Analysis of Calcium in Calcinate tablet from Prime Eastern Pharmaceuticals Raul Calzada, Steven Sullivan, Rose Thomas. Abstract: Analysis on the quantity of Calcium in dietary supplement was performed using complexiometric titration, potentiometry, and flame atomic absorption. Assuming an average weight of 1.7 g per tablet; the calcium content was found to be in a range from 513 mg to 685 mg. Analysis of the variance using Statcrunch computer program and alternative hypothesis testing at an α-level of .01 showed that the results are consistent and that they deviate from the stated content of 800 mg per tablet. It has been claimed that Prime Eastern Pharmaceuticals has decreased the content of calcium in its dietary supplement pills without relabeling their product. This is of interest because people have then been paying the same for a product that contains less calcium than advertised and this would result in an increase in the profits of Prime Eastern Pharmaceuticals. To analyze the calcium content in the pills we performed complexiometric titration with EDTA in a buffered solution at pH of 10, Potentiometric analysis with Ionselective electrode for calcium ion, and flame atomic absorption analysis. The calcium in the pills is contained in the form of calcium carbonate, and so it was treated with hydrochloric acid to separate the calcium and with ammonium to neutralize the solution. Our goal was to prove that Prime Eastern Pharmaceuticals has decreased the content of calcium in their pills from their claimed value of 800 mg per tablet. Experimental Section. Materials: A buffer of pH 10, Calmagite and methyl red was used in the EDTA titration, Potassium chloride was used in the potentiometric analysis. Other materials and chemicals used are listed in the procedures. Preparation of solutions: Two different solutions were used in this project: A and B. They were both prepared by pulverizing the calcinate tablets and treating them with hydrochloric acid and ammonium. Solution A and solution B contain 1.08 g and 1.0409 g of tablet respectively. They were diluted to different extents; A having an approximate concentration of 0.05M and B of 0.006M and has dilution factor of 0.128. Solution A was used for FAA and for potentiometric analysis, while B was used exclusively for EDTA titration. Complexiometric titration: 4 aliquots of 50 mL from solution B were analyzed by titration with EDTA. 15 mL of pH 10 buffer were added to get the solution to an optimum pH level for the EDTA. Methyl red and calmagite were used as indicators. The 4 volumes of EDTA used in this part were: 21.8 mL, 20.4 mL, 21.3 mL, and 20.3 mL. Potentiometric analysis: Solution A was diluted to 20/250 of its original 1 concentration. A 2 mL aliquot of this new diluted solution was mixed with 10 mL of potassium chloride and analyzed with an ion-selective-electrode. A standard solution of known calcium concentration (0.01M Ca) was made and measured with the ISE to make a calibration curve. The standard was prepared from calcium carbonate, and was treated with hydrochloric acid and boiled to expel carbon dioxide. Ammonium was used to neutralize the solution. The standard was used to make four different solutions of 1/100 1/50, 1/20, and 1/10 of the original concentration of .01M. Each of these solutions contain 10 mL of potassium chloride and the rest water in 100 mL volumetric flasks. A calibration curve was created and these functions obtained: Trial 1: y= 19.03x + 82.75. Trial 2 : y= 19.13x + 81.5 were “x” is the logarithm of the concentration of calcium and “y” is the voltage. This is the Nernst equation. FAA analysis: Solution A was diluted to approximately 20 ppm by a dilution of 2.7/250. Standard absorption values were provided for 5 ppm, 10 ppm, 15 ppm, and 20 ppm. A calibration curve was constructed and this equation was obtained: y = 0.003x + .001 were “x” is concentration in ppm and “y” is absorption. The analyte was then compared to the values from the calibration curve. Results and Discussion: It should be noted that to find the mass per tablet, an average weight of 1.7 g per tablet was assumed in all experiments to keep the results consistent. EDTA forms a 1:1 complex with calcium ions and so we were able to find the quantity of calcium in the unknown from the volume of the titration. For trials 1-4, the