1. What is m/z in HRMS?

The m/z (mass-to-charge ratio) is a fundamental quantity in mass spectrometry that represents the ratio of the ion's mass to its charge. In high resolution mass spectrometry (HRMS), precise m/z values are used to identify molecular formulas.

2. How Does the Calculator Work?

The calculator uses the HRMS equation:

Where:

• \( Molecular\ Mass \) — The neutral mass of the molecule (amu)
• \( Adduct \) — Mass of any attached ion (e.g., H+, Na+) (amu)
• \( Charge \) — Number of charges on the ion (integer)

Explanation: The equation calculates the mass-to-charge ratio by accounting for both the molecular mass and any adducts, divided by the charge state.

3. Importance of m/z Calculation

Details: Accurate m/z calculation is essential for interpreting mass spectra, identifying unknown compounds, and confirming molecular formulas in HRMS experiments.

4. Using the Calculator

Tips: Enter molecular mass in amu (must be positive), adduct mass in amu (can be zero or negative), and charge as a positive integer. Common adducts: H+ (+1.0078), Na+ (+22.9898).

5. Frequently Asked Questions (FAQ)

Q1: What are typical adducts in positive ion mode?
A: Common positive adducts include [M+H]+, [M+Na]+, [M+K]+, and [M+NH4]+ with masses +1.0078, +22.9898, +38.9637, and +18.0344 amu respectively.

Q2: How does resolution affect m/z measurements?
A: Higher resolution instruments can distinguish between m/z values that differ by very small amounts (e.g., 0.0001 amu).

Q3: What's the difference between monoisotopic and average mass?
A: Monoisotopic mass uses the most abundant isotope for each element, while average mass considers natural isotopic abundances.

Q4: How do I interpret negative m/z values?
A: Negative m/z values typically indicate negative ion mode with adducts like [M-H]- (-1.0078 amu).

Q5: What's the precision needed for HRMS?
A: High-resolution instruments often require m/z values with 4-6 decimal places for accurate formula assignment.