The complexity of many environmental and biological matrices and the need to discriminate among analytes that have very close physicochemical properties prompted the development of high-resolution separation techniques prior to sensitive element- or molecule-specific detection. One of these techniques based on the separation in an electric field is capillary electrophoresis (CE).
CE has certain advantages in comparison to chromatographic techniques, such as:
- simplicity,
- low running costs,
- high spead of analysis,
- unique selectivity and high degree of matrix tolerance (due to high theoretical plate numbers, i.e. normally ranging from 70,000 to 200,000).
The mechanism of separation of metal ions in CE is based on the difference in electrophoretic mobility of the metal ions. Sepatation can be achieved by several modes of CE, namely capillary zone electrophoresis (CZE), micellar electrokinetic capillary electrophoresis (MECE) or micellar electrokinetic capillary electrophoresis (MECC), capillary isotachophoresis (CI), capillary gel electrophoresis (CGE), ion-exchange electrokinetic chromatography (UIEEC), capillary isolectric focusing (CIEF), affinity capillary electrophoresis (IACE), capillary electrochromatography (CEC). While commonly based on the application of a high voltage, their separation principles are quite different, providing completely different mechanisms of characterization and identification for element species. While CE supplements conventional HPLC methods, it shows unique promise for separation purpose because it causes only a minor disturbance to the existing equilibrium between different species. There is no stationary phase, which has a huge surface area and gives
various possibilities for undesired interactions. Therefore, species
transformations are thought to be less frequent than with HPLC.
To achieve maximum separation by CE, optimization of CE parameters is critical. The independent parameters under the control of the analysts are:
- selection of the buffer
- pH of the buffer,
- ion strength of the buffer,
- applied voltage,
- temperature of the capillary,
- dimensions of the capillary,
- additives to the background electrolyte.
The coupling of CE as the separation module with ICP-MS as the element-selective detector is much less straightforward in comparison to the coupling with HPLC or GC. The main problems are the low flow rate of CE that limit the choice of a nebulizer and the necessity to apply a high voltage accross the capillary and keeping the electrode grounded. The nebulizer should not create via a venturi-effect an additional flow component to the electroosmotic flow that would disturb the separation. Also any dead-volumes created by the interface would lead to band-broadening that has to be kept as low as possible.
One possible design of an interface is using a make-up flow that both is reducing the influence of the nebulizer (suction effect) on the separation and also allows for easy grounding of the capillary (see figure below).
Fig. 1 CE-ICP-MS interface using a makeup buffer
As can be seen from the development of publications related to CE-ICP-MS shown in Fig.2, the technique is not very often applied and also has surpassed already the highest interest in 2000. Many of the earlier papers deal with the development and optimization of the interface between CE and ICP-MS. Since the ICP-MS is a mass-flow sensitive detector, sensitivity strongly depends on the analyte stream transported into the plasma. However the CE produces very low flow rates in the range of nL/min only. Also CE allows only very small sample volumes to be injected, while LC can accept orders of magnitude higher sample volumes. Therefore, while the absolute detection power might look very impressive, the realtive detection power given in concentration is less impressive and can often not compete with those provided by HPLC.
Fig. 2: Yearly publication rate for papers dealing with CE-ICP-MS for speciation analysis.
Tutorial web material related to capillary electrophphoresis
Simple diagram and explanation of CE MicroSolv: Capillary Electrophoresis Primer Dejan Milosavljevic, Die Kapillar-Elektrophorese (in German) LibreTexts: Capillary electrophoresis
Tutorial print material related to capillary electrophphoresis
Beckman Coulter: Introduction to Capillary Electrophoresis Agilent CE System: A Quick Start Guide to Maintenance and Troubleshooting
Reviews of CE-ICP-MS (newest first)
Darya Mozhayeva, Carsten Engelhard,
CE coupled to ICP-MS and Single Particle ICP-MS for Nanoparticle Analysis, in: C. Neusüß, K. Jooß (eds.), Capillary Electrophortesis-Mass Spectrometry, Springer, 2022, 243-257.
DOI: 10.1007/978-1-0716-2493-7_16
Jean Aupias, Frédéric Chartier,
Capillary Electrophoresis, in: Diane Beauchemin, Sample Introduction Systems in ICPMS and ICPOES. Elsevier, amsterdam, 2020, 299-356.
