Sample treatment has been the focus of intensive research from the GAC perspective in the past 20 years, since it is the bottleneck of analytical procedures.
It is worth stressing that the sample-preparation step largely determines the quality of the results obtained and is the main source of systematic errors and random lack of precision of analytical methodologies. The sample-treatment step must guarantee a quantitative recovery of target analytes, avoiding contamination and providing matrix isolation as far as possible, in order to reduce potential interferences and matrix effects during the measurement step.
We should notice that there is no universal sample-preparation technique suitable for all types of sample, and that sample preparation depends on the matrix, the nature of analytes and the final measurement mode. Moreover, an appropriate method for a target analyte may not be good for comprehensive screening of compounds.
In recent years, sample-preparation methodologies evolved from hard strategies to soft methods based on room-temperature, ultrasound-assisted leaching [19], [20] and [21] or microwave-assisted digestion using closed systems [22], [23] and [24], so providing a fast, safe methodology, especially for sample digestion and sample dissolution.
Analyte extraction has the double purpose of matrix isolation and analyte preconcentration, and the appropriate selection of solvents and reagents and the control of the preconcentration process are absolutely necessary in order to:
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separate quantitatively the target analyte from the matrix; and,
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increase the concentration level of the target analyte in the final solution to be measured.