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You are here:Home » Culture Media » Media-Microbiological » Phosphate Buffer, APHA, pH 7.2 (Butterfield's Buffered Phosphate Diluent) (Powder)

Phosphate Buffer, APHA, pH 7.2 (Butterfield's Buffered Phosphate Diluent) (Powder)


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Catalog #P4071-50
Intended UsePhosphate Buffer, pH 7.2 is used for the preparation of microbiological dilution blanks.
Product SummaryThe 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 ProcedurePhosphate 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.
AppearanceWhite to off-white, homogenous, free-flowing powder
Solubility Colorless, clear to slightly hazy, with or without trace precipitate
pH 7.2 ± 0.2
FormulationFormula g/Liter:
Potassium Dihydrogen Phosphate 26.22 Sodium Carbonate 7.78
Supplement Magnesium Chloride 5ml*
*81.1g MgCl26H2O per liter of ddH2O
Directions per LiterStock Solution
1. Dissolve 34g of the medium in one liter of purified water until evenly dissolved.
2. Autoclave at 121°C 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 Solution1. 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 121°C for 15 minutes.
4. Final pH is taken after Phosphate Buffer, pH 7.2 has been autoclaved and cooled to RT.
Storage and StabilityStore powdered media at RT. Opened bottles should be capped tightly and kept in a dark, low humidity environment. Prepared media should be kept at 4°C and used within a short period of time..
Important NoteThis 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.

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