results of mass of calcium per tablet are: 551 mg, 516 mg, 538 mg and 513 mg, with an overall average of 529 mg. The EDTA titration had the most consistent results and the smallest variance across all experiments (but its also had the largest sample). The problem with EDTA titration though, is that color indicators are not as reliable and carry a lot of the error; this could be a reason why the results obtained from the EDTA titration are slightly lower than the other procedures. In the potentiometric analysis we obtained values of 3.4 mV and -0.3 mV for the unknown, which translate into concentrations of 0.042M and 0.033M after correction for dilution (dilution factor = 1/625). From the concentrations we found the quantity of calcium per tablet with the results being 667 mg for trial 1 and 522 mg for trial 2 with an overall average of 595 mg. Both trials produced very close results, but the measurement of the unknown carries some error because it fell outside the range of the curve and so the values calculated are extrapolated from the func Unknown potential (mV) 3.4 -0.3 Concentration 6.77E-05 5.30E-05 correction for DF 0.042 0.033 Moles of Ca 0.011 0.008 424 332 39.3% 30.7% mg/tablet 667 522 average 595 Mass (mg) % composition Table of results of potentiometric analysis. tions. 2 The FAA analysis provides the best results because the values fall in the range of the calibration curve. Correcting for a dilution factor of 2.7/250 and knowing the volume of the original solution we found the mass per tablet to be 576 mg for trial 1, 685 mg for trial 2, and an overall average of 630 mg. 3 4 Statistical analysis: Its easy to see from one look that the average weight per tablet is lower than advertised, but we are also concerned with how the results vary with each other. Using Statcrunch, we performed an analysis of the variance of the data. Assuming that the samples came from normal populations and with similar variances, this ANOVA shows that the samples have the same mean. This is by comparing the F value obtained from the test with an F test table with 2 and 5 degrees of freedom (F.05 value at df 2,5 = 5.79. 5.79 > 2.0705) The F value is obtained by comparing 2 approximations of the variance, which are SS/(n-1) (sum of squares) and MS/(n-k) (mean square). Now that it is established that the samples have the same parent mean, we can test the hypothesis that Prime Eastern Pharmaceuticals has not changed the content in its dietary pills. For this we compare the average of all measurements with the claimed value of 800 mg. Overall mean: 571, standard deviation: 68.1, t.01 with 7 df: -2.9979. n:8 t obtained from test: ( 800571)/68.1/sqrt(8) = -9.51 Since we are interested with our mean being smaller that the claimed mean the fact that the t obtained is smaller than the t.01 confirms, with 99% confidence, that Prime Eastern Pharmaceuticals has changed the contents of its tablets. Although the statistical analysis can show mathematically that the results deviate from the claimed value, the ANOVA is a very robust analysis and big assumptions had to be made to make it work (like assuming all samples came from normal populations and had similar variances). Still, just comparing the average of 571 mg per tablet with 800 mg per tablet raises doubts on Prime Eastern Pharmaceuticals claim. Conclusion: Results obtained from the three methods are consistent with each other and show that Prime Eastern Pharmaceuticals has indeed changed the contents of its supplementary diet calcium tablet. The values of milligrams of calcium per tablet vary among the three experiments from 513 mg to 685 mg, and have an overall average of 571 mg, a change of 28% from 800 mg per tablet. This means that Prime Eastern Pharmaceuticals is theoretically saving 28% on the making of the tablet, while the costumers are uninformed of the changes. For better results, more samples could have been made, especially for FAA and potentiometric analysis since only two trials were performed in each. 5 Reference: 1) Harris, Daniel C. 1999, Quantitative Chemcial Analysis, W.H. Freeman and Company New York city, 19,77 p. 2) Johnson, Richard A. 2000, Probability and Statistics for Engineers, Prentice Hall, Upper Saddle River, NJ, 245-246, 392-397 p. 3) Fall 2011 CHEM 318 syllabus. 6

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