Chemistry_Questions_-_CSM_(2).docx

**[QUESTIONS]** **[SECTION A (50mks)]** 1. Diagram shows six volatile essential compounds in GLC, at isothermal of 160° C. image038 a. Describe the tow problems that result from this chromatograph (2mks) b. What would the effect of reducing the temperature be to the chromatogram?...

**[QUESTIONS]** **[SECTION A (50mks)]** 1. Diagram shows six volatile essential compounds in GLC, at isothermal of 160° C. image038 a. Describe the tow problems that result from this chromatograph (2mks) b. What would the effect of reducing the temperature be to the chromatogram? (2mks) c. How can the problem in (a) be corrected (1mk) d. Explain the principle of how flame ionization detector works (5mks) 2. Below is the van deemter equation H = A + B/u + (C~s~ + C~M~)u a. Define what the parameters in the equation mean (4mks) b. Describe the effect of C~s~u parameter would have on the efficiency of GLC (6mks) 3. Uv-vis reading has absorptivity 7.00\*10^3^ L. mol^-1^ cm^-1^ a. Calculate absorbance at 3.008\*10^-5^, at 1 cm length b. Calculate absorbance of the same concentration at 2.5cm and half the concentration of a c. Calculate the transmittance % of the absorbance in (a) and (b) d. From half the transmittance of (a), calculate the absorbance. 4. An analyst separated betamethasone velerate using HPLC. C-18, 25cm, 4.6mm, with mobile phase methanol:water (75:25). Using a VWD at 539nm. This resulted in a chromatograph with 2 peaks. a. What type of column did the analyst use? (2mks) b. The same compound was analysed in TLC and resulted in a chromatogram that had no impurity. How then can you explain the two peaks in the HPLC chromatogram? (4mks) c. Run time for the experiment is set at 20 minutes. As such the analyst, analyses small amount of sample since the lab is a busy lab. If you were the analyst, what would you do with the methanol:water mobile phase inorder to reduce the amount of elution time. Explain the reason to your answer (4mks) 5. Elution strength calculation (10mks) (chloroform and ethylacetate respectively) **[SECTION C(40mks)]** 1. The PMPB has written an article in the newspaper concerning a counterfeit drug. As a pharmacy student who is passionate about quality control, how would you confirm what the pmpb is saying using a simple TLC technique (explain how it works) (20mks) 2. Standard Concentration (g/ml) Absorbance ---------- ---------------------- ------------ 1 2 3 4 A tablet of aspirin, bla bla bla (Calculate % stated content) if claim is 300mg and the sample is at absorbance 0.316 (20mks)