Determination of various organochlorines in plant foods - GC method

2023-01-18 23:05:47

The widespread use of pesticides has played a positive role in the prevention and control of agricultural pests and diseases, but it has also contaminated crops and the natural environment to varying degrees. Many pesticides are stable in nature and are not easily degraded in nature. Some pesticides directly or indirectly remain in food and vegetables, causing food pollution and endangering human health. Organochlorine pesticides are characterized by high toxicity, refractory degradation, low water solubility and high ester solubility. They can be enriched and amplified with the food chain, causing great harm to human health and ecological environment. Therefore, countries have established stricter pesticide residue limit standards.

Method advantages:

Based on various standards, Dima Technology uses acetonitrile extraction based on the principle of QuEChERS method, concentrates the extract, dissolves it in 1 mL of ethyl acetate-n-hexane, removes it into the QuEChERS purification tube, and analyzes it on the machine. A gas chromatography method was developed to detect a variety of organochlorine pesticide residues in bamboo shoots, tomatoes, spinach and peanuts, which can achieve quasi-deterministic quantification.

1) The limit of quantification is cis-chlordane, trans-chlordane, chlorinated chlordane, PP'-DDD, Î²-endosulfan, OP'-DDT is 1.0 Î¼g/kg, others are 0.2 Î¼g/kg;

2) The advantages of simple pretreatment, less loss of recovery rate, obvious purification effect and good method reproducibility are widely used by analysts;

3) Applicable to all provinces and cities for entry and exit, quality inspection, disease control, food and drug inspection, third-party testing institutions, food testing institutions, large food producers, universities and research institutes.

The following is a detailed solution, please refer to!

Determination of various organic chlorines in plant foods - GC method

1. Scope of application

This scheme is applicable to Î±-hexachlorocyclohexane, pentachloronitrobenzene, lindane, heptachlor, aldrin, Î²-hexachlorocyclohexane, Î´-hexachlorocyclohexane, Î±-endosulfan in bamboo shoots, tomatoes, spinach and peanuts. , cis-chlordane, trans-chlordane, chlorinated chlordane, PP'-DDE, dieldrin, PP'-DDD, beta-endosulfan, PP'-DDT, OP'-DDT.

Quantification limits: cis-chlordane, trans-chlordane, chlorinated chlordane, PP'-DDD, Î²-endosulfan, OP'-DDT was 1.0 Î¼g/kg; others were 0.2 Î¼g/kg.

2, standard preparation

Single standard stock solution: Accurately weigh each standard and prepare a standard stock solution of 1.0 mg/mL with n-hexane.

Mixed standard stock solution: separately absorb each standard standard stock solution and prepare a mixed standard stock solution of 4.0 Î¼g/mL with n-hexane.

3, extraction

3.1 bamboo shoots and tomatoes

(1) 5 g sample, add 15 mL acetonitrile, vortex for 1 min, add 15 mL acetonitrile, 4 g sodium chloride, shake for 5 min, centrifuge at 8000 rpm for 2 min;

(2) Take 10 mL of the supernatant, blow dry with nitrogen under a water bath at 40 Â°C, add 1 mL of ethyl acetate: n-hexane (2:8), dissolve in ultrasound, and purify.

3.2 Spinach

(1) Take 5 g of sample, add 30 mL of acetonitrile, homogenize for 1 min, add 4 g of sodium chloride, shake for 2 min, centrifuge at 8000 rpm for 2 min, and collect 10 mL of supernatant;

(2) The supernatant was evaporated to dryness under reduced pressure in a water bath at 40 Â° C, and dissolved in 1 mL of ethyl acetate: n-hexane (2:8) to be purified.

3.3 Peanuts

(1) 5 g sample, add 15 mL acetonitrile, 2 mL 200 g / L lead acetate solution, 4 g sodium chloride, shake for 5 min, centrifuge at 8000 rpm for 2 min, collect the supernatant;

(2) Add 15 mL of acetonitrile to the residue of the lower layer, repeat the extraction twice in step (1), and combine the supernatant;

(3) Take 15 mL of the supernatant, blow dry with nitrogen under a water bath at 40 Â°C, add 1 mL of ethyl acetate: n-hexane (2:8), dissolve in ultrasound, and purify.

4, purification - ProElut QuE 2 mL Tube (Cat. #: 64576)

The liquid to be purified was transferred to a 2 mL ProElut QuEChERS purification tube, vortexed for 1 min, centrifuged at 8000 rpm for 2 min, and the supernatant was analyzed by GC.

5, chromatographic conditions

Column: DM-1701, 30 m Ã— 0.32 mm Ã— 0.25 Î¼m (Cat. #:7331)

Inlet temperature: 260 Â°C

Heating program: initial temperature 90 Â°C, hold for 1 min, heat up to 180 Â°C at 40 Â°C / min, hold for 4 min, 2.2 Â°C / min to 205 Â°C, hold for 7 min

Carrier gas: nitrogen, flow rate: 1 mL/min

Injection method: split injection

Injection volume: 1.0 Î¼L

ECD: 300 Â°C

6, add recycling results

Addition and recovery of various organic chlorines in bamboo shoots, tomatoes, spinach and peanuts (addition level 20 Î¼g/kg), standard addition: mixed standard stock solution 4.0 Î¼g/mL, 25 Î¼L.

NO.

Compound name

Recovery rate(%)

Bamboo shoot

tomato

spinach

peanut

--å…å…å…

81.97

83.27

102.29

89.66

Pentachloronitrobenzene

92.08

93.30

110.05

95.09

Lin Dan

81.57

83.97

98.39

89.04

Heptachlor

94.39

90.61

112.99

91.11

Aldrin

89.80

88.10

110.73

73.60

--å…å…å…

83.21

100.03

103.01

98.57

Î”-å…å…å…

83.78

92.03

92.78

91.74

Alpha-endosulfan

110.65

116.19

106.77

90.19

Chlordane

99.38

104.89

112.52

109.92

Chlordane

88.04

90.20

118.57

89.28

Chlordane

115.03

115.63

107.62

107.04

PP'-DDE

95.88

97.16

108.81

92.24

Dield

87.96

88.13

102.16

114.64

PP'-DDD

86.34

96.17

86.27

86.68

Beta-endosulfan

105.90

116.88

83.93

111.69

PP'-DDT

99.13

99.55

97.16

109.31

OP'-DDT

80.97

98.76

100.81

83.92