Effect of arsenic valence state on the certification measurements of primary calibration solutions by ICP-OES

ANYL 143

Lee L. Yu, lee.yu@nist.gov, Therese Butler, therese.butler@nist.gov, and Gregory C. Turk, turk@nist.gov. Analytical Chemistry Division, Spectrochemical Methods Group, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8391, Gaithersburg, MD 20899-8391
Standards prepared from arsenic metal were frequently found to have inexplicable disagreements between batches when analyzed by using ICP-OES. The disagreements, as great as a few percent at times, frustrate the efforts of producing an accurate standard. By using HPLC-ICPMS, we found arsenic +3 and +5 species in the standards; moreover, the standards with large mass fraction of arsenic +3 corresponded to those with the least sensitive response to ICP-OES detection. A detailed study of arsenic +3 and +5 speciation standards confirmed that arsenic +3 is less sensitive with ICP-OES detection relative to arsenic +5, which resulted in the aforementioned disagreement. The study also showed that once all arsenic species are oxidized to the +5 state by using iodine, the disagreement between the standards disappears. The digestion kinetics of arsenic was studied. Based on the findings of the study, a procedure is developed that produces pure arsenic +5 standards only, which eliminates the potential for disagreements between batches of standards as measured by ICP-OES.
 

General Papers
7:00 PM-9:00 PM, Sunday, 28 August 2005 Washington DC Convention Center -- Hall A, Poster

Division of Analytical Chemistry

The 230th ACS National Meeting, in Washington, DC, Aug 28-Sept 1, 2005