Analysis of Pyrethroid Pesticide Residues in Water Samples by Dispersion Method in Liquid Phase SPME Microextraction and Gas Chromatography
3
(College of Science, Hebei Agricultural University, Key Laboratory of Bioinorganic Chemistry, Baoding 071001)
Abstract A new method for high-sensitivity determination of seven pyrethroid pesticide residues in water samples was established by combining dispersion liquid 2-liquid microextraction (DLLME) and gas chromatography 2 electron capture detection (GC2ECD) technology. The factors affecting the extraction enrichment efficiency were optimized, and the extraction conditions were selected as: 5.0 mL
Add 1.0 μL chlorobenzene and 1.0 mL acetone to the sample solution, disperse and mix well, centrifuge at 5000 r / min for 5 min, and extract the extraction solvent chlorobenzene for direct analysis. Under optimized conditions, the enrichment multiples of the seven pyrethroid pesticides are as high as 708 to 1087 times. Taking α2 six six six as the internal standard, the seven pyrethroid pesticides have a good linear relationship in the range of 0.8 to 600 μg / L, and the number of relationships included in the linear phase Baidu website is between 0.9990 to 0.9999; The detection limit is
0. 04 ～ 0. 10μg / L (S / N = 3). This method has been applied to the analysis of actual water samples such as tap water, well water and river water.
Between 7610% and 116. 0%; the relative standard deviation is between 3.1% and 7.2%. The method has the characteristics of simple operation, high enrichment efficiency and high sensitivity, and can meet the detection requirements of pyrethroid pesticide residues in water samples.
Keywords dispersive liquid phase microextraction, gas chromatography, pyrethroid pesticides, water sample 2007209211 received; 2007212205 accepted by the Department of Natural Science Foundation of Hebei Province (NO. B2006000413) and the Research Fund of Hebei Agricultural University
3 E2mail: wangzhi @ hebau. Edu. Cn
1 Introduction Pyrethroid (pyrethroid) pesticides are a class of important synthetic pesticides that are widely used at present. With the expansion of the amount and scope of use, it will flow into the water body in large quantities with the drainage of farmland and the rinsing of the atmosphere by rainfall, which will not only poison fish, shellfish and other aquatic animals, but also seriously harm human health through drinking water. Foreign countries have made strict restrictions on its use, for example, the World Health Organization (WHO) drinking water quality guidelines require that the concentration of permethrin in drinking water should be less than 300μg / L. Therefore, it is of great significance to establish an analytical method for pyrethroid pesticide residues in water samples.
At present, the methods for determining the content of pyrethroid pesticides are mainly gas chromatography (GC) [1,2], gas chromatography 2 mass spectrometry (GC2
MS) [3] and liquid chromatography (HPLC) [4, 5] etc. The traditional sample pretreatment technology has the disadvantages of complicated and time-consuming operation, and the need to use a large amount of organic solvent accounting examinations that are toxic and harmful to the human body and the environment. Therefore, the development of new techniques for sample preparation that saves time and has high efficiency and low organic solvent consumption has become one of the hotspots in analytical chemistry research [6]. In recent years, a variety of microextraction techniques have been developed, such as solid phase microextraction [7], liquid phase microextraction [8], membrane extraction [9], etc. Assadi et al. [10] reported for the first time the technology of dispersive liquid microextraction (dispersive liquid2liquid microextrac2
tion, DLLME). Adding more than ten microliters of organic solvent to the sample solution, dispersing and mixing, centrifugal separation, the extraction solvent can be directly injected for analysis. This method integrates sampling, extraction and concentration into one, which is simple, fast, low cost, environmentally friendly and high in enrichment efficiency [10-12]. Research in this area has not been reported in China. In this experiment, a new method for the determination of the residues of 7 pyrethroid pesticides in water samples was established by the combination of dispersion liquid 2-liquid microextraction and gas chromatography. A satisfactory result was achieved.
2 Experimental part
2. 1 Instruments and reagents
GC9790â…¡ capillary gas chromatograph (China Fuli Company), equipped with electron capture detector (ECD); TD5A centrifuge (Changsha Yingtai Instrument Co., Ltd.).
Standards of α2 hexahexahexafluoride, cypermethrin, deltamethrin, deltamethrin, fenvalerate, cyhalothrin, cyfluthrin and permethrin standard at the concentration of 100.0 mg / L (Monitoring Institute); The remaining reagents are all made by Dongao Accounting Analytical Pure; the water is double distilled water.
The standard solution of 7 kinds of pyrethroid pesticides at 100. 0 mg / L was diluted with water to a mixed standard solution of 5.0 mg / L. The internal standard α2 was diluted with water to a stock solution with a concentration of 1.0 mg / L.
Volume 36
Research Report of Analytical Chemistry (FENXIHUAXUE) in June 2008
Chinese Journal ofAnalytical Chemistry
Issue 6
765 ～ 769
2. 2 chromatographic conditions
KB25 quartz capillary column (30 m × 0.23 mm × 0.25 μm, 5% phenyldimethyl polysiloxane column); inlet temperature
270 ℃; detector temperature 300 ℃; column temperature: temperature programmed: 70 ℃ (1.5 min)
22 ℃ / min
230 ℃
5 ℃ / min
285 ℃
(12 min); Carrier gas: high purity N2 (≥99.999%), flow rate 3.0 mL / min, makeup gas 30 mL / min; injection mode: splitless mode for the first 2 min, and then use Split mode, split ratio 1:10, injection volume is 1μL.
