Effect of Laser Energy Density on Data Quality during LA-ICP-MS Measurement

BACKGROUND Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a frequent instrument for the analysis of trace element content. When LA-ICP-MS is used to analyze the element content of minerals, the laser energy density will affect the denudation rate of the sample and thus affect the signal intensity during the analysis. OBJECTIVES To further clarify the impact of laser energy density changes on the quality of test data and the response of different natural minerals to laser energy density. METHODS The element content data of standard samples and nature minerals with different Mohs hardness under different laser energy densities were determined using LA-ICP-MS. Then authors analyzed the relative error (RE) between the test data and the reference values of the standard samples, average of the relative error of elements with RE within the limits of -20%-10% in the same standard sample, and the relative standard deviation of the standard samples and nature minerals test results to evaluate the effect of laser energy density on the test results. RESULTS The minimum laser energy density required to stabilize ablated quartz and fluorite was 4-5J/cm2, which was lower than the previously reported value (10J/cm2), whereas stable denudation of other minerals such as talc, apatite, and corundum require the minimum energy density of generally 1-2J/cm2. Under the different condition of laser energy density, the relative error of most trace elements in standard samples between analytical results and recommended values was less than 20% and the relative standard deviation was less than 10%. The relative standard deviation of most trace element test data was less than 20% for natural minerals with most element contents >1μg/g. Within a certain range, the greater the laser energy density, the smaller the average relative error of the data, and the better the overall quality. CONCLUSIONS Quartz and fluorite require higher laser energy density for stable ablation than other minerals. Within the appropriate range, laser energy density has little effect on the quality of the individual element data, but it affects the overall quality of the data.