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Li L, Ren DD, Zhang PY, Song YP, Li TX, Gao MH, Xu JN, Zhou L, Zeng ZC, Pu Q. Pushing the Limits of Capacitively Coupled Contactless Conductivity Detection for Capillary Electrophoresis. Anal Chem 2024; 96:10356-10364. [PMID: 38863415 DOI: 10.1021/acs.analchem.4c01367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2024]
Abstract
Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) has proven to be an efficient technique for the separation and detection of charged inorganic, organic, and biochemical analytes. It offers several advantages, including cost-effectiveness, nanoliter injection volume, short analysis time, good separation efficiency, suitability for miniaturization, and portability. However, the routine determination of common inorganic cations (NH4+, K+, Na+, Ca2+, Mg2+, and Li+) and inorganic anions (F-, Cl-, Br-, NO2-, NO3-, PO43-, and SO42-) in water quality monitoring typically exhibits limits of detection of about 0.3-1 μM without preconcentration. This sensitivity often proves insufficient for the applications of CE-C4D in trace analysis situations. Here, we explore methods to push the detection limits of CE-C4D through a comprehensive consideration of signal and noise sources. In particular, we (i) studied the model of C4D and its guiding roles in C4D and CE-C4D, (ii) optimized the bandwidth and noise performance of the current-to-voltage (I-V) converter, and (iii) reduced the noise level due to the strong background signal of the background electrolyte by adaptive differential detection. We characterized the system with Li+; the 3-fold signal-to-noise (S/N) detection limit for Li+ was determined at 20 nM, with a linear range spanning from 60 nM to 1.6 mM. Moreover, the optimized CE-C4D method was applied to the analysis of common mixed inorganic cations (K+, Na+, Ca2+, Mg2+, and Li+), anions (F-, Cl-, Br-, NO2-, NO3-, PO43-, and SO42-), toxic halides (BrO3-) and heavy metal ions (Pb2+, Cd2+, Cr3+, Co2+, Ni2+, Zn2+, and Cu2+) at trace concentrations of 200 nM. All electropherograms showed good S/N ratios, thus proving its applicability and accuracy. Our results have shown that the developed CE-C4D method is feasible for trace ion analysis in water quality control.
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Affiliation(s)
- Lin Li
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Dou-Dou Ren
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Peng-Yu Zhang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Yun-Peng Song
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Tang-Xiu Li
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Ming-Hui Gao
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Jia-Nan Xu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Lei Zhou
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Zhi-Cong Zeng
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
| | - Qiaosheng Pu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
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Warren CG, Dasgupta PK. Liquid phase detection in the miniature scale. Microfluidic and capillary scale measurement and separation systems. A tutorial review. Anal Chim Acta 2024; 1305:342507. [PMID: 38677834 DOI: 10.1016/j.aca.2024.342507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 03/18/2024] [Accepted: 03/19/2024] [Indexed: 04/29/2024]
Abstract
Microfluidic and capillary devices are increasingly being used in analytical applications while their overall size keeps decreasing. Detection sensitivity for these microdevices gains more importance as device sizes and consequently, sample volumes, decrease. This paper reviews optical, electrochemical, electrical, and mass spectrometric detection methods that are applicable to capillary scale and microfluidic devices, with brief introduction to the principles in each case. Much of this is considered in the context of separations. We do consider theoretical aspects of separations by open tubular liquid chromatography, arguably the most potentially fertile area of separations that has been left fallow largely because of lack of scale-appropriate detection methods. We also examine the theoretical basis of zone electrophoretic separations. Optical detection methods discussed include UV/Vis absorbance, fluorescence, chemiluminescence and refractometry. Amperometry is essentially the only electrochemical detection method used in microsystems. Suppressed conductance and especially contactless conductivity (admittance) detection are in wide use for the detection of ionic analytes. Microfluidic devices, integrated to various mass spectrometers, including ESI-MS, APCI-MS, and MALDI-MS are discussed. We consider the advantages and disadvantages of each detection method and compare the best reported limits of detection in as uniform a format as the available information allows. While this review pays more attention to recent developments, our primary focus has been on the novelty and ingenuity of the approach, regardless of when it was first proposed, as long as it can be potentially relevant to miniature platforms.
