ORBECO SP600, Instruction Manual, Page: 199 / 334

197
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 Ozone 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 Ozone 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 tablet is added (use 0.5 mol/l Sulfuric acid resp. 1 mol/l Sodium hydroxide).
4. Turbidity (lead to errors):
The use of the DPD No. 1 tablet in samples with high Calcium ion contents* and/or high
conductivity* can lead to turbidity of the sample and therefore incorrect measurements.
* it is not possible to give exactly values, because the development of
turbidity depends on nature and ingredients of the sample.
5. Exceeding of the measuring range:
Concentrations above 5 mg/l Ozone 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 Ozone.
10 ml of the diluted sample will be mixed with the reagent and the measurement
repeated.
6. If ??? is displayed at the diffentiated test result see page 325.
Oxidizing agents such as Bromine, Chlorine etc. interfere as they react like Ozone.