基于场放大进样和石墨烯量子点双重富集毛细管电泳分离检测三聚氰胺和双氰胺

doi:10.3724/SP.J.1123.2021.08017

摘要/Abstract

摘要：

通过热解法制备了硫掺杂的石墨烯量子点(S-GQDs),同石墨烯量子点(GQDs)相比,S原子的引入有效改善了GQDs的表面状态和化学特性、增强其对正电荷的捕获能力,使其更易与阳离子相互作用。以S-GQDs为载体,结合电堆积富集技术,发展了一种基于场放大进样(FASI)和S-GQDs放大的双重富集毛细管电泳(CE)分离检测三聚氰胺和双氰胺的方法。三聚氰胺和双氰胺在酸性介质中带正电荷,电动进样时快速迁移到毛细管入口端进行FASI预富集;同时带负电荷的S-GQDs向阳极端迁移,在样品与缓冲溶液的界面处通过静电作用吸附样品离子,S-GQDs作为载体使检测信号进一步放大。实验考察了缓冲溶液中S-GQDs的体积分数、缓冲溶液的组成及pH、进样时间等因素对富集分离效果的影响。当缓冲溶液的pH为4.6时,进样时间可延长至450 s。同常规电动进样(10 kV×10 s)相比,采用FASI与S-GQDs双重放大技术可使检测灵敏度提高1.6×10⁵倍。该方法对三聚氰胺和双氰胺检测的线性范围是1.0×10^-14~1.0×10^-8mol/L,相关系数(r²)大于0.999,检出限分别为2.6×10^-15和5.7×10^-15mol/L。实现了对盐酸二甲双胍中三聚氰胺和双氰胺的高灵敏检测,回收率分别为95.9%~102.4%和92.0%~106.0%,相对标准偏差(RSD)小于5%。该方法操作简单,分离效果好,准确度高,重现性好,适用于分离检测不同盐酸二甲双胍制剂中的三聚氰胺和双氰胺。

关键词: 硫掺杂石墨烯量子点, 毛细管电泳, 三聚氰胺, 双氰胺

Abstract:

Sulfur-doped graphene quantum dots (S-GQDs) were prepared by the pyrolysis of citric acid and mercaptopropionic acid. Compared with graphene quantum dots (GQDs), the S-GQDs have improved surface state and chemical reactivity, and thus, exhibited stronger interaction with cations. Based on its excellent affinity for cations, a dual preconcentration technique combining field-amplified sample injection (FASI) and S-GQDs as multianalyte carriers was developed for the determination of melamine and dicyandiamide by capillary electrophoresis (CE). During the FASI process, a large quantity of analytes was introduced into the capillary and accumulated at the capillary inlet. Concurrently, the S-GQDs migrated to the anode and captured the analytes on its surface at the boundary of the sample and buffer solution. The use of S-GQDs allows the capture of abundant analytes, which can amplify the detection signal. This new protocol was evaluated by the quantitative determination of melamine and dicyandiamide in metformin hydrochloride preparations. The effect of volume fraction of the S-GQDs in the buffer solution, the composition and pH of the buffer, and the sample injection time on the preconcentration and separation were investigated. By controlling the pH at 4.6, the sample injection time was prolonged to 450 s. A very large amount of melamine and dicyandiamide, bearing positive electric charges, were injected into the capillary and were captured by S-GQDs. The assay using FASI preconcentration and S-GQDs as enhancer resulted in a 1.6×10⁵-fold improved sensitivity compared with that obtained with traditional 10-kV electrokinetic injection for 10 s. The calibration curves of melamine and dicyandiamide were obtained in the concentration range from 1.0×10^-14 to 1.0×10^-8mol/L, with correlation coefficients (r²) >0.999. The detection limits (S/N=3) were 2.6×10^-15mol/L for melamine and 5.7×10^-15mol/L for dicyandiamide. The recoveries of the two analytes were 95.9%-102.4% and 92.0%-106.0%, respectively, with relative standard deviations (RSDs) of no more than 5%. The RSD values of peak height, peak area, and migration time were all less than 5.6%. This method is reliable, easy, and exhibits a good separation effect. This proves that the S-GQD-enhanced CE method could be developed into a new and sensitive technique for the determination of melamine and dicyandiamide in different preparations of metformin hydrochloride.

Key words: sulfur-doped graphene quantum dots (S-GQDs), capillary electrophoresis (CE), melamine, dicyandiamide

中图分类号:

O658

李超, 王琪, 张召香. 基于场放大进样和石墨烯量子点双重富集毛细管电泳分离检测三聚氰胺和双氰胺[J]. 色谱, 2022, 40(3): 289-295.

LI Chao, WANG Qi, ZHANG Zhaoxiang. Field-amplified sample injection and graphene quantum dot dual preconcentration in the analysis of melamine and dicyandiamide by capillary electrophoresis[J]. Chinese Journal of Chromatography, 2022, 40(3): 289-295.

