Okay, I need to figure out the correct answer for this question about the concentration of sodium fluoride used as a preservative in blood and urine samples for chemical analysis. Let's start by recalling what I know about sodium fluoride.

Sodium fluoride is commonly used as a preservative in blood samples to prevent glycolysis. Glycolysis can lower the pH of the sample and affect the accuracy of glucose measurements. So, the main purpose here is to inhibit glycolysis, ensuring that glucose levels remain stable until the sample is tested.

I remember that the typical concentration of sodium fluoride in blood collection tubes is around 1%. However, I'm a bit fuzzy on the exact concentration. Maybe it's 1%, 2%, or another percentage? Also, I need to check if there's a standard concentration recommended by organizations like CLSI (Clinical and Laboratory Standards Institute) or other medical guidelines.

Looking up some references, I find that sodium fluoride is usually present in concentrations of 1% to 2% in blood collection tubes. For example, a common tube might have 1.5 mg of sodium fluoride per mL of blood. But wait, the question is about the concentration, not the amount per mL. So 1% would be 10 mg/mL. Let me verify this.

Another source mentions that sodium fluoride is used at a concentration of 1% (10 mg/mL) in blood samples to prevent glycolysis. For urine samples, the same concentration might be used, but I need to confirm if urine preservation requires the same or a different concentration. However, the question combines both blood and urine, so the answer is likely the same for both.

Wait, but some sources might state 1.5% or another percentage. Let me cross-check. The CDC's guidelines or CLSI documents might have this. If I recall correctly, the standard concentration is 1% sodium fluoride. Therefore, the correct answer should be 1%.

Now, looking at the options provided (even though they are not listed here), the correct answer is likely option B or another labeled option with 1%. The other options would be incorrect. For example, if another option says 0.5%, that's too low to effectively inhibit glycolysis. Higher concentrations like 2% might be used in some cases but are less common. Alternatively, some might confuse it with other preservatives like potassium oxalate, which is used at different concentrations.

So, the core concept is sodium fluoride's role in inhibiting glycolysis by complexing with glycolytic enzymes like enolase. The correct concentration is 1%, and other options are either too low or not standard. The clinical pearl is that 1% sodium fluoride is the standard for blood and urine samples to prevent glucose breakdown.

**Core Concept**
Sodium fluoride inhibits glycolysis in blood and urine samples by binding to glycolytic enzymes (e.g., enolase), preventing false hypoglycemia. The concentration must be sufficient to halt enzymatic activity without causing sample degradation.

**Why the Correct Answer is Right**
The standard concentration of sodium fluoride as a preservative is **1% (10 mg/mL)**. This concentration effectively chelates calcium and inhibits glycolytic enzymes, preserving glucose and other analytes in blood and urine. It is widely adopted in clinical labs to ensure sample stability for 2

✓ Correct Answer: D. 100 mg/10 ml