1. What is Mass Accuracy?

Mass accuracy is a measure of how close a measured mass is to the true (exact) mass of a molecule or particle. It is typically expressed in parts per million (ppm) and is crucial in fields like mass spectrometry.

2. How Does the Calculator Work?

The calculator uses the mass accuracy formula:

Where:

• \( \text{Measured} \) — The experimentally determined mass (u)
• \( \text{Exact} \) — The theoretical exact mass (u)
• \( 10^6 \) — Conversion factor to parts per million

Explanation: The formula calculates the relative error between the measured and exact mass, scaled to ppm for easier interpretation.

3. Importance of Mass Accuracy

Details: High mass accuracy is essential for correct compound identification in mass spectrometry, particularly when distinguishing between isobaric species or confirming molecular formulas.

4. Using the Calculator

Tips: Enter both measured and exact masses in unified atomic mass units (u). The exact mass must be greater than zero for the calculation to work.

5. Frequently Asked Questions (FAQ)

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

Q2: Why use ppm instead of absolute error?
A: ppm allows comparison of accuracy across different mass ranges, making it more universally meaningful.

Q3: How does mass accuracy relate to mass resolution?
A: While related, they measure different things. Resolution is the ability to distinguish peaks, while accuracy is how close the measured value is to the true value.

Q4: Can mass accuracy be negative?
A: Yes, negative values indicate the measured mass was lower than the exact mass.

Q5: What factors affect mass accuracy?
A: Instrument calibration, peak shape, signal-to-noise ratio, and proper sample preparation all influence mass accuracy.