基于多壁碳纳米管改进QuEChERS法结合气相色谱-串联质谱法测定云木香中35种禁用农药残留

doi:10.3724/SP.J.1123.2023.07018

摘要/Abstract

摘要：

本研究以中药材云木香中的35种禁用农药为研究对象,利用多壁碳纳米管(MWCNTs)、十八烷基键合硅胶(C₁₈)和无水硫酸镁(MgSO₄)作为净化吸附剂,建立了QuEChERS技术与气相色谱-串联质谱法(GC-MS/MS)相结合的快速检测方法。样品由乙腈提取,经改进的QuEChERS净化后,用GC-MS/MS检测,多反应监测模式(MRM)分析,内标法定量。针对云木香的特点,对比了C₁₈、MWCNTs、N-丙基乙二胺(PSA)、石墨化炭黑(GCB)4种净化材料不同配比下的净化效果,确定了最优的吸附剂组合为450 mg MgSO₄、400 mg C₁₈和50 mg MWCNTs。该吸附剂组合比传统净化包具有更优异的净化效果,且不会吸附目标物,实验结果稳定可靠。方法学研究表明,35种农药线性良好,相关系数(r²)均≥0.9970; 3个添加水平下的平均回收率为69.6%~126.9%,相对标准偏差(RSD)均小于10%;检出限(LOD)为0.2~5.4 μg/kg,定量限(LOQ)为0.6~18.1 μg/kg。用该方法检测了20批送检云木香样品中35种农药的残留情况,其中6批样品中检出目标物。本方法简便、灵敏、准确,可用于云木香中农药残留的检测,为云木香的种植生产和质量管控提供技术支撑。

关键词: 气相色谱-串联质谱, QuEChERS, 多壁碳纳米管, 禁用农药, 云木香

Abstract:

Saussurea costus, a perennial herb belonging to the Asteraceae family, is a vital ingredient in traditional Chinese medicine. Increased demands for the herb have led to its widespread cultivation in China, but the corresponding increase in pesticide use has raised concerns about pesticide residues. Such residues would affect the safety and global market potential of Saussurea costus. Thus, a simple method is crucial to detect pesticide residues. The QuEChERS technique, in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), is commonly used for residue detection. However, traditional adsorbents may be unable to purify complex herbal mixtures well, affecting accuracy and instrument performance. Choosing suitable purification materials for Saussurea costus samples with complex matrices is of significant importance. This study focused on the detection of 35 prohibited pesticides in Saussurea costus. A rapid detection method was established by combining the QuEChERS technique with GC-MS/MS and utilizing a combination of multiwalled carbon nanotubes (MWCNTs), octadecylsilane-bonded silica gel (C₁₈), and anhydrous magnesium sulfate (MgSO₄) as the purification adsorbent. The samples were extracted with acetonitrile, purified by an improved QuEChERS process, subjected to GC-MS/MS analysis in multiple reaction monitoring (MRM) mode, and quantified using the internal standard method. The purification effects of four materials (C₁₈, MWCNTs, N-propyl ethylenediamine (PSA), and graphitized carbon black (GCB)) and their optimal dosages were investigated by considering the matrix characteristics of the samples. An orthogonal experimental design was employed to optimize the ratio of adsorbent combinations, and the optimal adsorbent combination was determined to be 450 mg of MgSO₄, 400 mg of C₁₈, and 50 mg of MWCNTs. Matrix effect (ME) evaluation of the S. costus matrix showed that 31 target compounds strongly exhibited matrix-enhancement effects. Thus, matrix-matched calibration was employed in this study. Methodological investigation revealed that the standard curves for the 35 pesticides exhibited good linearity, with correlation coefficients (r²) greater than 0.9970. The average recoveries at three spiked levels ranged from 69.6% to 126.9%, and the relative standard deviations (RSDs) for parallel groups were all less than 10%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.2 to 5.4 μg/kg and from 0.6 to 18.1 μg/kg, respectively. The developed method was used to screen and detect 35 pesticide residues in 20 batches of S. costus samples, and the target compounds were detected in six batches. The proposed method is simple, sensitive, and accurate. Thus, it is suitable for the rapid screening and detection of the 35 pesticide residues in S. costus and provides technical support for the cultivation, production, and quality control of the herb.

