Determine the accurate concentration

Reference no: EM132729648

Practice Questions

1. Express the following solutions as % w/v
a) 5 g solute in 500 ml
b) 12 g solute 60 ml
c) 2 g solute in 20 ml
d) 26 g solute in 500 ml
e) 2 mg solute in 10 µl

2. Express the following solutions as ppm.
a) 250 mg solute in 1000 ml
b) 10 mg solute in 200 ml
c) 2 mg solute in 50 ml
d) 8 mg solute in 250 ml
e) 100 mg solute in 100 ml

3. Given a 2.0 M solution of NaOH, what volume would be required to prepare the following solutions:
a) 2 L of a 1.0 M solution
b) 500 mL of a 0.2 M solution
c) 200 mL of a 0.4 M solution
d) 5 L of a 0.002 M (2 mM) solution
e) 4 L of a 50 mM solution

4. How much solute would be required for 1L of the following solutions?
a) 1 M NaCl
b) 0.2 M NaOH
c) 0.2 M HCl
d) 10 mM KCl
e) 0.05 M (50 mM) HNO3

5. What would be the molarity of the following solutions?
a) 77 g NaCl in 500 mL
b) 1.2 g NaOH in 100 mL
c) 14.6 g HCl in 200 mL
d) 377.5 mg KCl in 2 L
e) 21 g HNO3 in 250 mL

6. How much solute would be required for the following stock solutions?
a) 1 L of 250 ppm stock solution
b) 500 mL of 100 ppm stock solution
c) 2 L of 200 ppm stock solution
d) 1.5 L of 300 ppm stock solution
e) 200 mL of 400 ppm stock solution

7. Describe how you would prepare a 500 ppm stock solution of salicylic acid in water.

8. Using the solution described in Q7, describe how you would prepare solutions of 5, 10, 15, 20, and 25 ppm. (You may use volumetric flasks of 10, 25, 50, or 100 ml, and pipettes of 1, 2, 3, 4, or 5 mL)

Lab 1: Analysis of Aspirin API by UV Vis Spectrophotometry and Back Titration

The purpose of this experiment is to determine the percentage purity of a batch of aspirin API by:
a) UV spectrophotometry using a calibration method,
b) Back titration against a blank,
You will complete both experiments and then compare the results, considering any differences in accuracy and precision between the techniques.

3. Questions

1. Compare the results from both the UV and the titration assays and suggest reasons for any difference in the results.

2. What factors may cause a false or inaccurate result for either method?

3. How could the assay be performed more accurately?

Lab 2: Determination of Magnesium and Sodium in a Plasma Sample by Atomic Spectroscopy

a. Determination of Magnesium in Serum by Atomic Absorption Spectroscopy

b. Determination of Sodium by Atomic Emission Spectroscopy

Lab 3: Analysis of an Aspirin API by HPLC, and Analysis of Residual Solvents by GC.

a. Analysis of an Aspirin formulation by HPLC
b. Analysis of Residual Solvents by Gas Chromatography

Lab 4: Extraction of Eugenol from Cloves

Lab 5: Data Analysis Workshop

5. Record here the accurate weight (g), of sample used in the first assay. *

6. Record here the accurate molarity of the HCl used in the lab. *

7. The accurate molarity of the HCl used in the lab is not exactly the same as the molarity quoted in the lab guide (0.5 M). Therefore determine the factor of the titrant. *

8. Record here the volume (mL), of HCl required to titrate the first sample. *

9. Record here the volume (mL), of HCl required to titrate the blank. *

10. Using your titre results, determine the mass (g), of C9H8O4 (Mr=180.16), present in the first sample. *

11. Based on the results form your first assay, calculate the percentage purity (%), of the API. *

12. Record here the weight (in g), of reference aspirin transferred in your 20 mL volumetric flask in order to prepare your aspirin stock standard solution . *

13. Hence, determine the accurate concentration (mg/mL), of the diluted aspirin standards (i.e. Standards 1 and Standard 2), assuming 100% purity. *

14. Record here the peak area of the reference aspirin in the chromatogram of Standard 1 *

15. Record here the peak area of the aspirin in the Test Solution 1 chromatogram. *

16. Using the comparative method and the data entered above, calculate the actual concentration (mg/mL), of aspirin in Test Solution 1. *

17. Using your answer above, and by considering the dilution factor used, calculate the actual concentration (mg/mL), of aspirin in the API test stock solution. *

