94. Solving a chemistry problem

44. The content of nitroglycerin in tablets of the drug nitroglycerin is determined by HPLC using a standard solution, for which chromatograms of the analyzed and standard solutions are obtained.
To prepare a standard solution, place a standard sample containing 10 mg of nitroglycerin into a 25 ml volumetric flask, add about 15 ml of the mobile phase (methanol and water in a 1: 1 volume ratio), shake the mixture until the nitroglycerin is dissolved, bring the volume of the solution to flask to the mark with the mobile phase and mix. Take 10 ml of the resulting solution, transfer to a 50 ml volumetric flask, bring the volume of the solution in the flask to the mark with the mobile phase and mix. Get a standard solution.
On the day the analyzed solution is obtained, 20 tablets of the drug are weighed and crushed, the resulting mass is quantitatively transferred into a 25 ml volumetric flask, 15 ml of the mobile phase are added, the mixture is thoroughly mixed (for half an hour), the volume of the solution in the flask is adjusted to the mark with the mobile phase and filtered. Take 10 ml of the resulting filtrate, transfer to a 50 ml volumetric flask, bring the volume of the solution in the flask to the mark with the mobile phase and mix. Get the analyzed solution.
Alternately chromatograph 20 µl samples of the analyzed and standard solutions at least three times, measure the peak areas of nitroglycerin S (X) and S (st) on the chromatograms of the analyzed and standard solutions, respectively, calculate the average value of these areas based on the results of all measurements and their relationship
Calculate the mass of nitroglycerin in mg and its percentage in one tablet of the drug, if the ratio of the average peak areas on the chromatograms is found to be S(X)/S(st) = 0.98, and the average weight of one tablet is 60 mg. Answer: 0.49 mg; 0.82%.