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Affiliation(s)
- Cable G Warren
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, 76019-0065, United States
| | - Purnendu K Dasgupta
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, 76019-0065, United States.
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3
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Li L, Song YP, Ren DD, Li TX, Gao MH, Zhou L, Zeng ZC, Pu QA. A compact and high-performance setup of capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C 4D). Analyst 2024; 149:3034-3040. [PMID: 38624147 DOI: 10.1039/d4an00354c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) has the advantages of high throughput (simultaneous detection of multiple ions), high separation efficiency (higher than 105 theoretical plates) and rapid analysis capability (less than 5 min for common inorganic ions). A compact CE-C4D system is ideal for water quality control and on-site analysis. It is suitable not only for common cations (e.g. Na+, K+, Li+, NH4+, Ca2+, etc.) and anions (e.g. Cl-, SO42-, BrO3-, etc.) but also for some ions (e.g. lanthanide ions, Pb2+, Cd2+, etc.) that require complex derivatization procedures to be detected by ion chromatography (IC). However, an obvious limitation of the CE-C4D method is that its sensitivity (e.g. 0.3-1 μM for common inorganic ions) is often insufficient for trace analysis (e.g. 1 ppb or 20 nM level for common inorganic ions) without preconcentration. For this technology to become a powerful and routine analytical technique, the system should be made compact while maintaining trace analysis sensitivity. In this study, we developed an all-in-one version of the CE-C4D instrument with custom-made modular components to make it a convenient, compact and high-performance system. The system was designed using direct digital synthesis (DDS) technology to generate programmable sinusoidal waveforms with any frequency for excitation, a kilovolt high-voltage power supply for capillary electrophoresis separation, and an "effective" differential C4D cell with a low-noise circuitry for high-sensitivity detection. We characterized the system with different concentrations of Cs+, and even a low concentration of 20 nM was detectable without preconcentration. Moreover, the optimized CE-C4D setup was applied to analyse mixed ions at a trace concentration of 200 nM with excellent signal-to-noise ratios. In typical applications, the limits of detection based on the 3σ criterion (without baseline filtering) were 9, 10, 24, 5, and 12 nM for K+, Cs+, Li+, Ca2+, and Mg2+, respectively, and about 7, 6, 6 and 6 nM for Br-, ClO4-, BrO3- and SO42-, respectively. Finally, the setup was also applied for the analysis of all 14 lanthanide ions and rare-earth minerals, and it showed an improvement in sensitivity by more than 25 times.
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Affiliation(s)
- Lin Li
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
| | - Yun-Peng Song
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
| | - Dou-Dou Ren
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
| | - Tang-Xiu Li
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
| | - Ming-Hui Gao
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
| | - Lei Zhou
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
| | - Zhi-Cong Zeng
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
| | - Qi-Aosheng Pu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, China.
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Hu C, Xie B, Li H, Xiao D. A five-electrode capacitively coupled contactless conductivity detector with a low limit of detection. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2023; 15:2253-2261. [PMID: 37128967 DOI: 10.1039/d3ay00328k] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The conductivity detector is a broadly used device that allows for the highly efficient detection of analytes, and continuous efforts have been directed toward lowering the limit of detection. In this study, a five-electrode capacitively coupled contactless conductivity detector (TIC4D) is proposed, which uses copper mesh between the electrodes for a grounding shield to reduce the interference of stray capacitance and noise. After adding the copper mesh shield, the difference value between the response signal and baseline at low KCl concentration is effectively increased, achieving 33 mV for 10-9 M KCl solution. Meanwhile, for the unshielded detector, the difference is only 18 mV for the KCl solution at the same concentration. The response signal shows a linear function of the logarithm at the range of 10-4 M to 10-5 M KCl solution, and the TIC4D detector displays a higher slope (0.8448) than the conventional single-input capacitively coupled contactless conductivity detector (C4D: 0.5579) and dual-input capacitively coupled contactless conductivity detectors (DIC4D: 0.6173). Moreover, two TIC4D detectors are combined to achieve a dual-channel six-input differential capacitively coupled contactless conductivity detector (SIDC4D), reducing the high baseline levels caused by the multi-signal input. By differentially amplifying the output signal, the high baseline levels and noise interference can be effectively reduced. For the 10-3 M KCl solution, the ratio of the response signal to baseline for SIDC4D can reach 8.500, almost 7 times that of TIC4D, and a lower limit of detection (LOD) of 3 × 10-10 M is also achieved. This work may open a new door based on coupled contactless conductivity for detection performance.
