Factors affecting quantitative analysis in laser desorption/laser ionization mass spectrometry

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Organic Geochemistry

Background:

• Microprobe laser desorption/laser ionization mass spectrometry (microL(2)MS) is a sensitive technique for detecting trace organic compounds, especially polycyclic aromatic hydrocarbons (PAHs).
• Current research aims to establish microL(2)MS as a quantitative method, typically using internal standards to measure analyte signal ratios.

Purpose of the Study:

• To investigate factors influencing signal ratios in quantitative microL(2)MS.
• To identify sources of uncertainty and irreproducibility in the quantification of PAHs using microL(2)MS.

Main Methods:

• Analysis of signal ratios of polycyclic aromatic hydrocarbons (PAHs) using microprobe laser desorption/laser ionization mass spectrometry (microL(2)MS).
• Systematic variation of desorption laser power and wavelength, desorption-ionization delay time, ionization laser power, and ionization laser alignment.
• Testing on synthetic poly(vinyl chloride) membranes and Murchison meteorite powder samples.

Main Results:

• Desorption laser parameters and delay time significantly altered PAH signal ratios (up to 24-fold).
• Ionization laser power and alignment presented practical challenges for reproducible quantification due to their sensitivity and difficulty in control.
• Ratios varied more between dissimilar PAHs than between similar ones, suggesting the need for multiple internal standards for diverse PAH mixtures.

Conclusions:

• Precise control over laser desorption/ionization parameters is critical for accurate and reproducible quantitative microL(2)MS.
• Ionization laser power and alignment are key limitations for quantitative microL(2)MS, demanding careful optimization.
• Quantifying diverse PAH mixtures may require multiple internal standards to account for variations in signal response.