What is the main principle of TOF detection in MS?
Time-of-flight analyzer imparts equal kinetic energy to ions through high voltage acceleration into a field-free drift region. Kinetic energy equals zV = 1/2 mv², so velocity equals sqrt(2zV/m), making flight time proportional to sqrt(m/z). Thus lighter ions with lower m/z travel faster and arrive earlier at detector than heavier ions. Calibration converts measured time to accurate m/z values. Statement that all ions have same time or intensity proportional to energy is incorrect. This dependence forms basis for high-resolution analysis of proteins, peptides, and oligonucleotides over wide mass range without scanning.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.