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Affiliation(s)
- Chunqiong Hu
- College of Chemical Engineering, Sichuan University, Chengdu 610064, China.
| | - Bo Xie
- College of Chemical Engineering, Sichuan University, Chengdu 610064, China.
| | - Hongmei Li
- College of Chemistry, Sichuan University, Chengdu 610064, China
| | - Dan Xiao
- College of Chemical Engineering, Sichuan University, Chengdu 610064, China.
- College of Chemistry, Sichuan University, Chengdu 610064, China
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5
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Nie H, Li Z, Wang X, Gu R, Yuan H, Guo Y, Xiao D. An improved dual-channel capacitively coupled contactless conductivity detector with high detection performance. Analyst 2022; 147:2106-2114. [PMID: 35470820 DOI: 10.1039/d2an00330a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Conductivity detectors are widely used electrochemical sensors. It has long been a goal of researchers to improve detection performance. In this contribution, we propose a multi-input capacitively coupled contactless conductivity detector (MIC4D) with high sensitivity, and we carry out a detailed theoretical investigation of the detector. In order to overcome the problem of a rising baseline level as a result of sensitivity improvements when using the multi-input detection method, we innovatively combine MIC4D with differential detection to propose a further-improved detector (DFMIC4D). The detector is composed of two channels, one for the reference and the other for the analyte. The signal output from differential amplification can effectively reduce the high baseline level and detection interference. In KCl solution with a concentration range of 10-4 to 10-5 M, the response to the solution is a linear function of the logarithm of the concentration, and this detector has a high slope. The slope of DFMIC4D is 1.393, higher than a traditional single-input capacitively coupled contactless conductivity detector (C4D: 0.905) and a double-input capacitively coupled contactless conductivity detector (DIC4D: 1.314). For 10-3 M KCl solution, the response-to-baseline ratio is 1.776 for C4D, 1.779 for DIC4D, and 12.06 for DFMIC4D, with a ratio increase of nearly 6-fold shown by our new detector. At a S/N (signal-to-noise) ratio of 3, the limit of detection (LOD) of DFMIC4D is low, reaching 0.7 nM. In addition, DFMIC4D can be applied to the detection of low-conductivity solutions and total dissolved solids (TDS) analysis. Compared with a standard conductivity meter, our detector shows better detection performance.
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Affiliation(s)
- Hongyu Nie
- College of Chemistry, Sichuan University, Chengdu 610064, China.
| | - Zhihui Li
- College of Chemistry, Sichuan University, Chengdu 610064, China.
| | - Xiaokun Wang
- College of Chemical Engineering, Sichuan University, Chengdu 610064, China.
| | - Rongmeng Gu
- College of Chemical Engineering, Sichuan University, Chengdu 610064, China.
| | - Hongyan Yuan
- College of Chemical Engineering, Sichuan University, Chengdu 610064, China.
| | - Yong Guo
- College of Chemistry, Sichuan University, Chengdu 610064, China.
| | - Dan Xiao
- College of Chemistry, Sichuan University, Chengdu 610064, China. .,College of Chemical Engineering, Sichuan University, Chengdu 610064, China.
