两极隔离式双极电极的电化学发光行为及其分析特性研究

孙阿龙等
摘要设计了一种两极隔离式双极电极电化学发光装置,并以此装置为基础,研究了电化学发光试剂鲁米诺在此装置中的电化学发光行为和分析特性。通过外加电场的诱导,可以在双极电极的两极富集、分离对应的阴、阳离子,使鲁米诺阴离子富集于双极电极的阳极端,待检测的阳离子富集于双极电极阴极端。根据鲁米诺在阳极端的电化学发光信号定量分析阴极端所富集的阳离子的总量。\[15、16\]。其中非空间隔离式结构的双极电极的理论研究和应用特别广泛\[15\]。 Crooks等将非隔离式双极电极与微流控技术结合,研究人员发展了双极电极电化学发光化学\[8~14\]、生物传感\[17\],分析物分离富集\[18~24\]等方法,极大拓宽了双极电极的理论研究和分析应用范围\[15\]。
Zhang等系统研究了两极空间隔离式双极电极的电化学理论和分析特性\[16,25\],成功研制了两极隔离式双极纳米、微米电极\[16\],研究了此类双极电极的电化学传感和超微空间传感特性,极大拓展了两极隔离式双极电极的发展空间和应用范围。但是有关两极隔离式双极电极的电化学发光特性尚未见文献报道。
本研究设计了一种两极隔离式双极电极电化学发光装置,并以此装置为基础,研究了两极隔离式双极电极在鲁米诺电化学发光体系中电化学发光行为和分析特性。本方法具有如下的优点:(1)与微流控双极电极电化学发光装置相比,本装置具有设计简单、便宜、易于加工的特点;(2)双极电极的阳极端和阴极端被分隔在不同的电解室,分析物的富集、分离介质和电化学发光传感反应的介质可以完全依据各自反应的要求、方便选择,彼此没有干扰,为优化体系的分析特性和拓宽应用范围奠定了基础;(3)在此体系中,两极分处不同空间,彼此隔开。因此,发生在经典微流控双电极体系中的电渗流等液体流动对双极端的“扰动效应”等可降低或消除,增强了体系分析信号的稳定性和重现性。
2实验部分
2.1仪器与试剂
MPIA型电泳电化学发光检测仪(西安瑞迈公司);两根铂丝(驱动电极);自制隔离式双极电极,1.5 mL离心管(驱动电极的电解池);内径0.5 mm的聚四氟乙烯管;25×25 称量瓶(发光池); DDS11A型数字电导率仪(上海雷磁创益仪器仪表有限公司)。
鲁米诺(美国Sigma公司);NaH2PO4Na2HPO4缓冲液(PBS, pH 7.4)。实验所用试剂均为分析纯。实验用水为超纯水。
2.2两极隔离式双极电极的制备
截取长约4 cm玻璃管,将长1 cm、直径0.5 mm的铂丝装进玻璃管(一半在玻璃管内部,一半在玻璃管外部),将其放置在酒精喷灯上灼烧,直至玻璃管与铂丝完全密封。
2.3测量方法
3结果与讨论
3.1隔离式双极电极电化学发光装置的设计
隔离式双极电极电化学发光装置的设计如图1所示。在阳极池和连接管a中注入分析物溶液,在阴极池、连接管b和发光池中装入鲁米诺溶液,将两极隔离式双极电极垂直插入发光池中。当有一定的驱动电压施加于驱动电极两端时,在双极电极附近将会产生一个电势梯度,这个电势梯度会导致阴、阳离子在双极电极的两极富集\[26\]。同时,当施加的驱动电压足够大时,还会诱导双极电极表面的法拉第电化学过程。富集于双极电极阳极端的鲁米诺就会产生电化学发光信号,从而传感阴极端富集的阳离子。基于此装置的电化学发光信号可定量分析检测水中杂质离子的总量。
3.2双极电极阳极端氧化鲁米诺的电化学发光特性研究
为验证上述装置的预设功能,以鲁米诺为电化学发光传感试剂, 以低浓度且组成较为复杂的PBS缓冲溶液为分析物。当向驱动电极施加足够高的脉冲式电压激发信号时,插入发光池中的双极电极阳极端将产生强烈的发光信号,且当脉冲电压信号的施加时间为3 s、检测电化学发光信号的时间为40 s时,可产生良好的峰型电化学发光信号,其发光动力学曲线如图2所示。更为重要的是,当连续脉冲信号施加时,相应的电化学发光信号会持续增强,而当分析物中不含电解质溶液时,体系所产生电化学发光信号弱,且增强缓慢。因此,这一电化学发光信号可用于定量分析溶液中电解质的总量。
为了使鲁米诺的电化学发光信号具有较好的重现性和稳定性,研究了各种实验条件(如电极在电解池和发光池中的位置等)对鲁米诺电化学发光行为的影响。结果表明,当阴极池和阳极池中铂电极的位置、连接管在阴极池和阳极池中位置、双极电极的位置等均需保持稳定不变时,鲁米诺的电化学发光信号具有良好的重现性(图3),相对标准偏差为1.6%。
3.5发光池中支持电解质对双极电极体系中鲁米诺的ECL的影响
在本研究中,双极电极阳极端的电化学发光强度与其富集的鲁米诺有关,当发光池中有其它电解质存在时,必然导致富集的鲁米诺减少,从而使双极电极阳极端电化学发光强度降低。在发光池中加入支持电解质KCl溶液,鲁米诺的电化学发光强度
随KCl溶液浓度增加而降低,这可能是由于随着Cl
Symbolm@@ 的加入,双极电极阳极端富集的阴离子将产生竞争效应,使富集的鲁米诺阴离子减少,电化学发光强度降低。
3.6电化学发光分析特性
在最佳实验条件下,研究了鲁米诺电化学发光信号与水溶液中杂质离子浓度(以PBS溶液为代表)的关系(图5)。
3.7两极隔离式双极电极上鲁米诺电化学发光体系可能的发光机理
当施加脉冲电压时,两极隔离式双极电极通过溶液使整个回路畅通,此时,[TS(]图6电化学发光传感电导原理
此外,双极电极的阴、阳两极富集的阳阴离子需保持电荷平衡状态\[28\],样品中阳离子浓度越大,阳极富集的鲁米诺越多,发生氧化的鲁米诺就越多,产生的电化学发光信号越强;因此,体系中鲁米诺的ECL强度与双极电极阴极端富集的阳离子总量有关,因此,可根据发光信号定量分析溶液中的阳离子总量。
4结论
设计的两极隔离式双极电极电化学发光装置可广泛应用于分离富集领域;与已知的非隔离式双极电极电化学发光装置相比,此装置具有将分离、富集与电化学传感集于一体的特点,拓宽了电化学发光检测法的应用范围。
References
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AbstractA new closed bipolar electrode electrochemiluminescence (ECL)based device was designed, and further used to investigate the ECL behaviors of luminol in this device. Our results showed that, while a suitable voltage was applied to the two poles of the closed bipolar electrode, both the positively charged ions and luminolbased anionic ions could be enriched on the two poles of the closed bipolar electrode, respectively. More importantly, the ECL signals, generated from the electrooxidation of luminol on anodic pole, were found to be related to the total amount of positively charged ions on the cathodic pole of the closed bipolar electrode. Under the optimum experimental conditions, the ECL response was linearly to the concentration of analyte in the range of 1.0×10
