1. What is Mass Spec PPM Error?

Definition: PPM (parts per million) error measures the accuracy of mass spectrometry measurements by comparing experimental and theoretical masses.

Purpose: It helps researchers evaluate the precision of their mass spectrometry data and instrument calibration.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• Experimental Mass — Measured mass from the mass spectrometer (Daltons)
• Theoretical Mass — Expected mass based on molecular formula (Daltons)
• PPM Error — Parts per million difference between measured and expected mass

Explanation: The difference between experimental and theoretical mass is normalized to the theoretical mass and scaled to parts per million.

3. Importance of PPM Error Calculation

Details: PPM error helps assess mass accuracy, which is critical for compound identification, especially in high-resolution mass spectrometry.

4. Using the Calculator

Tips: Enter both masses in Daltons (Da). Theoretical mass must be greater than zero. Lower PPM values indicate better mass accuracy.

5. Frequently Asked Questions (FAQ)

Q1: What is considered a good PPM error?
A: Typically < 5 ppm is excellent for high-resolution instruments, while < 20 ppm may be acceptable for lower resolution instruments.

Q2: Can PPM error be negative?
A: Yes, negative values indicate the experimental mass was lower than theoretical.

Q3: Why use PPM instead of absolute mass difference?
A: PPM normalizes the error relative to mass, making it comparable across different mass ranges.

Q4: How do I get theoretical mass?
A: Calculate from molecular formula using elemental masses or use online tools like ChemCalc.

Q5: Does this work for MS/MS fragments?
A: Yes, the same calculation applies to fragment ions in tandem mass spectrometry.