Question

Mass of sample in picogram method is _________ gram.

• A. 1-10
• B. $<10^{-12}$
• C. $10^{-6}-0.001$
• D. 0.05-0.5g

Hint:

To remember metric prefixes in order of decreasing size: Milli ($10^{-3}$) $\rightarrow$ Micro ($10^{-6}$) $\rightarrow$ Nano ($10^{-9}$) $\rightarrow$ Picogram ($10^{-12}$) $\rightarrow$ Femtogram ($10^{-15}$).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Analytical methods are classified based on the mass of the sample analyzed, ranging from macro-analysis to ultra-micro and trace-level analysis.
Metric prefixes define the scale of measurement.

Step 3: Detailed Explanation:
Let us define the metric scale of mass measurements:
- Gram ($\text{g}$): The base unit of mass.
- Milligram ($\text{mg}$) = $10^{-3} \text{ g}$ (used in micro-analysis, $1\text{ to }10 \text{ mg}$).
- Microgram ($\mu\text{g}$) = $10^{-6} \text{ g}$ (used in sub-micro analysis).
- Nanogram ($\text{ng}$) = $10^{-9} \text{ g}$.
- Picogram ($\text{pg}$) = $10^{-12} \text{ g}$.
Therefore, analytical methods designed to analyze sample masses at the picogram level operate with mass ranges on the order of $< 10^{-12} \text{ grams}$.
Let us review the other options:
- $0.05 - 0.5 \text{ g}$ represents the macro-analysis scale.
- $10^{-6} - 0.001 \text{ g}$ ($1 \mu\text{g}\text{ to }1 \text{ mg}$) represents the micro-analysis scale.
- $1 - 10 \text{ g}$ represents large-scale bulk analysis.
Thus, the picogram method operates at masses $< 10^{-12} \text{ g}$.

Step 4: Final Answer:
The mass of a sample in the picogram method is $<10^{-12}\text{ g}$, corresponding to option (B).