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Preparation of Calibration Standard Solutions:
Standards solutions greater than 1000mg/l can be prepared directly without any dilution by simply mixing the
necessary quantity solvent or salt with deionized water. Standard solutions below 1000mg/l concentration
should be prepared by dilution technique. First a 1000mg/l standard stock solution should be prepared, and
then the required lower concentration standard solution should be prepared by applying the necessary dilution
procedures:
➢ For example, to prepare a 50mgC/l TOC only standard solution, first weigh 50 grams of the
1000mgC/l stock standard. Add 50 grams of the 1000mgC/l standard into a one-liter flask and add
enough deionized water to make the solution exactly 1 liter.
➢ For increased accuracy, standard solutions below 5mg/l (ppm) concentration should be prepared with
two or more steps dilution. For example, to prepare a 1mgC/l standard, first prepare a 100mgC/l
standard by adding 100 grams of the 1000mgC/l standard into a one-liter flask and by adding enough
deionized water to make it exactly a 1 liter solution. Then add 10 grams of the 100mgC/l standard into
a one-liter flask and add enough deionized water to make it exactly 1 liter.
➢ Standard solutions at μg/l (ppb) levels should be prepared with several dilution steps. For instance, a
1mgC/l (1000 μg/l) standard should be prepared with two or more steps dilution as described above.
To prepare a 50μg/l standard, add 50 grams of the 1000μg/l standard into a one-liter flask, and add
enough deionized water to make it exactly 1 liter.
Shelf Life and Storage of Calibration Standard Solutions:
❖
TOC standards prepared from Potassium Hydrogen Phthalate is typically stable for a month once it
is kept in a closed glass container and refrigerated at 4°C.
❖
All other standards such as TOC prepared with Acetic Acid and TIC standards are recommended to
be used within 48 hours of manufacture.
Use eye protection and gloves.
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