Question

Please answer it ALL completely and write clearly, thank you.

( 20 marks )

For the following samples, suggest a method/technique that can be used to satisfactorily perform the required analysis. The method/technique can be i) Two brands of unleaded petrol samples. The major and minor components in (ii) A fresh water sample obtained from a lake suspected to be polluted with spectroscopic, chromatographic or a combination of both. Explain your choice. the two petrol brands need to be identified. various organic compounds. The organic compounds need to be identified and determined at ppm levels. ii) A brackish water (air payau) sample collected near a shrimp farming area. Heavy metals such as Pb, Cd, Hg and Zn need to be determined up to ppb levels. iv) A sweet smelling essential oil extracted from the bark of a tree found in Gunung Jerai forest reserve. The structures and identities of the various components needs to identified. (v) A sample digested from intemal body tissue of a dead fish. Identities of the protein compounds found in the tissue needs to be identified. Isotope Abundance for Some Selected Elements Atomic No Mass bundance lement sotope TH 1 Hydrogen 1.007825 2.014102 3.016049 99.9885 0.115 Tritium "С "С "С 98.93 6 Carbon 12.000000 13.003355 14.003242 1.07 8 Oxygen 15.994915 16.999132 17.999160 99.757 0.038 0.205 8o 100 9 Fluorine 18.998403 14.003074 15.000109 99.632 Nitrogen 15N 0.368 35 75.78 24.22 34.968853 Cl 7 Chlorine scl 36.965903 CI 8.918338 50.69 35 Bromine Br80.916291 49.31

Answer 1

(i) In case of two petrol samples, we can use ESR ( Electron Spin Resonance) spectrometry, it will give the estimate of all the polynuclear hydrocarbons present in it. This is done by converting them into radical cations and then taking their ESR spectrum.

(ii) Infra red spectroscopy will be helpful in this case , because as we compare it's spectrum with the authentic sample, the impure sample will have poor and also some additional bands whereas pure sample will have sharp peaks and bands.

(iii) Chromatography technique will be helpful in this case.

(iv) Raman Spectroscopy will help you identify the structure and identity of different compounds present in it.

(v) Identity of the proteins can be easily identified by ESR spectroscopy as a definite correlation exists between the concentration of free radicals and the metabolic activity of the material.