Merits of EPA Method 1640 for Preconcentration of Trace Metals with Online Matrix Removal Coupled to a Highly Sensitive and Selective ICP-QQQ-MS Detection System

Oral Presentation

Prepared by T. Ugrai, H. Gürleyük, G. Leadbeater, M. Briscoe
Brooks Applied Labs, 18804 North Creek Parkway, Suite 100, Bothell, WA, 98011, United States

Contact Information:; 206-632-6206


Determination of trace metals in seawaters by ICP-MS is usually complicated by significant matrix effects and polyatomic interferences. EPA Method 1640 suggests the use of a preconcentration system where a variety of trace elements are initially acid solubilized and then neutralized with a buffer solution to allow chelation onto an iminodiacetate functionalized resin. Large volumes of an aqueous sample can be used to preconcentrate solubilized metals onto the resin. Group I and II metals, as well as many anions, are selectively removed from the resin by washing with an ammonium acetate buffer. The metals are then washed off the resin by elution with a small aliquot of dilute nitric acid and measured by ICP-MS. The matrix reduction step removes most of the common interferences that may inhibit the quality of data collected by ICP-MS. To achieve extremely low detection limits and interference-free analysis of seawaters and ambient waters, this automated preconcentration system was coupled to an ICP-QQQ-MS running in MS/MS mode with O2 or NH3. This combination provided sub-ppt detection limits for most of the elements studied (Ag, Cd, Co, Cu, Mn, Ni, Pb, V, Zn) where our MDLs were mostly limited by the cleanliness of our reagents. This routine method has also been found to be exceptionally good at preconcentration of rare earth elements with detection limits in the ppq range.