Spectrophotometric and high performance liquid-chromatographic determination of lansoprazole in pharmaceuticals

Abstract

Two rapid assay procedures based on visible spectrophotometry and high performance liquid chromatography (HPLC) have been developed for lansoprazole in bulk drug and in capsules. Spectrophotometric method is based on the formation of a charge-transfer (CT) complex between chloranilic acid (CAA) as a <img src='/image/spc_char/pi.gif' border=0>-acceptor and lansoprazole (LPZ) as an n-donor in acetonitrile solvent, the absorbance of the complex being measured at 520 nm. Beer’s law is obeyed for 5-80 <img src='/image/spc_char/micro.gif' border=0>g mL^-1 with an apparent molar absorptivity of 3.45<img src='/image/spc_char/cross.gif' border=0>10³ L mol^-1 cm^-1 and a Sandell sensitivity of 0.0011 µg cm^2-. The HPLC determination was performed on a reversed phase column (Hypersil C₁₈ 5 µm; 250<img src='/image/spc_char/cross.gif' border=0>4.6 <img src='/image/spc_char/micro.gif' border=0>m, i.d) using a mobile phase (1 mL min^-1) consisting of acetonitrile-0.1% phosphoric acid (<i style="">p</i>H 3)-70:30(<i style="">v</i>/<i style="">v</i>) with UV-detection at 284 nm. A reactilinear relationship between mean peak area and concentration of LPZ was observed in the range 6-248 <img src='/image/spc_char/micro.gif' border=0>g mL^-1 with a detection limit of 0.62 <img src='/image/spc_char/micro.gif' border=0>g mL^-1 and a quantitation limit of 1.86 <img src='/image/spc_char/micro.gif' border=0>g mL^-1. Intra-day and inter-day precision, and accuracy of the methods have been established according to the current ICH guidelines. The methods have been successfully applied to the assay of LPZ in tablet preparations with recoveries varying from 97.14 to 102.3% with standard deviation in the range of 0.57-1.65%. The results were statistically compared with those of the reference method by applying Student’s <i style="">t</i>-test and <i style="">F</i>-test. Accuracy, evaluated by means of the spike recovery method was in the range 97.66-106.6%, with precision (RSD) better than 3%.