1. What is Mass Accuracy?

Mass accuracy is a measure of how close a measured mass (observed mass) is to the true mass (experimental mass) of a molecule. It's typically expressed in parts per million (ppm) and is crucial in mass spectrometry applications.

2. How Does the Calculator Work?

The calculator uses the mass accuracy equation:

Where:

• Experimental Mass — The theoretical or known mass of the molecule (Da)
• Observed Mass — The measured mass from the instrument (Da)
• ppm — Parts per million (10^6)

Explanation: The equation calculates the relative difference between the expected and observed mass values, scaled to millionths of the experimental mass.

3. Importance of Mass Accuracy

Details: High mass accuracy is essential for confident compound identification in mass spectrometry. Lower ppm values indicate better agreement between observed and theoretical masses.

4. Using the Calculator

Tips: Enter both masses in Daltons (Da). Experimental mass must be greater than zero for valid calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is considered good mass accuracy?
A: In modern mass spectrometers, <5 ppm is generally good, <1 ppm is excellent for high-resolution instruments.

Q2: Why use ppm instead of absolute mass difference?
A: ppm provides a relative measure that's comparable across different mass ranges, unlike absolute differences which vary with mass.

Q3: How does mass accuracy affect compound identification?
A: Higher accuracy (lower ppm) reduces the number of possible molecular formulas matching the observed mass.

Q4: Can negative ppm values occur?
A: Yes, negative values indicate the observed mass was higher than the experimental mass.

Q5: How does resolution affect mass accuracy?
A: Higher resolution instruments typically provide better mass accuracy by more precisely determining the mass-to-charge ratio.