[Determination of salbutamol in human plasma by column-switching HPLC with UV detection]

To make better the RP-HPLC method with column-switching technique for the determination of salbutamol in human plasma.

A high-pressure flow channel selection valve and Kromasil C18 pretreatment column (20 x 4 mm, 5 microns), Ultrasphere Cyano analysis column (250 mm x 4.6 mm, 5 um, Beckman) were used. To the plasma sample 1.0 ml, 0.5 ml phosphate buffer (2.0 mol/L, pH 9.0) containing 0.4% diphenylboric acid 2-aminoethyl ester was added, then extraction was performed with the use of 4.0 ml chloroform containing 1% tetraoctylammonium bromide. The organic layer was removed and extracted again with 300 microliters (0.08 mol/L) acetic acid. 100 microliters of the acid layer was injected onto the column. The mobile phase of pH 2.8, 0.025 mol/L phosphate buffer-acetonitrile-methanol (95:4:1) was pumped at the rate of 0.9 and 1.0 ml.min-1 through the pretreatment and analysis column, respectively. The column-switching time was from 0.7 min to 1.5 min. The detector at 0.002 aufs was set at 224 nm.

The retention time for salbutamol was 6.7 min and that for internal standard (morphine) 7.6 min. The standard curve was linear over the concentration range from 0.5 to 32 micrograms/L. The lowest concentration of detection in plasma was 0.5 microgram/L. The method recovery was 96%-107%; the intra-day RSD less than 5%; the inter-day RSD less than 8%.

This method was found to be simple, rapid, sensitive and accurate for determination of salbutamol in human plasma.