Open-tubular capillary electrochromatography for the simultaneous determination of cadmium and copper in plants

We discuss the separation and determination of cadmium and copper in plant samples such as Triticum durum (wheat) and Helianthus annuus (sunflower) using open tubular capillary electrochromatography with indirect detection. Before performing the analysis, the samples were digested by microwave-assisted methods using HNO₃ . Regarding the electrophoretic system, several experimental parameters were previously evaluated such as the capillary surface, mobile phase composition, buffer, pH, and voltage applied. The baseline resolution of the studied metals was obtained within 8 min by using a capillary immobilized with carboxylic multi-walled carbon nanotubes and a background electrolyte composed of 6 mM imidazole, pH 4.0. The applied voltage and the temperature were set at 20 kV and 25°C, respectively. Precision, detection, and quantification limits, along with linearity were investigated. The limits of detection and quantification were 2.20 and 7.40 μg/kg, for Cu² ⁺ and 0.05 and 0.20 μg/kg in the case of Cd² ⁺. A good linearity was achieved over a concentration working range of 7.5-100 and 0.2-25 μg/kg for Cu² ⁺ and Cd² ⁺ accordingly. Recovery data for validation studies were found in a range of 98.2-101.5% for both analytes.