1. What is Mass Accuracy in PPM?

Mass accuracy in parts per million (ppm) is a measure of how close an observed mass (OM) is to the exact mass (EM) of a molecule. It's commonly used in mass spectrometry to assess the precision of mass measurements.

2. How Does the Calculator Work?

The calculator uses the mass accuracy formula:

Where:

• \( EM \) — Exact mass (theoretical mass) in Daltons (Da)
• \( OM \) — Observed mass (measured mass) in Daltons (Da)
• \( 10^6 \) — Conversion factor to parts per million

Explanation: The formula calculates the relative difference between the exact and observed mass, scaled to parts per million for easier interpretation.

3. Importance of Mass Accuracy

Details: High mass accuracy (low ppm values) is crucial in mass spectrometry for compound identification, especially in complex mixtures. Lower ppm values indicate better agreement between observed and theoretical masses.

4. Using the Calculator

Tips: Enter exact mass and observed mass in Daltons (Da). Both values must be positive numbers, and exact mass cannot be zero.

5. Frequently Asked Questions (FAQ)

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

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: Can this calculator be used for m/z values?
A: Yes, the same formula applies to mass-to-charge ratio (m/z) measurements in mass spectrometry.

Q4: What affects mass accuracy in instruments?
A: Factors include instrument calibration, resolution, sample preparation, and environmental conditions.

Q5: How does this relate to mass error?
A: Mass error is essentially the absolute value of the ppm calculation - it represents the magnitude without direction.