Andrei R. Timerbaev

Strategies for selectivity control in capillary electrophoresis of metal species

Capillary electrophoresis has recently attracted considerable attention as a promising analytical technique for metal ion separations. Significant advances that open new application areas for capillary electrophoresis in the analysis of metal species have occurred based on exploiting various auxiliary separation principles. These are mainly due to complexation, ion pairing, solvation and micellization interactions between metal analytes and electrolyte additives which alter the separation selectivity in a broad range. Likewise, many separation studies for metal ions have been concentrated on the use of pre-electrophoresis derivatisation methodology. Approaches suitable for manipulation of selectivity for different metal species including metal cations, metal complexes, metal oxoanions and organometallic compounds, are discussed, with special attention paid to the related electrophoretic system variables using illustrative examples. Discussion also presents guidelines for optimisation of separation conditions based on basic theoretical considerations.

Inorganic environmental analysis by capillary electrophoresis

a Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Kosygin Str. 19, 117975 Moscow, Russian Federation b Analysis and Air Quality Division, Environmental Technology Centre, Environment Canada, 3439 River Road, Ottawa, ON K1A OH3, Canada c Laboratory of Inorganic Analytical Chemistry, National Institute of Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, The Netherlands

Capillary zone electrophoresis of lanthanoid elements after complexation with aminopolycarboxylic acids

Capillary zone electrophoresis was applied to the separation of the lanthanoid elements chelated with aminopolycarboxylic acids. Several aminopolycarboxylic reagents (ethylenediaminetetraacetic acid and chemically similar analogues) were varied in an effort to optimize the separation resolution. By varying the pH and concentration of the electrophoretic buffer, it was also possible to manipulate the migration times, efficiency and detectability. Optimum resolution and analysis time (within 12 min) for lanthanoids(III), and also scandium(III) and yttrium(III), was achieved with cyclohexane-1,2-diaminetetraacetic acid (CDTA) and simple electrolytes such as a borate buffer (20 mmol l–1, pH 11.0) containing 1 mmol l–1 CDTA. Determination of the lanthanoid complexes was performed by direct UV detection at 214 nm. The calibration graphs were linear (r > 0.99) over at least two orders of magnitude of concentration. The detection limits were at the mid-ppb level and the relative standard deviation was about 2.8% at the mid-calibration range. The method appeared to be feasible to determining the lanthanoid elements in nuclear fuel waste, and may be also recommended for assessing lanthanoid impurities in nuclear fuel.

Characterization of interactions of metal‐containing nanoparticles with biomolecules by CE: An update (2012–2016)

The methodological developments and applications of CE related to studying biotransformations of metal‐based nanoscale particles of impending medicinal use are overviewed. This is an update to a previous review article (Aleksenko, S. S., Shmykov, A. Y., Oszwałdowski, S., Timerbaev, A. R., Metallomics 2012, 4, 1141–1148) and it covers the research papers published within the last five years. As was anticipated in that review, CE can now be seen as a customary technique in the analysis of biomolecular interactions that exert an impact on the mechanism of action of nanoparticles, comprising metabolism, delivery, cell processing, and targeting. Different ways by which the CE method is applied for such monitoring, including conjugation mode, sample preparation, separation, and detection, are critically assessed. Special emphasis is put on examinations using inductively coupled plasma MS detection recent advent of which to the area made CE a versatile speciation tool for biomedical studies of nanomaterials containing metals.

Characterization of the protein corona of gold nanoparticles by an advanced treatment of CE-ICP-MS data.

CE is well known not only as an efficient separation method, but also as a viable tool for studying chemical reactions, including kinetic assaying and analysis of chemical equilibria. In this communication, the latter feature of CE interfaced with ICP‐MS was exploited to determine the stoichiometric composition of the protein corona of gold nanoparticles (AuNPs) at equilibrium conditions. For both individual albumin and human serum involved in binding, the number of protein molecules bound per AuNP (n) was calculated. Since the time scale of the corona formation was previously found to be dependent on the particle size, two calculation algorithms were adopted here. In the case of 5‐nm AuNPs, rather slowly associating with the protein, the peak areas measured for the conjugated and free particles were taken in computation (the 34S signal due to bound protein was also monitored simultaneously to confirm that equilibrium is reached). In binding labile systems (10–50 nm AuNPs), the particles are converted into the protein‐bound form relatively fast due mostly to the favor of a much greater excess of the protein so that no peak of the free particles interacting with serum being recorded. Therefore, the n value was estimated by relating the sulfur peak area of each of these conjugates to that of 5‐nm AuNPs to calculate the number of bound albumin molecules that was then divided by the number of AuNPs. The AuNPs were found to react with from 13 to 292 albumin molecules that is in good agreement with the literature data.

Use of high-performance liquid chromatography–tandem electrospray ionization mass spectrometry to assess the speciation of a ruthenium(III) anticancer drug in the cytosol of cancer cells

The discovery of intracellular active forms is a crucial issue for the approval of further anticancer metal-based drugs. This challenge calls for an apt analytical methodology to scrutinize the speciation changes of a metallodrug in cancer cytosol. In the current study, we have developed an approach for portraying low-molecular-mass cytosolic species of a Ru(III) drug, indazolium trans-[tetrachloridobis(1H-indazole)ruthenate(III)], based on using capillary high-performance liquid chromatography combined with tandem electrospray ionization mass spectrometry. The approach, which featured the use of the transferrin adduct as an eventual drug entity entering the cell, facilitated identification of components of the cytosol of cancer cells and their ruthenated forms in which the metal proved to be in +3 or +2 charge states. The Ru species released from the protein-bound form were also characterized with respect to the ligand environment.

Erratum to: CE Separation and ICP-MS Detection of Gold Nanoparticles and Their Protein Conjugates

After publication of this work, we noted that we failed to include the complete list of all coauthors. The full list of authors has now been updated. The Authors’ Competing interests and the Acknowledgement section modified accordingly. We are publishing this erratum to update the author list, which is as follows:

CE Separation and ICP-MS Detection of Gold Nanoparticles and Their Protein Conjugates

A full understanding and mediation of nanoparticle–serum protein interactions is key to design nanoparticles with vivid functions within the body, and to solve this problem one needs to differentiate and characterize individual nano-protein conjugates. In this paper, the authors applied capillary electrophoresis combined with inductively coupled plasma mass spectrometry detection to study the behavior of gold nanoparticles of different geometry, size and surface functionalization upon interacting with serum proteins and their mixtures. Due to high-resolution and -sensitivity benefits of this combined technique baseline separations were attained for free nanoparticles (at real-life doses) and different protein conjugates, and the conversion into the protein-bound form was scrutinized in terms of reaction time.