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Determination of 9 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 organophosphorus 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. It is necessary to monitor pesticide residues contained in water.

Cleanert® LDC-PEP SPE cartridge is applicable to the pretreatment of large-volume water samples due to its advantages - fast sample loading, time saving and stable data.

Experimental

Materials and Reagents

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

Cleanert® LDC-PEP:1 g/200 mL;

9 kinds of pesticide-mixed standard working solutions: Dichlorvos, Dimethoate, Methyl Parathion, Chlorpyrifos, Malathion, α-BHC, β-BHC, γ- BHC and δ- BHC;

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 store it as the solution to be purified.

Activate and balance Cleanert® LDC-PEP columns with 10 mL of methanol (soak the columns for 5min after adding methanol to infiltrate the packing uniformly) and 10 mL of water in turn; load all the aforesaid solution to be purified to the columns at the flow rate of 90 mL/min; discard the effluent; keep pumping the columns for 30 min; connect a anhydrous sodium sulfate column under the columns; elute the columns 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: 10 mL/min)

Combustion gas: hydrogen (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 9 kinds of in-water pesticide residues 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 9 kinds of 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

2.129

74.2

4.1

Dimethoate

9.230

89.2

6.3

Methyl Parathion

10.421

106.1

3.2

Chlorpyrifos

10.970

87.8

0.4

Malathion

11.269

90.7

9.2

α-BHC

7.251

75.6

1.6

β-BHC

7.440

83.8

2.4

γ- BHC

7.680

94.2

4.3

δ- BHC

7.759

94.6

2.7

Figure 1 GC-ECD chromatogram of 0.1 µg/mL mixed standard solution of 4 kinds of BHC

Figure 2 GC-ECD chromatogram of spiked water sample (0.1 µg/mL)

Figure 3 GC-FPD chromatogram of standard solution of 5 kinds of organophosphorus pesticides mixed (0.1 µg/mL)

Figure 4 GC-FPD chromatogram of blank sample

Figure 5 GC-FPD chromatogram of spiked water sample (0.1 µg/mL)

Conclusion

This experiment establishes a pretreatment method for the 9 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 pesticide residues are between 70% and 110% (conforming to the detection requirement) and RSD is no more than 10% (showing the good detection stability), proving Cleanert® LDC-PEP column can be used for detecting the 9 kinds of pesticide residues in water.

Order Information

Products

Specification

Cat.No

Cleanert®   LDC-PEP

1 g / 200 mL

LPE000100

Nitrogen blowing   instrument

Maximal 15   sample

NV15-G

1.5 mL vials

Screw neck vials, 12 × 32 mm

AV1001-6

Caps and Septa

Screw neck cap, center hole; red silicone/white PTEE septa, slitted

AV2200-0

Syringe   Filter(Nylon)

Monofilm,   13 mm, 0.22 μm

AS021320

Disposable   Needle-Free injection systems

2 mL,100/pk

LZSQ-2ML


  • Cleanert LDC

    Cleanert LDC is a specially designed SPE format with a much larger cross-section area to allow a large flow rate through the column,

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