Determination of eight neonicotinoid pesticides in wastewater by solid phase extraction combined with liquid chromatography-tandem mass spectrometry

doi:10.3724/SP.J.1123.2023.11010

Abstract

Abstract:

Neonicotinoid pesticides are a relatively new class of pesticides that have garnered significant attention owing to their potential ecological risks to nontarget organisms. A method combining solid phase extraction with liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) was developed for the rapid and accurate detection of eight neonicotinoid pesticides (dinotefuran, E-nitenpyram, thiamethoxam, clothianidin, imidacloprid, imidaclothiz, acetamiprid, and thiacloprid) in wastewater. The chromatographic mobile phase and MS parameters were selected, and a single-factor method was used to determine the optimal column type, extraction volume, sample loading speed, and pH for SPE. The optimal parameters were as follows: column type, HLB column (500 mg/6 mL); sample extraction volume, 500 mL; sample loading speed, 10 mL/min; and sample pH, 6-8. The matrix effects of the wastewater samples were reduced by optimizing the chromatographic gradient-elution program, examining the dilution factor of the samples, and using the isotope internal standard calibration method. Prior to analysis, the wastewater samples were diluted 5-fold with ultrapure water for pretreatment. Subsequently, 2 mmol/L ammonium acetate aqueous solution containing 0.1% (v/v) formic acid and methanol was used as mobile phases for gradient elution on a ZORBAX Eclipse Plus C18 column (100 mm×2.1 mm, 1.8 μm). The samples were quantified using positive-ion multiple reaction monitoring (MRM) mode for 10 min. Imidacloprid-d4 was used as the isotope internal standard. The SPE process was further optimized by applying response surface methodology to select the type and mass of rinsing and elution solvents. The optimal pretreatment of the SPE column included rinsing with 10% methanol aqueous solution and elution with methanol-acetonitrile (1∶1, v/v) mixture (7 mL). The eight neonicotinoid pesticides showed satisfactory linearity within the relevant range, with linear correlation coefficients (r) all greater than 0.9990. The method detection limits (MDLs) ranged from 0.2 to 1.2 ng/L, and the method quantification limits (MQLs) ranged from 0.8 to 4.8 ng/L. The average recoveries of the eight neonicotinoid pesticides were in the range of 82.6%-94.2% at three spiked levels, with relative standard deviations (RSDs) ranging from 3.9% to 9.4%. Finally, the optimized method was successfully applied to analyze wastewater samples collected from four sewage treatment plants. The results indicated that the eight neonicotinoid pesticides could be generally detected at concentrations ranging from not detected (ND) to 256 ng/L. The developed method has a low MDL and high accuracy, rendering it a suitable choice for the trace detection of the eight neonicotinoid pesticides in wastewater when compared with other similar methods. The proposed method can be utilized to monitor the environmental impact and assess the potential risks of neonicotinoid pesticides in wastewater, thus promoting the protection of nontarget organisms and the sustainable use of these pesticides in agriculture.

Key words: liquid chromatography-tandem mass spectrometry (LC-MS/MS), solid phase extraction (SPE), neonicotinoid pesticides, wastewater, matrix effect, response surface methodology (RSM)

CLC Number:

O658

WANG Haitang, LI Hanyin, LU Qiwei, HE Shilong. Determination of eight neonicotinoid pesticides in wastewater by solid phase extraction combined with liquid chromatography-tandem mass spectrometry[J]. Chinese Journal of Chromatography, 2024, 42(9): 856-865.

Figures/Tables 13

Table 1 Retention times and MS parameters of the target compounds

Compound	Retention time/min	Precursor ion (m/z)	Product ion (m/z)	Fragmentor/V	Collision energy/eV
Dinotefuran	3.35	203.2	129.1^*	80	12
			87.1	80	14
E-Nitenpyram	3.87	271.1	99.1	95	14
			56.2^*	95	23
Thiamethoxam	5.07	292.1	211.0^*	80	10
			131.8	80	18
Clothianidin	5.37	250.1	168.9^*	85	14
			131.8	85	16
Imidacloprid-d4	6.09	260.1	213.1^*	100	14
			179.1	100	20
Imidacloprid	6.11	256.1	209.1^*	85	12
			175.1	85	18
Imidaclothiz	6.26	262.1	181.0^*	95	16
			122.0	95	35
Acetamiprid	6.72	223.1	126.0^*	110	20
			56.1	110	16
Thiacloprid	7.45	253.1	125.9^*	110	20
			89.9	110	45

Fig. 1 Response values of the target compounds using different mobile phases

Fig. 2 Effect of different factors on the recoveries of the target compounds (n=3) a. extraction column; b. extraction volume; c. sample loading speed; d. pH.

