EGTA tetrasodium salt *10 mM aqueous solution*

Important

Expiration date is 12 months from the date of receipt.

Sample Protocol for Calcium Measurement:

Titrate the concentration of free Ca²⁺ in solution by mixing different amounts of K₂EGTA and CaEGTA. The reactions of these solutions with Fluo-3, Fluo 4, Fluo-8, Cal-520, or Calbryte 520 dye should be at room temperature, pH 7.2 and 100 mM KCl. Under these conditions, the K_d for EGTA is 150 nM. Measure the Fluo-3, Fluo 4, Fluo-8, Cal-520, or Calbryte 520 fluorescence intensity with a fluorescence microplate reader at Ex/Em = 490/525 nm.

1. Mix the relative volumes of K₂EGTA (Cat.# 21008) and CaEGTA according to the following table.

2. Calculate the concentration of free Ca²⁺ in each solution using the following formula:

[Ca²⁺]_free = K_d^EGTA x {[CaEGTA]/[K₂EGTA]} (Note: the K_d of EGTA is 150 nM).

3. Add 1 uL of 1 mM Fluo-3, Fluo 4, Fluo-8, Cal-520, or Calbryte 520 into each solution including the blank.

4. Read the fluorescence intensity of each solution with a fluorescent microplate reader at Ex/Em = 490/525 nm.