2. 3 Dispersion liquid 2-liquid micro-extraction operation method Tap water, well water and river water samples are vacuum filtered by 0.45μm microporous membrane. In a 10 mL spiked centrifuge tube, add
5. 0 mL sample solution, 10. 0 μL chlorobenzene (extraction solvent), 1.0 mL acetone (dispersant), and gently shake for 1 min to form a water / acetone / chlorobenzene emulsion system. Chlorobenzene is evenly dispersed in the aqueous phase, placed at room temperature for 2 min, centrifuged at 5000 r / min for 5 min, the extraction solvent chlorobenzene dispersed in the aqueous phase is deposited on the bottom of the test tube, and 1 μL of the extraction solvent is drawn directly into the micro-sampler. SAMPLE.
2. 4 Drawing the standard curve Pipette appropriate mixed standard solution (5.0 mg / L) of 7 pyrethroid pesticides into a 50 mL volumetric flask, add 250 μL 1.0 mg / L
The internal standard solution was made up with water to a volume to make a series of mixed standard solutions with concentrations of 0.80, 2.0, 10.0, 30.0, 200.0 and 600.0 μg / L. Each sample was extracted according to the method in Section 2.3 and directly injected for analysis. Each concentration was measured three times in parallel, and the ratio of the analyte to the internal standard peak area Y versus the concentration X (μg / L) was used to make a standard curve (analytes with isomers are the sum of the peak areas of the peaks Peak area of ​​the substance).
3 Results and discussion The sample solutions used in the optimization experiment were 7 pyrethroid pesticides with a concentration of 2.0 μg / L and 5.0 μg / Lα2 six six six (internal standard)
Mixture.
3. 1 Selection of extraction solvent The choice of extraction solvent is an important factor that affects the extraction efficiency. The first condition to be satisfied by the extraction solvent is that its density must be greater than that of water, followed by the large dissolving ability of the substance to be tested. Chlorobenzene (density 1.11 g / mL), carbon tetrachloride (density 1.59 g / mL) and bromobenzene were investigated
(Density 1.50 g / mL) The extraction ability of pyrethroid pesticides in water samples showed that the extraction efficiency using chlorobenzene was the best. So choose chlorobenzene as the extractant.
3.2 Selection of dispersant and volume of dispersant The choice of dispersant is a key factor that affects the extraction efficiency of this method. It is required that the dispersant not only has good solubility in the extraction solvent but also can be miscible with water, so that the extraction solvent is in The water phase is dispersed into fine droplets, which increases the contact area with the analyte, thereby improving the extraction efficiency. In this experiment, SPME investigated the extraction effect when acetone, acetonitrile and methanol were used as dispersants. The experimental results showed that the extraction effect of acetone was the best, so acetone was used as the dispersant in this experiment.
The volume of the dispersant acetone directly affects the formation of the "water / acetone / chlorobenzene emulsion" system, which causes the degree of dispersion of the extractant in water to change and affect the extraction efficiency. The effect of acetone volume (0.5, 0.8, 1.0 and 1.2 mL) on the extraction efficiency was investigated. The experimental results showed that the extraction efficiency first increased with the increase of the acetone volume and reached at 1.0 mL The maximum value then decreases as the volume of acetone increases.
This is because when the volume of acetone is small, the extractant is not uniformly dispersed in the aqueous phase, and the extraction efficiency is low; when the volume of acetone is large, the solubility of the test substance in water is increased, and the extraction efficiency is low. Therefore, the volume of acetone is 1.0 mL.
3. 3 Selection of extraction time In the two-liquid microextraction of the dispersion, the extraction time refers to the period between the injection of chlorobenzene and acetone into the aqueous phase before the mixture starts to centrifuge. The effect of extraction time (3, 10, 20, 30 and 40 min) on extraction efficiency was investigated. The results show that the extraction time has no significant effect on the extraction efficiency. This is because after the solution forms an emulsion, the contact area between the organic solvent and the aqueous phase is large, and the analyte can be quickly transferred from the aqueous phase to the organic phase, and quickly To achieve two-phase balance. The extraction time is 3 min.
3.4 Effect of salt concentration The effect of salt concentration on extraction efficiency was investigated by adding NaCl (0 ～ 5%) to the solution to be tested. The results show that with
As the NaCl concentration increases, the measured recovery rate decreases. This is because as the ionic strength increases, the solubility of the organic extractant in the aqueous phase decreases
(The corresponding enrichment factor also decreases), the volume of the organic phase increases. So no salt was added in the experiment.
7 66 Analytical Chemistry Volume 36 Figure 1 Standard chromatograms of 7 pyrethroid pesticides (both at a concentration of 2.0 μg / L)
Fig. 1 Chromatogram of samp le standard at each concen2
tration of 2. 0μg / L for 7 pyrethroid pesticides
1. Internal standard α2 å…å…å… (internal standard α2benzene hexachloride);
2. Fenvalerate (fenp ropathrin); 3, 4. Cypermethrin (lambda2cy2
halothrin); 5, 6. permethrin; 7, 8, 9. cyfluthrin
(cyhfluthrin); 10, 11, 12. cypermethrin; 13, 14.
Fenvalerate (fenvalerate); 15, 16. deltamethrin (deltamethrin).
3.5 The accuracy, linear range, and detection limit of the method were extracted and determined under a series of standard solutions under optimized experimental conditions. The results are shown in Table 1. The 7 pyrethroid pesticides
0.8 to 600μg / L has a good linear relationship. The detection limit is between 0.04 ～ 0.10μg / L, which can fully meet the measurement of actual samples. For example, the detection limit of deltamethrin is 0.08μg / L, which is far lower than the national standard [13] 0. 02 mg / L, also lower than the detection limit of the national standard [14] (0. 0002 mg / L). The detection limit of permethrin is
0. 10μg / L, far lower than the maximum 300μg / L limit required by the third edition of the WHO Guidelines for Drinking Water Quality. The standard sample chromatogram is shown in Figure 1.
