Visualizing the Solute Vaporization Interference in Flame Atomic Absorption Spectroscopy

摘要

Every day, tens of thousands of chemists use analytical atomic spectroscopy in their work, often without knowledge of possible interferences. We present a unique approach to study these interferences by using modern response surface methods to visualize an interference in which aluminum depresses the calcium atomic absorption signal. Calcium atomic absorption measurements are performed on solutions that contain calcium only, calcium plus aluminum, and calcium plus aluminum with lanthanum added as a releasing agent. The interferences are known to be affected by flame temperature, so measurements were made under conditions of varied flame stoichiometry and observation height. Results are displayed using response surfaces generated by regression analysis of the results of a factorial design in which burner height and fuel ratios are varied. Response surface methods allow students to recognize the tradeoffs required to optimize instrumental parameters. The user can chose to optimize operating conditions based on minimizing the solute vaporization interference, maximizing the absorbance, optimizing signal-to-noise ratio, or any combination of these three diagnostic parameters. The conditions needed for stable, reproducible chemical analyses were substantially different from those that produce the maximum signal.