Key words: gas chromatography-tandem mass spectrometry (GC-MS/MS), QuEChERS, multi-walled carbon nanotubes, prohibited pesticides, Saussurea costus

中图分类号:

O658

易从圣, 刘瑞, 吴志鹏, 刘博, 杜磊. 基于多壁碳纳米管改进QuEChERS法结合气相色谱-串联质谱法测定云木香中35种禁用农药残留[J]. 色谱, 2024, 42(3): 282-290.

YI Congsheng, LIU Rui, WU Zhipeng, LIU Bo, DU Lei. Determination of 35 prohibited pesticide residues in Saussurea costus by modified QuEChERS method based on multi-walled carbon nanotubes coupled with gas chromatography-tandem mass spectrometry[J]. Chinese Journal of Chromatography, 2024, 42(3): 282-290.

图/表 8

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No.	Pesticide	Retention time/min	Quantitative ion pair (m/z)	Qualitative ion pairs (m/z)	CEs/eV	C/ (μg/mL)
1	demeton-O (内吸磷-O)	11.92	88.0>60.0	88.0>59.0, 88.0>45.0	4, 20, 25	20
2	ethoprophos (灭线磷)	12.40	199.7>157.8	157.8>96.7, 157.8>113.8	5, 20, 15	40
3	chlordimeform (杀虫脒)	12.75	152.0>117.0	196.0>181.0	15, 5	40
4	sulfotep (治螟磷)	12.95	322.0>174.0	322.0>294.0, 322.0>202.0	15, 10, 20	40
5	phorate (甲拌磷)	13.12	260.0>75.0	230.8>175.0, 230.8>128.6	5, 10, 25	40
6	α-hexachlorocyclohexane (α-六六六)	13.47	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
7	terbufos (特丁硫磷)	13.73	230.8>129.0	230.8>175.0, 230.8>203.0	25, 13, 5	40
8	demeton-S (内吸磷-S)	13.79	88.0>60.0	88.0>59.0, 88.0>45.0	4, 20, 25	20
9	γ-hexachlorocyclohexane (γ-六六六)	14.44	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
10	monocrotophos (久效磷)	14.48	127.0>109.0	127.0>95.0, 127.0>79.0	12, 16, 20	60
11	fipronil-desulfinyl (氟甲腈)	14.77	388.0>333.0	388.0>281.0	20, 35	40
12	β-hexachlorocyclohexane (β-六六六)	15.06	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
13	δ-hexachlorocyclohexane (δ-六六六)	15.71	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
14	aldrin (艾氏剂)	15.81	263.0>193.0	276.8>240.7, 276.8>169.7	35, 10, 35	100
