الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Catalytic methods of analysis are very popular examples for the application of kinetics in
analytical chemistry. Their sensitivities are generally orders of magnitude better than
conventional equilibrium methods. Therefore, th:ey found recent widespread applications in many
fields; especially in environmental and biochemical studies.
In the present dissertation, two new spectrophotometric methods were developed for trace level
determination of chromium and molybdenum. These methods were applied to the analysis of potable,
natural and industrial waste waters.
A simple, highly selective and sensitive method was developed for the determination ofCrv’ in
natural and highly polluted waste-waters. The method was based on the catalytic effect of Crv’ on
the oxidation of 2- aminophenol (AP) with hydrogen peroxide. The reaction is followed
spectrophotometrically by tracing the oxidation product at 43’0 nm after 10 minutes of mixing
the reagents. The optimum reaction conditions are 2 x 1o·3
mol r’ AP, 0.3 mol r’ HzOz and 2.5 X 10’2 mol r’ phosphate buffer (pH 6.45 ± 0.02), at 40°C.
The linear
range of the calibration graph was up to 7.0 ng mr’ of
CrVI and the detection limit (3Sb) was 0.10 ng mr’. Interferences of No2·, Mov’, Cr111 and
Fe111 ions were
eliminated using a sulfamate-citrate-fluoride masking mixture along with a quantitative
co-precipitation with Al(OH)J, rendering the method highly selective for Crv1• Such a
co-precipitation step could eliminate the strong interferences of 10, 0.2, 20 and 200 !-lg mr 1
levels of these ions, respectively. Spectrophotometric determination of as little as 1.0 ng mr 1
ofCrv1 in aqueous solutions gave an average recovery of 99.5% with a relative standard
deviation of 1.2% (n = 5). The implemented method was conveniently applied to natural and highly
polluted industrial waste waters. A comparison of published catalytic-spectrophotometric .methods
for chromium determination was also presented.
Moreover, a highly selective, sensitive, and simple catalytic method was developed for the
determination of molybdenum in natural and waste waters. The method was also based on the
catalytic effect of MoVI on the oxidation of 2-aminophenol (AP) with H202 • The reaction was
followed spectrophotometrically by tracing the oxidation product at 430 nm after 10 min of
mixing the
reagents. The optimum reaction conditions are: 4.0 x 1o·3
mol r 1 AP, 4.0xl0.2 mol r 1 H202, and phosphate buffer
(2.5x10”2 mol r 1 ) of pH= 6.75±0.05, at 40 °C. Addition of
800 !-lg mr 1 EDTA along with the use of phosphate buffer conferred high selectivity for
the developed method.
However, the interfering effects of Au 111, Cr111, Crv 1 and
Fe111 ions were eliminated following a reduction and a co precipitation steps with SnCh and
Al(OH) 3, respectively.
Following the recommended procedure, MoVI can be determined with a linear calibration graph up
to 11.0 ng ml” 1 and a detection limit, based on the 3Sb-criterion, of
0.10 ng ml” 1 • The unique selectivity and sensitivity of the
implemented method allowed its direct application to the determination of MoVI in natural and waste
waters. Moreover, the catalytic spectrophotometric methods for
MoVI detenm.natw.
n were compare d .
Statistical treatment of analytical results could not detect any systematic error and showed the
applicability and the high accuracy and precision of the developed methods.