Metal Analysis Information

Atomic spectrometry instruments are the most popular instruments used for trace metal analysis. Depending on the sample throughput, cost, sensitivity/detection limit, concentration range, matrices, and regulation requirements, different instruments can be chosen for different environmental applications. For instance, many metal elements can be analyzed easily and economically with ICP-OES but elements such as arsenic and lead are better analyzed by ICP-MS due to their low regulatory limit in drinking water.

Although metal analysis can be conducted directly from solid matrix through coupling of ICP-OES or ICP-MS with laser ablation instruments, the majority of the samples are analyzed in the liquid form. To make sure metal elements are totally dissolved in liquid samples, acid digestion  is often used. Depending on the matrix difference and analytes of interest, different acids or acid mixtures are used for the best digestion results and minimum interferences in downstream analysis. 

One of the biggest concerns using ICP-OES and ICP-MS is to overcome interferences. There are three types of interferences: physical, chemical and spectral.

Physical interferences occur when the physical properties of the sample are vastly different than the physical properties of the calibration standards. Examples of physical properties would include viscosity, density and surface tension. Physical interferences within the sample, injection and subsequently inside the plasma.

When analyzing thousands of samples in a large contract lab, operators are often frustrated with low productivity and efficiency. There are multiple ways to improve productivity:

• Fast sample introduction
• Automated sample dilution including prescriptive and intelligent dilution
• Integrated software with "get ready" functionality and more importantly,  highly stable performance

Instrument operation may look simple and straightforward, but there are many tips and tricks for sample analysis precision. Both instruments and sample preparation methods play important roles in getting high-precision results:

• Sample preparation: precipitation
• Sample preparation: gas production during the run
• Sample preparation: plasma drift due to the sample matrix
• Instruments: nebulizer type, gas flow rate, and peristaltic pump tubing
• Instruments: extraction lens and mirror adjustment
• Instruments: maintenance and use of skimmer cone inserts

Elemental speciation using IC-ICP-MS

Not all the species of an element contribute equally to toxicity. Speciation is an important tool to separate and quantify toxic from nontoxic species. One of the most efficient techniques for speciation is to use IC-ICP-MS. The metal-free IC, high resolution ion exchange columns, simple online connectivity, together with high sensitivity ICP-MS and integrated software are a powerful combination for fast and efficient metal speciation.

Mercury is a toxic element and is regulated in drinking water, wastewater, soil, and air. Under the Clean Water Act (CWA), the U.S. EPA regulates wastewater effluent discharge into surface water under the National Pollutant Discharge Elimination System (NPDES) program. Municipalities and industrial users must obtain NPDES permits to discharge their treated wastewater. Mercury is one of the most important heavy metal elements regulated under NPDES. The U.S. EPA approved multiple methods to measure the trace mercury concentration in effluent . EPA 200.8 is also an approved method that uses ICP-MS to determine the concentration of mercury.

Hydraulic Fracturing

The impact of hydraulic fracturing (fracking) on the environment has been a hot topic of discussion for many years. Currently, there is no federal regulation on fracking water analysis although there are some basic analysis requirements from a few states. It is critical to know the types of metals present in fracking flowback and/or produced water. We provide comprehensive solutions for the analysis of metals, anions, and organic compounds in fracking water.

Water Regulations

The U.S. EPA requires specific analytical methods to be used for metals analysis in compliance with drinking water and solid waste regulations. For instance, for drinking water, the EPA methods 200.5 (Axial ICP-OES), 200.7 (ICP-OES), 200.8 (ICP-MS), and 200.9 (GFAA) are mandatorily used for different metals; for solid waste, SW846 methods 6010c (ICP-OES), 6020 (ICP-MS), and 6020A (ICP-MS) are used for metals analysis for groundwater, sludges, soil, and solid waste as a performance guidance. We have a regulatory guide and many applications for specific regulatory methods.

For metal analysis, other countries use different regulatory methods. For instance:

• France: ISO 15587-1, 15587-2, 11885, 17294-1, 17294-2;
• UK: ISO 17025 and MCERTS performance standard;
• Germany: DIN EN ISO 14911 (E34), 11885 (E22), 17294-2 (E29)