Quantification Of Silver Nanoparticles In A Pharmaceutical Product By Spectrophotometry And Potentiometry: A Proposal For Practical Classes In Analytical Chemistry

Spectrophotometry and potentiometry techniques were used to quantify silver in an ophthalmic solution. A standard solution of silver nanoparticles was synthesized, from which an analytical method was developed to quantify silver in the sample. Potentiometric titration of three samples were made, using an electrochemical cell containing an alternative metallic indicator electrode and an Ag vertical bar AgCl double junction reference electrode, connected to a potentiometer. A digital burette containing a standard solution 5.00 x 10(-3) mol L-1 NaCl was used. Characterization of the ophthalmic solution by spectrophotometry showed that Ag in this medicine is in the form of nanoparticles. The sample preparation for potentiometric measurements was carried out using a mixture of 50 mu L. of the ophthalmic solution and 2.00 mL of nitric acid. The average concentrations of Ag obtained were 1.65 +/- 0.03% (w/v) by spectrophotometry, and 1.73 +/- 0.06% (w/v) by potentiometry. The relative standard deviations were 2% and 4%. respectively. The precision of the measurements obtained by the cited methods showed no significant differences (f test). It was also observed that average silver concentrations obtained by the two methods were not statistically different (t test). Both tests were made at a 95% confidence level.