By constructing a calibration curve using known solutions, the concentration of Salicylic Acid ( ) in the unknown drugs was determined with an error of average %RSD = 0.31%. In this laboratory work, the possibility of using optical UV spectrometry to determine the active substance concentration was investigated. The accuracy of the obtained mean was checked using the statistical tool %RSD, as shown in equations 7 and 8. Table 3 illustrates the calculated concentrations, including the dissolution factor (df) of the active ingredient. Summary of results for three Aspirin tablets and three unknowns. Table 2 provides a summary of the mass of ASA in the three samples and the three unknowns and their light absorption. It was taken into account that tablets A, B, and C were dissolved in 50 mL of NaOH solution, whereas the three unknown samples were dissolved in only 25 mL. The linear regression equation was used to calculate the triplet concentration from Aspirin tablets and a series of three unknowns (Equations 5 and 6). Calibration curve for a series of five salicylic acid solutions with different concentrations of the substance. Consolidated data for a series of calibration solutions of salicylic acid. It is worth noting that both in this study and in the scientific work cited, a similar analyte composition was used. The calculated value coincided perfectly with the known literature value 1, and the calculation error was no more than 0.6%. Using this graph’s slope and the Beer-Lambert law, it was possible to find the molar absorptivity (Equations 1, 3). Measured at this wavelength, the optical densities of all five solutions, whose concentrations are given in Table 1, allowed the calibration curve shown in Figure 2 to be plotted. The recorded wavelength showing an intense peak for the solution was 297 nm. Results and DiscussionĪn analytical solution containing 3 mL of salicylic acid was utilized to calibrate the spectrophotometer. From the data obtained, the concentration of the substance in the three unknown solutions was calculated. Three samples of ground Aspirin tablets (5 in each set) were dissolved in sodium hydroxide, after which their optical densities were measured at the wavelength determined by calibration. To construct a calibration curve, a spectrum was taken from the calibration solution with the mean amount of salicylic acid (3.00 mL) at maximum light absorption. Various amounts of stock salicylic acid solution were placed in them and mixed with 10 mL of 0.50 M NaOH solution. Five analytically clean volumetric flasks were prepared in advance to create a series of samples. This laboratory work was performed as described in the Instrumental Methods of Analysis Chem 447 Winter 2020 manual experiment titled Quantitative Analysis of Aspirin Tablets by Ultraviolet Absorption Spectrophotometry written by Judith Bazzi. Perkin Elmer Lambda35 double beam spectrophotometer.Subsequently, this solution was moved to a 250 mL flask for storage and dissolved in the amount of water to the mark on the container. Salicylic acid weighing 0.1234 g was dissolved successively in 25 mL of 0.50 M sodium hydroxide solution and 25 mL of distilled water. The resulting solution was placed in a 500 mL flask for storage and later use. 9.9880 g of sodium hydroxide substance was weighed by the difference method on a scale then dissolved in 400 mL of distilled water and thoroughly mixed. five Bayer aspirin tablets, high purity (×3).Hydrolysis reaction of acetylsalicylic acid to salicylic and acetic acids. Thus, the purpose of this laboratory work was to identify the concentration of acetylsalicylic acid in Aspirin tablets using concentrations of substances of known compositions. This point was the basic idea for performing this study, in which acetylsalicylic acid, which is the main component of analgesics, was actively hydrolyzed to salicylic acid: the reaction is shown in Figure 1. To find the concentration of an unknown substance, the principle of constructing a calibration curve was used to estimate the desired value. From this data, it is possible to calculate the analyte’s unknown concentration using the formula expression of the Beer-Lambert law: Equations 1 and 2. Aspirin (acetylsalicylic acid), C 9H 8O 4, used in this laboratory work, has a cyclic aromatic structure, which means that several output peaks characterize it.
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