Metallothionein isoforms separation and cadmium speciation by capillary electrophoresis with ultraviolet and quadrupole-inductively coupled plasma mass spectrometric detection

A complete characterisation of metallothioneins (MTs) in biological systems requires first an optimal separation of the different isoforms and sub-iso forms present. A method for the adequate separation of rabbit liver MT1 and MT2 mixtures by capillary zone electrophoresis (CZE) with UV detection is developed here. Different experimental conditions affecting both, peak shap e and resolution achieved, are investigated in detail. Thus, the influence of the composition, ionic strength and pH of the buffer solution, and the s eparation voltage, have been studied. In order to improve the resolution be tween sub-isoforms, the electroosmotic flow has been also changed and its e ffect investigated by adding organic modifiers. Analytical performance char acteristics are evaluated: calibration graphs were linear between 70 and 20 5 mug ml(-1) for MT1 and between 83 and 242 mug ml(-1) for MT2, while the d etection limits were 4 and 3 mug ml(-1), respectively. Speciation of the me tal-MTs compounds has been accomplished by the coupling CZE-ICP-MS by means of different nebulisers: a conventional concentric Meinhard nebuliser, a B abington type one and a high efficiency nebuliser (HEN). Finally, real sample MTs analyses have been carried out in mussel hepatopan creas cytosols, previously exposed to a metal enriched environment. (C) 200 1 Elsevier Science B.V. All rights reserved.