A new kinetic method is described for the determination of ultramicro amounts of Cu(II) based on its catalytic effect on the oxidation of trisodium-2-hydroxy 1-(4-sulphonato-1-naphthylazo)naphthalene-6,8-disulphonato (red artificial color PONCEAU 4R) by hydrogen peroxide in borate buffer (B.B). The detection limit given by Perez-Bendito is 0.8 ng/cm3, but the detection limit that we experimentaly determined is 3.8 ng/cm3. The relative error ranges between 7.77 and 2.09%for the concentration interval 3.8 to 50.1 ng/cm3. Kinetic equations are proposed for the investigated process. The effects of certain foreign ions upon the reaction rate were determined for an assessment of the selectivity of the method. The method was applied for the determination of Cu(II) ions in samples of alloy.
Anew, sensitive and simple kinetic method has been developed for the determination of traces of Co(II) ions based on their catalytic effect in the oxidation of trisodium-2-hydroxy-1-(4-sulphonato-1-naphthylazo)naphthalene-6,8-disulphonate (red artificial color Ponceau 4R) by hydrogen peroxide in borate buffer. The reaction was followed spectrophotometrically by tracing the oxidation product at 478.4 nm within 1 min after the initiation of the reaction. The optimum reaction conditions are: borate buffer (pH 10.50), Ponceau 4R (8 x10-6 mol/dm3), H2O2 (3 x10-2 mol/dm3) at 22 ?C. Following this procedure, Co(II) can be determined with a linear calibration graph up to 1.17 ng/cm3 and a detection limit of 0.20, based on the 3??criterion. The relative error ranges between 4.80-3.25 % for the concentration interval of Co(II) ions 1.76-17.61 ng/cm3. The effects of certain foreign ions on the reaction rate were determined for an assessment of the selectivity of the method. The method was applied for the determination of Co(II) in pharmaceutical samples.
A kinetic spectrophotometric method for determining the residues of herbicide
bromofenoxim (BrFX) has been developed and validated. The proposed method is
based on the inhibitory effect of BrFX on the oxidation of sulfanilic acid
(SA) by hydrogen peroxide in the presence of Cu(II) ion, which was monitored
at 370 nm. The variables affecting the rate of the reaction were investigated
and the optimum conditions were established. BrFX can be measured in the
range of 0.041 - 0.46 ?g/ml and 0.46 - 13.86 ?g/ml. The detection limit of
the method with 3? criteria is 0.0077 ?g/ml. The relative standard deviations
for five replicate determinations of 0.041, 0.24 and 0.46 ?g/ml BrFX are 3.0,
5.32 and 2.85%, respectively. This method can be successfully used to
determine BrFX concentration in baby juice samples. The HPLC method is used
to verify the results. The results obtained for the same samples by the two
methods are quite comparable. [Projekat Ministarstva nauke Republike Srbije,
br. 172061]
A kinetic spectrophotometric method for measuring 2,4-dichlorphenoxyacetic acid (2,4-D) is described in this study. The proposed method is based on the inhibitory effect of 2,4-D on the oxidation of sulfanilic acid by hydrogen peroxide in the presence of Co(II) ion, which was monitored at 370 nm. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. 2,4-D can be measured in the range of 0.07 -2.35 μg mL -1 and from 2.35 to 23.50 μg mL -1 with the detection limit of 0.004 μg mL -1 . This method was used to determined traces of 2,4-D in baby fruit juices. The HPLC method was used like a comparative method to verify the results. The results obtained by the proposed method were compared with those obtained by HPLC using UV -DAD detection and they showed a good agreement.
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