Credibility of an analytical method of sample preparation depends on the quantitative conversion of a solid into a homogeneous solution.
Matrix dissolution is conventionally employed for wet sample preparation, wherein a large volume of reagent is heated for several hours using a hot plate or oven. The process is done when the analyst decides ‘at sight’ that the digestion is complete.
Disadvantages of this type of digestion include:
- Large quantities of reagents
- Potential for contamination
- Continuous release of hot acid vapour into the laboratory environment
An alternative method is microwave decomposition, which uses a completely different technology that improves digestion efficiency and increases the safety of laboratory personnel. This is because microwave instruments have been specifically designed to improve the process of sample preparation.
In view of the advantages of microwave assisted sample preparation, USA Environmental Protection Agency (US-EPA) developed a range of methods that employ this innovative technology. These procedures enable the rapid analysis of metals in water samples (US-EPA 3015) and of metals in soils (US-EPA 3051, US-EPA 3052).
The US-EPA3052 method describes the procedure for total sample digestion. In particular, it refers to the treatment of matrices containing silicates such as soils and sediments as well as organic matrices (soil polluted by oil and hydrocarbons).
The microwave digestion system can also be applied to determination of organic pollutants such as pesticides, herbicides, phenols, PCB and PCDD/PCDF.
For example, the most commonly used method is US-EPA3546 for the sample preparation required for chromatographic analysis.
US-EPA3546 requires a treatment time of just 30 minutes. In addition to significantly saving time, the method is also highly efficient, keeping the solvent and solute at the same extraction temperature.
Advantages of microwave-assisted sample preparation
- Modern microwave digestion systems feature advanced technology and offer maximum ease of use
- High quality standards of software and hardware allow the operator to optimise the sample preparation process
- Units are equipped with the latest generation sensors for temperature and pressure control in all vessels
- Vessels are engineered for safety
Future Possibilities and Versatility of the Technique
Analytical laboratories need different products and matrices are very heterogeneous, therefore, manufacturers have decided to develop and produce carousels with varying technical specifications for different temperature and pressure limits.
These solutions increase the versatility of microwave platforms and offer the best solution for all the application fields.
The Milestone ETHOS 1 advanced microwave digestion system is designed for four major applications including acid digestion, solvent extraction, evaporation and microwave fusion.
Milestone ETHOS 1 is available from John Morris Scientific , a specialist scientific instrumentation supplier in Australia offering a comprehensive range of laboratory and testing equipment for diverse applications.