基于多齿功能单体的三聚氰胺印迹材料的制备及应用

doi:10.7503/cjcu20200129

摘要/Abstract

摘要：

以三聚氰胺(MEL)为模板分子, 采用沉淀聚合方法研究了以衣康酸(IA)为多齿功能单体, 乙二醇二甲基丙烯酸酯(EGDMA)为交联剂时, 组分之间摩尔比对三聚氰胺印迹聚合物(MIP)选择性的影响. 研究发现, 当MEL与IA摩尔比为1:1.5时, 所合成的MIP对三聚氰胺具有最佳选择性, 选择性系数k=10.41(以三聚氰酸为对照物). 此时IA的识别位点(羧基)与三聚氰胺的可识别位点(胺基)摩尔比为1:1, 因此, 不会出现由过量功能单体引起的非特异性吸附. Scatchard分析结果表明, 这种MIP能够在更宽的三聚氰胺浓度范围(1~100 mg/L)内只表现出特异性吸附. 以灭蝇胺为对照物时, k_NIP<1但k_MIP>1, 该结果证明MIP对分子的形状有良好的识别能力. 最后, 以制备的MIP为固相萃取吸附剂, 结合高效液相色谱/紫外检测器(HPLC/UV)建立了三聚氰胺测定方法. 当牛奶(奶粉)中MEL的加标浓度分别为15, 600和4500 μg/L(μg/kg)时检测的加标回收率为92.34%~109.4%.

关键词: 分子印迹, 多齿功能单体, 衣康酸, 三聚氰胺, 固相萃取

Abstract:

A molecularly imprinted polymer(MIP) was prepared using melamine(MEL) as template, itaconic acid(IA) as functional monomer and ethylene glycol dimethacrylate(EGDMA) as cross-linker. The effect of molar ratio among these components on the selectivity of MIP was investigated. It is found that the prepared MIP presents the best selectivity to MEL when molar ratio of MEL to IA is 1:1.5. The selectivity coefficient(k) of the synthesized MIP to MEL is 10.41(CYA as control). Since the molar ratio of carboxyl groups(recognition sites) of IA and amino groups(recognizable groups) of MEL is exactly 1: 1, the non-specific adsorption caused by excessive functional monomers will be avoided. Scatchard analysis indicates that MIP only exhibits specific binding to MEL within the concentration range from 1 to 100 mg/L of MEL. On the other hand, when CYR is used as the control, the k_NIP is less than 1 but the k_MIP is greater than 1. This result implies the synthesized MIP has good discriminating ability for the shape of molecules. Using the prepared MIP as the adsorbent of solid phase extraction(SPE), a method of MISPE hyphenated to high performance liquid chromatography with UV detector(MISPE-HPLC/UV) was established for determination of melamine. The recoveries of MEL in the spiked milk and milk powder samples vary from 92.34% to 109.4%.

Key words: Molecular imprinting, Multidentate functional monomer, Itaconic acid, Melamine, Solid phase extraction

中图分类号:

O657

TrendMD:

王晓如,张娜,邢钧. 基于多齿功能单体的三聚氰胺印迹材料的制备及应用. 高等学校化学学报, 2020, 41(7): 1521.

WANG Xiaoru,ZHANG Na,XING Jun. Preparation and Application of Melamine Imprinted Material Using Itaconic Acid as Multidentate Functional Monomer. Chem. J. Chinese Universities, 2020, 41(7): 1521.

图/表 14

Scheme 1 Molecular structures of IA, MEL, CYR and CYA.

Scheme 2 Synthetic route of melamine imprinted polymer.。。

Table 1 Performance of MIPs under different synthetic conditions

MIPs	Molar ratio of reactant			Q/(mg·g^-1)	IF^*	k
MIPs	MEL/IA	IA/EGDMA		Q/(mg·g^-1)	IF^*	k
MIP1	1:1.0		1:13.5	0.33	1.94	1.24
MIP2	1:1.5		1:13.5	0.49	2.88	1.36
MIP3	1:2.0		1:13.5	0.45	2.67	1.17
MIP4	1:1.5		1:15	0.56	2.15	1.12
MIP5	1:1.5		1:10	0.51	1.70	1.23
MIP6	1:1.5		1:5	0.64	2.46	1.38
MIP7	1:1.5		1:4	1.02	3.00	1.96
MIP8	1:1.5		1:3	1.07	2.32	1.42

Fig.1 FTIR spectra(A) and SEM images of MIP(B) and NIP(C)