DOI: 10.1016/B978-0-444-59482-2.00006-3
A. Stolz, K. Jooß, O. Höcker, J. Römer, J. Schlecht, C. Neusüß,
Recent advancesd in capillary electrophoresis-mass spectrometry: Instrumentation, methodology and applications, Electrophoresis, 40/1 (2019) 79-112.
DOI: 10.1002/elps.201800331
A.J. Chetwyd, E.J. Guggenheim, S.M. Briffa, J.A. Thorn, I. Lynch, E. Valsami-Jones, Current
Application of Capillary Electrophoresis in Nanomaterial Characterisation and Its Potential to Characterise the Protein and Small Molecule Corona, Nanomaterials, 8/2 (2018) 99.
DOI: 10.3390/nano8020099
H. Holtkamp, G. Grabmann, C.G. Hartinger,
Electrophoretic separation techniques and their hyphenation to mass spectrometry in biological inorganic chemistry, Electrophoresis, 37/7-8 (2016) 959-972.
DOI: 10.1002/elps.201500502
Christina Hein, Jonas M. Sander and Ralf Kautenburger,
Speciation via Hyphenation–Metal Speciation in Geological and Environmental Samples by CE-ICP-MS, J. Anal. Bioanal. Tech., 5/6 (2014) 225.
DOI: 10.4172/2155-9872.1000225 Andrei R. Timerbaev, Katarzyna Pawlak, Svetlana S. Aleksenko, Lidia S. Foteeva, Magdalena Matczuk, Maciej Jarosz,
Advances of CE-ICP-MS in speciation analysis related to metalloproteomics of anticancer drugs, Talanta, 102 (2012) 164-170.
DOI: 10.1016/j.talanta.2012.07.031 Petr Kuban, Pavlina Houserova, Pavel Kuban, Peter C. Hauser, Vlastimil Kuban,
Mercury speciation by CE: a review, Electrophoresis, 28/1-2 (2007) 58-68.
DOI: 10.1002/elps.200600457 Andreas Prange,
Daniel Pröfrock,
Application of CE-ICP-MS and CE-ESI-MS in metalloproteomics: challenges, developments, and limitations, Anal. Bioanal. Chem., 383/3 (2005) 372-389.
DOI: 10.1007/s00216-005-3420-0 Bernhard Michalke,
Capillary electrophoresis-inductively coupled plasma-mass spectrometry: A report on technical principles and problem solutions, potential, and limitations of this technology as well as on examples of application, Electrophoresis, 26/7-8 (2005) 1584-1597.
DOI: 10.1002/elps.200410314 Gloria Alvarez-Llamas, María del Rosario Fernández de la Campa,
Alfredo
Sanz-Medel,
ICP-MS for specific detection in capillary electrophoresis, Trends Anal. Chem. (Pers. Ed.), 24/1 (2005) 28-36.
DOI:10.1016/j.trac.2004.09.007 S.S. Kannamkumarath, K. Wrobel, K. Wrobel, C. B'Hymer,
Joseph A. Caruso,
Capillary electrophoresis-inductively coupled plasma-mass spectrometry:
an attractive complementary technique for elemental speciation
analysis, J. Chromatogr. A, 975/2 (2002) 245-266.
DOI:10.1016/S0021-9673(02)01218-9 J.W. Olesik, J.A. Kinzer, E.J. Grunwald, K.K. Thaxton, S.V. Olesik,
The potential and challenges of elemental speciation by capillary electrophoresis - inductively coupled plasma mass spectrometry and electrospray or ionspray mass spectrometry, Spectrochim. Acta, Part B, 53/2 (1998) 239-251.
DOI: 10.1016/S0584-8547(97)00145-6
Studies on the instrumentation and instrumental parameters of CE-ICP-MS Vahid Majidi, Nancy Miller-Ihli,
Potential sources of error in capillary electrophoresis-inductively coupled plasma mass spectrometry for chemical speciation, Analyst (London), 123/5 (1998) 809-813.
DOI: 10.1039/A708256H Dirk Schaumlöffel, Andreas Prange,
A new interface for combining capillary electrophoresis with inductively coupled plasma mass spectrometry, Fresenius J. Anal. Chem., 364/5 (1999) 452-456.
DOI: 10.1007/s002160051366 Anders Tangen,
Walter Lund,
Capillary electrophoresis-inductively coupled plasma mass spectrometry interface with minimised dead volume for high separation efficiency, J. Chromatogr. A, 891/1 (2000) 129-138.
