Activated carbon nanofiber produced from electrospun PAN nanofiber as a solid phase extraction sorbent for the preconcentration of organophosphorus pesticides

Figures & data

Table 1. Design of experiment (factors and levels).

Coded values	Actual values
	Amount of sorbent, ${\xi }_1$ (mg)	Solution pH, ${\xi }_2$	Flow rate, ${\xi }_4$ (mL min^−^1)	Amount of salt, ${\xi }_3$ (mg)
−1	10	4	10	0
0	15	7	20	100
1	20	10	30	200

Figure 1. SEM micrographs and fibre diameter distribution of: (a) PAN nanofiber, and (b) PAN-derived CNFs.

Figure 2. FTIR spectra of (a) PAN, and (b) PAN-derived CNFs.

Table 2. Experimental design and results of the central composite design.

Run	Variables				Responses
	Sorbent (mg)	Solution pH	Flow rate (mL min^−^1)	Salt (mg)	Ethion recovery (%)	Fenitrothion recovery (%)	Diazinon recovery (%)
1	15	7	20	100	21.47	9.40	68.41
2	15	4	20	100	66.80	37.82	65.37
3	20	10	30	0	10.42	4.13	70.42
4	15	7	30	100	18.46	7.21	78.74
5	10	7	20	100	2.66	10.62	65.87
6	15	10	20	100	25.04	2.57	52.47
7	20	10	10	0	17.55	4.50	44.37
8	15	7	20	100	23.21	12.50	61.79
9	20	4	30	200	9.81	8.26	7.15
10	10	4	30	0	17.95	5.10	68.06
11	15	7	20	100	24.20	6.66	59.74
12	15	7	10	100	22.31	14.07	65.73
13	15	7	20	100	22.48	13.13	58.81
14	10	4	10	0	28.76	2.11	64.78
15	15	7	20	0	12.68	6.18	58.66
16	15	7	20	200	28.03	13.43	65.55
17	20	4	10	200	21.22	9.20	65.80
18	10	10	30	200	20.95	11.27	63.94
19	10	10	10	200	34.03	19.60	76.71
20	20	7	20	100	11.75	5.74	37.49
21	15	7	20	100	33.99	11.48	67.24

Table 3. ANOVA analysis for responses Y1 (ethion recovery) and Y2 (fenitrothion recovery).

Source	Sum of squares	Degree of freedom	Mean square	F-value	Prob > F-value
For Y1
Model	3163.93	14	226.00	11.09	0.0037
Residual	122.23	6	20.37
Lack of fit	18.78	2	9.39	0.36	0.7163
Pure error	103.45	4	25.86
Total	3286.17	20
$R^2=0.9628$
Adequate precision = 16.814
For Y2
Model	1116.66	14	79.76	8.15	0.0083
Residual	58.71	6	9.79
Lack of fit	30.97	2	15.49	2.23	0.2233
Pure error	27.74	4	6.94
Total	1175.38	20
$R^2=0.9500$
Adequate precision = 13.333

Figure 3. Comparison between the actual and predicted value of: (a) ethion, and (b) fenitrothion recovery.

Figure 4. Main effect plots of factors on ethion recovery: (a) amount of sorbent, (b) solution pH, (c) flow rate, and (d) amount of salt.

Figure 5. Response surface and contour plots showing the effect of: (a) salt and sorbent amount, and (b) salt amount and solution pH, on ethion recovery.

Figure 6. Response surface and contour plots showing the effect of salt and sorbent amount on fenitrothion recovery.

Table 4. Results of determination and recoveries of Rodsar river water samples spiked at concentration level of 3 ng mL⁻¹ of each OPPs.

OPPs	Initial	Found (ng mL^−^1)	Recovery percent (%)
Ethion	Not detected	3.15	105
Fenitrothion	Not detected	2.94	98
Diazinon	Not detected	3.06	102

Figure 7. HPLC chromatograms of Roudsar river water sample of: (a) unspiked, and (b) spiked with 3 ng mL⁻¹ ethion, fenitrothion and diazinon under optimized conditions.

Table 5. Comparison of the current PF-SPE method with the other previously reported methods for determination of OPPs in water samples.

Method	Final determination technique	LOD	Recovery percent (%)	References
SPE	GC-MS	8.9–19 µg L^−^1	–	^[^23^]
HS-SPME	GC-FTD/MS	10–40 ng L^−^1	80–120	^[^24^]
LPME	HPLC-DAD	10 µg L^−^1	92.3–96.7	^[^25^]
Magnetic SPE	HPLC-UV	0.11–0.15 µg L^−^1	83–98	^[^26^]
PF-SPE	HPLC-DAD	0.09–0.22 µg L^−^1	37–78	This work

Table A1. SEM micrographs and fibre diameter distribution of PAN nanofibers electrospun under different conditions.

No.	Concentration (wt%)	Voltage (kV)	Distance (cm)	SEM micrographs	Fibre diameter distribution	AFD (nm)	Standard FD (nm)
1	16	20	10			294	31
2	16	10	15			398	18
3	8	20	15			100	19
4	8	10	10			48	9
5	9.6	15	12.5			123	31
6	14.4	15	12.5			108	21
7	12	12	12.5			146	28
8	12	18	12.5			95	27
9	12	15	11			98	18
10	12	15	14			94	22
11	12	15	12.5			98	12

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