Endress+Hauser TOCII CA72TOC, Руководство по эксплуатации

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Installation TOCII CA72TOC
18 Hauser
Preparing the parent solution from citric acid
"
Caution!
• Nitric acid is highly caustic.
• Citric acid can irritate the skin and eyes and cause respiratory problems. Never attempt to swallow
any of the solution prepared.
• Wear protective goggles, gloves and protective clothing.
• Always add acids to water, not vice versa.
Shelf life : Storable parent solutions with concentrations of 100,000 mg/l are stable for 6 months
if stored in a cool, dark place at 4 to 8 °C (40 to 46 °F). Prepared standard solutions must be used
within four weeks even if stored in a cool, dark place.
Concentrations: Depends on the application.
Material :
• 1-liter volumetric flask
• Citric acid monohydrate C
6
H8O
7
& H
2
O (purity: p.a.)
• Nitric acid HNO
3
(65 %, purity: p.a.)
Procedure :
For an organic carbon solution with a concentration of 100,000 mg/l, dissolve 291.6 g of citric acid
monohydrate in 500 ml of deionized water in a 1-liter volumetric flask (other concentrations of the
solution are listed in the table below). Carefully add 55.0 ml (77.0 g) of nitric acid. Once the
chemicals have dissolved, top up the mixture with water until the 1-liter mark is reached. Stir the
solution once more. Label the container, indicating the contents and the date of preparation.
The solution with a concentration of 100,000 mg/l is stable (particularly when refrigerated). It is
recommended to perform
serial dilutions on the basis of a standard substance of 100,000 mg/l to
reduce the concentrations if needed. Example:
• If 10 ml of a solution with a concentration of 100,000 mg/l is diluted with 90 ml deionized water,
this results in a concentration of 10,000 mg/l.
• If 10 ml of a solution with a concentration of 10,000 mg/l is diluted with 90 ml deionized water,
this results in a concentration of 1,000 mg/l.
• If 10 ml of a solution with a concentration of 1,000 mg/l is diluted with 90 ml deionized water,
this results in a concentration of 100 mg/l.
Serial dilution is the preferred method to create lower concentrations instead of diluting 1 ml of the
100,000 mg/l solution with 99 ml deionized water. The latter method can result in measurement
errors.
mg/l carbon Citric acid in g Nitric acid in ml Volume
100,000 291.6 55.0 1 l
50,000 145.8 55.0 1 l
10,000 29.16 55.0 1 l