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A Novel Planar Grounded Capacitively Coupled Contactless Conductivity Detector for Microchip Electrophoresis. MICROMACHINES 2022; 13:mi13030394. [PMID: 35334684 PMCID: PMC8953769 DOI: 10.3390/mi13030394] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 02/19/2022] [Accepted: 02/25/2022] [Indexed: 11/30/2022]
Abstract
In the microchip electrophoresis with capacitively coupled contactless conductivity detection, the stray capacitance of the detector causes high background noise, which seriously affects the sensitivity and stability of the detection system. To reduce the effect, a novel design of planar grounded capacitively coupled contactless conductivity detector (PG-C4D) based on printed circuit board (PCB) is proposed. The entire circuit plane except the sensing electrodes is covered by the ground electrode, greatly reducing the stray capacitance. The efficacy of the design has been verified by the electrical field simulation and the electrophoresis detection experiments of inorganic ions. The baseline intensity of the PG-C4D was less than 1/6 of that of the traditional C4D. The PG-C4D with the new design also demonstrated a good repeatability of migration time, peak area, and peak height (n = 5, relative standard deviation, RSD ≤ 0.3%, 3%, and 4%, respectively), and good linear coefficients within the range of 0.05–0.75 mM (R2 ≥ 0.986). The detection sensitivity of K+, Na+, and Li+ reached 0.05, 0.1, and 0.1 mM respectively. Those results prove that the new design is an effective and economical approach which can improve sensitivity and repeatability of a PCB based PG-C4D, which indicate a great application potential in agricultural and environmental monitoring.
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7
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Wang C, Xing H, Zheng B, Yuan H, Xiao D. Simulation and Experimental Study on Doubled-Input Capacitively Coupled Contactless Conductivity Detection of Capillary Electrophoresis. Sci Rep 2020; 10:7944. [PMID: 32409736 PMCID: PMC7224287 DOI: 10.1038/s41598-020-64896-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 03/26/2020] [Indexed: 11/08/2022] Open
Abstract
In this contribution, we optimize the structure of double-input capacitively coupled contactless conductivity detector (DIC4D) that proposed before by our group and successfully applied it in the capillary electrophoresis of inorganic ion analysis. Furthermore, we present the detail theoretical analysis and simulation to exploring the working mechanism of DIC4D. Compared with C4D, under identical experimental conditions and by using the same current-to-voltage converter, both the theoretical and experimental results suggest that the effectiveness and feasibility of DIC4D. The improved DIC4D diminished the baseline drift effects in C4D, provides lower noise, higher sensitivity and notably stable baseline. The LODs of DIC4D are 1.0 μM for K+ and 1.5 μM for Li+ (S/N = 3). DIC4D provides a better linear relationship (R = 0.997 and 0.998 for K+ and Li+, respectively) with the range of 2.0 μM ~ 2.5 mM.
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Affiliation(s)
- Chunling Wang
- College of Chemical Engineering, Sichuan University, Chengdu, 610064, People's Republic of China
| | - Haoyang Xing
- College of Physical Science and Technology, Sichuan University, Chengdu, 610065, People's Republic of China
| | - Baozhan Zheng
- College of Chemistry, Sichuan University, Chengdu, 610065, People's Republic of China
| | - Hongyan Yuan
- College of Chemical Engineering, Sichuan University, Chengdu, 610064, People's Republic of China.
| | - Dan Xiao
- College of Chemical Engineering, Sichuan University, Chengdu, 610064, People's Republic of China.
- College of Chemistry, Sichuan University, Chengdu, 610065, People's Republic of China.
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8
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Martinez-Cisneros C, da Rocha Z, Seabra A, Valdés F, Alonso-Chamarro J. Highly integrated autonomous lab-on-a-chip device for on-line and in situ determination of environmental chemical parameters. LAB ON A CHIP 2018; 18:1884-1890. [PMID: 29869662 DOI: 10.1039/c8lc00309b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The successful integration of sample pretreatment stages, sensors, actuators and electronics in microfluidic devices enables the attainment of complete micro total analysis systems, also known as lab-on-a-chip devices. In this work, we present a novel monolithic autonomous microanalyzer that integrates microfluidics, electronics, a highly sensitive photometric detection system and a sample pretreatment stage consisting on an embedded microcolumn, all in the same device, for on-line determination of relevant environmental parameters. The microcolumn can be filled/emptied with any resin or powder substrate whenever required, paving the way for its application to several analytical processes: separation, pre-concentration or ionic-exchange. To promote its autonomous operation, avoiding issues caused by bubbles in photometric detection systems, an efficient monolithic bubble removal structure was also integrated. To demonstrate its feasibility, the microanalyzer was successfully used to determine nitrate and nitrite in continuous flow conditions, providing real time and continuous information.