The mixed standard solution samples containing 20, 100 and 400 μg / L pyrethroid pesticides were measured in parallel five times.
2. Between 3% and 5.1%.
3. The enrichment factor of method 6 is calculated as follows: The concentration of the organic phase is calculated. The concentration of 7 pyrethroid pesticides prepared with chlorobenzene as the solvent is 015,
1. 0, 2.0 and 3.0 mg / L of the standard mixed solution, using the peak area versus concentration as the standard curve of 7 pyrethroid pesticides, and the organic phase concentration was obtained based on the measured peak area of ​​the sample. The enrichment factor F is the ratio of the concentration in the final organic phase online lecture to the initial concentration in the aqueous solution. The results showed that the enrichment multiples of the seven pyrethroid pesticides were as high as 708 to 1087 times (see Table 1).
Table 1 Detection limits of linear equations, correlation coefficients and methods of 7 pyrethroid pesticides
Table 1 Regression equations, correlation coefficients and limits of detections (LODs) for 7 pyrethroid pesticides
pesticide
Pesticides
Linear range
Linear range
(μg / L)
Regression equation
Regression
equation
Correlation coefficient (r)
Correlation
coefficient
Enrichment multiple
Enrichment
factor
The detection limit
LOD
(μg / L)
Fenp ropathrin 0.8 to 600 Y = 29. 72X + 0.33 0.99 994 838 0.04
Cyhalothrin Lambda2cyhalothrin 0. 8 ～ 600 Y = 77. 49X + 0. 29 0. 9999 1075 0. 04
Permethrin 0.8 to 600 Y = 11. 40X + 0.17 0.995 1087 0. 10
Cyfluthrin 0.8 to 600 Y = 50. 76X + 0.30 0.9990 832 0.08
Cypermethrin 0. 8 ～ 600 Y = 63. 48X + 0. 33 0. 9991 890 0. 08
Fenvalerate 0. 8 ～ 600 Y = 62. 56X + 0.23 0.996 835 0.06
Deltamethrin Deltamethrin 0.8 ~ 600 Y = 51.78X + 0.21 0.999993 708 0.08
3. 7 Sample determination Figure 2 River water sample chromatogram
Fig. 2 Chromatogram of riverwater samp le
1. α2 å…å…å… (α2benzene hexachloride); 2. cyhalothrin
(lambda2cyhalothrin); 3, 4. Fenvalerate (fenvalerate).
According to the above chromatographic method, the samples of river water, well water and tap water in this area were determined. Take 5.0 mL of the sample solution in a centrifuge tube and measure according to the "2.3" method. Residues of pyrethroid pesticides were not detected in well water and tap water samples. Residues of cyfluthrin and fenvalerate in river water samples were 0.21 and 0.16 μg / L, respectively. The chromatogram of river water samples is shown in Figure 2. Current national water quality standards for training and counseling tables GB 38382
2002 [14] only stipulates that the detection limit of deltamethrin pesticide residue determination method is 0.2 μg / L, and its maximum allowable limit is 0.02 mg / L. The detection limit of deltamethrin in this method is 0.08μg / L, which can meet the requirements of the measurement sensitivity.
For the measured water samples, the standard addition method was used to measure 5 times in parallel at 3 concentration levels, and the recovery rate and relative standard deviation were calculated. The results are shown in Table 2. The recovery rate of the 7 pyrethroid pesticides was 76.0% ~ 116. 0%; the relative standard deviation RSD is less than 7.2%, the precision and reproducibility of this method are satisfactory.
Issue 6 Zang Xiaohuan et al .: Dispersed liquid phase microextraction 2 gas chromatography combined with analysis of pyrethroid pesticide residues in water samples 7 67
Table 2 Determination and recovery rate of pyrethroid pesticide residues in river water, well water and tap water
Table 2 Determinations of pyrethroid pesticide residues and sp iked recoveries in river, well and tap waters samp les
pesticide
Pesticides
Spiked amount in water sample
Sp iked
(μg / L)
Riverwater (n = 5)
Detection amount
Found
(μg / L)
Recovery rate
Recovery
(%)
RSD
(%)
Well water (n = 5)
Detection amount
Found
(μg / L)
Recovery rate
Recovery
(%)
RSD
(%)
Tap water (n = 5)
Detection amount
Found
(μg / L)
Recovery rate
Recovery
(%)
RSD
(%)
Fenp ropathrin
0 ND ND ND
5 5. 2 104. 0 3. 9 5. 1 102. 0 4. 6 5. 1 102. 0 5. 2
20 18. 9 94. 5 5. 2 18. 4 92. 0 5. 1 17. 9 89. 5 4. 7
Cyhalothrin
Lambda2cyhalothrin
0 0. 21 3. 4 ND ND
5 4. 9 93. 8 4. 3 4. 9 98. 0 3. 9 4. 8 96. 0 3. 7
20 21. 2 104. 9 4. 9 19. 5 97. 5 3. 7 20. 2 101. 0 4. 8
Permethrin
0 ND ND ND
5 3. 8 76. 0 6. 2 3. 9 78. 0 3. 1 4. 1 82. 0 4. 3
20 15. 7 78. 5 5. 1 17. 0 85. 0 5. 3 17. 5 87. 5 3. 4
Cyfluthrin
0 ND ND ND
5 5. 7 114. 0 5. 8 5. 2 104. 0 5. 2 4. 8 96. 0 3. 3
20 22. 5 112. 5 4. 9 21. 2 106. 0 3. 2 18. 9 94. 5 5. 1
Cypermethrin
0 ND ND ND
5 5. 87 116. 0 7. 2 5. 1 102. 0 4. 8 5. 2 104. 0 6. 4
20 21. 9 109. 5 6. 4 18. 9 94. 5 3. 1 19. 0 95. 0 4. 6
Fenvalerate
0 ND ND ND
5 5. 4 104. 8 5. 1 5. 3 106. 0 5. 5 5. 4 108. 0 4. 1
20 21. 4 106. 2 6. 3 21. 8 109. 0 4. 3 21. 0 105. 0 3. 7
Deltamethrin
0 ND ND ND
5 5. 3 106. 0 4. 7 5. 2 104. 0 4. 7 5. 3 106. 0 5. 4
20 22. 0 110. 0 6. 5 21. 1 105. 5 4. 5 18. 7 93. 5 3. 1
ND: not detected.
