Direct electrokinetic injection of inorganic cations from whole fruits and vegetables for capillary electrophoresis analysis

• A direct injection method was developed to introduce sample in the capillary electrokinetically.
• A high viscosity polymer was added to BGE to obtain precise and repeatable injections.
• Quantitative analysis of inorganic cations in fruits and vegetables was achieved successfully.
• The results obtained by CE were in close agreement (r2 = 0.98) with the traditional ICP-MS analysis.
• The developed method was used to determine inorganic cations across different varieties of apples.

A novel approach for the direct injection from plant tissues without any sample pre-treatment has been developed by simply placing a small piece of the tissue into a capillary electrophoresis vial followed by application of a voltage for electrokinetic injection. Separations of sodium, potassium, calcium and magnesium were achieved using a BGE comprising 10 mM imidazole and 2.5 mM 18-crown-6-ether at pH 4.5. The addition of 2% (m/v) hydroxypropylmethyl cellulose to the separation buffer allowed for precise and accurate electrokinetic injection of ions from the plant material by halting the movement of tissue fluid into the capillary. This method provides both qualitative and quantitative data of inorganic cations, with quantitation in zucchini, mushroom and apple samples in agreement with Sector Field Inductively Coupled Plasma Mass Spectrometric analysis (r2 = 0.98, n = 9). This method provides a new way for rapid, quantitative analysis by eliminating sample preparation procedures, and has great potential for a range of applications in plant science and food chemistry.