Background: For acquiring information on accessibility, mobility, chemical behavior and
fate of elements, it is necessary to determine their specific chemical species. Relevance of microwave
energy for chemical speciation analysis has been extensively investigated over a wide range of applications
since more than last three decades. The aim of writing this review would be to discuss salient features
of important procedures applying microwave-assisted extraction followed by multi-elemental speciation
through sequential extraction and speciation of several selected elements with complicated speciation
Methods: The use of microwave assisting dissolution, extraction and derivatization leads to a breakthrough
in sample pretreatment for speciation analysis. After extraction, analytes were determined by
atomic spectrometry such as AAS and ICP MS. A higher leaching rate could be achieved by applying
focused-microwave followed by simultaneous multi-elemental detection through ICP TOFMS then that
had been applied in continuous leaching followed by high resolution ICP HRMS.
Results: A drastic reduction in time viz., from 68 h in the classical method to < 3.5 h in the microwave
enhanced multi-elemental speciation methodology was reported and the scheme reduces the risk of contamination
and involves a clean process technology. Detection limit of the order of picogram was reported
for inorganic arsenic species in coal using microwave treatment followed by HPLC-HG AFS.
Open focused microwave extraction using low power and less time (40-60W, 2-4 min) leads to not only
reproducible and quantitative recovery but also saves the organo- mercury species intact in nanogram
level. On-line non-chromatographic method for monitoring inorganic selenium species employing microwave
has been found to be extremely useful for real-time speciation with picogram detection limit.
Microwave-assisted extraction followed by HPLC-ES MS allows an environmentally clean method of
tin speciation with femtogram detection limit.
Conclusion: The use of microwave energy to prepare sample for speciation is now a necessity because
tedious sample preparation procedures can not only be drastically reduced in time and simplified, but
also it brings about the possibility of on-line automation. The pretreatment protocols proposed for metal
species determination allow to extend the potential of these rapid sample preparation procedures to environmental
matrices. Several methods have immense possibility of applying microwave-enhanced speciation
in future because they are green in nature.
Keywords: Arsenic, biological tissue, environmental samples, green methods, mercury, microwave extraction, natural water,
sediment, selenium, sequential extraction, soil, speciation, tin.
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