Chromatographic conditions were selected after
several trials on different columns using mobile phases
comprising of methanol and water in different propor
tions. The HiQSil C18 column and mobile phase of
methanol : water (60 : 40%, v/v) gave adequate resolu
tion and satisfactory peak shapes for guaifenesin and
internal standard. The detection wavelength of 230 nm
was chosen for maximum sensitivity.