A flow injection spectrophotometric method for the assay of ciprofloxacin was developed. The method was based on the chelation of iron(III) with the drug in 0.023 mol dm-3 sulfuric acid solution in a 72 cm long coil and the brown-red complex produced was monitored at 447 nm. The super modified simplex computer program was employed for the optimization of the system and chemical parameters with respect to throughput and sensitivity as a measure of system performance. A working range for ciprofloxacin determination of 50-500 ppm for a 110 mm3 sample size with an optimum of 250 samples per hour was achieved with a relative standard deviation of less than 0.92%. The method was successfully applied to the determination of ciprofloxacin in drug formulations.

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An accurate spectrophotometric method is proposed for the determination of paracetamol. Cerium(lV) sulphate is used to oxidise paracetamol in 5 M H2S04 to p-benzoquinone, which is then determined at 410 nm. The method has been successfully applied to the analysis of commercial pharmaceutical preparations and the results have been statistically compared with those obtained by the official (BP) method.

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For the first time sequential injection analysis (SIA) technique has been employed for titrimetry. A new SI titrimetric spectrophotometric method for the assay of vitamin C in drug formulations was explored. The method is based on the oxidation reaction of vitamin C with cerium(IV) in sulfuric acid media using a spectrophotometer as a detector with the wavelength monitored at 410 nm. A 2(3) factorial design chemometric approach was employed to study the interaction effect of the chemical and system variables, mainly cerium(IV), sulfuric acid concentrations and the flow rate. The results of the chemometric optimization revealed that the optimum operating conditions for the SI titrimetric analysis of vitamin C were 7.0 x 10(-3) M cerium(IV), 0.455 M sulfuric acid and 28.9 microL s-1 flow rate. A linear calibration plot for the determination of vitamin C was obtained in the concentration range between 30 to 200 ppm. The method was applied to the determination of vitamin C in pharmaceutical preparations and no excipient was found to pose any interference, thus rendering the method suitable for the determination of the drug in pharmaceutical preparations. The SIA method is found to be accurate when the results were statistically compared with the results obtained by the BP standard method. The SIA method is superior when compared to the conventional titration method, the BP standard method and previous methods with respect to precision and automation in solution handling.