Efficient sample clean-up and online preconcentration for sensitive determination of melamine in milk samples by capillary electrophoresis with contactless conductivity detection.

Based on an efficient sample clean-up and field-amplified sample injection online preconcentration technique in capillary electrophoresis with contactless conductivity detection, a new analytical method for the sensitive determination of melamine in milk samples was established. In order to remove the complex matrix interference, which resulted in a serious problem during field-amplified sample injection, liquid-liquid extraction was utilized. As a result, liquid-liquid extraction provides excellent sample clean-up efficiency when ethyl acetate was used as organic extraction by adjusting the pH of the sample solution to 9.

Use of capillary electrophoresis with conductivity detection to anions.

Capillary electrophoresis with conductivity detection was used to separate and detect chloride (Cl-), nitrate (NO3-), bicarbonate (HCO3-) and dihydric phosphate (H2PO4-) ions. The proposed method was carried out by using citric acid and sodium citrate as buffer solution, under the condition of a-10 kV high voltage power supply. The effects of various buffers, concentrations, pH values and running voltages on separation were investigated.