDE 2,4′-DDD endosulfan II cis-nonachor 4,4′-DDD 2,4′-DDT endrin endosulfan sulfate 4,4′-DDT tetramethrin (I, II) bifenthrin fenpropathrin phenothrin (I, II) λ-cyhalothrin (I, II) acrinathrin cyphenothrin (I, II, III) permethrin (I, II) cyfluthrin (I, II, III, IV) cypermethrin (I, II, III, IV) flucythrinate (I, II) τ-fluvalinate (I, II) fenvalerate (I, II) deltamethrin
pentachlorobenzene (13C6) α-BHC (13C6) hexachlorobenzene (13C6) d5-bifenthrin β-BHC (13C6) lindane (13C6) d5-bifenthrin δ-BHC (13C6) endosulfan I (13C9) d5-bifenthrin heptachlor (13C10) endosulfan I (13C9) aldrin (13C12) endosulfan I (13C9) endosulfan I (13C9) Oxychlordane(13C10) cis-heptachlorepoxide (13C10) cis-heptachlorepoxide (13C10) trans-chlordane (13C10) d5-bifenthrin d5-bifenthrin 2,4′-DDE (13C12) endosulfan I (13C9) endosulfan I (13C9) trans-nonachor (13C10) endosulfan I (13C9) dieldrin (13C12) 4,4′-DDE (13C12) 2,4′-DDD (13C12) endosulfan II (13C9) cis-nonachor (13C10) 4,4′-DDD (13C12) 2,4′-DDT (13C12) endrin (13C12) endosulfan sulfate (13C9) 4,4′-DDT (13C12) d5-bifenthrin d5-bifenthrin d5-bifenthrin d5-bifenthrin d5-bifenthrin d5-bifenthrin d6-cis-permethrin d6-cis-permethrin d6-cis-cypermethrin d6-cis-cypermethrin d6-cis-cypermethrin d6-cis-cypermethrin d6-cis-cypermethrin d6-cis-cypermethrin
RRF 0.92 1 0.85 0.93 0.94
1 0.95
0.95 1 1.4 0.99
0.97 0.89 1.12 1.18 1.03 1.04 0.94 1 1.19 0.92 1.1
mode (SIM). Pesticides were identified according to retention times, the quantitative ions and three qualitative ions (Table 1), and the chromatogram is shown in the Supporting Information. Four ions were selected following the EU regulation (EEC657/2002). Pesticides were monitored in different time segments, and the dwell time for each ion was 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
GC-MS/MS
r
LOD (μg/kg)
LOQ (μg/kg)
0.9975 0.9999 0.9982 0.9971 0.9959 0.9975 0.9985 0.9969 0.9982 0.9986 0.9970 0.9987 0.9978 0.9968 0.9983 0.9959 0.9997 0.9969 0.9993 0.9981 0.9977 0.9983 0.9985 0.9977 0.9993 0.9959 0.9992 0.9989 0.9993 0.9998 0.9998 0.9961 0.9926 0.9982 0.9981 0.9663 0.9973 0.9974 0.9979 0.9969 0.9967 0.9981 0.9996 0.9968 0.9981 0.9974 0.9946 0.9993 0.9991 0.9954
0.03 0.5 0.03 0.03 0.3 0.1 0.03 1.1 0.04 0.03 3 0.07 1.2 0.07 0.01 0.2 0.2 0.4 0.5 0.01 0.4 1.7 0.2 0.2 2.1 0.05 1.8 4.5 3 0.1 0.3 4.1 4.1 3.2 0.03 0.6 0.3 0.1 0.06 0.7 0.02 0.05 0.1 0.7 0.08 0.06 0.03 0.04 0.02 0.02