References
1 Wan Yi2Qun (万 益群), Yan Ai2Ping (鄢爱平), XieMing2Yong (谢明勇). Chinese J. Anal. Chem. (Analytical Chemistry), 2005,
33 (5): 614 ～ 618
2 Sharif Z, Man YBC, Hamid NSA, Keat C CJ Chrom atogr. A, 2006, 1127 (1/2): 254 ～ 261
3 L i Feng2Ge (æŽé”‹ æ ¼), Quan Xiao2Dun (å…¨ 晓 Shield). Chinese J. Anal. Chem. (Analytical Chemistry), 2005, 33 (6): 838 ～ 842
4 Wen Yu2Yun (温裕云), Gong Zhen2Bin (弓 振 æ–Œ), Yao J ian2Min (姚剑æ•). Chinese J. Anal. Chem. (Analytical Chemistry),
2005, 33 (3): 301 ～ 304
5 DuanWei (段 伟), Li Zheng2Guo (æŽæ£å›½), Wang Guo2Min (王国民), Yang Ying2Wu (æ¨ è¿Ž ä¼), Li Ying2Guo (æŽ åº” 国), Xia Yu2Xian (å¤ çŽ‰ å…ˆ). Chinese J. Anal. Chem. (Analytical Chemistry) , 2006, 34 (12): 1776 ～ 1778
6 Raynie D E. Anal. Chem., 2004, 76: 4659 ～ 4664
7 Arthur CL, Pawliszyn J. Anal. Chem., 1990, 62: 2145 ～ 2148
8 JeannotM A, Cantwell F. Anal. Chem., 1996, 68: 2236 ～ 2240
9 Psillakis E, Kalogerakis N. Trends Anal. Chem., 2002, 21 (1): 53 ～ 64
10 RezaeeM, Assadi Y, Milani HosseiniM R, Aghaee E, Ahmadi F, Berijani SJ Chrom atogr. A, 2006, 1116: 1 ～ 9
11 Berijani S, Assadi Y, AnbiaM, Milani HosseiniM R, Aghaee EJ Chrom atogr. A, 2006, 1123: 1 ～ 9
12 FariÌa L, Boido E, Carrau F, Dellacassa EJ Chrom atogr. A, 2007, 1157 (1/2): 46 ～ 50
13 Standardization Administration of the Peop le ’s Republic of China (National Standardization Administration). S tandards for Drink ingWater
Quality GB 574922006 (Sanitary Standards for Drinking Water GB574922006 Biejing (Beijing): 2006
14 Standardization Administration of the Peop le ’s Republic of China (National Standardization Administration). Environm entalQuality S tand2
ards for SurfaceWer GB 383822002 (surface water environmental quality standard GB383822002). Beijing (Beijing): 2002
7 68 Analytical Chemistry Volume 36
Ana lysis of Pyrethro id Pestic ides in Wa ter Samples by D ispersive
L iquid2liquidM icroextraction Coupled with Ga s Chroma tography
ZANG Xiao2Huan, WANG Chun, GAO Shu2Tao, ZHOU Xin, WANG Zhi
3
(Key Laboratory of B ioinorganic Chem istry, College of Science, Agricultural University of Hebei, B aoding 071001)
Abstract A novelmethod was developed for the determination of pyrethroid pesticide residues in water sam2
p les by dispersive liquid2liquid microextraction (DLLME) coup led with cap illary gas chromatographywith elec2
tron cap ture detection (GC2ECD). Some important parameters that influence the extraction efficiency, such as
the kind of the extraction and disperser solvent, their volume and the extraction time, were investigated. In
the method, 10. 0μL chlorobenzene and 1. 0 mL acetone were rap idly injected into a 5. 02mL water samp le.
After centrifugation at 5000 r / min for 5 min, the sedimented chlorobenzene phase was directly injected into
the GC for analysis. Under the op timum conditions, as high as 7082 to 10872fold enrichment factors were
achieved. Usingα2benzene hexachloride as the internal standard, a good linear relationship was obtained in
the range of 0. 8-600μg / L of the analyteswith the correlation coefficients of 0. 9990-0. 9999 and the detec2
tion limits of 0. 04-0. 10μg / L (S / N = 3), respectively. Thismethod has been successfully app lied for the
determination of pyrethroid pesticide residues in realwater samp les (tap, well and riverwaters) with satisfacto2
ry results. The recoveries fell in the range from 76. 0% to 116. 0% and the relative standard deviations were
between 3. 1% and 7. 2%. The method was p roven to be simp le and environmental benign with high
enrichment factor and low cost.
