Sequential injection technique for automated titration: Spectrophotometric assay of vitamin C in pharmaceutical products using cerium(IV) in sulfuric acid

Abstract

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.

Monosegemented flow potentiometric titration for the determination of chloride in milk and wine

“…The analytical performance of the proposed system is comparable to monosegmented titrators described in the literature, 22,23,[25][26][27] presenting an advantage when compared with ordinary sequential injection analysis titration systems, [15][16][17] since it does not need a calibration step with standard solutions. …”

“…Although SIA systems provide a different way to process sample and titrant solution, they usually require a calibration step with standard solutions to determine the analyte concentration in the sample. [15][16][17] Recently, Arlem and Bartroli 18 have described a SIA-batch system to perform titrations without the need of a calibration curve while Pimenta et al 19 have employed the Gran method to determine the end point of potentiometric titrations.…”

“…Although SIA systems provide a different way to process sample and titrant solution, they usually require a calibration step with standard solutions to determine the analyte concentration in the sample. [15][16][17] Recently, Arlem and Bartroli 18 have described a SIA-batch system to perform titrations without the need of a calibration curve while Pimenta et al 19 have employed the Gran method to determine the end point of potentiometric titrations.A multisegmented flow system has been proposed by Fleet and Ho 20 to perform flow titration, implemented by keeping the flow rates of sample and titrant solutions constant while the titrant concentration is changed. In this case, a calibration with standard solutions is also necessary to calculate the concentration of the sample.…”

Application of sequential injection analysis to pharmaceutical analysis

“…However, the rate could have been increased without loosing reliability, in the absence of the mixing chamber. In 1999, Sultan et al were the first to describe a spectrophotometric titration employing the SIA technique [88]. In this innovative work, Vitamin C was determined after its oxidation with cerium(IV) in sulphuric acid medium, measuring the decrease in absorbance of cerium(IV) at 410 nm.…”

Simultaneous multiple injection to perform titration and standard addition in mono-segmented flow analysis

“…The peak width is proportional to the analyte concentration, which is calculated through an analytical calibration curve. Sequential injection analysis has been employed by Sultan et al [26] to implement a spectrophotometri c¯ow titration methodology to determine vitamin C in pharmaceutical products. A Ce(IV) standard solution was used as titrant and a calibration curve was necessary to carry out the analysis.…”