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9
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Duarte Junior GF, Fracassi da Silva JA, Mendonça Francisco KJ, do Lago CL, Carrilho E, Coltro WKT. Metalless electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips. Electrophoresis 2015; 36:1935-40. [DOI: 10.1002/elps.201500033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/05/2015] [Accepted: 03/13/2015] [Indexed: 01/17/2023]
Affiliation(s)
| | - José Alberto Fracassi da Silva
- Instituto de Química; Universidade Estadual de Campinas; Campinas São Paulo Brasil
- Instituto Nacional de Ciência e Tecnologia de Bioanalítica; Campinas São Paulo Brasil
| | | | | | - Emanuel Carrilho
- Instituto de Química de São Carlos; Universidade de São Paulo; São Carlos São Paulo Brasil
- Instituto Nacional de Ciência e Tecnologia de Bioanalítica; Campinas São Paulo Brasil
| | - Wendell K. T. Coltro
- Instituto de Química; Universidade Federal de Goiás; Goiânia Goiás Brasil
- Instituto Nacional de Ciência e Tecnologia de Bioanalítica; Campinas São Paulo Brasil
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10
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Zheng H, Li M, Dai J, Wang Z, Li X, Yuan H, Xiao D. Double Input Capacitively Coupled Contactless Conductivity Detector with Phase Shift. Anal Chem 2014; 86:10065-70. [DOI: 10.1021/ac501199e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Hao Zheng
- College
of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China
| | - Meng Li
- College
of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China
| | - Jianyuan Dai
- College
of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China
| | - Zhen Wang
- College
of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China
| | - Xiuting Li
- College
of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China
| | - Hongyan Yuan
- College
of Chemical Engineering, Sichuan University, Chengdu 610065, People’s Republic of China
| | - Dan Xiao
- College
of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China
- College
of Chemical Engineering, Sichuan University, Chengdu 610065, People’s Republic of China
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11
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Zhai H, Li J, Chen Z, Su Z, Liu Z, Yu X. A glass/PDMS electrophoresis microchip embedded with molecular imprinting SPE monolith for contactless conductivity detection. Microchem J 2014. [DOI: 10.1016/j.microc.2014.01.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Stojkovic M, Schlensky B, Hauser PC. Referenced Capacitively Coupled Conductivity Detector for Capillary Electrophoresis. ELECTROANAL 2013. [DOI: 10.1002/elan.201300413] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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13
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Contactless impedance sensors and their application to flow measurements. SENSORS 2013; 13:2786-801. [PMID: 23447011 PMCID: PMC3658714 DOI: 10.3390/s130302786] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 01/31/2013] [Accepted: 02/01/2013] [Indexed: 11/16/2022]
Abstract
The paper provides a critical discussion of the present state of the theory of high-frequency impedance sensors (now mostly called contactless impedance or conductivity sensors), the principal approaches employed in designing impedance flow-through cells and their operational parameters. In addition to characterization of traditional types of impedance sensors, the article is concerned with the use of less common sensors, such as cells with wire electrodes or planar cells. There is a detailed discussion of the effect of the individual operational parameters (width and shape of the electrodes, detection gap, frequency and amplitude of the input signal) on the response of the detector. The most important problems to be resolved in coupling these devices with flow-through measurements in the liquid phase are also discussed. Examples are given of cell designs for continuous flow and flow-injection analyses and of detection systems for miniaturized liquid chromatography and capillary electrophoresis. New directions for the use of these sensors in molecular biology and chemical reactors and some directions for future development are outlined.
