Preparation of 10X TB salts

Overview:

TB salt solution is nothing but a potassium phosphate buffer. A 10x TB salt solution contains 170 mM Potassium phosphate monobasic (KH2PO4) and 720 mM Potassium phosphate dibasic (K2HPO4). It can be prepared by dissolving 23.135 g of KH2PO4 (Molecular Weight: 136.09) and 125.41 g of K2HPO4 (Molecular Weight: 174.18) in water to a final volume of 1L. The solution is sterilized by autoclaving.

In the following section, we describe a procedure to prepare 250 ml of 10X TB salts.

REQUIREMENTS

Reagents and solutions
Potassium phosphate monobasic (KH2PO4)
Potassium phosphate dibasic (K2HPO4)

Equipment and disposables
Measuring cylinder
Conical flask / Beaker

Composition
170 mM Potassium phosphate monobasic (KH2PO4) 
720 mM Potassium phosphate dibasic (K2HPO4)

Objective
Preparation of 250 ml of 10X TB salts

PROCEDURE

Step 1: To prepare 250 ml of 10x TB salts, weigh out 5.78g KH2PO4  (Molecular Weight: 136.09) and 31.35 g of K2HPO4 (Molecular Weight: 174.18) in a 250 ml conical flask/beaker. Add ≈ 200 ml deionized/Milli-Q water and mix until dissolved completely.  

Tip:
One can use manual shaking using a glass pipette to mix the ingredients. Magnetic stirrer makes the dissolving process easy and convenient.

Precaution:
Do not dissolve in 250 ml of deionized / Milli-Q water. In most cases, solution volume increases when a large amount of solute is dissolved in a solvent.

Step 2: Adjust the volume to 250 ml with deionized / Milli-Q water. Mix it again.

Step 3: Sterilize the solution by autoclaving (20 minutes at 15 lb/sq.in. (psi) from 121-124°C on liquid cycle).

Storage
The solution can be stored at room temperature.

Follow the table to prepare 10X TB salt of various volumes (100, 250 ml, 500 ml, and 1000 ml)
Solution concentration / Volume100 ml250 ml500 ml1000 ml
KH2PO42.31 g5.78 g11.6723.135 g
K2HPO412.54 g31.35 g62.7 g125.41 g

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