Cobalt complexes as internal standards for capillary zone electrophoresis–mass spectrometry studies in biological inorganic chemistry

  • Hannah U. Holtkamp
  • Stuart J. Morrow
  • Mario Kubanik
  • Christian G. Hartinger
Original Paper
Part of the following topical collections:
  1. AsBIC8: 8th Asian Biological Inorganic Chemistry Special Issue


Run-by-run variations are very common in capillary electrophoretic (CE) separations and cause imprecision in both the migration times and the peak areas. This makes peak and kinetic trend identification difficult and error prone. With the aim to identify suitable standards for CE separations which are compatible with the common detectors UV, ESI-MS, and ICP-MS, the CoIII complexes [Co(en)3]Cl3, [Co(acac)3] and K[Co(EDTA)] were evaluated as internal standards in the reaction of the anticancer drug cisplatin and guanosine 5′-monophosphate as an example of a classical biological inorganic chemistry experiment. These CoIII chelate complexes were considered for their stability, accessibility, and the low detection limit for Co in ICP-MS. Furthermore, the CoIII complexes are positively and negatively charged as well as neutral, allowing the detection in different areas of the electropherograms. The background electrolytes were chosen to cover a wide pH range. The compatibility to the separation conditions was dependent on the ligands attached to the CoIII centers, with only the acetylacetonato (acac) complex being applicable in the pH range 2.8–9.0. Furthermore, because of being charge neutral, this compound could be used as an electroosmotic flow (EOF) marker. In general, employing Co complexes resulted in improved data sets, particularly with regard to the migration times and peak areas, which resulted, for example, in higher linear ranges for the quantification of cisplatin.

Graphical abstract


CZE–ICP-MS Internal standards Co coordination compounds Cisplatin 5′-GMP 



Capillary zone electrophoresis


Background electrolyte


Inductively coupled plasma-mass spectrometry


Electrospray ionization-mass spectrometry


Guanosine 5′-monophosphate






Potassium ethylenediaminetetraacetatocobaltate(III)



We thank the organizations and foundations that have supported our research efforts in this area, especially the University of Auckland (University of Auckland Doctoral Scholarship to H. H. and M. K.), the India-New Zealand Education Council, Education New Zealand, the India-New Zealand Research Institute, and the Royal Society of New Zealand and COST CM1105. We thank Auckland Science Analytical Services of the University of Auckland for access to their facilities. We are grateful to Prof. Gordon Miskelly for useful discussions.

Supplementary material

775_2016_1426_MOESM1_ESM.pdf (630 kb)
CZE–ESI-MS data; ICP-MS measurement parameters; kinetic data on the reaction of cisplatin with GMP; effects of internal standardization on the migration times; and BGE-dependent migration of cisplatin and its reaction products (PDF 629 kb)


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Copyright information

© SBIC 2017

Authors and Affiliations

  • Hannah U. Holtkamp
    • 1
  • Stuart J. Morrow
    • 1
  • Mario Kubanik
    • 1
  • Christian G. Hartinger
    • 1
  1. 1.School of Chemical SciencesUniversity of AucklandAucklandNew Zealand

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