Radioisotopes in molecular biology: approximate half-life of phosphorus-32 (32P) Choose the closest standard half-life used for planning labeling experiments and safety.

Introduction / Context:
Phosphorus-32 is a high-energy beta emitter widely used for nucleic acid labeling and kinase assays. Knowing its half-life is critical for experimental planning, decay correction, waste management, and radiation safety.

Given Data / Assumptions:

• Half-life is the time required for activity to decrease to one-half its initial value.
• 32P is typically supplied in orthophosphate or ATP forms.
• Laboratories plan orders and experiments around predictable decay.

Concept / Approach:
The accepted half-life of 32P is approximately 14.3 days. For routine planning, it is commonly rounded to about 14 days. This informs when to reorder, how to schedule high-specific-activity experiments, and how to manage exposure.

Step-by-Step Solution:
Recall the tabulated physical constant: t1/2(32P) ≈ 14.3 days.Match the closest option; 14 days is the best approximation among the choices.Recognize that longer values like 28–42 days correspond to other nuclides (for example, 35S ≈ 87 days).

Verification / Alternative check:
Decay charts in supplier documentation and radiation safety manuals list 32P half-life near 14.3 days, corroborating the selection.

Why Other Options Are Wrong:
28, 30, and 42 days are too long; 7 days is too short.

Common Pitfalls:
Confusing 32P with 33P (half-life ≈ 25 days) or 35S; mixing up physical half-life with biological half-life in vivo.

Final Answer:
14 days.