Metal Standards: Arsenic Line Interferences from Iron

Mike was reviewing some split sample results; XRF with intensive sample preparation vs. an ICP-OES EPA method. He was looking for information about potential negative interferences for ICP-OES in slag samples. He noted that the Fe ranged from 10-30% and that he was especially interested in the arsenic accuracy at 10 ppm levels.

Dear Mike,

The analysis of any sample containing high amounts of Fe is subject to spectral interferences - both positive and negative. The type of interference will depend upon the line used as well as the choice of background correction points. Due to the very large number of possibilities, this topic is too large to attempt to cover here. Please feel free to call me at the 1-800 number listed below and I would be glad to discuss specific details and possible interferences.

In the case of As, high levels of Fe will spectrally interfere with ALL of the As emission lines. The two best lines are the 189.042 and the 228.812 nm lines where there is a strong Fe line on the low wavelength side of the both of these As emission lines. In both cases, a negative interference would be experienced if a background correction point is selected on the low wavelength side of either line. An inspection of the spectra and the mode of background correction used should point out any problems.

Please feel free to call with any specific questions and good luck with your comparison.

Serving you in chemistry,

Paul R. Gaines, Ph.D.
CEO of Inorganic Ventures & Fellow Chemist

DISCLAIMER: Advice offered by the chemists at Inorganic Ventures is intended for the individual posing the question. Feel free to contact us to verify whether these suggestions apply to your unique circumstances.