CBMS208 / CBMS608 Chemical Analysis I 2017
QUESTIONS ON FLOW INJECTION ANALYSIS
Use this tutorial set to practise solving problems in the topic. There is no need to submit any work.
Hand in solutions to 1 and 2 before 6 pm on Friday, November 10, 2017. Please put down your postal address on the submission page as well.
1. Consider the following FIA apparatus. In the labels used,
TEA buffer = a buffer containing a mixture of Tris base, EDTA and acetic acid NAD = nicotinamide adenine dinucleotide
INT = 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium
GLDH = glutamate dehydrogenase
300 μL Injection
INT solution Diaphorase solution
(flow rates in mL/min)
Spectrophotometer λ = 492 nm
thermostated to 25oC
- (a) Calculate the Dmax of the apparatus, assuming a 300 μL injection volume corresponds to 7 times S1⁄2 for this system.
- (b) The pump in the above apparatus is a peristaltic pump. If a 1.37 mm internal diameter (ID) pump tube was used to supply flow for the 1.5 mL/min TEA buffer/X-100 reagent line, calculate the ID of the pump tubes for the 3.0, 0.2 and 0.05 mL/min lines.
2. Potassium bromate is added to flour to improve its bread making qualities. The maximum allowable level of potassium bromate in bread is typically 50 mg/kg of flour mass. The official method for the determination of bromate in bread is by iodometry and it is performed as follows:
- (a) a solution of ammonium molybdate is added to an acidified solution of the sample to be tested. The ammonium molybdate is used to increase the rate at which iodine is formed in the next step.
- (b) a solution of potassium iodide is then added to the solution from (a). Any bromate present in the sample will oxidise the I- added, forming iodine.
- (c) any iodine produced is then determined colourimetrically by the addition of a starch solution to the solution from (b). The starch reacts with any free iodine producing a blue coloured complex, the concentration of which can be monitored by absorbance at 570 nm.The overall reaction for the determination is:
BrO3- + 6H+ + 6I- → 3I2 + Br- + 3H2O
Design an FIA apparatus to perform the above analysis. You need not work out concentrations of reagents, etc, however you should detail the criteria you used in your decision of flow rate(s), tubing internal diameter(s), injection volume (in terms of S1⁄2), and any other relevant parameters. Depending on your design, you should also calculate, or at least estimate, the Dmax for your apparatus and comment on the implications of your Dmax on the sensitivity of your design.
Page 2 of 2