18. Record here the mass (g) of aspirin API that you used to prepare the API test stock solution. *

19. Hence, determine the percentage purity (%) of the aspirin API. (Use the values you have submitted above to calculate this answer). *

20. Record the concentration (in mg/mL), of Impurity B (salicylic acid), in Reference solution A. *

21. Record here the peak area of principle peak in the Reference solution A chromatogram. *

22. Record here the peak area of Impurity A in the Test Solution 2 chromatogram. *

23. Does the level of Impurity A pass the limit test? *

Yes No

24. Record here the peak area of Impurity B in the Test Solution 2 chromatogram. *

25. Does the level of Impurity B pass the limit test? *

Yes No

26. Record here the peak area of Impurity C in the Test Solution 2 chromatogram. *

27. Does the level of Impurity C pass the limit test? *

Yes No

28. Record here the peak area of Impurity D in the Test Solution 2 chromatogram. *

29. Does the level of Impurity D pass the limit test? *

Yes No

30. Record here the mass (g) of API that you transferred in your 10 mL volumetric flask. *

31. Record here peak area of MeOH in the Reference Standard. *

32. Record here peak area of EtOH in the Reference Standard. *

33. Record here peak area of IS in the Reference Standard. *

34. Determine the RRF for MeOH vs IS. *

35. Determine the RRF for EtOH vs IS. *

36. Record here peak area of MeOH in the test sample. *

37. Record here peak area of EtOH in the test sample. *

38. Record here peak area of IS in the test sample. *

39. Using your RRF (as entered above), determine the concentration (ppm), of MeOH in the API sample solution. *

40. Now calculate the % w/w content of MeOH in the API sample you weighed. *

41. According to the limit set by the British Pharmacopeia for residual solvents, does your API pass the test? *

Yes No

42. Using your RRF (as entered above), determine the concentration (ppm), of EtOH in the API sample solution. *

43. Now calculate the % w/w content of EtOH in the API sample you weighed. *

44. According to the limit set by the British Pharmacopeia for residual solvents, does your API pass the test? *

Yes No

45. If you have not been able to use your own LC and/or GC chromatograms to answer the above questions, then explain why in the space below. *

46. Which components were present in the initial distillate? *

Check all that apply.

Eugenol Acetyl eugenol
Humulene (alpha-caryophyllene) Beta-caryophyllene

47. Which components were present in the 3 M NaOH aqueous extraction? *

Check all that apply.

Eugenol Acetyl eugenol
Humulene (alpha-caryophyllene) Beta-caryophyllene

48. Following acidification of the previous extract and addition of DCM, which components were present in the organic layer? *

Check all that apply.

Eugenol Acetyl eugenol
Humulene (alpha-caryophyllene) Beta-caryophyllene

Eugenol Reference NMR Spectra

δ 3.13 (2H, d, J = 6.5 Hz) δ 3.79 (3H, s)
δ 4.80 - 4.91 (2H, dd, J = 17.1, 2.4 Hz)
δ 5.67 (1H, ddt, J = 17.1, 10.6, 6.5 Hz)
δ 6.54 (1H, dd, J = 8.5, 2.8 Hz)
δ 6.59 (1H, d, J = 2.8 Hz)
δ 6.63 (1H, d, J = 8.5 Hz)

50. Which signal corresponds to the proton(s) attached to carbon 4? *

51. Which signal corresponds to the proton(s) attached to carbon 6? *

53. Which signal corresponds to the proton(s) attached to carbon 10? *

54. Which signal corresponds to the proton(s) attached to carbon 11? *

55. Which signal corresponds to the proton(s) attached to carbon 12? *

56. Record here the percentage extraction of eugenol from cloves you achieved in the lab (%) *

57. Record here the purity of your eugenol sample as determined in the data analysis workshop (by peak area percent). *

58. Which practical lab classes did you enjoy?

59. Please indicate your level of understanding in each of the practical lab classes

Assessment Structure - please read before answering questions below
In previous iterations of this module students were asked to prepare a full lab report from a selection of the practical sessions they had attended. This year we have opted to assess students based on the submission of a Google Form, a series of pre-lab MCQ's, and a selection of their lab book data via Turitin. We hope that this approach allows students to better spread the load of this assessment, and reduce the amount of time needed to prepare the submission, as most of this coursework may be completed either in the lab or in students own time throughout the semester.

60. Please answer the following questions relating to the structure of the assessment.

Attachment:- Pharmaceutical Chemistry Lab Guide.rar

Reference no: EM132729648

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