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Analysis of 11 Kinds of Pesticide Residues in Water

Application Introduction

Pesticides can be used for killing insects, fungi and other bionts which are hazardous to crop growth.

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Introduction

Pesticides can be used for killing insects, fungi and other bionts which are hazardous to crop growth. The earliest pesticides used include DDT, BHC, etc., which can kill plenty of pests. However, they were eliminated because they could exist in the environment for a long term and continuously accumulate in animals, plants and human bodies due to their good stability. Later the earliest pesticides were replaced by organophosphorus pesticides (such as Dichlorvos). However, the phosphorus contained in the organo-phosphorus pesticides is easy to result in water eutrophication. During agricultural production, pesticides enter the water environment via sedimentation, surface runoff and other ways, causing a series of problems including water resource pollution, water ecosystem destruction, food security, etc. Therefore it is necessary to monitor pesticide residues contained in water.

Experimental

Materials and Reagents

Methanol, dichloromethane and acetone were HPLC grade; High purity water;

Cleanert® PEP:150 mg/6 mL;

11 kinds of pesticide-mixed standard working solutions: Dichlorvos, Dimethoate, Methyl Parathion, Chlorpyrifos, Malathion, α-BHC, β-BHC, γ- BHC, δ- BHC, o,p`DDT, p,p`DDT;

Sample Preparation

Sample 500 mL of water, add methanol to the water until the proportion between methanol and water reaches 5%; mix the solution uniformly, and keep it as the solution to be purified.

Activate and balance Cleanert® PEP cartridge with 5 mL of methanol and 5 mL of water in turn; load all the aforesaid solution to be purified to the cartridge at the flow rate of 10 mL/min; discard the effluent; keep blowing the cartridge with nitrogen for 30 min; elute the cartridge with 10 mL of acetone and 5 mL of dichloromethane; collect the effluent, blow it to nearly dry with nitrogen at 40 °C and add n-hexane into it until the total volume reaches 1 mL; divide the sample into two: one for GC-ECD detection and the other one for GC-FPD detection.

Instrumentation

GC-ECD

DA-5MS chromatographic column, 30 m × 0.25 mm × 0.25 μm

Injection port temperature: 250 °C

Column temperature: 110 °C (kept for 0.5 min) to 320 °C (kept for 5 min)(15 °C/min rise)

Carrier gas: nitrogen (purity ≥ 99.999%, flow rate: 3.5 mL/min)

Sample size: 1 µL

Injection mode: Splitless injection

 

GC-FPD

DB-17 chromatographic column, 30 m × 0.25 mm × 0.25 μm

Injection port temperature: 250 °C

Detector temperature: 300 °C

Column temperature: 150 °C (kept for 2 min) to 210 °C (8 °C/min rise), then to 250 °C (5 °C/min rise) and kept for 15 min

Carrier gas: nitrogen (purity ≥ 99.999%, line speed: 70 cm/sec)

Combustion gas: hydrogen (purity ≥ 99.999%, flow rate: 90 mL/min)

Oxidizing gas: air (flow rate: 90 mL/min)

Sample size: 1 µL

Injection mode: Splitless injection

Results and Discussion

As is shown in Table 1, the standard addition recoveries of the 11 kinds of in-water pesticide residues are detected by GC-ECD and GC-FPD methods based on SPE technology are between 70% and 110%, conforming to the detection requirement. As shown in Figure 1 ~ Figure 6, the detection results of the 11 kinds of in-water pesticide residues detected with DA-5MS and DB-17 chromatographic columns show good peak shapes and stable retention time.

Table 1 Recoveries and reproducibility of pesticides in water samples (n=3, spiked sample 0.1 mg/kg)

Pesticide

Retention   time/min

Recoveries/%

RSD/%

Dichlorvos

2.105

82.5

4.1

Dimethoate

9.278

95.8

6.3

Methyl Parathion

10.405

108.9

3.2

Chlorpyrifos

10.921

93.0

0.4

Malathion

11.232

95.3

9.2

α-BHC

5.879

93.0

4.0

β-BHC

6.341

97.9

2.7

γ- BHC

6.486

108.6

2.6

δ- BHC

6.716

88.2

1.4

o,p`DDT

9.120

73.9

12.5

p,p`DDT

9.654

85.0

11.6

Figure 1 GC-ECD chromatogram of 0.1 µg/mL standard solution of α-BHC, β-BHC, γ- BHC, δ- BHC, o,p`DDT, p,p`DDT mixed

Figure 2 GC-FPD chromatogram of blank sample

Figure 3 GC-ECD chromatogram of spiked water sample (0.1 µg/mL)

Figure 4 GC-FPD chromatogram of standard solution of 5 kinds of organophosphorus pesticides mixed (0.1 µg/mL)

Figure 5 GC-FPD chromatogram of blank sample

Figure 6 GC-FPD chromatogram of spiked water sample (0.1 µg/mL)

Conclusion

This experiment establishes a pretreatment method for the 11 kinds of pesticide residues contained in water and respectively detects the sample by GC-ECD and GC-FPD methods. The detection results show that, for the water sample added with standard solution (concentration: 0.1 µg/mL), the recoveries of the pesticide residues are between 70% and 110% (conforming to the detection requirement) and RSD is no more than 15% (showing the good detection stability), proving Cleanert® PEP cartridge can be used for detecting the 11 kinds of pesticide residues contained in water.

Order Information

Products

Specification

Cat.No

Cleanert®   PEP

150 mg / 6 mL,   30/pk

PE1506

SPE-M08 Positive   Pressure SPE Device

8 positions

SPE-M08

Syringe Filter   (Nylon)

0.22 μm, diameter   13 mm, 200/pk

AS021320

Syringe

2 mL Without   Needle

LZSQ-2ML

1.5 mL vials

Short-thread and   transparent, 32 × 11.6 mm, 100/pk

AV1001-6

1.5 mL vials caps

9 mm center bore,   blue cap, red rubber/beige PTFE pad, 45. Shore A 1.0 mm, 100/pk

AV2200-0

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