John Morris Scientific discusses the determination of inorganic micro-pollutants in soil and water.
Sample preparation is the most restricting barrier in the analytical process.
Furthermore, the credibility of an analytical method depends on the quantitative conversion of a solid into a homogeneous solution.
The traditional method for wet sample preparation is matrix dissolution.
A large volume of reagent (15-100ml) is heated for several hours with a hot plate or oven.
This process is finished when the analyst decides at sight that the digestion is complete.
The disadvantages of this type of digestion are: the large quantities of reagents employed, 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 the sample preparation.
In view of the advantages of microwave assisted sample preparation, US Environmental Protection Agency (US-EPA) developed a range of methods that employ this 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 (soils, sediments) and organic matrices (soil polluted by oil and hydrocarbons).
The microwave technique can also be applied to determinations of organic pollutants, for example pesticides, herbicides, phenols, PCB and PCDD/PCDF.
For example, the most commonly used method is US- EPA3546 and its application enables the sample preparation needed for chromatographic analysis.
US-EPA3546 requires a treatment time of 30min.
The main advantage, apart from time reduction, is the efficiency of the process in which solvent and solute are at the same extraction temperature.
The success of modern microwave systems is due to two major aspects: the high technological level and the maximum ease of use.
All parts, including software and hardware, have been built to reach maximum quality standards, allowing the operator to optimise the sample-preparation process.
These units are equipped with the latest-generation sensors for temperature and pressure control in all vessels.
Particular attention has been made to the engineering of various types of vessels, both in the choice of materials and in the safety systems: they can only release the excess pressure from the vessel.
Analytical laboratories need different products and matrices are very heterogeneous; therefore, the manufactures have decided to develop and produce carousels with different technical specifications for different temperature and pressure limits.
These solutions are said to increase the versatility of microwave platforms and offer the best solution for all the application fields.
The Milestone Ethos 1 further develops this concept, since it is not dedicated totally to acid digestion, but also to solvent extraction, evaporation and microwave fusion.
Four major applications are available with one system.