Keywords Dispersive liquid2liquid microextraction, gas chromatography, pyrethroids pesticide, water
samp le
(Received 11 Sep tember 2007; accep ted 5 December 2007)
Analysis of Pyrethroid Pesticide Residues in Water Samples by Dispersed Liquid Phase Microextraction 2 Combined with Gas Chromatography
3
(College of Science, Hebei Agricultural University, Key Laboratory of Bioinorganic Chemistry, Baoding 071001)
Abstract A new method for high-sensitivity determination of seven pyrethroid pesticide residues in water samples was established by combining dispersion liquid 2-liquid microextraction (DLLME) and gas chromatography 2 electron capture detection (GC2ECD) technology. The factors affecting the extraction enrichment efficiency were optimized, and the extraction conditions were selected as: 5.0 mL
Add 1.0 μL chlorobenzene and 1.0 mL acetone to the sample solution, disperse and mix well, centrifuge at 5000 r / min for 5 min, and extract the extraction solvent chlorobenzene for direct analysis. Under optimized conditions, the enrichment multiples of the seven pyrethroid pesticides are as high as 708 to 1087 times. Taking α2 six six six as the internal standard, the seven pyrethroid pesticides have a good linear relationship in the range of 0.8 to 600 μg / L, and the number of relationships included in the linear phase Baidu website is between 0.9990 to 0.9999; The detection limit is
0. 04 ～ 0. 10μg / L (S / N = 3). This method has been applied to the analysis of actual water samples such as tap water, well water and river water.
Between 7610% and 116. 0%; the relative standard deviation is between 3.1% and 7.2%. The method has the characteristics of simple operation, high enrichment efficiency and high sensitivity, and can meet the detection requirements of pyrethroid pesticide residues in water samples.
Keywords dispersive liquid phase microextraction, gas chromatography, pyrethroid pesticides, water sample 2007209211 received; 2007212205 accepted by the Department of Natural Science Foundation of Hebei Province (NO. B2006000413) and the Research Fund of Hebei Agricultural University
3 E2mail: wangzhi @ hebau. Edu. Cn
1 Introduction Pyrethroid (pyrethroid) pesticides are a class of important synthetic pesticides that are widely used at present. With the expansion of the amount and scope of use, it will flow into the water body in large quantities with the drainage of farmland and the rinsing of the atmosphere by rainfall, which will not only poison fish, shellfish and other aquatic animals, but also seriously harm human health through drinking water. Foreign countries have made strict restrictions on its use, for example, the World Health Organization (WHO) drinking water quality guidelines require that the concentration of permethrin in drinking water should be less than 300μg / L. Therefore, it is of great significance to establish an analytical method for pyrethroid pesticide residues in water samples.
At present, the methods for determining the content of pyrethroid pesticides are mainly gas chromatography (GC) [1,2], gas chromatography 2 mass spectrometry (GC2
MS) [3] and liquid chromatography (HPLC) [4, 5] etc. The traditional sample pretreatment technology has the disadvantages of complicated and time-consuming operation, and the need to use a large amount of organic solvent accounting examinations that are toxic and harmful to the human body and the environment. Therefore, the development of new techniques for sample preparation that saves time and has high efficiency and low organic solvent consumption has become one of the hotspots in analytical chemistry research [6]. In recent years, a variety of microextraction techniques have been developed, such as solid phase microextraction [7], liquid phase microextraction [8], membrane extraction [9], etc. Assadi et al. [10] reported for the first time the technology of dispersive liquid microextraction (dispersive liquid2liquid microextrac2
tion, DLLME). Adding more than ten microliters of organic solvent to the sample solution, dispersing and mixing, centrifugal separation, the extraction solvent can be directly injected for analysis. This method integrates sampling, extraction and concentration into one, which is simple, fast, low cost, environmentally friendly and high in enrichment efficiency [10-12]. Research in this area has not been reported in China. In this experiment, a new method for the determination of the residues of 7 pyrethroid pesticides in water samples was established by the combination of dispersion liquid 2-liquid microextraction and gas chromatography. A satisfactory result was achieved.
2 Experimental part
2. 1 Instruments and reagents
GC9790â…¡ capillary gas chromatograph (China Fuli Company), equipped with electron capture detector (ECD); TD5A centrifuge (Changsha Yingtai Instrument Co., Ltd.).
Standards of α2 hexahexahexafluoride, cypermethrin, deltamethrin, deltamethrin, fenvalerate, cyhalothrin, cyfluthrin and permethrin standard at the concentration of 100.0 mg / L (Monitoring Institute); The remaining reagents are all made by Dongao Accounting Analytical Pure; the water is double distilled water.
The standard solution of 7 kinds of pyrethroid pesticides at 100. 0 mg / L was diluted with water to a mixed standard solution of 5.0 mg / L. The internal standard α2 was diluted with water to a stock solution with a concentration of 1.0 mg / L.
Volume 36
Research Report of Analytical Chemistry (FENXIHUAXUE) in June 2008
Chinese Journal ofAnalytical Chemistry
Issue 6
765 ～ 769
2. 2 chromatographic conditions
KB25 quartz capillary column (30 m × 0.23 mm × 0.25 μm, 5% phenyldimethyl polysiloxane column); inlet temperature
270 ℃; detector temperature 300 ℃; column temperature: temperature programmed: 70 ℃ (1.5 min)
22 ℃ / min
230 ℃
5 ℃ / min
285 ℃
(12 min); Carrier gas: high purity N2 (≥99.999%), flow rate 3.0 mL / min, makeup gas 30 mL / min; injection mode: splitless mode for the first 2 min, and then use Split mode, split ratio 1:10, injection volume is 1μL.