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14
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Shen D, Li Y, Zhang Z, Zhang P, Kang Q. Determination of amino acids by capillary electrophoresis with differential resonant contactless conductivity detector. Talanta 2013; 104:39-43. [DOI: 10.1016/j.talanta.2012.11.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 11/08/2012] [Accepted: 11/10/2012] [Indexed: 11/15/2022]
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15
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Qiao L, Sartor R, Gasilova N, Lu Y, Tobolkina E, Liu B, Girault HH. Electrostatic-Spray Ionization Mass Spectrometry. Anal Chem 2012; 84:7422-30. [DOI: 10.1021/ac301332k] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Liang Qiao
- Laboratoire d’Electrochimie Physique
et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
| | - Romain Sartor
- Laboratoire d’Electrochimie Physique
et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
| | - Natalia Gasilova
- Laboratoire d’Electrochimie Physique
et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
| | - Yu Lu
- Laboratoire d’Electrochimie Physique
et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
| | - Elena Tobolkina
- Laboratoire d’Electrochimie Physique
et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
| | - Baohong Liu
- Department of Chemistry, Institute
of Biomedical Sciences, Fudan University, Shanghai, 200433, P.R. China
| | - Hubert H. Girault
- Laboratoire d’Electrochimie Physique
et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
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16
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Mark JJP, Scholz R, Matysik FM. Electrochemical methods in conjunction with capillary and microchip electrophoresis. J Chromatogr A 2012; 1267:45-64. [PMID: 22824222 DOI: 10.1016/j.chroma.2012.07.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 07/01/2012] [Accepted: 07/06/2012] [Indexed: 02/06/2023]
Abstract
Electromigrative techniques such as capillary and microchip electrophoresis (CE and MCE) are inherently associated with various electrochemical phenomena. The electrolytic processes occurring in the buffer reservoirs have to be considered for a proper design of miniaturized electrophoretic systems and a suitable selection of buffer composition. In addition, the control of the electroosmotic flow plays a crucial role for the optimization of CE/MCE separations. Electroanalytical methods have significant importance in the field of detection in conjunction with CE/MCE. At present, amperometric detection and contactless conductivity detection are the predominating electrochemical detection methods for CE/MCE. This paper reviews the most recent trends in the field of electrochemical detection coupled to CE/MCE. The emphasis is on methodical developments and new applications that have been published over the past five years. A rather new way for the implementation of electrochemical methods into CE systems is the concept of electrochemically assisted injection which involves the electrochemical conversions of analytes during the injection step. This approach is particularly attractive in hyphenation to mass spectrometry (MS) as it widens the range of CE-MS applications. An overview of recent developments of electrochemically assisted injection coupled to CE is presented.
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Affiliation(s)
- Jonas J P Mark
- Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Regensburg, Germany
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17
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Abstract
AbstractThis review summarizes the development of capillary ion chromatography (CIC) over approximately the last 5 years. It mainly focuses on the technologic aspects of several key components associated with CIC, including micropump, microscale electrodialytic eluent generator, microscale suppressor and the detector.
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Zhang Z, Li D, Liu X, Subhani Q, Zhu Y, Kang Q, Shen D. Determination of anions using monolithic capillary column ion chromatography with end-to-end differential contactless conductometric detectors under resonance approach. Analyst 2012; 137:2876-83. [PMID: 22576018 DOI: 10.1039/c2an35150a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An end-to-end differential measurement approach with capacitively coupled contactless conductivity detection (C(4)D) was applied to anion-exchange monolithic capillary column ion chromatography. The column was prepared by thermally initiated radical polymerization of poly(glycidyl methacrylate) in a fused-silica capillary of 320 μm i.d. and modified by quaternary ammonium latex surface coating. Two C(4)Ds were placed near both ends of the capillary column and the output difference between them was measured. With 15 mM potassium hydrogen phthalate used as the eluent, good separation of a mixture of inorganic anions (F(-), Cl(-), NO(2)(-), NO(3)(-)) was achieved. The detection limits of conventional C(4)D are 1.6, 0.28, 0.53, and 0.47 mg L(-1) for F(-), Cl(-), NO(2)(-), and NO(3)(-), respectively. To further enhance the sensitivity, the capacitive impedance from C(4)D was neutralized by an inductive impedance from a piezoelectric resonator. An increase in sensitivity by a factor of 7-8 was achieved in the resonating C(4)D in comparison with the conventional C(4)D. The detection limits of the resonating C(4)D are 0.23, 0.041, 0.065, and 0.059 mg L(-1) for F(-), Cl(-), NO(2)(-), and NO(3)(-), respectively. The response of the resonating C(4)D was analyzed based on an equivalent circuit model.
