Mohammad Zairy Azren, Jainal@ Zainal
(2007)
Voltammetric Determination of Nickel in Chocolate by
Differential Pulse Cathodic Stripping Analysis.
Other.
PPSP, Universiti Sains Malaysia.
(Submitted)
Abstract
The determination of nickel in the chocolate was performed by Differential Pulse
Cathodic Stripping Analysis(DPCSV). Chocolate was a complex sample with a high
content of organic compounds such as sugar, protein, fat, lecithin and many more and its
analysis generally involves digestion procedures that might include the risk of losses
and/or contamination. Wet digestion by using concentrated nitric acid and 1:1 ratio of
distilled water-hydrochloric acid on the sample was selected on this study because of its
availability and low cost . Sample was then processed to the sample analysis stage. Prior
to the sample analysis by DPCSV, the optimum pH for the supporting electrolyte,
Britton-Robinson Buffer (BRB}, 0.04 M and optimum parameters for the analysis was
determined. Optimum pH for the supporting electrolyte, BRB was pH 4. Initial potential,
Ei of -0.68 V, final potential, Er of-1.15 V, scan rate of0.050 V/s, deposition potential of
-1.4 V, equilibration time of 5 s and deposition time, tacc of 20 s were the optimized
parameters used in this study. The validation of methodology was performed by plotting
a calibration curve peak height, ip versus different concentrations of nickel (5 ppm) as the
stock solution. A linear graph with the regression equation of Y= 0.820+ 23.322X,
correlation coefficient of 0.966, standard deviation of 1.129, sensitivity of 23.322
nA/ppm and limit of detection of 0.145 ppm was obtained. 3 different brands of chocolate
were analyzed. The results in all samples show absence of nickel.
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