. The pH of the freshly collected blood in CPD solution bag is –
**Core Concept**
The pH of blood in a CPD (Citrate, Phosphate, Dextrose) solution bag is a critical parameter in blood banking. CPD solution is used as an anticoagulant to prevent blood clotting and preserve blood components for transfusion. Maintaining the optimal pH range is essential for the stability and function of blood cells and enzymes.
**Why the Correct Answer is Right**
The CPD solution is formulated to maintain a pH range between 6.8 and 7.4. This narrow pH range is achieved by the presence of citrate, which acts as a buffer to stabilize the pH. The citrate ions bind to calcium ions, forming a calcium-citrate complex, which in turn prevents the activation of blood coagulation factors. The phosphate ions in the CPD solution also help to maintain the pH by forming a buffer system. The dextrose in the CPD solution provides energy to the red blood cells and prevents their lysis.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not provide any information about the pH range of the CPD solution.
* **Option B:** This option is incorrect because it suggests a pH range that is too acidic, which would be detrimental to the stability and function of blood cells and enzymes.
* **Option C:** This option is incorrect because it suggests a pH range that is too alkaline, which would also be detrimental to the stability and function of blood cells and enzymes.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that the pH range of the CPD solution is critical for maintaining the stability and function of blood cells and enzymes. A pH range outside of the optimal range can lead to the degradation of blood cells and the activation of blood coagulation factors, making the blood unsuitable for transfusion.
**Correct Answer: C. 7.4**