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Affiliation(s)
- Zhenli Zhang
- The Key Lab in Molecular and Nano-materials Probes of the Ministry of Education of China, College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan, 250014, PR China
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Lima RS, Piazzetta MHO, Gobbi AL, Rodrigues-Filho UP, Nascente PAP, Coltro WKT, Carrilho E. Contactless conductivity biosensor in microchip containing folic acid as bioreceptor. LAB ON A CHIP 2012; 12:1963-1966. [PMID: 22549415 DOI: 10.1039/c2lc40157f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report a glass/PDMS-based microfluidic biosensor that integrates contactless conductivity transduction and folic acid, a target for tumor biomarker, as a bioreceptor. The device presents relevant advantages such as direct determination--dismiss the use of redox mediators as in faradaic electrochemical techniques--and the absence of the known drawbacks related to the electrode-solution interface. Characterizations of the functionalization processes and chemical sensor are described in this communication.
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Affiliation(s)
- Renato S Lima
- Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
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20
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Elbashir AA, Aboul-Enein HY. Recent advances in applications of capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D): an update. Biomed Chromatogr 2012; 26:990-1000. [PMID: 22430262 DOI: 10.1002/bmc.2729] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 02/12/2012] [Indexed: 11/06/2022]
Abstract
Capillary electrophoresis with a capacitively contactless conductivity detector (CE-C⁴D) is becoming a significant useful technique for the analysis of analytes in various fields such as pharmaceutical, biomedical, food and environmental. This review is an update describing the recent developments in the application of CE with a C⁴D detector.
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Kubáň P, Timerbaev AR. CE of inorganic species - A review of methodological advancements over 2009-2010. Electrophoresis 2011; 33:196-210. [DOI: 10.1002/elps.201100357] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Revised: 07/30/2011] [Accepted: 07/30/2011] [Indexed: 01/13/2023]
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22
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Analytical applications of the electrochemiluminescence of tris(2,2′-bipyridyl)ruthenium(II) coupled to capillary/microchip electrophoresis: A review. Anal Chim Acta 2011; 704:16-32. [DOI: 10.1016/j.aca.2011.07.016] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 07/09/2011] [Accepted: 07/11/2011] [Indexed: 11/24/2022]
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23
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Affiliation(s)
- Yuqing Lin
- Department of Chemistry, University of Gothenburg, S-41296, Gothenburg, Sweden
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Liu J, Wang J, Chen Z, Yu Y, Yang X, Zhang X, Xu Z, Liu C. A three-layer PMMA electrophoresis microchip with Pt microelectrodes insulated by a thin film for contactless conductivity detection. LAB ON A CHIP 2011; 11:969-973. [PMID: 21135967 DOI: 10.1039/c0lc00341g] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A three-layer poly (methyl methacrylate) (PMMA) electrophoresis microchip integrated with Pt microelectrodes for contactless conductivity detection is presented. A 50 μm-thick PMMA film is used as the insulating layer and placed between the channel plate (containing the microchannel) and the electrode plate (containing the microelectrode). The three-layer structure facilitates the achievement of a thin insulating layer, obviates the difficulty of integrating microelectrodes on a thin film, and does not compromise the integration of microchips. To overcome the thermal and chemical incompatibilities of polymers and photolithographic techniques, a modified lift-off process was developed to integrate Pt microelectrodes onto the PMMA substrate. A novel two-step bonding method was created to assemble the complete PMMA microchip. A low limit of detection of 1.25 μg ml(-1) for Na(+) and high separation efficiency of 77,000 and 48,000 plates/m for Na(+) and K(+) were obtained when operating the detector at a low excitation frequency of 60 kHz.
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Affiliation(s)
- Junshan Liu
- Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian, Liaoning 116023, China.
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25
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Kubáň P, Hauser PC. Capacitively coupled contactless conductivity detection for microseparation techniques - recent developments. Electrophoresis 2010; 32:30-42. [DOI: 10.1002/elps.201000354] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Revised: 08/12/2010] [Accepted: 08/13/2010] [Indexed: 11/09/2022]
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Ha K, Joo GS, Jha S, Yeon IJ, Kim YS. Miniaturisation of a capillary electrophoresis microchip for the sensing of endocrine disruptors. IET Nanobiotechnol 2010; 4:103-8. [DOI: 10.1049/iet-nbt.2010.0006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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