Flow Injection–Spectrophotometric Determination of Trace Amounts of Bromide by Its Catalytic Effect on the 4,4′-Bis(dimethylamino)diphenylmethane–Chloramine T Reaction

Abstract

The determination of bromide has received increased interest in a variety of fields, but the bromide found in many natural samples occurs often at fairly low concentrations of µg l -1 level. We have reported a kineticspectrophotometric method for the determination of trace amounts of bromide based on its catalytic effect on the tetrabase-Chloramine T reaction. 1 This method is highly sensitive, but the catalyzed reaction proceeds so rapidly as to complete in 30 s at 20˚C. Hence, in order to follow the reaction, an elaborate procedure is required and a home-made device for in-cell mixing is used.Flow injection analysis is widely used as a simple and convenient approach to rapid analyses, in which the reaction time can easily be controlled by varying the flow rate of the solution and the length of reaction coil. Hence the application of a flow injection technique to the above-mentioned catalytic method based on a rather rapid reaction should offer a reproducible and rather convenient procedure for routine determinations of trace concentrations of bromide. Although some FIA methods for the determination of bromide have been reported [2][3][4][5][6][7] , these methods were not sensitive enough to determine bromide in µg l -1 level. The present paper describes an investigation regarding the adaptation of the tetrabase-Chloramine T method for the determination of bromide to a flow injection system. The effects of reaction variables, particularly pH, were examined in greater detail. It was observed that the use of acetate buffer of higher concentration, which leads the reaction solution to higher ionic strength, alleviates interferences of several ions. The resulting method is more sensitive, more reproducible and suffers less interference, yet has higher sample throughput, than the batch procedure:1 by the proposed method, as low as 1 µg l -1 of bromide can be determined with the relative standard deviation of 6.4 or 8.7%, while the detection limit of the batch procedure was 2 µg l -1 , at which the relative standard deviation was 17.1%. This method has been successfully applied to the determination of bromide in natural water samples. ExperimentalReagents Pure water was prepared by purifying distilled water with a Millipore Milli-Q SP system just before use. Reagent-grade chemicals were used throughout. A potassium bromide stock solution (0.1 M) was standardized by a Volhard titration. The working solutions were prepared by diluting this solution with water. A potassium iodide stock solution (0.1 M) was also standardized by Volhard titration. The working solutions were prepared by diluting this solution with water. An acetate buffer solution (pH 3.8) was prepared by mixing 176 ml of 2.0 M acetic acid and 19 ml of 2.0 M A flow injection analysis method is proposed for the spectrophotometric determination of trace amounts of bromide based on its catalytic effect on the oxidation of 4,4′-bis(dimethylamino)diphenylmethane (tetrabase) by Chloramine T in a weakly acidic solution. The effects of the reagent concentrations a...

Direct Electrochemical Analysis in Seawater: Evaluation of Chloride and Bromide Detection

“…(1) However, there is necessarily a lack of accuracy, as it is an estimated value depending on salinity that primarily indicates the overall ion concentration rather than the chemical composition [7,35]. For bromide quantification, there are several techniques available, e.g., kinetic spectrophotometry [38][39][40][41][42][43][44][45], chromatography [46,47], capillary electrophoresis [48][49][50][51][52] and electrochemistry [53][54][55][56], but they have drawbacks from different perspectives, which have been discussed by Chen et al [57]. In brief, kinetic spectrophotometry may not be ideal for natural samples, as the oxidising agent could react with other ions present [38,43] and dilution of the sample is required [38].…”

Automatic flow analysis procedure for the determination of bromide in L-alanine by chemiluminescence detection

“…Procedures for bromide determination in different matrices employing potentiometry, 4,5 ion exchange chromatography, 6 capillary electrophoresis, 7 spectrophotometry [8][9][10][11] have been proposed. Generally, spectrophotometric methods present adequate sensitivity, nevertheless the time consumed to perform an analysis is very long.…”

“…Additional procedures for bromide determination in water exploiting the catalytic potential afforded by bromide ion on the oxide-reduction reactions have also been proposed. 13,14 Procedures based on ionic exchange chromatography for bromide determination in water attained low limit of detection. 15 This technique has been recognized as an efficient tool for ions separation, nevertheless for complex matrix extraction step is required, thus lessening the sampling throughput.…”

Kinetic-spectrophotometric method for the determination of trace amounts of bromide in seawater

“…Some kineticspectrophotometric methods for bromide determination have been reported. They use several types of indicator reaction [11][12][13][14][15][16][17][18]; for example, the reaction systems with pyrocatechol violet in the presence of H 2 O 2 [12] and 4,4'-bis-(dimethylamino)-diphenylmethane (Tetrabase) in the presence of chloramine T [16] were applied to the determination of bromide. However, these methods are severely interfered from iodide, and some of the kinetic methods must be carried out at elevated temperatures for improving sensitivity [18].…”