CATALYTIC KINETIC SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF ETHYLENEDIAMINETETRAACETIC ACID BASED ON ITS CATALYTIC EFFECT ON THE REACTION OF RHODAMINE B AND POTASSIUM DICHROMATE

摘要

A new method for the determination of trace ethylenediaminetetraacetic acid (EDTA) was developed using catalytic kinetic spectrophotometry based on the principle that in the medium of 0.10 mol/L sulfuric acid, trace EDTA has a catalytic effect on the oxidation of rhodamine B by potassium dichromate, and a suitable amount of 6.0 mol/L NaOH solution can inhibit the catalytic reaction. At the maximum absorption wavelength of 546 nm, the linear range for the determination of EDTA was shown over the concentration range 5.0 X 10~(-5)-7.0 X 10~(-4) mol/L and the detection limit of this method for EDTA was 0.0501 mmol/L. The linear regression equation for the determination of EDTA and regression coefficient were (DELTA)A velence 512C (C: mol/L) + 0.0966, gamma velence 0.9993, respectively. The apparent activation energy of the catalytic reaction was 81.57 KJ/mol. The proposed method has been successfully applied to the determination of trace ethylenediaminete-traacetic acid in water and apple tinned foodstuff samples with satisfactory results. The relative standard deviation of 13 replicate determinations of EDTA was 1.15-2.37percent and the recovery of the method was 99.90-102.7percent, respectively. The determined results were in good agreement with that of established method Fe(III)-H_(2)O_(2)-bromothymol blue system inhibitory-kinetic spectrophotometry.