2. 3 Dispersion liquid 2-liquid micro-extraction operation method Tap water, well water and river water samples are vacuum filtered by 0.45μm microporous membrane. In a 10 mL spiked centrifuge tube, add
5. 0 mL sample solution, 10. 0 μL chlorobenzene (extraction solvent), 1.0 mL acetone (dispersant), and gently shake for 1 min to form a water / acetone / chlorobenzene emulsion system. Chlorobenzene is evenly dispersed in the aqueous phase, placed at room temperature for 2 min, centrifuged at 5000 r / min for 5 min, the extraction solvent chlorobenzene dispersed in the aqueous phase is deposited on the bottom of the test tube, and 1 μL of the extraction solvent is drawn directly into the micro-sampler. SAMPLE.
2. 4 Drawing the standard curve Pipette appropriate mixed standard solution (5.0 mg / L) of 7 pyrethroid pesticides into a 50 mL volumetric flask, add 250 μL 1.0 mg / L
The internal standard solution was made up with water to a volume to make a series of mixed standard solutions with concentrations of 0.80, 2.0, 10.0, 30.0, 200.0 and 600.0 μg / L. Each sample was extracted according to the method in Section 2.3 and directly injected for analysis. Each concentration was measured three times in parallel, and the ratio of the analyte to the internal standard peak area Y versus the concentration X (μg / L) was used to make a standard curve (analytes with isomers are the sum of the peak areas of the peaks Peak area of ​​the substance).
3 Results and discussion The sample solutions used in the optimization experiment were 7 pyrethroid pesticides with a concentration of 2.0 μg / L and 5.0 μg / Lα2 six six six (internal standard)
Mixture.
3. 1 Selection of extraction solvent The choice of extraction solvent is an important factor that affects the extraction efficiency. The first condition to be satisfied by the extraction solvent is that its density must be greater than that of water, followed by the large dissolving ability of the substance to be tested. Chlorobenzene (density 1.11 g / mL), carbon tetrachloride (density 1.59 g / mL) and bromobenzene were investigated
(Density 1.50 g / mL) The extraction ability of pyrethroid pesticides in water samples showed that the extraction efficiency using chlorobenzene was the best. So choose chlorobenzene as the extractant.
3.2 Selection of dispersant and volume of dispersant The choice of dispersant is a key factor that affects the extraction efficiency of this method. It is required that the dispersant not only has good solubility in the extraction solvent but also can be miscible with water, so that the extraction solvent is in The water phase is dispersed into fine droplets, which increases the contact area with the analyte, thereby improving the extraction efficiency. In this experiment, SPME investigated the extraction effect when acetone, acetonitrile and methanol were used as dispersants. The experimental results showed that the extraction effect of acetone was the best, so acetone was used as the dispersant in this experiment.
The volume of the dispersant acetone directly affects the formation of the "water / acetone / chlorobenzene emulsion" system, which causes the degree of dispersion of the extractant in water to change and affect the extraction efficiency. The effect of acetone volume (0.5, 0.8, 1.0 and 1.2 mL) on the extraction efficiency was investigated. The experimental results showed that the extraction efficiency first increased with the increase of the acetone volume and reached at 1.0 mL The maximum value then decreases as the volume of acetone increases.
This is because when the volume of acetone is small, the extractant is not uniformly dispersed in the aqueous phase, and the extraction efficiency is low; when the volume of acetone is large, the solubility of the test substance in water is increased, and the extraction efficiency is low. Therefore, the volume of acetone is 1.0 mL.
3. 3 Selection of extraction time In the two-liquid microextraction of the dispersion, the extraction time refers to the period between the injection of chlorobenzene and acetone into the aqueous phase before the mixture starts to centrifuge. The effect of extraction time (3, 10, 20, 30 and 40 min) on extraction efficiency was investigated. The results show that the extraction time has no significant effect on the extraction efficiency. This is because after the solution forms an emulsion, the contact area between the organic solvent and the aqueous phase is large, and the analyte can be quickly transferred from the aqueous phase to the organic phase, and quickly To achieve two-phase balance. The extraction time is 3 min.
3.4 Effect of salt concentration The effect of salt concentration on extraction efficiency was investigated by adding NaCl (0 ～ 5%) to the solution to be tested. The results show that with
As the NaCl concentration increases, the measured recovery rate decreases. This is because as the ionic strength increases, the solubility of the organic extractant in the aqueous phase decreases
(The corresponding enrichment factor also decreases), the volume of the organic phase increases. So no salt was added in the experiment.
7 66 Analytical Chemistry Volume 36 Figure 1 Standard chromatograms of 7 pyrethroid pesticides (both at a concentration of 2.0 μg / L)
Fig. 1 Chromatogram of samp le standard at each concen2
tration of 2. 0μg / L for 7 pyrethroid pesticides
1. Internal standard α2 å…å…å… (internal standard α2benzene hexachloride);
2. Fenvalerate (fenp ropathrin); 3, 4. Cypermethrin (lambda2cy2
halothrin); 5, 6. permethrin; 7, 8, 9. cyfluthrin
(cyhfluthrin); 10, 11, 12. cypermethrin; 13, 14.
Fenvalerate (fenvalerate); 15, 16. deltamethrin (deltamethrin).
3.5 The accuracy, linear range, and detection limit of the method were extracted and determined under a series of standard solutions under optimized experimental conditions. The results are shown in Table 1. The 7 pyrethroid pesticides
0.8 to 600μg / L has a good linear relationship. The detection limit is between 0.04 ～ 0.10μg / L, which can fully meet the measurement of actual samples. For example, the detection limit of deltamethrin is 0.08μg / L, which is far lower than the national standard [13] 0. 02 mg / L, also lower than the detection limit of the national standard [14] (0. 0002 mg / L). The detection limit of permethrin is
0. 10μg / L, far lower than the maximum 300μg / L limit required by the third edition of the WHO Guidelines for Drinking Water Quality. The standard sample chromatogram is shown in Figure 1.
