DETERMINATION OF BROMINE BY THE FLUORESCEIN METHOD (PHOTOMETRIC)
Scope
This test method covers the determination of 1 µg Br (0.2 µg Br/g U) when it exists as bromide or bromate, in uranyl nitrate solutions.
Summary of Test Method
Bromine is determined spectrophotometrically by the bromination of fluorescein to form eosin after the oxidation of bromide. Bromates are reduced with sodium nitrite, followed by oxidation of bromides with permanganate. The oxidation is apparently the limiting step in all procedures involving bromide. In order to avoid loss of bromine during the oxidation, the bromine produced is extracted by carbon tetrachloride concurrently with its production in the nitrous acid solution of permanganate. Prior chilling of the sample solution is necessary. Fluorescein is added to the bromine-carbon tetrachloride solution, and the absorbance of the resulting eosin is measured at 510 nm.
Interferences
Large quantities of chloride and iodide of uranium do not interfere in the basic procedure.
Equipments
· Spectrophotometer
· Centrifuge, clinical
Reagents
· Bromide Standard Solution A (1 mL = 10 µg Br). Dilute a 10 mL aliquot of the bromide stock solution B to 1 L in a volumetric flask.
· Bromide stock Solution B. Dissolve 0.3723 g of potassium bromide (KBr) in water, dilute to 250 mL in volumetric flask, and mix well. Prepare fresh daily.
· Carbon tetrachloride (CCl4), boiling range 0.4 oC or less.
· Fluorescein Solution, Buffered (35 g/L). Dissolve 35 g of sodium dihydrogen phosphate (NaH2PO4) in 500 mL of water. Using a pH meter, adjust the pH to 6.0 with saturated disodium phosphate solution (Na2HPO4). Then add 40 mL of stock fluorescein solution, dilute the mixture to 1 L, and store in a brown bottle.
· Fluorescein Stock Solution (0,1 g/L). Dissolve 0.1 g of disodium fluorescein in water and dilute to 1 L.
· Potassium Permanganate Solution (5 g/L). Dissolve 0.5 g KmnO4 in water, dilute to 100 mL and store in a brown bottle. Prapare a fresh solution every 2 to 3 weeks.
· Sodium Nitrate Solution (2 g/L). Dissolve 0.5 g of NaNO2 in water and dilute to 250 mL.
Calibration
· Transfer quantities of 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 1.0 mL of standard bromide solution A, representing 0.0, 1, 2, 3, 4, 5, and 10 µg of bromine, to a series of 100 mL beaker.
· Transfer an aliquot of bromine free uranyl nitrate, containing about 5 g of uranium. To each beaker.
· Process each standard, one at a time , through the procedure outlined in step 1 through step 14.
· Subtract the absorbence of the blank (0.0 mL of bromine added) from the absorbance of each of the standards. Plot the resulting absorbance versus micrograms of bromine on coordinate paper.
Procedure
· Weigh a portion of sample solution containing about 5 g of uranium into a 100 mL beaker and dilute to 50 mL.
· Cool the solution to 15 oC in an ice bath.
· Transfer the cooled solution to a 125 mL separatory funnel.
· Add 1 mL of NaNO2 solution and swirl the solution to mix.
· Add 10 mL of CCl4 and 1 mL of KMnO4 solution, then shake the funnel for 5 to 10 s.
· Combine the organic layers in the smaller funnel and discard the aqueous layer.
· Add 10 mL of water to the smaller funnel and shake for 5 s
· Transfer the organic layer to another 60 mL separatory funnel and discard the aqueous layer.
· Add 5 ml of buffered fluorescein solution to the organic solution and shake for 1.5 min.
· Discard the organic layer and transfer the aqueous layer to a centrifuge tube.
· Centrifuge until a clear solution is obtained.
· Measure at 510 nm in 2 cm cells using a buffered fluorescein solution which has benn extracted for 1.5 min with 10 mL of CCl4 as a reference.
· Determine a reagent blank by carrying 30 mL of water through the procedure step 2 to step 14.
· Prepare the calibration curve by carrying 0.1 µg of bromine through the procedure step 2 to step 14 in the presence of 5 g of uranium.
Calculation
Calculate the bromide content as follows
Bromide = (A-B) / C = µg/g
Where
A = bromide found in the sample solution, µg
B = bromide found in the reagent blank, µg
C = uranium contained in the sample solution, g
w
Precision
The limit of error at the 95% confidence level for a single determination is ± 50%.
