What is the best dilution water to use for diluting microbiological samples?

Document ID

Document ID TE346

Published Date

Published Date 27/05/2017
Question
What is the best dilution water to use for diluting microbiological samples?
Summary
Water for diluting microbiological samples
Answer
Use water that is buffered to a neutral pH and sterilized for microbiological testing. Hach dilution water containing magnesium chloride and potassium phosphate is recommended for dilution of most nonpotable and wastewater samples. This solution is packaged in 99 mL bottles for convenience (catalog number 1430598).

-Add 11 mL of sample to a bottle and mix. This will result in a 10-fold dilution. See the Hach procedure for the test that you are using for more specific instructions.

This can also be prepared from magnesium chloride and potassium phosphate powder pillows (catalog number 2143166).
This item contains 25 magnesium chloride pillows (large) and 25 potassium phosphate pillows (small).
-Add one pillow of magnesium chloride and one pillow of potassium phosphate to one liter of distilled water and autoclave for 15 minutes.
-Use Butterfield's Buffered Phosphate Diluent ready-made (catalog number 2319109, 2319125, 2319145, or 2319110) or in powder form (catalog number 2323668) when testing food samples, or whenever the procedure specifies this water for dilution.
-Use Peptone Dilution Water (catalog number 2142964) when following a Standard Methods procedure that specifies it. Peptone contains nitrogen, which helps enrich organisms that are stressed.