[Determination of osteopontin at trace levels by non-gel sieving capillary electrophoresis].

A method of non-gel sieving capillary electrophoresis (NGSCE) was established to determine osteopontin at trace levels. The capillary used was uncoated fused silica with a size of 57 cm×75 μm i.d. and an effective length of 50 cm. The electrode buffer was a 150 (mmol/L) boric acid-borate buffer containing 30 g/L polyethylene glycol 20000 (pH 10.0). Other conditions were as follows: separation voltage 23 kV; detection wavelength 214 nm; pressure of injecting sample 3.4 kPa (0.5 psi)×5 s; and column temperature 25 ℃. The NGSCE method had excellent linearity with correlation coefficient of 0.996, and reproducibility with the relative standard deviation of migration time of osteopontin less than 5%. The recovery was 95% and better, the sensitivity was 0.079 g/L. Osteopontin secreted by vascular smooth muscle cells was determined by the NGSCE method at different times after serum withdrawal, and the results were in agreement with those of Western blot method. The results indicate that NGSCE is a simple and rapid method of determining osteopontin at trace levels. This method only needs a micro-amount of sample and is easily automated.