Skip the beat: minimizing aliasing error in LA-ICP-MS measurements.

Area of Science:

• Analytical Chemistry
• Geochemistry
• Spectroscopy

Background:

• Pulsed laser ablation sampling coupled with sequential isotope detection can introduce signal beat.
• This signal beat can lead to significant biases in intensity ratios and concentrations, especially when aerosol transport times approach mass scan durations.

Purpose of the Study:

• To develop and validate a method to eliminate systematic bias caused by signal beat in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).
• To improve the accuracy of quantitative LA-ICP-MS measurements.

Main Methods:

• Averaging signal intensities based on the least common multiple (LCM) of scan duration and laser pulse period.
• Experimental investigation using an ablation cell with specific washout times and quadrupole-based ICP-MS acquisition.
• Comparison and extension of experimental data with numerical simulations.

Main Results:

• The systematic bias due to signal beat can exceed the inherent noise in LA-ICP-MS experiments.
• The LCM averaging method effectively minimizes this bias.
• Simulation revealed that the effectiveness of LCM averaging depends on the integer multiple relationship between laser pulses and isotopes acquired per scan.

Conclusions:

• LCM averaging is a viable method to prevent systematic bias in LA-ICP-MS measurements.
• The method enhances the accuracy of quantitative laser ablation experiments.
• Considerations for element imaging applications include potential increases in pixel size due to averaging parameters.