0.1 1.7 0.1 0.1 0.9 0.4 0.08 3.6 0.1 0.09 10 0.3 4.2 0.3 0.02 0.6 0.6 1.4 1.8 0.02 1.4 5.6 0.7 0.7 7.1 0.2 5.9 15 10 0.3 0.9 13.6 13.6 10.7 0.08 2 0.9 0.3 0.2 2.3 0.06 0.2 0.4 2.4 0.3 0.2 0.1 0.1 0.08 0.05
LOD (μg/kg)
0.3
0.2 0.3 0.3 0.4 0.4 0.1
4.0 2.1
0.4
2.1 0.7 0.4 4.0 0.2 0.5 0.6 5.0 0.6 0.5 0.3 0.3 0.3 0.2
quantification of the OCPs, quantitative values were calculated using isotope dilution technique through a relative response factor (RRF) calculation. GC-NCI-MS/MS Identification. GC-MS/MS identification was also conducted on a 450GC-320MS under NCI mode. The other parameters were the same as for the GC-NCI-MS method except for the ion source energy. With the ion source energy of 20 eV, ions with larger mass were more easily acquired, which is helpful for MS/MS detection. The mass 7095
dx.doi.org/10.1021/jf5012424 | J. Agric. Food Chem. 2014, 62, 7092−7100
Journal of Agricultural and Food Chemistry
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Table 3. Experimental Results of Accuracy and Precision in Blank Tea Matrix (n = 6) average recoveries (%) low spiked level, 0.010 mg/kg
a
a
no.
pesticide
recovery
RSD
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
pentachlorobenzene α-BHC hexachlorobenzene empenthrin β-BHC lindane tefluthrin δ-BHC vinclozolin transfluthrin heptachlor o′,p-dicofol aldrin dicofol fenson oxychlordane cis-heptachlorepoxide trans-heptachlorepoxide trans-chlordane allethrin prallethrin 2,4′-DDE cis-chlordane endosulfan I trans-nonachor chlorfenson dieldrin 4,4′-DDE 2,4′-DDD endosulfan II cis-nonachor 4,4′-DDD 2,4′-DDT endrin endosulfan sulfate 4,4′-DDT tetramethrin (I, II) bifenthrin fenpropathrin phenothrin (I, II) λ-cyhalothrin (I, II) acrinathrin cyphenothrin (I, II, III) permethrin (I, II) cyfluthrin (I, II, III, IV) cypermethrin (I, II, III, IV) flucythrinate (I, II) τ-fluvalinate (I, II) fenvalerate (I, II) deltamethrin
94.9 121.7 120.6 85.2 98.0 99.4 87.1 115.8 88.1 92.6 94.4 94.9 66.7 85.9 98.1 77.4 76.6 77.7 98.7 105.3 100.1 91.2 68.1 80.0 89.1 92.8 63.6 90.2 95.2 88.1 68.3 87.5 62.5 78.2 88.1 87.3 85.4 107.3 113.7 115.4 82.9 93.2 111.0 86.9 76.0 92.4 70.4 71.4 105.5 103.0
