Essay Question Quiz 2 - 2024 PDF

Instruction: 2 essay questions worth 20 points. Please submit your answer to the drop box in the lounge room by noon of 6 Nov 2024. 15. You, a professional chromatographer is tasked to separate several unknown small molecules. These molecules are derived from oxidation of plastic wastes and forms a...

Instruction: 2 essay questions worth 20 points. Please submit your answer to the drop box in the lounge room by noon of 6 Nov 2024. 15. You, a professional chromatographer is tasked to separate several unknown small molecules. These molecules are derived from oxidation of plastic wastes and forms a relatively complex mixture. Please answer Q1-Q3 as below using the knowledge you’ve learnt in the lecture of liquid chromatography. A preliminary guess to the product is here (Figure 1): Figure 1 Q1. Your manager asked you for the budget and other resources you need. In this case, what in type of liquid chromatography (LC) you will ask for and what column and gradient system you will choose to separate those small molecules? (5 marks) a. Describe at least 2 LC types, including their principles and applications that can be used for this case and chose one. Give the reason why this LC types are preferred than the other one. (3 marks) b. Propose a LC gradient (flow rate, buffers, solvents, gradients etc.) as a starting point. (1 mark) c. Look online. List the column, solvent, and buffer you plan to use. Include brand, product number, and price for a budget. For column, please describe the structure and principle of the solid phase, the size of the column and why you choose this size, and the pro and con of this specific column. (1 mark) Tips: you can always ask technical support from the vendor. Q2. Upon first test, you find the mixture is too complicated for 1-dimensional LC, what can you do to reduce the complexity and achieve a better resolved LC peaks? Describe the approach and your reasoning behind. (1 mark) Q3. Now, you finally get a better separation and understanding of the nature of the mixture. In brief, the mixture contains three classes of compounds. An analytical flow LC chromatogram of these compounds is shown here (Figure 2) together with a zoomed view (upper panel of Figure 2). (4 marks total. 1 mark for each question under Q3) Figure 2 A. Now the upper management getting interested in the identity of the compounds. They demand the identification meet the most stringent criteria. Now you have to separate and collect the unknown compounds for later LC-MS, NMR, and even X-ray crystallography analysis. Describe what can you do to alter the gradient to better separate compounds highlighted in Figure 2 (Compound 1, 2, and 3). Draw your gradient with details. (1 mark) B. Suppose you can only load samples at half of the column’s loading capacity (the column you picked from Q1 c). We assume that the peaks shown in the zoomed figure have: i. Peak 1: 2% of totally sample weight, ii. Peak 2: 0.8% of the sample weight, iii. Peak 3: 1% of the sample weight. Based on the sample amount needed for LC-MS, NMR, and X-ray identification. How many LC runs you need to meet sample amount requirement for: (1 mark) 1. LC-MS (1ng) 2. NMR (10 mg) 3. X-ray (5g) C. Suppose for each minute, the cost for LC is around S$1. What is the total cost for collecting enough of these samples for (1 mark) 1. LC-MS 2. NMR 3. X-ray D. Now, what type of LC and column you plan to use, and why? (1 mark) 16. If the diameter of a lens is 2.5 m and the wavelength of light is 400 nm, Q1. what is the size of the smallest object that can be seen using the lens from a building that is 10 km away from the object? Please explain your calculation step and elaborate on how the Rayleigh criterion is applied to this scenario (word limit: less than 100 words). Tips: please refer to Figure 3 and use the knowledge you learnt from the lectures of electron microscopy (5 marks) Q2. You find that you cannot see clearly an object with the size you get in Q1. What could be the possible reasons? Please list at least 3 reasons and use the knowledge you learnt from the lectures on electron microscopy to explain how they can compromise the resolution. (word limit: less than 200 words) (5 marks) Figure 3