Technical Data
Media
Phosphate Buffer, APHA, pH 7.2 (Butterfield's Buffered Phosphate Diluent) (Powder)
P4071-50
Microbiological Grade
Storage RT/4C    Shipping RT
Formula g/Liter:
Potassium Dihydrogen Phosphate26.22
Sodium Carbonate7.78
Supplement
Magnesium Chloride5ml*
*81.1g MgCl26H2O per liter of dH2O
Intended Use:
Phosphate Buffer, pH 7.2 is used for the preparation of microbiological dilution blanks.

Product Summary:
The formula for phosphate buffer is specified by the American Public Health Association (APHA) for use in diluting test samples. Phosphate Buffer, pH 7.2 is specified for use in diluting water, dairy products and food for microbiological methods. In the examination of water and dairy products the addition of magnesium chloride is recommended.

This buffer is also referred to as Butterfield's Buffered Phosphate Diluent and recommended for examination of food (2). Phosphate Buffer, pH 7.2 stabilizes the pH of water used for dilutions.

Principles of the Procedure:
Phosphate Buffer, pH 7.2 is used in the preparation of dilution blanks for use in microbiological testing. Phosphate Buffer is used rather than unbuffered water in order to standardize this potential variable due to the wide variation in the pH of distilled water from multiple sources.

Appearance:
White to off-white, homogenous, free-flowing powder

Solubility: Colorless, clear to slightly hazy, with or without trace precipitate

pH: 7.2 0.2

Formulation:
Formula g/Liter:

Potassium Dihydrogen Phosphate 26.22
Sodium Carbonate 7.78

Supplement
Magnesium Chloride 5ml*

*81.1g MgCl26H2O per liter of ddH2O

Directions per Liter:
Stock Solution
1. Dissolve 34g of the medium in one liter of purified water until evenly dissolved.
2. Autoclave at 121C for 15 minutes, if desired. Store under refrigeration.
3. Final pH is taken after Phosphate Buffer, pH 7.2 has been autoclaved and cooled to RT.

Working Solution:
1. Add 1.25ml of Stock Solution and 5ml of a magnesium chloride solution to purified water and make up to one liter.
2. Dispense into bottles or tubes to provide 99 2.0ml, 9 0.2ml or other appropriate quantities.
3. Autoclave at 121C for 15 minutes.
4. Final pH is taken after Phosphate Buffer, pH 7.2 has been autoclaved and cooled to RT.

Storage and Stability:
Store powdered media at RT. Opened bottles should be capped tightly and kept in a dark, low humidity environment. Prepared media should be kept at 4C and used within a short period of time..


Directions: Stock Solution: 1. Dissolve 34g of the medium in 1 liter of dH2O until evenly dissolved. 2. Autoclave at 121C for 15 minutes, if desired. Store under refrigeration. 3. Final pH is taken after Phosphate Buffer, pH 7.2 has been autoclaved and cooled to RT.Working Solution: 1. Add 1.25ml of Stock Solution and 5ml of a magnesium chloride solution (81.1g MgCl26H2O per liter of purified water) to purified water and make up to one liter. 2. Dispense into bottles or tubes to provide 99 2.0ml, 9 0.2ml or other appropriate quantities. 3. Autoclave at 121C for 15 minutes. 4. Final pH is taken after Phosphate Buffer, pH 7.2 has been autoclaved and cooled to RT.


Important Note: This product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications without the expressed written authorization of United States Biological.