2.4 3.2 1.5 1.3 2.0 2.7 1.3 2.9 2.7 2.2 4.9 2.4 3.5 3.7 4.1 1.8 3.7 0.7 3.6 1.6 1.5 4.2 1.7 2.5 2.9 4.0 1.0 11.1 3.2 0.5 2.1 1.3 3.1 8.2 2.2 3.1 4.2 1.5 7.8 2.9 2.8 7.4 4.8 2.8 1.9 10.4 3.3 0.9 3.7 3.6
middle spiked level, 0.020 mg/kg b
a
RSD
recovery
RSD
7.5 10.7 1.5 1.3 4.0 26.1 1.3 17.6 14.0 2.2 17.3 14.0 24.3 5.5 4.1 10.4 7.5 7.8 9.5 3.6 19.2 2.7 15.2 13.2 19.7 18.1 5.6 22.9 12.0 6.8 3.1 1.2 10.4 8.2 4.9 4.4 6.2 8.9 15.1 12.0 6.3 13.1 4.9 3.1 3.1 18.5 20.6 2.9 18.7 15.9
103.7 111.8 114.9 91.6 107.0 110.1 92.3 113.0 101.4 89.9 114.1 101.4 78.1 102.2 77.0 97.5 99.9 82.3 103.3 93.6 93.5 79.5 95.3 98.8 90.6 91.7 87.9 80.3 97.9 95.3 76.8 83.5 60.1 97.4 86.7 81.4 81.8 100.3 96.1 77.4 102.0 78.6 87.9 79.7 78.0 80.7 95.5 77.1 83.6 92.1
12.1 22.3 8.8 1.2 10.0 10.7 1.7 13.7 17.2 2.0 10.8 17.2 10.0 10.4 20.3 10.5 15.9 3.5 19.9 1.9 2.6 5.9 14.5 21.9 14.9 18.7 12.4 10.9 8.9 13.8 11.6 0.0 2.6 7.9 10.0 2.1 4.2 2.1 2.4 1.7 4.2 11.7 0.9 4.0 4.2 10.5 8.9 7.0 6.7 8.0
b
high spiked level, 0.100 mg/kg
RSD
recovery
RSDa
RSDb
8.8 14.2 14.8 16.9 12.0 23.2 15.3 19.3 9.0 13.8 23.5 9.0 9.6 14.3 11.4 7.1 12.6 10.0 14.3 9.7 8.5 9.3 8.9 12.4 13.4 18.4 10.1 10.1 9.6 7.8 9.7 12.2 3.6 21.6 8.3 3.0 5.5 1.3 14.5 13.8 18.8 17.1 14.8 7.9 9.7 9.1 13.6 7.5 6.8 17.6
90.8 104.0 109.7 71.4 79.0 84.7 95.2 105.1 95.0 101.0 87.2 95.0 67.2 80.6 76.0 87.7 91.5 72.3 97.0 116.6 114.5 93.5 96.2 101.4 88.9 71.3 84.6 103.1 104.4 95.2 74.9 94.3 68.7 80.4 90.6 86.7 102.1 96.8 103.1 114.5 106.9 85.3 119.9 76.4 86.2 96.4 90.9 71.5 101.8 87.1
0.9 3.5 5.5 3.0 3.1 2.0 1.3 7.9 5.8 2.2 2.1 5.8 4.1 10.3 1.6 1.8 2.1 3.4 4.2 0.7 0.7 4.9 2.9 4.2 2.6 1.4 2.4 7.7 2.1 2.3 1.7 9.2 2.1 0.6 1.5 2.6 5.9 0.8 8.8 0.7 3.9 1.8 2.7 14.6 5.7 6.1 17.6 4.8 5.3 6.7
5.9 3.3 8.3 3.0 10.0 16.7 3.0 27.3 20.8 12.1 15.6 20.8 6.3 18.9 9.2 10.6 7.8 2.6 6.8 9.3 20.0 12.8 8.4 8.6 7.6 2.3 6.5 5.7 4.2 6.6 2.5 7.4 2.1 9.3 2.9 4.9 7.2 1.3 1.3 16.2 3.9 11.0 9.5 9.1 3.9 7.9 10.6 7.7 14.7 5.8
Interday recovery RSDs. bIntraday recovery RSDs. Quality Control. A positive sample containing bifenthrin and cypermethrin and a positive sample with 4,4′-DDE and dicfol were chosen as quality control samples. The quality control samples were both tested and quantified in every batch. A procedural blank, a matrix blank, and QC samples must be run in each batch to check for contamination, peak identification, and accurate quantification.