15	parathion-methyl (甲基对硫磷)	16.11	263.1>109.0	263.1>136.0, 263.1>79.0	13, 5, 35	40
16	fipronil-sulfoxide (氟虫腈亚砜)	16.43	420.0>351.0	420.0>255.0	12, 20	40
17	dicofol (三氯杀螨醇)	16.44	250.0>139.0	139.0>111.0, 250.0>215.0	15, 15, 5	100
18	fipronil (氟虫腈)	16.52	367.0>213.0	351.0>255.0, 367.0>255.0	35, 20, 25	40
19	parathion (对硫磷)	16.70	291.0>109.0	291.0>81.0, 139.0>109.0	25, 30, 10	100
20	2,4'-dicofol (2,4'-三氯杀螨醇)	16.98	250.0>139.0	139.0>111.0, 250.0>215.0	15, 15, 5	100
21	isofenphos-methyl (甲基异柳磷)	17.03	241.0>120.8	241.0>199.0, 241.0>166.7	20, 5, 10	40
22	isocarbophos (水胺硫磷)	17.42	135.7>108.0	120.7>65.0, 121.0>93.0	15, 20, 15	100
23	fipronil-sulfone (氟虫腈砜)	17.92	383.0>255.0	383.0>213.0, 452.0>383.0	20, 32, 8	40
24	α-endosulfan (α-硫丹)	17.93	240.8>205.6	240.8>170.0, 194.8>159.0	15, 25, 10	100
25	p,p'-dichlorodiphenyldichloroethylene (4,4'-滴滴伊)	18.37	246.0>176.0	316.0>246.0, 246.0>210.0	30, 25, 28	100
26	fenamiphos (苯线磷)	18.58	303.1>122.0	303.1>154.0, 303.1>195.0	20, 30, 25	40
27	dieldrin (狄氏剂)	18.59	263.0>193.0	276.8>240.7, 276.8>169.7	35, 10, 35	100
28	Posfolan-methyl (甲基硫环磷)	19.06	168.0>109.0	227.0>92.0	15, 10	60
29	nitrofen (除草醚)	19.44	201.8>138.7	282.8>253.0, 282.8>201.8	28, 10, 15	100
30	o,p'-dichlorodiphenyltrichloroethane (2,4'-滴滴涕)	19.45	235.0>165.0	235.0>199.0, 237.0>165.0	25, 15, 25	100
31	p,p'-dichlorodiphenyldichloroethane (4,4'-滴滴滴)	19.62	235.0>165.0	237.0>165.0, 235.0>199.0	25, 25, 18	100
32	β-endosulfan (β-硫丹)	19.88	206.8>171.8	194.8>124.7, 194.8>159.0	15, 30, 10	100
33	p,p'-dichlorodiphenyltrichloroethane (4,4'-滴滴涕)	20.18	235.0>165.0	235.0>199.0, 237.0>165.0	25, 18, 25	100
34	endosulfan sulfate (硫丹硫酸酯)	20.80	271.8>236.7	273.8>238.9, 271.8>141.0	15, 15, 40	100
35	coumaphos (蝇毒磷)	23.89	361.8>109.0	361.8>81.0, 361.8>225.8	16, 32, 14	100
36	triphenyl phosphate (磷酸三苯酯, IS)	21.27	326.0>233.0	326.0>215.0, 326.0>169.0	10, 25, 30	100