Fig. 3 Chromatograms of the target compounds under different gradient elution programs Gradient elution program: a. 0-3 min, 10%B-45%B; 3-7 min, 45%B-80%B; 7-7.1 min, 80%B-10%B; 7.1-8.1 min, 10%B. b. 0-5 min, 10%B-45%B; 5-9 min, 45%B-80%B; 9-9.1 min, 80%B-10%B; 9.1-10.1 min, 10%B. Peak identifications: 1. dinotefuran; 2. E-nitenpyram; 3. thiamethoxam; 4. clothianidin; 5. imidacloprid; 6. imidaclothiz; 7. acetamiprid; 8. thiacloprid.

Fig. 4 Effects of different dilution folds and quantitative methods on the matrix effects (MEs) of the target compounds

Table 2 Three factors and three levels of response surface methodology test

Factor	Code	Levels
Factor	Code	-1	0	1
Volume fraction of methanol	X₁	0	5	15
in water/%
Volume fraction of acetonitrile	X₂	0	50	100
in methanol/%
Volume of eluent/mL	X₃	3	6	9

Table 3 Analysis of variance (ANOVA) of regression model

Source	Sum of square	Degree of freedom	Mean square	F- value	P- value
Model	288.37	9	32.04	26.06	0.0001^*
X₁	3.19	1	3.19	2.59	0.1514
X₂	10.24	1	10.24	8.33	0.0235^*
X₃	112.5	1	112.5	91.5	<0.0001^*
X₁X₂	0.0025	1	0.0025	0.002	0.9653
X₁X₃	0.0006	1	0.0006	0.0005	0.9826
X₂X₃	0.0306	1	0.0306	0.0249	0.879
$X 1 2$	0.005	1	0.005	0.0041	0.9509
$X 2 2$	32.79	1	32.79	26.67	0.0013^*
$X 3 2$	121.78	1	121.78	99.05	<0.0001^*
Residual	8.61	7	1.23
Lack of fit	0.2144	3	0.0715	0.0341	0.9903
Pure error	8.39	4	2.1
Cor total	296.98	16

Table 3 Analysis of variance (ANOVA) of regression model

Source	Sum of square	Degree of freedom	Mean square	F- value	P- value
Model	288.37	9	32.04	26.06	0.0001^*
X₁	3.19	1	3.19	2.59	0.1514
X₂	10.24	1	10.24	8.33	0.0235^*
X₃	112.5	1	112.5	91.5	<0.0001^*
X₁X₂	0.0025	1	0.0025	0.002	0.9653
X₁X₃	0.0006	1	0.0006	0.0005	0.9826
X₂X₃	0.0306	1	0.0306	0.0249	0.879
$X 1 2$	0.005	1	0.005	0.0041	0.9509
$X 2 2$	32.79	1	32.79	26.67	0.0013^*
$X 3 2$	121.78	1	121.78	99.05	<0.0001^*
Residual	8.61	7	1.23
Lack of fit	0.2144	3	0.0715	0.0341	0.9903
Pure error	8.39	4	2.1
Cor total	296.98	16

Fig. 5 Response surface methodology plots of effect of rinsing, elution solvent and elution volume on the recoveries of thiacloprid

Table 4 Optimal parameters of the eight neonicotinoid pesticides obtained by response surface methodology

Compound	X₁/%	X₂/%	X₃/mL	Recovery/%
Dinotefuran	10.49	50	7.056	96.17
E-Nitenpyram	13.32	80	6.561	96.38
Thiamethoxam	9.32	50	6.444	96.63
Clothianidin	4.24	80	7.137	93.81
Imidacloprid	3.92	60	6.711	95.16
Imidaclothiz	6.08	30	6.678	96.01
Acetamiprid	6.66	60	7.026	98.53
Thiacloprid	12.10	70	6.714	96.47

