Refluxed ampicillin trihydrate was determined using conventional and derivative UV absorption spectrophotomerty.The calibration curve for refluxed ampicillin trihydrate at 339 nm was found to have a linear range extended from 4 to 200 ppm with relative standard deviation for the slope of 0.0082 and correlation coefficient of 0.9999 with detection limit of 0.5 ppm. The effect of pH on the determination of ampicillin trihydrate at this wavelength was investigated. The best pH was found to be 8.Addition copper(II) and iron(III) have a large effect on the determination of ampicillin trihydrate due to their overlapped spectra. Therefore, first and second derivative spectrum at 362 and 338 nm, respectively, were used to overcome this problem.The calibration curve for the first derivative spectra has a linear range of (4-200) ppm with relative standard deviation of the slope of 0.0052 and correlation coefficient of 0.9999 and the calibration curve for the second derivative spectra has a linear range of (4-200) ppm with a relative standard deviation of the slope of 0.0083 and correlation coefficient of 0.9999 in the presence of Cu(II) and Fe(III).Na+, k+, Ca+2 and Zn+2 have shown no interaction when added to refluxed ampicillin trihydrate solution as shown by spectrophotometric method.
