Thermo Scientific AQUAfast AQ3700, User Manual

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Thermo Scientific Orion AQUAfast AQ3700 Colorimeter User Guide
1.1 Methods
Notes:
1. Vial cleaning:
As many household cleaners (e.g. dishwasher detergent) contain reducing substances,
the subsequent determination of Bromine may show lower results. To avoid any
measurement errors, only use glassware free of Chlorine demand.
Preparation: Put all applicable glassware into Sodium hypochlorite solution (0.1 g/l) for
one hour, then rinse all glassware thoroughly with deionized water.
2. Preparing the sample:
When preparing the sample, the escape of Bromine gases, e.g. by pipetting or shaking,
must be avoided. The analysis must take place immediately after taking the sample.
3. The DPD color development is carried out at a pH value of 6.2 to 6.5. The reagent
tablet therefore contains a buffer for the pH adjustment. Strong alkaline or acidic water
samples must be adjusted between pH 6 and pH 7 before the reagent is added
(use 0.5 mol/l Sulfuric acid resp. 1 mol/l Sodium hydroxide).
4. Exceeding the measuring range:
Concentrations above 22 mg/l Bromine can lead to results showing 0 mg/l.
In this event, the water sample must be diluted with water free of Bromine.
10 ml of the diluted sample should be mixed with the reagent and the measurement
repeated.
Oxidizing agents such as Chlorine, Ozone etc. interfere as they react in the same way
as Bromine.