The mixed standard solution samples containing 20, 100 and 400 μg / L pyrethroid pesticides were measured in parallel five times.
2. Between 3% and 5.1%.
3. The enrichment factor of method 6 is calculated as follows: The concentration of the organic phase is calculated. The concentration of 7 pyrethroid pesticides prepared with chlorobenzene as the solvent is 015,
1. 0, 2.0 and 3.0 mg / L of the standard mixed solution, using the peak area versus concentration as the standard curve of 7 pyrethroid pesticides, and the organic phase concentration was obtained based on the measured peak area of ​​the sample. The enrichment factor F is the ratio of the concentration in the final organic phase online lecture to the initial concentration in the aqueous solution. The results showed that the enrichment multiples of the seven pyrethroid pesticides were as high as 708 to 1087 times (see Table 1).
Table 1 Detection limits of linear equations, correlation coefficients and methods of 7 pyrethroid pesticides
Table 1 Regression equations, correlation coefficients and limits of detections (LODs) for 7 pyrethroid pesticides
pesticide
Pesticides
Linear range
Linear range
(μg / L)
Regression equation
Regression
equation
Correlation coefficient (r)
Correlation
coefficient
Enrichment multiple
Enrichment
factor
The detection limit
LOD
(μg / L)
Fenp ropathrin 0.8 to 600 Y = 29. 72X + 0.33 0.99 994 838 0.04
Cyhalothrin Lambda2cyhalothrin 0. 8 ～ 600 Y = 77. 49X + 0. 29 0. 9999 1075 0. 04
Permethrin 0.8 to 600 Y = 11. 40X + 0.17 0.995 1087 0. 10
Cyfluthrin 0.8 to 600 Y = 50. 76X + 0.30 0.9990 832 0.08
Cypermethrin 0. 8 ～ 600 Y = 63. 48X + 0. 33 0. 9991 890 0. 08
Fenvalerate 0. 8 ～ 600 Y = 62. 56X + 0.23 0.996 835 0.06
Deltamethrin Deltamethrin 0.8 ~ 600 Y = 51.78X + 0.21 0.999993 708 0.08
3. 7 Sample determination Figure 2 River water sample chromatogram
Fig. 2 Chromatogram of riverwater samp le
1. α2 å…å…å… (α2benzene hexachloride); 2. cyhalothrin
(lambda2cyhalothrin); 3, 4. Fenvalerate (fenvalerate).
According to the above chromatographic method, the samples of river water, well water and tap water in this area were determined. Take 5.0 mL of the sample solution in a centrifuge tube and measure according to the "2.3" method. Residues of pyrethroid pesticides were not detected in well water and tap water samples. Residues of cyfluthrin and fenvalerate in river water samples were 0.21 and 0.16 μg / L, respectively. The chromatogram of river water samples is shown in Figure 2. Current national water quality standards for training and counseling tables GB 38382
2002 [14] only stipulates that the detection limit of deltamethrin pesticide residue determination method is 0.2 μg / L, and its maximum allowable limit is 0.02 mg / L. The detection limit of deltamethrin in this method is 0.08μg / L, which can meet the requirements of the measurement sensitivity.
For the measured water samples, the standard addition method was used to measure 5 times in parallel at 3 concentration levels, and the recovery rate and relative standard deviation were calculated. The results are shown in Table 2. The recovery rate of the 7 pyrethroid pesticides was 76.0% ~ 116. 0%; the relative standard deviation RSD is less than 7.2%, the precision and reproducibility of this method are satisfactory.
Issue 6 Zang Xiaohuan et al .: Dispersed liquid phase microextraction 2 gas chromatography combined with analysis of pyrethroid pesticide residues in water samples 7 67
Table 2 Determination and recovery rate of pyrethroid pesticide residues in river water, well water and tap water
Table 2 Determinations of pyrethroid pesticide residues and sp iked recoveries in river, well and tap waters samp les
pesticide
Pesticides
Spiked amount in water sample
Sp iked
(μg / L)
Riverwater (n = 5)
Detection amount
Found
(μg / L)
Recovery rate
Recovery
(%)
RSD
(%)
Well water (n = 5)
Detection amount
Found
(μg / L)
Recovery rate
Recovery
(%)
RSD
(%)
Tap water (n = 5)
Detection amount
Found
(μg / L)
Recovery rate
Recovery
(%)
RSD
(%)
Fenp ropathrin
0 ND ND ND
5 5. 2 104. 0 3. 9 5. 1 102. 0 4. 6 5. 1 102. 0 5. 2
20 18. 9 94. 5 5. 2 18. 4 92. 0 5. 1 17. 9 89. 5 4. 7
Cyhalothrin
Lambda2cyhalothrin
0 0. 21 3. 4 ND ND
5 4. 9 93. 8 4. 3 4. 9 98. 0 3. 9 4. 8 96. 0 3. 7
20 21. 2 104. 9 4. 9 19. 5 97. 5 3. 7 20. 2 101. 0 4. 8
Permethrin
0 ND ND ND
5 3. 8 76. 0 6. 2 3. 9 78. 0 3. 1 4. 1 82. 0 4. 3
20 15. 7 78. 5 5. 1 17. 0 85. 0 5. 3 17. 5 87. 5 3. 4
Cyfluthrin
0 ND ND ND
5 5. 7 114. 0 5. 8 5. 2 104. 0 5. 2 4. 8 96. 0 3. 3
20 22. 5 112. 5 4. 9 21. 2 106. 0 3. 2 18. 9 94. 5 5. 1
Cypermethrin
0 ND ND ND
5 5. 87 116. 0 7. 2 5. 1 102. 0 4. 8 5. 2 104. 0 6. 4
20 21. 9 109. 5 6. 4 18. 9 94. 5 3. 1 19. 0 95. 0 4. 6
Fenvalerate
0 ND ND ND
5 5. 4 104. 8 5. 1 5. 3 106. 0 5. 5 5. 4 108. 0 4. 1
20 21. 4 106. 2 6. 3 21. 8 109. 0 4. 3 21. 0 105. 0 3. 7
Deltamethrin
0 ND ND ND
5 5. 3 106. 0 4. 7 5. 2 104. 0 4. 7 5. 3 106. 0 5. 4
20 22. 0 110. 0 6. 5 21. 1 105. 5 4. 5 18. 7 93. 5 3. 1
ND: not detected.