Fig.2 Binding isotherms(A) and scatchard analysisof MIP(B) and NIP(C)

Table2 Comparison of binding characteristics and affinity of MIP towards melamine

Molar ratio^a	c/(mg·L^-1)	V/mL	m^b/mg	m_MIP/mg	Q_max/(mg·g^-1)		m'^c/mg	Ref.
Molar ratio^a	c/(mg·L^-1)	V/mL	m^b/mg	m_MIP/mg	Specific	Non-specific	m'^c/mg	Ref.
3: 4	20—120	10	1.2	20	0.077	32.07	0.641	[24]
1: 1.6	5—60	15	0.9	30	5.50	13.50	0.405	[26]
1: 8	1—1000	5	5.0	50	1.023	9.261	0.463	[27]
3: 4	0.5—1000	6	6.0	20	20.34	102.8	2.055	[28]
1: 1	1—100	5	0.5	20	2.338	—	0.047	This work

Fig.3 Kinetic adsorption isotherms of MIP and NIP

Table 3 Selectivity factors of MIP and NIP to MEL(non-competition)

	Analyte	Q/(mg·g^-1)	K_D/(L·g^-1)	k
MIP	MEL	1.146	0.177	—
	CYR	0.442	0.054	3.28
	CYA	0.084	0.017	10.41
NIP	MEL	0.316	0.032	—
	CYR	0.306	0.034	0.94
	CYA	0.082	0.017	1.88

Table 4 Comparison of selectivity factors of MIP to MEL

Target	Control	Functional monomer	k	Ref.
MEL	CYA	9-VC^b	2.53	[33]
DTY^a	CYA	MAA	2.05	[9]
MEL	CYA	IA	10.41	This work

Table 5 Selectivity factors of MIP and NIP using mixed solution of MEL(10 mg/L) and CYR(10 mg/L)

	Analyte	Q/(mg·g^-1)	K_D/(L·g^-1)	k
MIP	MEL	0.942	0.105	1.96
	CYR	0.530	0.054	—
NIP	MEL	0.313	0.027	0.82
	CYR	0.348	0.033	—

Fig.4 Optimization of MISPE conditions: loading solvent(A), washing solvent(B) and eluting solvent(C) (C) Elution sovent: a. Vmethanol: Vacetic acid=8:2; b. Vmethanol: Vacetic acid=9:1; c. Vmethanol: V N H 3 · H 2 O =8:2; d. Vmethanol: V N H 3 · H 2 O =9:1.

Table 6 Comparison with previous methods based on molecularly imprinting technology

Sample	Method	Linear range/(μg·L^-1)	LOD/(μg·L^-1)	Ref.
Milk powder, feed	MISBSE^a-HPLC/UV	2—200	0.54	[22]
Milk	MMISPE^b-HPLC/MS/MS	10—1000	2.6	[34]
Milk	MISPE UPLC/UV	27—2700	0.8	[35]
Egg	MISPE HPLC/UV	100—25000	0.5	[36]
Milk	MIDE^c-HPLC/DAD	—	0.6	[37]
Milk, milk powder	MISPE-HPLC/UV	1—1000	0.3	This work

Table 7 Recoveries of MEL in spiked milk and milk powder samples

Sample	Spiking concentration(μg· $L - 1 a$ , μg·k $g - 1 b$ )	Recovery(%)	RSD(%, n=3)
Milk 1	15	92.34	3.1
	600	98.73	4.1
	4500	101.40	2.2
Milk 2	15	95.22	4.1
	600	100.30	6.5
	4500	105.70	3.9
Milk powder 1	15	95.01	6.4
	600	94.67	2.5
	4500	107.20	3.0
Milk powder 2	15	95.35	4.4
	600	95.50	4.9
	4500	109.40	3.2

Table 7 Recoveries of MEL in spiked milk and milk powder samples

Sample	Spiking concentration(μg· $L - 1 a$ , μg·k $g - 1 b$ )	Recovery(%)	RSD(%, n=3)
Milk 1	15	92.34	3.1
	600	98.73	4.1
	4500	101.40	2.2
Milk 2	15	95.22	4.1
	600	100.30	6.5
	4500	105.70	3.9
Milk powder 1	15	95.01	6.4
	600	94.67	2.5
	4500	107.20	3.0
Milk powder 2	15	95.35	4.4
	600	95.50	4.9
	4500	109.40	3.2

Fig.5 MISPE-HPLC/UV chromatograms of milk spikedwith MEL at 600 μg/L(A) and milk powder spiked at 4500 μg/kg(B)

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