parameters are provided in Table 1. The positive samples of pyrethroids were verified by the established GC-NCI-MS/MS method for the limited isotope-labeled IS. For OCPs, one-to-one IS were used leading to more reliable quantitation and qualitative analysis by GC-NCI-MS. Identification of the target compounds in the tea matrix was based on criteria set by Commission Decision 2002/657/EC.20 7096
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2 5
0.05 5
concn ND−0.377 ND−0.100 ND−2.624 ND−1.802 ND−0.411 ND−3.848 ND−0.070 ND−0.139 ND−3.244 ND−0.055 ND−0.499 ND−0.887 ND−0.217 ND−0.045
0.02 0.05 1.10 0.45 0.10 1.00 0.00 0.01 0.11 0.00 0.14 0.00 0.00 0.00
median
total
7097
2 5
0.05 5
concn ND−0.002 ND ND−0.035 ND−0.017 ND−0.072 ND−0.154 ND−0.007 ND ND−0.068 ND−0.003 ND−0.037 ND−0.020 ND ND
0.00 0.00 0.02 0.01 0.05 0.09 0.00 0.00 0.02 0.00 0.02 0.00 0.00 0.00
median
dark tea
50.0 0.0 50.0 12.5 100.0 75.0 0.0 0.0 37.5 0.0 50.0 37.5 0.0 0.0
DR%
24.8 15.8 46.5 63.4 56.4 63.4 7.9 17.8 55.4 6.9 46.5 8.9 24.8 6.9
DR%
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
ER%
1.0 0.0 0.0 0.0 4.0 0.0 0.0 1.0 1.0 0.0 0.0 0.0 3.0 0.0
ER%
concn
ND−0.037 ND−0.294 ND−2.624 ND−1.802 ND−0.202 ND−3.848 ND−0.070 ND−0.006 ND−0.492 ND−0.025 ND−0.496 ND−0.040 ND ND−0.045
concn
ND−0.002 ND−0.322 ND−1.872 ND−0.888 ND−0.159 ND−3.848 ND−0.070 ND−0.006 ND−0.492 ND−0.025 ND−0.496 ND−0.040 ND ND−0.045
0.00 0.05 1.10 0.45 0.09 1.00 0.00 0.00 0.11 0.00 0.14 0.00 0.00 0.00
median
oolong tea
0.00 0.01 0.21 0.16 0.04 0.19 0.00 0.01 0.08 0.00 0.04 0.00 0.00 0.00
median
green tea
7.7 46.2 69.2 84.6 100.0 100.0 15.4 30.8 100.0 7.7 84.6 30.8 0.0 30.8
DR%
39.5 16.3 39.5 52.1 46.5 50.0 11.4 9.1 34.1 2.3 20.5 0.0 27.3 0.0
DR%
0.0 0.0 0.0 0.0 7.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
ER%
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.3 0.0
ER%
conn
ND−0.010 ND−0.054 ND−0.113 ND−0.279 ND−0.023 ND−0.828 ND−0.004 ND−0.006 ND−0.200 ND−0.006 ND−0.089 ND ND−0.038 ND
concn
ND−0.377 ND−0.099 ND−2.381 ND−1.073 ND−0.411 ND−2.671 ND−0.021 ND−0.139 ND−3.244 ND−0.055 ND−0.499 ND−0.887 ND−0.217 ND−0.010
0.00 0.00 0.01 0.09 0.02 0.05 0.00 0.00 0.05 0.00 0.04 0.00 0.00 0.00
median
black tea
0.02 0.01 0.15 0.14 0.10 0.18 0.00 0.01 0.06 0.00 0.03 0.00 0.00 0.00
median
scented tea
7.7 7.1 15.4 61.5 53.8 71.4 0.0 7.1 57.1 14.3 64.3 0.0 35.7 0.0
DR%
8.3 8.3 62.5 79.2 37.5 54.2 4.2 37.5 70.8 12.5 58.3 8.3 33.3 12.5
DR%
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
ER%
4.2 0.0 0.0 0.0 8.3 0.0 0.0 4.2 4.2 0.0 0.0 0.0 8.3 0.0
ER%
The 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′-DDE, 4,4′-DDE, 2,4′-DDD, 4,4′-DDD, 2,4′-DDT, 4,4′-DDT), and endosulfans (α-endosulfan, β-endosulfan, endosulfan sulfate), were calculated individually and then added for the total amounts. bThe concentrations of the two or more than two enantiomers of allethrin, prallethrin, tetramethrin, phenothrin, λ-cyhalothrin, cyphenothrin, permetrin, cyfulthrin, cypermethrin, flucythrinate, τ-fluvalinate, and fenvalerate were calculated together.
