ORBECO SP600, Instruction Manual, Page: 45 / 334

43
SP600 Spectrophotometer 01/2008
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 consumption.
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 colour development is carried out at a pH value of 6.3 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 of the measuring range:
Concentrations above 22 mg/l Bromine can produce results within the measuring
range up to 0 mg/l. In this event, the water sample must be diluted with water free
of Bromine. 10 ml of the diluted sample will be mixed with the reagent and the
measurement repeated.
Oxidizing agents such as Chlorine, Ozone etc. interfere as they react like Bromine.