Determination of As in Sediment

Al, a new student at a prominent university, was doing a research study on the environmental impact at an abandoned arsenic mine. His samples consisted of sediment and water. He hoped Paul would offer the best technique to analyze these samples to determine for arsenic and other toxic elements.

	RE: Determination of As in Sediment Dear Al,      I would suggest the use of graphite furnace atomic absorption according to EPA Method 200.9. This method is applicable to a number of toxic metals including As. As a new student you may want to: Perform a literature search on the topic and choose a method that has been fully validated. Get a copy of 200.9 and other published methods and determine which method(s) can be performed in your laboratory. Validate the method in your laboratory or at lease perform an analysis of a CRM certified for As and the other metals of interest. Be careful to decide upon the use of multi-element techniques such as ICP-OES of ICP-MS that may suffer from severe interferences. For example, ICP-MS is a common technique used for As. You can use this technique because it is a multi-element technique and will save time. However, the sample preparation will require the use of nitric and HCl where As can suffer significant interference from ArCl depending upon the instrument capabilities (reaction cells, resolution -- high resolution ICP-MS would be good etc), the ability of the operator to make spectral/mass corrections, the level of As in the sample digestate, etc.      In short, I recommend that you check the literature and seriously consider 200.9. Best of luck with your project.     Paul R. Gaines, Ph.D. Serving you in chemistry