a
20
0.5
10 0.20 30 2
0.20
China
3
0.02
1 2 3 4 5 6 7 8 9 10 11 12 13 14
20 30 0.02 5 0.02 0.1 15
EU
compound
HCHsa heptachlor dicfol endosulfan DDTs bifenthrin fenpropathrin phenothrin λ-cyhalothrinb cyfluthrin cypermethrin τ-fluvalinate fenvalerate deltamethrin
no.
MRL (mg/kg)
Table 5. Results for Multiple Pesticides in Different Tea Samples
20
0.5
10 0.20 30 2
0.20
China
3
0.02
1 2 3 4 5 6 7 8 9 10 11 12 13 14
20 30 0.02 5 0.02 0.1 15
EU
compound
HCHs heptachlor dicfol endosulfan DDTs bifenthrin fenpropathrin phenothrin λ-cyhalothrin cyfluthrin cypermethrin τ-fluvalinate fenvalerate deltamethrin
no.
MRL (mg/kg)
Table 4. Results for OCPs and PYs in Chinese Tea Samples
Journal of Agricultural and Food Chemistry Article
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Table 6. Occurrence of OCPs and PYs in Chinese Tea Samples DR% compound
concn (mg/kg)
MRL
VR%
green tea
scented tea
dark tea
oolong tea
black tea
GB2763
EU
GB
EU
24.8 2.9
1.0
2013 2012
this research 26
4.0
this research 1 25 26
HCHs
ND−0.377 ND−0.385
39.5
8.3
50.0
7.7
7.7
0.02
0.20
DDTs
ND−0.411 ND−0.011 ND−0.044 ND−0.189
46.5
37.5
100.0
100.0
53.8
0.02
0.20
endosulfan
ND−1.802 ND−0.115
52.1
79.2
12.5
84.6
61.5
dicfol
ND−2.624 ND−0.992
39.5
62.5
50.0
69.2
15.4
bifenthrin
ND−3.848 ND−0.203 0.020−7.020
50.0
54.2
75.0
100.0
71.4
30
5
cyhalothrin
ND−3.244 0.010−0.490
34.1
70.8
37.5
100.0
57.1
3
15
cypermethrin
ND−0.499 0.020−1.370 0.010−0.050 ND−0.106
20.5
58.3
50.0
84.6
64.3
20
fenvalerate
ND−0.217 ND−0.317 0.010−2.320 0.050−0.250
27.3
33.3
0.0
0.0
35.7
2
■
52.3
73.4
30
year
ref
0
0
2013 2007 2012 2012
0
0 0
2013 2012
this research 25
0
2013 2007
this research 1
0
0
2013 2007 2006−2008
this research 1 24
1.0
0
2013 2006−2008
this research 24
0.5
0
1.0
2013 2006−2008 2007
this research 24 23 25
0.05
0
3.0
2013 2007 2006−2008 2007
this research 1 24 23
10
20
3.0
analysis in tea samples was established for the first time. All of the positive samples were verified by the GC-MS/MS method. Method Validation. Validation parameters for quantification of 31 OCPs and 19 PYs were obtained under the optimal conditions. Good linearity regression for all of the pesticides were in 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 analytes from blank sample spiked extract with signal-to-noise ratios (S/N) of 3:1 and 10:1, respectively. The LODs and LOQs were 0.02−4.5 and 0.1−15 μg/kg for GC-NCI-MS determination, respectively (Table 2). The LODs for GC-MS/MS determination 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 blank tea 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 relative standard deviations (RSDs) of 0.5−17.7% for interday recovery and 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 solution calibration curves and matrix-matched calibration curves were constructed. The responses of most pesticides were slightly enhanced compared with that in the solvent; however, with the internal standards calibration, the matrix enhancement did not have much influence on the quantitation results.