图/表 10

图1 (a)S-GQDs的制备和(b)三聚氰胺和双氰胺在S-GQDs上的吸附

Fig. 1 (a) Preparation of sulfur-doped graphene quantum dots (S-GQDs) and (b) adsorption of melamine and dicyandiamide on the S-GQDs

图2 基于场放大进样和石墨烯量子点双重富集的CE分离检测示意图

Fig. 2 Schematic diagrams of CE separation based on field-amplified sample injection and graphene quantum dot dual preconcentration a. field-amplified sample injection preconcentration; b. preconcentration of S-GQDs as multianalyte carriers; c. CE separation. Veo: velocity of electroosmotic flow; Vep: velocity of electrophoresis.

图3 S-GQDs的(a)TEM图、(b)粒径分布图和(c)XRD谱图

Fig. 3 (a) Transmission electron microscopy (TEM) image, (b)particle size distribution, and (c) X-ray diffraction (XRD) pattern of the as-prepared S-GQDs

图4 (a) S-GQDs的XPS全谱图和(b)S 2p的高分辨XPS谱图

Fig. 4 (a) Full-range X-ray photoelectron spectrum (XPS) of S-GQDs and(b) high resolution XPS of S 2p

图5 缓冲溶液中S-GQDs的体积分数对三聚氰胺和双氰胺富集分离的影响

Fig. 5 Effect of the volume fraction of S-GQDs in the buffer on the analysis of melamine and dicyandiamide Volume fraction of S-GQDs: a. 0; b. 10%; c. 20%; d. 25%. Peak 1: melamine; peak 2: dicyandiamide.

图6 进样时间对三聚氰胺和双氰胺的峰高和分离效率的影响

Fig. 6 Effect of injection time on peak height and separation efficiency of melamine and dicyandiamide

图7 富集前后对比

Fig. 7 Comparison of electropherograms without (a) and with (b) FASI and S-GQDs dual preconcentration a. 50 mmol/L phosphate buffer solution; pH 4.6. The concentrations of both melamine and dicyandiamide were 1.0×10-6mol/L. Sample injection volume: 10 kV×10 s. b. Buffer solution (50 mmol/L phosphate+25% (v/v) S-GQDs). The concentrations of both melamine and dicyandiamide were 1.0×10-10mol/L. FASI volume: 10 kV×450 s. Peaks: 1. melamine; 2. dicyandiamide.

表1 三聚氰胺和双氰胺的回归方程、相关系数、线性范围、检出限和精密度(n=5)

Table 1 Regression equations, correlation coefficients (r2), linear ranges, LODs, and precisions (RSDs) of melamine and dicyandiamide (n=5)

Compound	Regression equation	r²	linear range/ (mol/L)	LOD/ (mol/L)	RSDs/%
Compound	Regression equation	r²	linear range/ (mol/L)	LOD/ (mol/L)	Peak height	Peak area	Migration time
Melamine	y=-238.8x+3349.1	0.9996	10^-14-10^-8	2.6×10^-15	2.8	2.6	4.3
Dicyandiamide	y=-219.6x+3074.3	0.9992	10^-14-10^-8	5.7×10^-15	3.2	3.7	5.6
y: peak height; x: -log c; c: concentration, mol/L.

表2 与其他测定三聚氰胺和双氰胺的方法的比较

Table 2 Comparison with other methods for the determination of melamine and dicyandiamide

Method	Detection limits				Reference
Method	Melamine		Dicyandiamide		Reference
LC-MS	54	μg/L	5.4	μg/L	[1]
HPLC-MS	0.1	mg/kg	0.4	mg/kg	[2]
Tandem dual solid phase extraction cartridges-HPLC-electrospray	1.48	μg/kg	13.61	μg/kg	[3]
ionization multi-stage MS
Magnetic surface molecularly imprinted polymers-HPLC	15	μg/L	-		[4]
FASI+S-GQDs CE	2.6×10^-15	mol/L	5.7×10^-15	mol/L	this work

表3 盐酸二甲双胍样品中三聚氰胺和双氰胺的加标回收率及其RSD(n=5)

Table 3 Spiked recoveries of melamine and dicyandiamide and their RSDs in metformin hydrochloride samples (n=5)

Sample	Melamine					Dicyandiamide
Sample	Original/ (μg/L)	Added/ (μg/L)	Found/ (μg/L)	Recovery/ %	RSD/ %	Original/ (μg/L)	Added/ (μg/L)	Found/ (μg/L)	Recovery/ %	RSD/ %
1^#	82.5	80.0	159.2	95.9	3.3	5.6	5.0	10.2	92.0	2.2
2^#	67.9	80.0	149.8	102.4	2.9	1.2	5.0	6.5	106.0	4.4
3^#	96.2	80.0	175.1	98.6	4.8	2.9	5.0	7.6	94.0	2.8

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