No.	Pesticide	Retention time/min	Quantitative ion pair (m/z)	Qualitative ion pairs (m/z)	CEs/eV	C/ (μg/mL)
1	demeton-O (内吸磷-O)	11.92	88.0>60.0	88.0>59.0, 88.0>45.0	4, 20, 25	20
2	ethoprophos (灭线磷)	12.40	199.7>157.8	157.8>96.7, 157.8>113.8	5, 20, 15	40
3	chlordimeform (杀虫脒)	12.75	152.0>117.0	196.0>181.0	15, 5	40
4	sulfotep (治螟磷)	12.95	322.0>174.0	322.0>294.0, 322.0>202.0	15, 10, 20	40
5	phorate (甲拌磷)	13.12	260.0>75.0	230.8>175.0, 230.8>128.6	5, 10, 25	40
6	α-hexachlorocyclohexane (α-六六六)	13.47	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
7	terbufos (特丁硫磷)	13.73	230.8>129.0	230.8>175.0, 230.8>203.0	25, 13, 5	40
8	demeton-S (内吸磷-S)	13.79	88.0>60.0	88.0>59.0, 88.0>45.0	4, 20, 25	20
9	γ-hexachlorocyclohexane (γ-六六六)	14.44	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
10	monocrotophos (久效磷)	14.48	127.0>109.0	127.0>95.0, 127.0>79.0	12, 16, 20	60
11	fipronil-desulfinyl (氟甲腈)	14.77	388.0>333.0	388.0>281.0	20, 35	40
12	β-hexachlorocyclohexane (β-六六六)	15.06	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
13	δ-hexachlorocyclohexane (δ-六六六)	15.71	181.0>145.0	218.7>182.9, 218.9>147.0	15, 5, 10	100
14	aldrin (艾氏剂)	15.81	263.0>193.0	276.8>240.7, 276.8>169.7	35, 10, 35	100
15	parathion-methyl (甲基对硫磷)	16.11	263.1>109.0	263.1>136.0, 263.1>79.0	13, 5, 35	40
16	fipronil-sulfoxide (氟虫腈亚砜)	16.43	420.0>351.0	420.0>255.0	12, 20	40
17	dicofol (三氯杀螨醇)	16.44	250.0>139.0	139.0>111.0, 250.0>215.0	15, 15, 5	100
18	fipronil (氟虫腈)	16.52	367.0>213.0	351.0>255.0, 367.0>255.0	35, 20, 25	40
19	parathion (对硫磷)	16.70	291.0>109.0	291.0>81.0, 139.0>109.0	25, 30, 10	100
20	2,4'-dicofol (2,4'-三氯杀螨醇)	16.98	250.0>139.0	139.0>111.0, 250.0>215.0	15, 15, 5	100
21	isofenphos-methyl (甲基异柳磷)	17.03	241.0>120.8	241.0>199.0, 241.0>166.7	20, 5, 10	40
22	isocarbophos (水胺硫磷)	17.42	135.7>108.0	120.7>65.0, 121.0>93.0	15, 20, 15	100
23	fipronil-sulfone (氟虫腈砜)	17.92	383.0>255.0	383.0>213.0, 452.0>383.0	20, 32, 8	40
24	α-endosulfan (α-硫丹)	17.93	240.8>205.6	240.8>170.0, 194.8>159.0	15, 25, 10	100
25	p,p'-dichlorodiphenyldichloroethylene (4,4'-滴滴伊)	18.37	246.0>176.0	316.0>246.0, 246.0>210.0	30, 25, 28	100
26	fenamiphos (苯线磷)	18.58	303.1>122.0	303.1>154.0, 303.1>195.0	20, 30, 25	40
27	dieldrin (狄氏剂)	18.59	263.0>193.0	276.8>240.7, 276.8>169.7	35, 10, 35	100
28	Posfolan-methyl (甲基硫环磷)	19.06	168.0>109.0	227.0>92.0	15, 10	60
29	nitrofen (除草醚)	19.44	201.8>138.7	282.8>253.0, 282.8>201.8	28, 10, 15	100
30	o,p'-dichlorodiphenyltrichloroethane (2,4'-滴滴涕)	19.45	235.0>165.0	235.0>199.0, 237.0>165.0	25, 15, 25	100
31	p,p'-dichlorodiphenyldichloroethane (4,4'-滴滴滴)	19.62	235.0>165.0	237.0>165.0, 235.0>199.0	25, 25, 18	100
32	β-endosulfan (β-硫丹)	19.88	206.8>171.8	194.8>124.7, 194.8>159.0	15, 30, 10	100
33	p,p'-dichlorodiphenyltrichloroethane (4,4'-滴滴涕)	20.18	235.0>165.0	235.0>199.0, 237.0>165.0	25, 18, 25	100
34	endosulfan sulfate (硫丹硫酸酯)	20.80	271.8>236.7	273.8>238.9, 271.8>141.0	15, 15, 40	100
35	coumaphos (蝇毒磷)	23.89	361.8>109.0	361.8>81.0, 361.8>225.8	16, 32, 14	100
36	triphenyl phosphate (磷酸三苯酯, IS)	21.27	326.0>233.0	326.0>215.0, 326.0>169.0	10, 25, 30	100

