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Analytical Chemistry Question Paper

Analytical Chemistry

Course:Bachelor Of Science In Food, Nutrition And Dietetics

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2008/2009
SECOND SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR
OF SCIENCE IN FOOD NUTRITION AND DIETETICS
HFN 317: ANALYTICAL CHEMISTRY

INSTRUCTIONS
Answer QUESTION ONE and any other TWO questions.

QUESTION ONE - (30 MARKS)
(a) Discuss the importance of the following steps in the analysis of samples:
(i) Plan of analysis [3 marks]
(ii) Sampling [3 marks]
(iii) Removal of interference [3 marks]
(iv) Drying [2 marks]

(b)Explain the principle of atomic emission spectroscopy for the determination of
metals.
[3 marks]
(c)Stable compound formation is one of the chemical interferences encountered in
atomic spectroscopy. Explain how the problem of stable compound formation can be
tackled.
[4 marks]
(d)Distinguish between the following terms as used in photo-luminescence methods:
(i) fluorescence and phosphorescence [2 marks]
(ii) internal conversion and inter-system crossing. [2 marks]

(e)
(i) Explain the principle of x-ray fluorescence spectroscopy. [1 mark]

(f)Explain the following terms as used in chromatography:
(i) retardation factor [1 mark]
(ii) retention time [1 mark]
(iii) resolution of peaks [2 marks]

QUESTION TWO - (20 MARKS)
(a)Describe the environmental and structural factors that affect fluorescence intensity
of a fluorescent compound.
[7 marks]
(b)Spectrofluorimetric method cannot be directly used for non-fluorescent compounds
(i) Provide the general name of reagent that must be used to react with non- fluorescent compound before fluorimetric method is used. [1 mark]
(ii) Describe the characteristics of the ideal reagent that is used for reacting
with non-fluorescent sample prior to analysis by fluorimetric method.
[5 marks]

(c)The concentration of quinine in a drug was determined by fluorescence method.
The following results were obtained:
Concentration of Quinine Standard
(ppb) 0 10 20 30 40 45
SAMPLE 0 20 38 58 78 88 45

(i) Draw the calibration graph of fluorescence intensity versus concentration of
quinine standard.
[2 marks]

(ii) Calculate the concentration of quinine in the drug sample. [2 marks]

(d)Distinguish between dynamic and static quenching.
[1 mark]

(e)Explain why lasers are not preferred as light source in fluorimetric method.
[2 marks]

QUESTION THREE – (20 MARKS)
(a)
(i) Draw a block diagram of atomic absorption spectrometer in which denterium lamp is incorporated.
[2 marks]
(ii) Explain the role of denterium lamp in the instrument drawn in part (i) and
how this role is achieved.
[3 marks]
(b)Describe how you would determine the concentration of EITHER Lead in a tomato fruit
OR Mercury in fish using atomic absorption spectroscopy. [6 marks]
Page 2 of 3

(c)Explain the principle of operation of the commonly used light source in an atomic
absorption spectrometer.
[5 marks]
(d)Explain the following as used in atomic absorption spectroscopy
(i) Self absorption [2 marks]
(ii) Modulation of light source [2 marks]

QUESTION FOUR – (20 MARKS)
(a)Using suitable analytical method, explain how you would carry out qualitative
analysis of a sample containing several amino acids.
[5 marks]
(b)
(i) Draw a block diagram of a Gas chromatograph. [2 marks]
(ii) Describe briefly the various components of a Gas chromatograph.
[7 marks]

(c)Explain how you would determine quantitatively the concentration of glucose in a
sample mixture containing fructose, sucrose, glucose and maltose by gas chromatography.
[6 marks]

Analytical Chemistry Question Paper

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