Exact Mass Calculator for Mass Spectrometry

Exact Mass Calculation:

\[ \text{Exact Mass} = \sum (\text{Atomic Mass of Each Element} \times \text{Number of Atoms}) \]

Exact Mass (Da):

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1. What is Exact Mass?

Exact mass is the calculated mass of an ion or molecule determined by summing the atomic masses of its constituent elements. Unlike average molecular weight, exact mass uses the most abundant isotope mass for each element, making it essential for mass spectrometry applications.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \text{Exact Mass} = \sum (\text{Atomic Mass of Each Element} \times \text{Number of Atoms}) \]

Where atomic masses are based on the most abundant isotopes:

H — 1.007825 Da
C — 12.000000 Da
N — 14.003074 Da
O — 15.994915 Da
F — 18.998403 Da
P — 30.973762 Da
S — 31.972071 Da
Cl — 34.968853 Da
Br — 78.918338 Da
I — 126.904473 Da

Explanation: The calculator parses the molecular formula and sums the exact masses of all atoms in the molecule.

3. Importance of Exact Mass Calculation

Details: Exact mass calculation is crucial in mass spectrometry for compound identification, elemental composition determination, and distinguishing between isobaric compounds with similar molecular weights.

4. Using the Calculator

Tips: Enter the molecular formula using standard chemical notation (e.g., C6H12O6 for glucose). Element symbols are case-sensitive (first letter uppercase, second lowercase if applicable).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between exact mass and molecular weight?
A: Exact mass uses the mass of the most abundant isotope of each element, while molecular weight uses the weighted average of all naturally occurring isotopes.

Q2: Why is exact mass important in mass spectrometry?
A: High-resolution mass spectrometers can measure mass with such precision that exact mass measurements can help determine elemental composition of unknown compounds.

Q3: What elements are supported by this calculator?
A: The calculator currently supports H, C, N, O, F, P, S, Cl, Br, and I. Other elements can be added upon request.

Q4: How accurate are the calculations?
A: Calculations use internationally accepted isotope masses and are accurate to 6 decimal places, sufficient for most mass spectrometry applications.

Q5: Can this calculator handle complex formulas with parentheses?
A: Currently, the calculator supports simple formulas without parentheses. For complex formulas, please expand them before entry (e.g., (CH3)2CO should be entered as C3H6O).