Thermo Scientific Orion AquaMate UV-Vis, Руководство пользователя

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Chapter 5
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Orion AQUAfast Reagent Chemistry Instructions for Orion AquaMate
Thermo Scientific Orion AquaMate Spectrophotometer User Manual | 61
Preparation: Put all applicable glassware into sodium hypochlorite solution (0.1 g/l) for one
hour and then rinse all glassware thoroughly with deionized water.
• For individual testing of free and total chlorine, the use of different sets of glassware is
recommended (EN ISO 7393-2, 5.3).
• Preparing the sample: When preparing the sample, the escape of chlorine gases, i.e. by
pipetting or shaking, must be avoided. The analysis must take place immediately after
taking the sample.
•
The DPD color development is carried out at a pH value of 6.2 to 6.5. The reagents
therefore contain 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 or 1 mol/l sodium hydroxide).
•
Exceeding the measuring range: Concentrations above 10 mg/l chlorine using tablets can
lead to results showing 0 mg/l. In this event, the water sample must be diluted with water
free of chlorine. 10 ml of the diluted sample should be mixed with the reagent and the
measurement repeated.
•
Turbidity can 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.
• Oxidizing agents such as bromine or ozone interfere as they react in the same way as
chlorine.