Pesticide	Linear range/ (μg/kg)	r²	LOD/ (μg/kg)	LOQ/ (μg/kg)	Recoveries (RSDs)/%
Pesticide	Linear range/ (μg/kg)	r²	LOD/ (μg/kg)	LOQ/ (μg/kg)	Low	Medium	High
Demeton-O	10-200	0.9996	2.4	8.1	101.5 (6.7)	89.6 (4.2)	88.9 (4.5)
Ethoprophos	20-400	0.9991	1.5	5.1	102.0 (5.4)	86.7 (3.8)	86.9 (4.7)
Chlordimeform	20-400	0.9994	2.7	9.1	78.8 (1.9)	75.3 (5.3)	82.6 (1.8)
Sulfotep	20-400	0.9993	2.3	7.5	114.4 (3.5)	107.0 (2.8)	105.7 (4.7)
Phorate	20-400	0.9997	3.1	10.3	107.0 (7.8)	94.4 (4.4)	93.5 (4.7)
α-Hexachlorocyclohexane	50-1000	0.9993	2.0	6.6	123.1 (4.7)	125.7 (2.6)	111.1 (3.6)
Terbufos	20-400	0.9993	3.4	11.2	91.5 (4.7)	85.1 (4.1)	87.3 (5.2)
Demeton-S	10-200	0.9992	2.2	7.3	95.2 (3.6)	84.0 (3.4)	88.0 (6.0)
γ-Hexachlorocyclohexane	50-1000	0.9993	0.6	1.9	119.1 (2.3)	115.6 (6.4)	116.0 (2.4)
Monocrotophos	30-600	0.9990	3.6	12.0	71.3 (6.0)	97.1 (7.5)	120.7 (2.6)
Fipronil-desulfinyl	20-400	0.9998	0.2	0.6	116.9 (3.8)	89.6 (5.9)	96.8 (1.4)
β-Hexachlorocyclohexane	50-1000	0.9998	2.7	8.9	124.8 (4.8)	116.4 (2.2)	111.3 (3.1)
δ-Hexachlorocyclohexane	50-1000	0.9997	1.1	3.8	105.4 (6.3)	100.1 (3.0)	116.3 (2.5)
Aldrin	50-1000	0.9997	1.7	5.8	93.7 (5.1)	85.3 (3.0)	84.7 (5.6)
Parathion-methyl	20-400	0.9994	2.5	8.3	87.5 (3.9)	84.4 (3.0)	85.5 (3.3)
Fipronil-sulfoxide	20-400	0.9990	0.2	0.7	115.5 (8.2)	115.2 (4.7)	117.1 (6.9)
Dicofol	50-1000	0.9997	0.4	1.4	118.5 (9.2)	105.2 (2.5)	109.4 (2.1)
Fipronil	20-400	0.9996	2.8	9.4	101.6 (7.0)	97.5 (3.7)	99.4 (6.2)
Parathion	50-1000	0.9991	3.3	11.0	126.9 (2.9)	122.1 (1.4)	116.4 (3.2)
2,4'-Dicofol	50-1000	0.9994	0.6	2.1	119.1 (3.6)	122.0 (2.2)	104.8 (1.6)
Isofenphos-methyl	20-400	0.9992	0.3	1.1	112.0 (6.0)	114.3 (4.6)	111.0 (4.9)
Isocarbophos	50-1000	0.9970	4.0	13.2	78.1 (6.7)	95.5 (2.4)	91.4 (1.7)
Fipronil-sulfone	50-1000	0.9996	0.8	2.8	106.2 (6.4)	93.3 (4.6)	92.3 (2.9)
α-Endosulfan	20-400	0.9999	0.9	3.1	81.9 (2.7)	85.0 (3.4)	81.0 (3.7)
p,p'-Dichlorodiphenyldichloroethylene	50-1000	0.9999	0.5	1.8	84.2 (6.2)	76.0 (5.0)	73.5 (4.9)
Fenamiphos	20-400	0.9992	1.6	5.2	88.0 (3.5)	89.1 (5.3)	81.8 (1.8)
Dieldrin	50-1000	0.9999	2.3	7.8	102.5 (5.2)	96.8 (3.3)	93.1 (8.4)
Posfolan-methyl	30-600	0.9991	4.4	14.7	88.1 (5.7)	99.4 (3.3)	100.2 (5.7)
Nitrofen	50-1000	0.9995	1.2	4.1	69.8 (7.2)	70.0 (1.6)	69.6 (3.2)
o,p'-Dichlorodiphenyltrichloroethane	50-1000	0.9999	2.3	7.6	95.0 (2.7)	89.0 (4.4)	85.8 (2.7)
p,p'-Dichlorodiphenyldichloroethane	50-1000	0.9993	2.1	6.9	123.8 (3.6)	118.4 (1.7)	115.3 (2.2)
β-Endosulfan	50-1000	0.9998	3.3	10.9	98.0 (5.5)	95.5 (2.9)	91.8 (2.0)
p,p'-Dichlorodiphenyltrichloroethane	50-1000	0.9998	0.4	1.2	115.7 (4.7)	110.8 (3.3)	108.1 (1.1)
Endosulfan sulfate	50-1000	0.9997	3.8	12.7	99.0 (7.3)	104.4 (5.3)	86.3 (3.8)
Coumaphos	50-1000	0.9997	5.4	18.1	96.9 (6.0)	93.0 (9.9)	94.5 (2.5)

