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Analytical Method: Bromate in water and drinking water - low range - Hint

Photometric determination with 3,3'-dimethylnaphtidine and iodide


Information for the application of Bromate using our Spectroquant® Prove Spectrophotometers.


Dear user,


We offer for customers which are interested in measuring Bromate an application which allows analyzing Bromate in the following measuring ranges:
2.5 – 0.100 µg/l BrO3- by using a 100-mm rectangular cell.
5.0 – 0.200 µg/l BrO3- by using a  50-mm rectangular cell.
For more details please see below. For the analysis the following reagents and accessories are required:


Cat. No. 103122           3,3‘-Dimethylnaphthidine
Cat. No. 100063           Acetic acid 100% for analysis
Cat. No. 100983           Ethanol abs. for analysis
Cat. No. 105043           Potassium iodide for analysis
Cat. No. 100519           Perchloric acid 70 - 72 % for analysis
Cat. No. 116754           Water for analysis


Cat. No. 174011           Rectangular cell 100-mm or
Cat. No. 114944           Rectangular cells 50-mm
Cat. No. SLAP02550    Syringe filter glass fiber
Cat. No. SLLGM25NS  Syringe filter 0.20 µm
Cat. No. 114901           Flat-bottomed long tubes with screw caps, for measurements in 100-mm cell; or
Cat. No. 114724           Empty cells with screw caps 16-mm, for measurements in 50-mm cell


Cat. No. 173018           Spectroquant® Prove 600 Spectrophotometer or
Cat. No. 173017           Spectroquant® Prove 300 Spectrophotometer or
Cat. No. 173016           Spectroquant® Prove 100 Spectrophotometer



Measuring ranges and confidence interval (P = 95%):
The measurement in the 100-mm cell is only possible at the Prove 600!
100-mm rectangular cell: 2.5 – 100.0 µg/l BrO3- (Confidence interval ± 3.0 µg/l)
50-mm rectangular cell: 5.0 – 200.0 µg/l BrO3- (Confidence interval ± 5.0 µg/l)


In the application it is described how the reagents have to be prepared and what sample preparation must be done before analyzing. The detection itself is very easy too. Users, which are interested to get the detail application, should send an E-mail with your detailed address incl. phone and E-mail and the serial no. of the photometer to the following E-mail You will receive the application at your earliest convenience.


Please understand that we supply this application only to our customers' on request having our instruments or buying an instrument from us.




The vessels used must be clean and free from surfactant residues or similar substances. Pre-treat with a mixture of isopropyl alcohol and hydrochloric acid, if necessary. Subsequently, rinse thoroughly with distilled water. Prepare the isopropyl alcohol/hydrochloric acid mixture by placing 3 parts isopropyl alcohol in a glass beaker and slowly adding 1 part of hydrochloric acid 25%. Follow the respective safety regulations!

Due to the low bromate concentration, which is accepted as the limit for drinking water (according to WHO and EU Direktive 10 µg/l), we recommend with each new batch of 3,3‘-dimethylnaphthidine to check the recovery rate by means of a bromate standard in the area of the application concentration and to recalibrate the method, if necessary. An instruction for the recalibration can be obtained separately.

1. Preparing the reagents


Preparation of an acetic acid / ethanol mixture
Reagent 1
Reagent 2



Reagent 2 has to be prepared freshly on each workday and must be prepared and stored protected from light in closed containers. A storing in the refrigerator does not improve the shelf-life.



2. Analysis


The sample solution must be clear. If necessary, filter through a fluted filter and subsequently through a

0.20 µm syringe filter (Cat. No. SLLGM25NS).

Select method 308 (Bromate Low Range) from the concentration mode of the photometer. Analyze the sample against a reagent blank value.


Preparation using the 100-mm rectangular cell:
Reagent blank and measuring sample can be prepared at the same time.
Flat-bottomed long tubes with screw caps or glass beakers are suitable as mixing vessels. To 20 ml of water for analysis (reagent blank) or 20 ml of sample add 0.2 ml reagent 1 and mix, then add 0.4 ml reagent 2 and mix, subsequently add 0.4 ml perchloric acid 70 - 72 % for analysis and mix. Leave to stand for 30 minutes at room temperature. Filter all test samples through a 0.20 µm syringe filter, Cat. No. SLLGM25NS, prior to measurement.
The measurement is conducted in a 100-mm rectangular cell. Measure the preparation with water as reagent blank.


Preparation using the 50-mm rectangular cell:
Reagent blank and measuring sample can be prepared at the same time.
16-mm cells with screw caps or glass beakers are suitable as mixing vessels.
To 10 ml of water for analysis (reagent blank) or 10 ml of sample add 0.1 ml reagent 1 and mix, then add 0.2 ml reagent 2 and mix, subsequently add 0.2 ml perchloric acid 70 - 72 % for analysis and mix. Leave to stand for 30 minutes at room temperature. Filter all test samples through a 0.20 µm syringe filter, Cat. No. SLLGM25NS, prior to measurement.
The measurement is conducted in a 50-mm rectangular cell. Measure the preparation with water as reagent blank.


3. Interfering substances:

Up to the concentration of foreign substances indicated in the table, the determination is not disturbed yet:








Parameter Tolerance without interference [mg/l]
Ca2+ 4500
Mg 2+ 3000
NO2- 0.2
Na+ 3500
SO42- 150
ClO3- 10000
IO3- 10
Cl- 10000
Cl2 1
OCl- 1
Fe3+ 1
Mn2+ 1000









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