Understanding Metal Digestion

Metals are compounds that are relatively abundant in our environment. There are different types of metals that have been grouped together as our understanding of them has evolved over time. One such group are the heavy metals like lead and cadmium, which are considered toxic. An excess of heavy metals in the body typically arises as a result of bioaccumulation, which means the concentration of metallic elements in the body increases over time. This typically occurs due to drinking water contaminated by pollutants. Determining the metal content of soils, sediments, and water is subsequently a challenging environmental imperative.

However, metals also form the basis of life. Copper and iron from the base metal group, for instance. Trace levels of copper are important for maintaining good metabolic health, and iron is responsible for carrying oxygen to all the cells inside our bodies.

Ultimately metals are also responsible for global technological progress, and they are what mining companies routinely survey for to drive world economies.

Efficient metal digestion plays into each of these application areas to ensure continued health and economic progress.

An Introduction to Metals Analysis & Digestion

Acids are the primary reagents used for breaking down metal containing compounds. The most used acids are nitric acid (HNO3), hydrochloric acid (HCl), sulfuric acid (H2SO4), perchloric acid (HClO4), and hydrofluoric acid (HF). Various forms and combinations of these acids can be used to digest a variety of samples and liberate the metals within.

One of the most common applications is the digestion of gold ore by using an acid combination called Aqua Regia. Aqua Regia, Latin for Royal water, is the combination of three-part HCl to one-part HNO3. This combination is great at dissolving gold and stabilizing it in solution ready for elemental analysis later.

Another mixture that is widely used is the combination of four acids HNO3, HCl, HClO4, and HF. This highly reactive acid mixture can dissolve even the toughest matrices including silica. This is important as most of the earth’s crust is rich in silicate minerals which can trap other valuable metals.

Knowing which of these acids to apply when trying to digest metals is therefore important to obtaining optimal results. Additionally, researchers are often faced with a choice between cost and quality when it comes to metal determination. Microwave metal digestion was developed to maximise analyte retention but came at the expense of increased risk due to high pressure requirements and equipment user friendliness. Microwave-based metal digestion can be costly and time-consuming. 

Hot plate metal digestion can be valuable for aqueous samples and wastes, but where trace and ultra-trace level accuracy is the goal, the potential loss of volatile elements as off-gas rendered this method unfit for purpose.

To truly accelerate metal determination by ICP-MS/ICP-OES, we need a metal digestion method that yields complete matrix decomposition with little-to-no loss of sample content as with microwaves, but at faster rates than those of hotplates. Fortunately, at ColdBlock Technologies, we have the solution.

Read More: What is ColdBlock Digestion?

ColdBlock Metal Digestion

We have developed a unique digestion system that offers rapid matrix decomposition with accuracy and reproducibility for a wide range of sample matrices. The ColdBlock™ system has already been employed by mining operations and quality control laboratories around the world.

Contact us today if you would like to discuss your operating requirements with a member of the ColdBlock team.