RESULTS AND DISCUSSION Sample Preparation. In this research, tea samples were soaked in hot water for 30 min and then extracted with acetone and hexane, which can effectively extract the target compounds and remove water-soluble impurities such as caffeine and tea polyphenols.18 Considering the nonpolar or semipolar properties of OCPs and PYs, cartridges of Florisil, Carb-NH2, diatomite, and neutral aluminum oxide were used to check the cleanup effect for tea extracts. The results showed that most of the pesticides could not be eluted from the neutral aluminum oxide cartridge, and the recoveries of some pesticides were not satisfied with the diatomite column. The Florisil and Carb-NH2 cartridges were much more preferred. Considering the low cleanup ability to 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 the pigments and other impurities such as fatty acids, organic acids, sugars,11,21,22 and extra water from the matrix, the mixture of 150 mg of PSA powder and 500 mg of anhydrous sodium sulfate was placed on the sieve plate of the Florisil cartridge for better cleanup. GC-NCI-MS and GC-NCI-MS/MS Detection. Although GC-MS provides qualitative and quantitative information on pesticide residues in foods, there were still some potential difficulties for the accurate qualitation because of the complicated matrix effect. For more accurate qualitation and higher sensitivity, a GC-MS/MS method under NCI mode for PYs 7098
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Funding
Therefore, considering easy performance, the calibration curve by solvent was preferred. Quality Control Results. The results of the quality control samples were relatively stable with the RSD of less than 3% for 12 batch analysis, indicating the reliable analysis results of all tea samples. Contamination Levels of PYs in Chinese Tea. As shown in Tables 4 and 5, the most frequently detected PY in Chinese tea was bifenthrin, with the detection rate (DR) of 63.4% at concentrations 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 during the years of 2006−2008 were 0.020−7.020 mg/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 major pesticides 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 plantation in China from 1999, was detected only in green tea samples and scented tea samples with a violation rate (VR) of 3.0%. A study in 200723 reported that the concentration of fenvalerate in 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 plantation was decreased after strict management by the government. In addition, there were two scented tea samples containing phenothrin 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, some OCPs were still detected in Chinese tea, such as endosulfan with a DR of 63.4% and the concentration range of ND− 1.802 mg/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 for DDTs (0.20 mg/kg). The major DDT residues in Chinese tea were 2,4′-DDD and 2,4′-DDE. As OCPs have been banned for decades in China, it was presumed that the DDTs were mainly from the soil or water through the ecological cycle. Moreover, DDTs were used as intermediates in the production of the pesticides dicofol and may occur as a major impurity in the final products. In all, most of the OCPs and PYs were in compliance with the MRLs established in China and Europe, and thus Chinese tea was safe enough for human consumption and exportation in terms of OCP and PY residues.
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The research presented and the preparation of the manuscript were supported financially by the National Nature Science Foundation of China (No. 30700664) and the National Science and Technology Support Program of China (No. 2011BAK10B06). Notes
The authors declare no competing financial interest.
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ABBREVIATIONS USED SPE, solid phase extraction; GC-MS, gas chromatography−mass spectrometry; OCPs, organochlorine pesticides; GC-MS/MS, gas chromatography−tandem mass spectrometry; NCI, negative chemical ionization; MRLs, maximum residue levels; IS, internal standard; LODs, limits of detection; LOQs, limits of quantification; RSDs, relative standard deviations; SIM, selective ion monitoring; EI, electron impact; HCHs, hexachlorocyclohexanes; DDTs, dichlorodiphenyltrichloroethanes
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REFERENCES
AUTHOR INFORMATION
Corresponding Authors
*(H.M.) Phone: +86-010-67770158. E-mail:
[email protected]. *(Y.-N.W.) Phone: +86-010-67779118. E-mail: wuyongning@ cfsa.net.cn 7099
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