Chapter 5
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Orion AQUAfast Reagent Chemistry Instructions for Orion AquaMate
Thermo Scientific
Orion AquaMate Spectrophotometer User Manual
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97
9.
Transfer the contents of the vial with glycine solution into the vial containing the DPD No. 1
and DPD No. 3 tablets.
10.
Close the vial tightly with the cap and swirl or invert several times until the tablets are
dissolved. Wipe the exterior of the vial.
11.
Place the vial into the holder in the sample chamber. Close the sample chamber door.
12.
Wait for a reaction period of 2 minutes.
13.
Press the Measure Sample function key to display the result in mg/L ozone.
Notes:
•
Vial cleaning: As many household cleaners (i.e. 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 demand.
Preparation: Put all applicable glassware into a sodium hypochlorite solution (0.1 g/l) for
one hour and then rinse all glassware thoroughly with deionized water.
•
Preparing the sample: When preparing the sample, the lost of ozone, 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 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 or 1 mol/l sodium hydroxide).
•
Exceeding the measuring range: Concentrations above 6 mg/l ozone can lead to results
showing 0 mg/l. In this case, the water sample must be diluted with water free of ozone. 10
ml of the diluted sample should be mixed with the reagent and the measurement repeated.
•
Oxidizing agents such as bromine and chlorine interfere as they react in the same way as
ozone.