Microwave Sample Digestion – a great time and money saving technique for sample dissolution

Microwave sample digestion is a closed-system technique for dissolving samples such as minerals, ores, rocks, soils, ceramics, and coal, using mineral acids under pressurized heating that can reach 250-300°C, offering faster digestion times, lower acid consumption, and reduced chemist exposure to corrosive fumes compared with conventional open-vessel acid digestion.

Sample dissolution has been a challenge for the analytical chemist. Dissolution of samples such as minerals, ores, rocks, soils, ceramics, oxides and coal test your patience as digestions take several hours or even days to complete under harsh conditions involving highly corrosive acids and heat.

Wet chemical digestions involve use of mineral acids conventionally in open systems. Closed microwave digestion systems offer several benefits which are highlighted below:

• Maximum heating temperature is limited by boiling point of the acid but can be raised to 250 – 300°C under pressurized conditions of closed systems
• Acid consumption is much less
• High extraction efficiency of analytes from sample matrix
• Minimum exposure of chemist to corrosive and pungent acid fumes
• Digestions generally take less than one hour in comparison to much longer time for open digestions
• 8 – 12 samples simultaneous digestions contribute significantly to increased laboratory productivity
• Due to closed system operation there is no loss of volatile elements during the digestion process and contamination from the environment is also eliminated.

The advantages offered far outweigh the initial investment and today several laboratories have introduced microwave digestion systems.

The sequence of images  below will illustrate a typical digestion carried out using a commercial microwave digestion system.

Sample in Powder form in Digestion acid in digestion tube

On Shaking Sample remains as a Suspension without Dissolving

Digestion tube being inserted into protective casing

Protective Cover fixing on top

Tube being mounted in the holder rack

Tightening of Rack Cover

Tightening of top cover screw diagonally

Fixing of Cover Shield

Top View of Shield Cover

Digestion tube assembly mounted inside Microwave Reaction System

Real time display of digestion parameters inside mounted sample tube

Real time display of digestion parameters inside mounted sample tubes

Removal of top cover of digestion tube on completion of digestion

Clear dissolved sample in digestion tube after removal from digestion assembly