Pesticide	Linear range/ (μg/kg)	r²	LOD/ (μg/kg)	LOQ/ (μg/kg)	Recoveries (RSDs)/%
Pesticide	Linear range/ (μg/kg)	r²	LOD/ (μg/kg)	LOQ/ (μg/kg)	Low	Medium	High
Demeton-O	10-200	0.9996	2.4	8.1	101.5 (6.7)	89.6 (4.2)	88.9 (4.5)
Ethoprophos	20-400	0.9991	1.5	5.1	102.0 (5.4)	86.7 (3.8)	86.9 (4.7)
Chlordimeform	20-400	0.9994	2.7	9.1	78.8 (1.9)	75.3 (5.3)	82.6 (1.8)
Sulfotep	20-400	0.9993	2.3	7.5	114.4 (3.5)	107.0 (2.8)	105.7 (4.7)
Phorate	20-400	0.9997	3.1	10.3	107.0 (7.8)	94.4 (4.4)	93.5 (4.7)
α-Hexachlorocyclohexane	50-1000	0.9993	2.0	6.6	123.1 (4.7)	125.7 (2.6)	111.1 (3.6)
Terbufos	20-400	0.9993	3.4	11.2	91.5 (4.7)	85.1 (4.1)	87.3 (5.2)
Demeton-S	10-200	0.9992	2.2	7.3	95.2 (3.6)	84.0 (3.4)	88.0 (6.0)
γ-Hexachlorocyclohexane	50-1000	0.9993	0.6	1.9	119.1 (2.3)	115.6 (6.4)	116.0 (2.4)
Monocrotophos	30-600	0.9990	3.6	12.0	71.3 (6.0)	97.1 (7.5)	120.7 (2.6)
Fipronil-desulfinyl	20-400	0.9998	0.2	0.6	116.9 (3.8)	89.6 (5.9)	96.8 (1.4)
β-Hexachlorocyclohexane	50-1000	0.9998	2.7	8.9	124.8 (4.8)	116.4 (2.2)	111.3 (3.1)
δ-Hexachlorocyclohexane	50-1000	0.9997	1.1	3.8	105.4 (6.3)	100.1 (3.0)	116.3 (2.5)
Aldrin	50-1000	0.9997	1.7	5.8	93.7 (5.1)	85.3 (3.0)	84.7 (5.6)
Parathion-methyl	20-400	0.9994	2.5	8.3	87.5 (3.9)	84.4 (3.0)	85.5 (3.3)
Fipronil-sulfoxide	20-400	0.9990	0.2	0.7	115.5 (8.2)	115.2 (4.7)	117.1 (6.9)
Dicofol	50-1000	0.9997	0.4	1.4	118.5 (9.2)	105.2 (2.5)	109.4 (2.1)
Fipronil	20-400	0.9996	2.8	9.4	101.6 (7.0)	97.5 (3.7)	99.4 (6.2)
Parathion	50-1000	0.9991	3.3	11.0	126.9 (2.9)	122.1 (1.4)	116.4 (3.2)
2,4'-Dicofol	50-1000	0.9994	0.6	2.1	119.1 (3.6)	122.0 (2.2)	104.8 (1.6)
Isofenphos-methyl	20-400	0.9992	0.3	1.1	112.0 (6.0)	114.3 (4.6)	111.0 (4.9)
Isocarbophos	50-1000	0.9970	4.0	13.2	78.1 (6.7)	95.5 (2.4)	91.4 (1.7)
Fipronil-sulfone	50-1000	0.9996	0.8	2.8	106.2 (6.4)	93.3 (4.6)	92.3 (2.9)
α-Endosulfan	20-400	0.9999	0.9	3.1	81.9 (2.7)	85.0 (3.4)	81.0 (3.7)
p,p'-Dichlorodiphenyldichloroethylene	50-1000	0.9999	0.5	1.8	84.2 (6.2)	76.0 (5.0)	73.5 (4.9)
Fenamiphos	20-400	0.9992	1.6	5.2	88.0 (3.5)	89.1 (5.3)	81.8 (1.8)
Dieldrin	50-1000	0.9999	2.3	7.8	102.5 (5.2)	96.8 (3.3)	93.1 (8.4)
Posfolan-methyl	30-600	0.9991	4.4	14.7	88.1 (5.7)	99.4 (3.3)	100.2 (5.7)
Nitrofen	50-1000	0.9995	1.2	4.1	69.8 (7.2)	70.0 (1.6)	69.6 (3.2)
o,p'-Dichlorodiphenyltrichloroethane	50-1000	0.9999	2.3	7.6	95.0 (2.7)	89.0 (4.4)	85.8 (2.7)
p,p'-Dichlorodiphenyldichloroethane	50-1000	0.9993	2.1	6.9	123.8 (3.6)	118.4 (1.7)	115.3 (2.2)
β-Endosulfan	50-1000	0.9998	3.3	10.9	98.0 (5.5)	95.5 (2.9)	91.8 (2.0)
p,p'-Dichlorodiphenyltrichloroethane	50-1000	0.9998	0.4	1.2	115.7 (4.7)	110.8 (3.3)	108.1 (1.1)
Endosulfan sulfate	50-1000	0.9997	3.8	12.7	99.0 (7.3)	104.4 (5.3)	86.3 (3.8)
Coumaphos	50-1000	0.9997	5.4	18.1	96.9 (6.0)	93.0 (9.9)	94.5 (2.5)