Distillation and liquid extraction methods, properly applied, can fulfil
the first two criteria, but not the third: the sample has to be transferred from
the container in which it was delivered to appropriate laboratory glassware
(possibility of loss of analytes), apparatus for distillation or extraction must
be used (possibility of contamination), and also solvents must be used (possibility
of contamination). In the case of extraction, the extract obtained must
often be concentrated, usually by solvent evaporation. This operation is
linked with the risk of analyte loss and sample contamination – contaminants
also become concentrated.