Quantification of Bromide by APHA 4500 Method
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This document describes a quantitative analysis of bromide (Br-) in water samples using the phenol red colorimetric method. When bromide ions are treated with chloramine-T in the presence of phenol red indicator and buffered to pH 4.5-4.7, the resulting brominated compound produces a color ranging from reddish to violet depending on the bromide concentration. Seven bromide standards were prepared and their absorbances at 590 nm were measured. A calibration curve was generated showing good linearity with an R2 value of 0.9992. The LAMBDA 465 UV/Vis spectrophotometer and UV Lab software allowed for rapid analysis and processing of the bromide concentration data.
Quantification of Bromide by APHA 4500 Method
- 1. A P P L I C A T I O N N O T E Introduction In this application note, the quantitative analysis of bromide (Br – ) was performed by the phenol red colorimetric method. Data are rapidly acquired using the LAMBDA™ 465 UV/Vis Spectrophotometer and processed using the UV Lab® Software. Principle When a sample containing bromide ions (Br – ) is treated with a dilute solution of chloramine-T in the presence of phenol red, the oxidation of bromide and subsequent bromination of the phenol red occur readily. If the reaction is buffered to pH 4.5 to 4.7, the color of the brominated compound will range from reddish to violet, depending on the bromide concentration. This compound is measured at 590 nm. Quantification of Bromide by APHA 4500 Method: Phenol Red Colorimetric Method UV/Visible Spectroscopy
- 2. 2 Reagents and Apparatus 1. Stock bromide solution - Dissolve 744.6 mg anhydrous KBr in D.I water and make up to 1000 mL; 1.00 mL = 500 μg Br – 2. Standard bromide solution - Dilute 10.00 mL stock bromide solution to 1000 mL with D.I water ; 1.00 mL = 5.00 μg Br – . 3. Acetate buffer solution - Dissolve 90 g NaCl and 68 g sodium acetate tri-hydrate, NaC2H3O2∙3H2O, in D.I water. And 30 mL conc. (glacial) acetic acid and make up to 1 L. The pH should be 4.6 to 4.7. 4. Phenol red indicator solution - Dissolve 21 mg phenolsulfonephthalein sodium salt and dilute to 100 mL with D.I water. 5. Chloramine-T solution - Dissolve 500 mg chloramine-T, sodium p-toluenesulfonchloramide, and dilute to 100 mL with D.I water. Store in a dark bottle and refrigerate. 6. Sodium thiosulfate, 2 M - Dissolve 31.6 g Na2S2O3 or 49.6 g Na2S2O33∙ 5H2O and dilute to 100 mL with D.I water. 7. LAMBDA 465 (PDA UV/Vis Spectrophotometer) 8. UV Lab Software 9. Cuvette (10 mm pathlength) Procedure 1. Prepare seven standards, 0, 0.05, 0.1. 0.2, 0.4, 0.6 and 0.8 mg Br – /L, by diluting 0.0, 0.5, 1.0. 2.0, 4.0, 6.0 and 8.0 mL standard bromide solution to 50.00 mL with D.I water. Treat standards using the following procedure. 2. Add 2 mL buffer solution, 2 mL phenol red solution, and 0.5 mL chloramine-T solution to 50 mL standards. Mix thoroughly, immediately after each addition. 3. Exactly 20 min after adding chloramine-T, de-chlorinate by adding, with mixing, 0.5 mL sodium thiosulfate solution. 4. In Quantification Standard mode, measure the absorbance of the standards with reference to standard 1 (0 μg/L) at 590 nm. Instrument Parameters The instrument parameters of the LAMBDA 465 are as follows: Figure 1 shows experimental setup. Experiment Setup Data type: Absorbance Sampling: Single cell Mode: (Scan no.: 30/ Integration no.:1) Experiment Method Use wavelength: 590 nm Curve dimension: 1 Figure2.Thespectra ofBr– standards by phenolredcolorimetricmethod. Name Conc. (μg/L) AU (590 nm) Standard 1 0 0.0002 Standard 2 50 0.0181 Standard 1 100 0.0266 Standard 1 200 0.0506 Standard 1 400 0.1044 Standard 1 600 0.1506 Standard 1 800 0.2026 R2 = 0.9992 Function :Y = 0.0002X + 0.0022 Table 1. Calibrationdata ofBr– standards. Figure1.Experimentalsetupfor Bromideanalysis. Result 1. Calibration curve Figure 2 shows spectra of Br – standards. Table 1 and Figure 3 show data and calibration curve of seven standards. Correlation coefficient R2 is 0.9992. μg/L
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