Cobalt complexes as internal standards for capillary zone electrophoresis–mass spectrometry studies in biological inorganic chemistry
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.
KeywordsCZE–ICP-MS Internal standards Co coordination compounds Cisplatin 5′-GMP
Capillary zone electrophoresis
Inductively coupled plasma-mass spectrometry
Electrospray ionization-mass spectrometry
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.
- 5.Schluga P, Hartinger CG, Egger A, Reisner E, Galanski M, Jakupec MA and Keppler BK (2006) Dalton Trans:1796–1802. http://pubs.rsc.org/en/content/articlelanding/2006/dt/b511792e#!divAbstract
- 23.Buckingham DA, Clark CR (1987) In: Wilkinson G, Gillard RD, McCleverty JA (eds) Comprehensive coordination chemistry: the synthesis, reactions, properties & applications of coordination compounds. Pergamon, Oxford, pp 635–900Google Scholar