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, organisations such
as the 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 (soils,
sediments) and organic matrices (soil polluted by oil and hydrocarbons).
technique can also be applied to determinations of organic pollutants
e.g. pesticides, herbicides, phenols, PCB and PCDD/PCDF. For example,
the most commonly used method is US-EPA3546: its application enables the
sample preparation needed for chromatographic analysis.
US-EPA3546 requires a
treatment time of just 30 minutes. The main advantage apart from
time-reduction is the efficiency of the process in which solvent and
solute are at the same extraction temperature.
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 optimize 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.
And Versatility Of The Technique - Analytical laboratories need
different products and matrices are very heterogeneous; therefore, the
manufactures have decided to develop and produce carousels with
different technical specifications both for different temperature and
pressure limits. These solutions increase the versatility of microwave
platforms and offer the best solution for all the application fields.
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.
For further information please call 1800 251 799