Short-End Injection Capillary Electrophoresis and Multivariate Analysis for Simultaneous Determination of Heavy Metals in Tea.

An ultra-fast method for the simultaneous determination of heavy metals in Passiflora incarnata tea by capillary electrophoresis (CE) using a short-end injection combined with multivariate analysis was proposed. Separation was conducted by hydrodynamic injection (5 s at 0.5 psi) using the short-end injection procedure in a fused uncoated silica capillary (50 cm total length, 10.2 cm effective length, 50 µm i.d.) with separation time less than 2 min. An indirect UV detection at 214 nm was employed by using imidazole as a chromophore. The buffer used was 6 mmol/L hydroxybutyric acid (HIBA). The optimum conditions by full factorial with a central point were achieved by 18-crown-6 concentration (23.3 mmol L−1), voltage (+11.4 kV), methanol concentration (3.8%), and temperature (20 °C). The method showed good linearity (R2 > 0.998) for both Cd and Pb, inter-day precision of less than 14.49%, and an adequate limit of quantification only for Cd (LOQ < 0.5 µg mL−1 for Cd) based on the US Pharmacopeial Convention limit requirements for elemental impurities. After method validation, the method was applied to Passiflora incarnata tea samples from a local market. Furthermore, the developed method showed great potential for the determination of metals in other samples with proper sample preparation procedures.