Literature
Literature
ASTM-C799, Standard Methods for “Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical analysis of Nuclear-Grade Uranyl Nitrate solution”
Scope
This test method covers the determination of 1 µg Br (0.2 µg Br/g U) when it exists as bromide or bromate, in uranyl nitrate solutions.
Summary of Test Method
Bromine is determined spectrophotometrically by the bromination of fluorescein to form eosin after the oxidation of bromide. Bromates are reduced with sodium nitrite, followed by oxidation of bromides with permanganate. The oxidation is apparently the limiting step in all procedures involving bromide. In order to avoid loss of bromine during the oxidation, the bromine produced is extracted by carbon tetrachloride concurrently with its production in the nitrous acid solution of permanganate. Prior chilling of the sample solution is necessary. Fluorescein is added to the bromine-carbon tetrachloride solution, and the absorbance of the resulting eosin is measured at 510 nm.
Interferences
Large quantities of chloride and iodide of uranium do not interfere in the basic procedure.
Equipments
· Spectrophotometer
· Centrifuge, clinical
Reagents
· Bromide Standard Solution A (1 mL = 10 µg Br). Dilute a 10 mL aliquot of the bromide stock solution B to 1 L in a volumetric flask.
· Bromide stock Solution B. Dissolve 0.3723 g of potassium bromide (KBr) in water, dilute to 250 mL in volumetric flask, and mix well. Prepare fresh daily.
· Carbon tetrachloride (CCl4), boiling range 0.4 oC or less.
· Fluorescein Solution, Buffered (35 g/L). Dissolve 35 g of sodium dihydrogen phosphate (NaH2PO4) in 500 mL of water. Using a pH meter, adjust the pH to 6.0 with saturated disodium phosphate solution (Na2HPO4). Then add 40 mL of stock fluorescein solution, dilute the mixture to 1 L, and store in a brown bottle.
· Fluorescein Stock Solution (0,1 g/L). Dissolve 0.1 g of disodium fluorescein in water and dilute to 1 L.
· Potassium Permanganate Solution (5 g/L). Dissolve 0.5 g KmnO4 in water, dilute to 100 mL and store in a brown bottle. Prapare a fresh solution every 2 to 3 weeks.
· Sodium Nitrate Solution (2 g/L). Dissolve 0.5 g of NaNO2 in water and dilute to 250 mL.
Calibration
· Transfer quantities of 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 1.0 mL of standard bromide solution A, representing 0.0, 1, 2, 3, 4, 5, and 10 µg of bromine, to a series of 100 mL beaker.
· Transfer an aliquot of bromine free uranyl nitrate, containing about 5 g of uranium. To each beaker.
· Process each standard, one at a time , through the procedure outlined in step 1 through step 14.
· Subtract the absorbence of the blank (0.0 mL of bromine added) from the absorbance of each of the standards. Plot the resulting absorbance versus micrograms of bromine on coordinate paper.
Procedure
· Weigh a portion of sample solution containing about 5 g of uranium into a 100 mL beaker and dilute to 50 mL.
· Cool the solution to 15 oC in an ice bath.
· Transfer the cooled solution to a 125 mL separatory funnel.
· Add 1 mL of NaNO2 solution and swirl the solution to mix.
· Add 10 mL of CCl4 and 1 mL of KMnO4 solution, then shake the funnel for 5 to 10 s.
· Combine the organic layers in the smaller funnel and discard the aqueous layer.
· Add 10 mL of water to the smaller funnel and shake for 5 s
· Transfer the organic layer to another 60 mL separatory funnel and discard the aqueous layer.
· Add 5 ml of buffered fluorescein solution to the organic solution and shake for 1.5 min.
· Discard the organic layer and transfer the aqueous layer to a centrifuge tube.
· Centrifuge until a clear solution is obtained.
· Measure at 510 nm in 2 cm cells using a buffered fluorescein solution which has benn extracted for 1.5 min with 10 mL of CCl4 as a reference.
· Determine a reagent blank by carrying 30 mL of water through the procedure step 2 to step 14.
· Prepare the calibration curve by carrying 0.1 µg of bromine through the procedure step 2 to step 14 in the presence of 5 g of uranium.
Calculation
Calculate the bromide content as follows
Bromide = (A-B) / C = µg/g
Where
A = bromide found in the sample solution, µg
B = bromide found in the reagent blank, µg
C = uranium contained in the sample solution, g
w
Precision
The limit of error at the 95% confidence level for a single determination is ± 50%.
Literature
Literature
ASTM-C799, Standard Methods for “Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical analysis of Nuclear-Grade Uranyl Nitrate solution”
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