Table 5 Linear regression equations, correlation coefficients (r), linear ranges, method detection limits (MDLs) and method quantification limits (MQLs) of the eight neonicotinoid compounds

Compound	Regression equation	r	Linear range/(μg/L)	MDL/(ng/L)	MQL/(ng/L)
Dinotefuran	y=1.723x+0.0374	0.9996	0.5-100	0.8	3.2
E-Nitenpyram	y=1.545x+0.0376	0.9995	0.2-100	0.4	1.6
Thiamethoxam	y=3.734x+0.0654	0.9996	0.2-100	0.5	2.0
Clothianidin	y=0.499x+0.013	0.9991	0.2-100	0.6	2.4
Imidacloprid	y=1.345x+0.0458	0.9995	0.5-100	1.2	4.8
Imidaclothiz	y=1.302x+0.0256	0.9993	0.2-100	0.4	1.6
Acetamiprid	y=7.443x+0.201	0.9994	0.1-100	0.2	0.8
Thiacloprid	y=7.342x+0.091	0.9995	0.1-100	0.3	1.2

Table 6 Recoveries and RSDs of the eight neonicotinoid compounds at three spiked levels (n=3)

Compound	Added/(ng/L)	Recovery/%	RSD/%	Compound	Added/(ng/L)	Recovery/%	RSD/%
Dinotefuran	10	86.4	8.7	Imidacloprid	10	87.1	9.4
	200	93.8	6.5		200	91.8	5.9
	1000	94.2	7.9		1000	87.5	5.5
E-Nitenpyram	10	91.8	7.9	Imidaclothiz	10	85.4	8.6
	200	93.5	6.5		200	92.5	7.8
	1000	93.8	5.8		1000	91.7	6.9
Thiamethoxam	10	89.4	9.4	Acetamiprid	10	82.6	6.8
	200	92.1	8.4		200	86.8	4.7
	1000	94.1	5.2		1000	92.7	6.2
Clothianidin	10	87.2	9.3	Thiacloprid	10	85.8	6.4
	200	92.1	5.8		200	91.1	4.5
	1000	93.3	6.7		1000	93.4	3.9

Table 7 Comparison with other literatures

Analytes	Sample type	Sample volume/ (mL)	MDL/ (ng/L)		Linear range/ (μg/L)		RSD/%		RE/%	Ref.
Dinotefuran, E-nitenpyram, thiamethoxam, clothianidin, imidacloprid, imidaclothiz, acetamiprid, thiacloprid	wastewater	100	0.2-	1.2	0.1-	100^*	3.9-	9.4	82.6-94.2	this study
Acetamiprid, imidacloprid, thiacloprid, thiamethoxam, clothianidin, dinotefuran	wastewater	500	1.8-	6.8	1-	500	5.26-	11.5	33.7-116	[17]
Dinotefuran, thiamethoxam, clothianidin, imidacloprid, imidaclothiz, acetamiprid, thiacloprid	drinking water	500	0.01-	0.2	0.01-	200	1.6-	7.3	74.0-123	[9]
Thiamethoxam, clothianidin, imidacloprid, acetamiprid,	sea water	1000	0.1-	7.8	0.05-	100	3-	18	72.0-117	[24]
thiacloprid	river water		0.1-	1.0

Table 8 Contents and MEs of the eight neonicotinoid compounds in real wastewater samples

Compound	Contents/(ng/L)				ME/%
Compound	S1	S2	S3	S4	ME/%
Dinotefuran	ND	5.49	6.69	23.1	84.3-98.7
E-Nitenpyram	ND	4.83	5.39	13.2	80.9-96.2
Thiamethoxam	11.6	18.1	9.46	15.2	90.4-103.5
Clothianidin	8.91	13.4	10.7	17.9	89.7-108.1
Imidacloprid	31.1	256	178	189	97.2-113.7
Imidaclothiz	ND	14.5	14.2	12.3	93.2-104.8
Acetamiprid	8.45	17.9	16.6	57.2	96.9-112.7
Thiacloprid	135	1.98	2.47	1.89	87.6-105.3

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