pH and duration of Action of EDTA is
The core concept here is understanding the properties of EDTA. Chelating agents like EDTA work by binding metal ions, which can be important in processes like anticoagulation. The pH of EDTA solutions is typically around 4-5 because it's a weak acid. The duration of action would relate to how long it remains effective in binding ions once it's applied.
Now, the correct answer is likely to be option C, but I need to verify. Let's think: EDTA is used in blood collection tubes to prevent clotting. Its duration of action is immediate upon mixing with blood and lasts until the sample is processed. The pH being slightly acidic is important for its chelating action. So if option C states pH 4-5 and immediate duration, that's correct.
The wrong options might have different pH values, like higher or lower, and incorrect durations. For example, option A might suggest a higher pH, which would be wrong because EDTA is a weak acid. Option B could have a duration that's too long, not immediate. Option D might mix up EDTA with another anticoagulant like heparin, which has a different pH and action duration.
Clinical pearl: Remember that EDTA is used in CBC tests because it preserves cell morphology, and its acidic pH helps in preventing clotting by chelating calcium ions. Students often confuse EDTA with other anticoagulants like citrate or heparin, so knowing the specific properties is key.
**Core Concept**
EDTA (ethylenediaminetetraacetic acid) is a chelating agent that binds calcium ions, preventing blood coagulation. Its pH and duration of action are critical for its function in anticoagulant tubes and laboratory applications.
**Why the Correct Answer is Right**
EDTA solutions have a pH of **4–5**, which is slightly acidic due to its weak acid properties. This pH optimizes its ability to chelate calcium, a key coagulation factor. The duration of action is **immediate and sustained** upon mixing with blood, ensuring rapid anticoagulation and prolonged stability of blood samples for complete blood count (CBC) analysis.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect pH (e.g., neutral or basic) would reduce EDTA’s chelating efficiency.
**Option B:** A short duration (e.g., minutes) is false; EDTA remains effective until the sample is processed.
**Option D:** Confuses EDTA with citrate (used in coagulation tests) or heparin (alkaline pH, shorter duration).
**Clinical Pearl / High-Yield Fact**
EDTA is the preferred anticoagulant for CBC due to its pH-dependent calcium chelation and preservation of cellular morphology. Avoid using EDTA for coagulation studies (e.g., PT/INR), where citrate is standard.
**Correct Answer: C. pH 4–5, immediate and sustained**