Overcoming Interferences Impacting Heavy Metals Analyses by ICPMS

Oral Presentation

Prepared by M. Flournoy
Eurofins Frontier Global Sciences, 11720 North Creek Parkway N., Suite 400, Bothell, WASHINGTON, 98011, United States


Contact Information: michael.flournoy@gmail.com; 717-413-6937


ABSTRACT

Background

Inductively Coupled Plasma Mass Spectrometer (ICPMS) is a powerful instrument to determine heavy metals concentrations in a variety of matrices. Not only can the instrument determine concentrations at fairly low levels, sometimes in the part per trillion (ppt) or part per billion (ppb) levels and has a fairly large dynamic range to detect both low and high concentrations., but the instrument has the capability of mitigating interferences impacting heavy metals.

Although ICPMS analysis is very powerful, it does have some setbacks. For example, high levels of minerals (Ca, Na, and other minerals found in saline or brackish water) can cause high biases for some metals elements requiring high dilutions to determine trace metals concentrations. Additionally, there are other heavy metals that can impact trace levels if the concentrations are high enough. Unfortunately the dilution increases the detection limit by the same factor of the dilution.

The good news is that this is not a new problem. In the mid 90ís the Environmental Protection Agency (EPA) and several laboratories and experts set forth to validate and verify an appropriate method to determine trace metals at EPA Water Quality Criteria (WQC) limits. Through this research, a chelation pre-concentration specialty method was developed called EPA Method 1640. The method primarily references 7 heavy metal elements (As, Cd, Cu, Pb, Ni, Ag, and Zn), but the method could be used for other trace metals. In a nutshell, this method removes mineral interferences via reductive precipitation or other chelation techniques. There has been a great deal of technology improvements that have enabled automation.

Additionally, the invention of the ICP-QQQ, instruments are capable of resolving interferences in many cases that do not require additional manipulations to provide reliable trace concentration data.

Approach

This presentation will focus on comparing several trace metals in brackish water samples and samples with high concentrations with interfering elements using standard 200.8 analysis, manual reductive precipitation analysis, automated analysis using an ESI DX4 SeaFast pre-concentration analysis, and analysis using an Agilent ICP-QQQ.