Based on this finding, a new ECL method for sensing the solution conductance was developed.
KeywordsElectrochemiluminescnce; Closed bipolar electrode; Luminol; Solution conductance
25Cox J T, Guerrette J P, Zhang B. Anal. Chem., 2012, 84(20): 8797-8804
26Dhopeshwarkar R, Hlushkou D, Nguyen M, Tallarek U, Crooks R M. J. Am. Chem. Soc., 2008, 130(32): 10480-10481
27GUO ZiCheng. The Second Volume of Physical Chemistry. Beijing: Chemical Industry Press, 2013: 7-11
郭子成. 物理化学(下册), 北京: 化学工业出版社, 2013: 7-11
28Mavre F, Chow K F, Sheridan E, Chang B Y, Crooks J A, Crooks R M. Anal. Chem., 2009, 81(15): 6218-6225
AbstractA new closed bipolar electrode electrochemiluminescence (ECL)based device was designed, and further used to investigate the ECL behaviors of luminol in this device. Our results showed that, while a suitable voltage was applied to the two poles of the closed bipolar electrode, both the positively charged ions and luminolbased anionic ions could be enriched on the two poles of the closed bipolar electrode, respectively. More importantly, the ECL signals, generated from the electrooxidation of luminol on anodic pole, were found to be related to the total amount of positively charged ions on the cathodic pole of the closed bipolar electrode. Under the optimum experimental conditions, the ECL response was linearly to the concentration of analyte in the range of 1.0×10
Based on this finding, a new ECL method for sensing the solution conductance was developed.
KeywordsElectrochemiluminescnce; Closed bipolar electrode; Luminol; Solution conductance
25Cox J T, Guerrette J P, Zhang B. Anal. Chem., 2012, 84(20): 8797-8804
26Dhopeshwarkar R, Hlushkou D, Nguyen M, Tallarek U, Crooks R M. J. Am. Chem. Soc., 2008, 130(32): 10480-10481
27GUO ZiCheng. The Second Volume of Physical Chemistry. Beijing: Chemical Industry Press, 2013: 7-11
郭子成. 物理化学(下册), 北京: 化学工业出版社, 2013: 7-11
28Mavre F, Chow K F, Sheridan E, Chang B Y, Crooks J A, Crooks R M. Anal. Chem., 2009, 81(15): 6218-6225
AbstractA new closed bipolar electrode electrochemiluminescence (ECL)based device was designed, and further used to investigate the ECL behaviors of luminol in this device. Our results showed that, while a suitable voltage was applied to the two poles of the closed bipolar electrode, both the positively charged ions and luminolbased anionic ions could be enriched on the two poles of the closed bipolar electrode, respectively. More importantly, the ECL signals, generated from the electrooxidation of luminol on anodic pole, were found to be related to the total amount of positively charged ions on the cathodic pole of the closed bipolar electrode. Under the optimum experimental conditions, the ECL response was linearly to the concentration of analyte in the range of 1.0×10
Based on this finding, a new ECL method for sensing the solution conductance was developed.
KeywordsElectrochemiluminescnce; Closed bipolar electrode; Luminol; Solution conductance
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