DOI: 10.1016/S0021-9673(00)00617-8 Zhi-xin Wang,
Andreas Prange,
Use of Surface-Modified Capillaries in the Separation and Characterization of Metallothionein Isoforms by Capillary Electrophoresis Inductively Coupled Plasma Mass Spectrometry, Anal. Chem., 74/3 (2002) 626-631.
DOI: 10.1021/ac010862y Gloria Alvarez-Llamas, María del Rosario Fernández de la Campa,
Alfredo Sanz-Medel,
Sample stacking capillary electrophoresis with ICP-(Q)MS detection for Cd, Cu and Zn speciation in fish liver metallothioneins, J. Anal. At. Spectrom., 18/5 (2003) 460-466.
DOI: 10.1039/b300709j J.E. Sonke, D.J. Furbish, V.J.M. Salters,
Dispersion effects of laminar flow and spray chamber volume in capillary electrophoresis-inductively coupled plasma-mass spectrometry: a numerical and experimental approach, J. Chromatogr. A, 1015 (2003) 205-218.
DOI: 10.1016/S0021-9673(03)01210-X Enrique G. Yanes, Nancy J. Miller-Ihli,
Use of a parallel path nebulizer for capillary-based microseparation techniques coupled with an inductively coupled plasma mass spectrometer for speciation measurements, Spectrochim. Acta, Part B, 59/6 (2004) 883-890.
DOI: 10.1016/j.sab.2004.03.005 Qi Jun Song, Gillian M. Greenway, Tom McCreedy,
Interfacing a microfluidic electrophoresis chip with inductively coupled plasma mass spectrometry for rapid elemental speciation, J. Anal. At. Spectrom., 19/7 (2004) 883-887.
DOI: 10.1039/b401657b Douglas D. Richardson,
Sasi S. Kannamkumarath,
Rodolfo G. Wuilloud,
Joseph A. Caruso,
Hydride Generation Interface for Speciation Analysis Coupling Capillary Electrophoresis to Inductively Coupled Plasma Mass Spectrometry, Anal. Chem., 76/23 (2004) 7137-7142.
DOI: 10.1021/ac049066t Jean Chamoun, Agnès Hagège,
Sensitivity enhancement in capillary electrophoresis-inductively coupled plasma-mass spectrometry for metal/protein interactions analysis by using large volume stacking with polarity switching, J. Anal. At. Spectrom., 20/10 (2005) 1030-1034.
DOI: 10.1039/b502838h
EVISA Database system Journals related to Electrophoresis Organizations (Societies, Associations) related to Electrophoresis Companies: Manufacturers of CE Systems Instruments: Commercially available CE Systems Instruments: Commercially availabe CE-ICP-MS Interface kits Scientists working with capillary electrophoresis
EVISA link pages
Resources related to analytical sciences
Resources related to mass spectrometry
Resources related to quality assurance/quality control
Instrument manufacturer's application notes
Agilent Technologies: #5988-4332EN: Technical Features of the ICP-MS Plasma Chromatographic Software
Agilent Technologies: #5989-6160EN: Handbook of Hyphenated ICP-MS Applications (First edition)
Agilent Technologies: #5990-9473EN: Handbook of Hyphenated ICP-MS Applications (Second edition)
Other web resources:
Agilent web site on Capillary Electrophoresis Instruments and Application Notes Analytical Methods Committee, Report of the Instrumental Criteria Subcommittee: Part XII (2000): Instrumentation for Capillary Electrophoresis
Further chapters on techniques and methodology for speciation analysis:
Chapter 1:
Tools for elemental speciation Chapter 2: ICP-MS - A versatile detection system for speciation analysis Chapter 3: LC-ICP-MS - The most often used hyphenated system for speciation analysis Chapter 4: GC-ICP-MS- A very sensitive hyphenated system for speciation analysis Chapter 5: CE-ICP-MS for speciation analysis Chapter 6: ESI-MS: The tool for the identification of species Chapter 7: Speciation Analysis - Striving for Quality Chapter 8: Atomic Fluorescence Spectrometry as a Detection System for Speciation Analysis Chapter 9: Gas chromatography for the separation of elemental species Chapter 10: Plasma source detection techniques for gas chromatography Chapter 11: Fractionation as a first step towards speciation analysis Chapter 12: Flow-injection inductively coupled plasma mass spectrometry for speciation analysis Chapter
13: Gel electrophoresis combined with laser ablation inductively
coupled plasma mass spectrometry for speciation analysis Chapter 14: Non-chromatographic separation techniques for speciation analysis
last time modified: November 11, 2024
