Electron Ionization Mass Spectrometry Calculator

Calculator

Example Data Table

Formula Used

The molecular ion value is calculated as m/z = molecular mass divided by charge. Exact mass uses monoisotopic masses from the formula. Nominal mass uses whole number isotope masses.

Excess electron energy is electron energy minus ionization energy. Ion kinetic energy is charge times acceleration voltage in electron volts.

Time of flight uses v = square root of two times kinetic energy divided by ion mass. Then time equals flight length divided by velocity.

The magnetic sector estimate uses m/z = B squared times radius squared divided by two times voltage, converted to daltons per charge.

How to Use This Calculator

1. Enter a molecular formula, such as C6H6 or C6H5Cl.
2. Use manual mass only when formula data is unavailable.
3. Set the charge state, electron energy, and ionization energy.
4. Add source temperature and intensity values for signal review.
5. Enter voltage, flight length, field, and radius if needed.
6. Add neutral losses separated by commas or spaces.
7. Press Calculate to show results above the form.
8. Use CSV or PDF buttons to save the report.

Electron Ionization Mass Spectrometry Guide

Why EI Data Matters

Electron ionization mass spectrometry gives a firm way to study volatile molecules. The method uses energetic electrons, often near seventy electron volts. A molecule loses one electron and becomes a radical cation. That molecular ion may stay intact, or it may break into smaller charged fragments. The resulting peaks help reveal mass, formula clues, and structural patterns.

What This Calculator Reviews

This calculator supports that first review. It accepts a formula or a known molecular mass. It then estimates the molecular ion m/z for the chosen charge. It also reports nominal mass, exact mass, mass defect, and rough isotope peak clues. The isotope section is not a replacement for full simulation. It is a fast guide for common atoms, such as carbon, chlorine, bromine, sulfur, silicon, and oxygen.

Electron Energy and Fragmentation

Electron energy also matters. When electron energy exceeds the ionization energy, the extra energy can drive fragmentation. The tool shows this excess value, so a user can judge whether harsh ionization is expected. Higher excess energy often gives richer fragment spectra. Lower excess energy may preserve more molecular ion signal.

Ion Motion in the Instrument

The motion section helps with instrument learning. If acceleration voltage and flight length are entered, the calculator estimates ion kinetic energy, velocity, and time of flight. These values show why heavier ions travel slower at the same charge and voltage. If magnetic field and radius are supplied, the page also estimates a magnetic analyzer m/z. That gives another view of ion separation.

Fragment Loss Planning

Fragment loss entries make the page practical. Enter neutral losses, such as 15, 18, 28, 31, 43, or 44. The calculator subtracts each loss from the molecular mass and divides by charge. This creates a quick fragment table. It can guide peak assignment, class notes, and early report drafts.

Export and Review

Results can be exported as CSV or a simple PDF report. Use these exports for records, worksheets, or lab discussions. Always compare calculated values with calibrated spectra. Exact instruments may use different resolving power, calibration methods, and abundance corrections. Use this page as a transparent study aid, not as a final identification system. For best results, enter realistic voltages, known formula notation, and measured fragment losses. Record assumptions beside every exported spectrum summary. Then review uncertainties before sharing analytical conclusions with another chemist.

FAQs