Catalytic-kinetic spectrophotometric determination of vanadium (V) based on the Celestine blue-bromate-vanadium (V)-citric acid reaction

Abstract

A novel sensitive and relatively selective kinetic method is presented for the determination of V(V) based on its catalytic effect on the oxidation reaction of Celestine blue by potassium bromate in the presence of citric acid as an activator. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of Celestine blue at a maximum absorption wavelength of 540 nm between 0.5 and 9 min (the fixed-time method) in an H 3 PO 4 medium at 45°C. The effect of various parameters such as concentrations of H 3 PO 4 , citric acid, potassium bromate and Celestine blue, ionic strength, reaction temperature and time on the rate of V(V) catalyzed reaction was studied. The method is free from the most interferences, especially from large amounts of V(IV). The decrease in absorbance is proportional to the concentration of V(V) over the entire concentration range tested (0.025-1.25 µg⋅mL −1 ) with a detection limit of 6.80 µg⋅L −1 (according to statistical 3S blank /k criterion) and a coefficient of variation (CV) of 1.78% (for ten replicate measurements at 95% confidence level). The proposed method suffers from a few interferences such as Cr(VI) and Hg(II) ions. The method was successfully applied to the determination of V(V) in river water, lake water, tap water, natural drinking water samples and a certified standard reference material such as SRM-1640 with satisfactory results. The vanadium contents of natural water samples were detected by using both linear calibration curve and standard addition curve methods. The recoveries of spiked vanadium (V) into the certified standard water sample were found to be quantitative, and the reproducibility was satisfactory. It was observed that the results of the SRM 1640 were in good agreement with the certified value.

Determination of Trace Levels of Nitrite in Beverages Samples Through Micellar Improved Catalytic Kinetic Spectrophotometry

“…These methods have advantages such as high sensitivity, extremely low detection limit, good selectivity, fast analysis rate and cheap instruments [14] The use of an activator in catalyzed reactions is usually designed to increase sensitivity and thus reduce the detection limit for the catalyst and increase the selectivity and sensitivity of the determination. Another way for this is the use of organic microheterogen system surface active agents [15]. Surfactant molecules and their aggregates above or around the critical micelle concentration (CMC) over the last two decades are increasingly being used by analytical techniques to change the time of analysis, including reactivity of analytes, as well as their sample rate and properties [16][17][18].…”

Kinetic Spectrophotometric Method for Determination of Vanadium in Syrian Oil Using 1,5-Diphenylcarbazide Reagent

“…Kinetic methods have certain advantages as selectivity and elimination of additive interferences, which affect direct spectrophotometric methods [12][13][14][15]. The literature is still poor in analytical assay methods based on kinetics for the determination of V(V) in oil forms, therefore, there is a need for another kinetic approach to estimate V(V) in oil forms.…”

“…Three different methods have been reported for determination of osmium in a weakly acid solution by using DPCI to form complex with ratio 1:1 (Os: DPCI) [2].A new, quite, rapid, simple and selective voltammetric method has been described to determine Cr(VI), by using DPCI at pH between 1 and 2 to form-modified carbon paste electrode.[3], and flow injection analysis [4]. Many spectrophotometric studies to assay vanadium in various media were carried out [5][6][7][8][9][10][11].Kinetic methods have certain advantages as selectivity and elimination of additive interferences, which affect direct spectrophotometric methods [12][13][14][15]. The literature is still poor in analytical assay methods based on kinetics for the determination of V(V) in oil forms, therefore, there is a need for another kinetic approach to estimate V(V) in oil forms.…”