References
1 Wan Yi2Qun (万 益群), Yan Ai2Ping (鄢爱平), XieMing2Yong (谢明勇). Chinese J. Anal. Chem. (Analytical Chemistry), 2005,
33 (5): 614 ～ 618
2 Sharif Z, Man YBC, Hamid NSA, Keat C CJ Chrom atogr. A, 2006, 1127 (1/2): 254 ～ 261
3 L i Feng2Ge (æŽé”‹ æ ¼), Quan Xiao2Dun (å…¨ 晓 Shield). Chinese J. Anal. Chem. (Analytical Chemistry), 2005, 33 (6): 838 ～ 842
4 Wen Yu2Yun (温裕云), Gong Zhen2Bin (弓 振 æ–Œ), Yao J ian2Min (姚剑æ•). Chinese J. Anal. Chem. (Analytical Chemistry),
2005, 33 (3): 301 ～ 304
5 DuanWei (段 伟), Li Zheng2Guo (æŽæ£å›½), Wang Guo2Min (王国民), Yang Ying2Wu (æ¨ è¿Ž ä¼), Li Ying2Guo (æŽ åº” 国), Xia Yu2Xian (å¤ çŽ‰ å…ˆ). Chinese J. Anal. Chem. (Analytical Chemistry) , 2006, 34 (12): 1776 ～ 1778
6 Raynie D E. Anal. Chem., 2004, 76: 4659 ～ 4664
7 Arthur CL, Pawliszyn J. Anal. Chem., 1990, 62: 2145 ～ 2148
8 JeannotM A, Cantwell F. Anal. Chem., 1996, 68: 2236 ～ 2240
9 Psillakis E, Kalogerakis N. Trends Anal. Chem., 2002, 21 (1): 53 ～ 64
10 RezaeeM, Assadi Y, Milani HosseiniM R, Aghaee E, Ahmadi F, Berijani SJ Chrom atogr. A, 2006, 1116: 1 ～ 9
11 Berijani S, Assadi Y, AnbiaM, Milani HosseiniM R, Aghaee EJ Chrom atogr. A, 2006, 1123: 1 ～ 9
12 FariÌa L, Boido E, Carrau F, Dellacassa EJ Chrom atogr. A, 2007, 1157 (1/2): 46 ～ 50
13 Standardization Administration of the Peop le ’s Republic of China (National Standardization Administration). S tandards for Drink ingWater
Quality GB 574922006 (Sanitary Standards for Drinking Water GB574922006 Biejing (Beijing): 2006
14 Standardization Administration of the Peop le ’s Republic of China (National Standardization Administration). Environm entalQuality S tand2
ards for SurfaceWer GB 383822002 (surface water environmental quality standard GB383822002). Beijing (Beijing): 2002
7 68 Analytical Chemistry Volume 36
Ana lysis of Pyrethro id Pestic ides in Wa ter Samples by D ispersive
L iquid2liquidM icroextraction Coupled with Ga s Chroma tography
ZANG Xiao2Huan, WANG Chun, GAO Shu2Tao, ZHOU Xin, WANG Zhi
3
(Key Laboratory of B ioinorganic Chem istry, College of Science, Agricultural University of Hebei, B aoding 071001)
Abstract A novelmethod was developed for the determination of pyrethroid pesticide residues in water sam2
p les by dispersive liquid2liquid microextraction (DLLME) coup led with cap illary gas chromatographywith elec2
tron cap ture detection (GC2ECD). Some important parameters that influence the extraction efficiency, such as
the kind of the extraction and disperser solvent, their volume and the extraction time, were investigated. In
the method, 10. 0μL chlorobenzene and 1. 0 mL acetone were rap idly injected into a 5. 02mL water samp le.
After centrifugation at 5000 r / min for 5 min, the sedimented chlorobenzene phase was directly injected into
the GC for analysis. Under the op timum conditions, as high as 7082 to 10872fold enrichment factors were
achieved. Usingα2benzene hexachloride as the internal standard, a good linear relationship was obtained in
the range of 0. 8-600μg / L of the analyteswith the correlation coefficients of 0. 9990-0. 9999 and the detec2
tion limits of 0. 04-0. 10μg / L (S / N = 3), respectively. Thismethod has been successfully app lied for the
determination of pyrethroid pesticide residues in realwater samp les (tap, well and riverwaters) with satisfacto2
ry results. The recoveries fell in the range from 76. 0% to 116. 0% and the relative standard deviations were
between 3. 1% and 7. 2%. The method was p roven to be simp le and environmental benign with high
enrichment factor and low cost.
Keywords Dispersive liquid2liquid microextraction, gas chromatography, pyrethroids pesticide, water
samp le
(Received 11 Sep tember 2007; accep ted 5 December 2007)
Analysis of Pyrethroid Pesticide Residues in Water Samples by Dispersed Liquid Phase Microextraction 2 Combined with Gas Chromatography
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