Phenol Red (Sulfonphthal) is a pH indicator, red dye, and diagnostic aid for measurement of renal function. It is used also for researches of the gastrointestinal and other systems.

Instructions for use
I. Solution preparation
1. Preparation of mother solution: Dissolve Phenol in an appropriate solvent. Phenol is soluble in alkaline solutions, such as sodium hydroxide or sodium carbonate solutions. The commonly used concentration is 5 mg/mL or 20 mg/mL.
2. Preparation of working solution: The commonly used final concentration of Phenol is 15–20 mg/L.
Note: Please filter and sterilize: Filter with a 0.22 µm filter membrane to ensure that the solution is sterile. Dispense the solution into a light-proof container and store at 4°C or -80°C.
II. Operation steps
Indication function: Phenol changes color in the pH range of 6.8–8.2, which can indicate the pH state of the culture medium.
1. Application in pH determination
Measurement range: Phenol is suitable for determination of pH 6.5–8.4.
1). Sample preparation: Take 10 mL of the test solution in a colorimetric cup.
2) Add indicator: Add appropriate amount of phenol red solution (e.g. 6 drops) and mix well.
3) Colorimetric determination: Use a colorimeter to measure the absorbance at an appropriate wavelength, or compare with a standard colorimetric card to determine the pH value.