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J Biol Inorg Chem. 2017 Jul;22(5):789-798. doi: 10.1007/s00775-016-1426-z. Epub 2017 Jan 2.

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

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School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.


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.


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

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