154
PRELIMINARY
OPE RATIONS
Box 4.5
4 The Measurement Process in Chemistry
Fig. 4.8. Direct and indirect
effects of preliminary operations of a CMP on the
different types of analytical
properties
"Clean methods" are CMPs where the potential adverse effects of the analytical tools to be
used in the preliminary operations on laboratory personnel and the environment have been
considered. This approach, which is becoming increasingly popular and endorsed in Analytical Chemistry, can be real ized in two different ways, namely:
(a) By minimizing or avoiding the use of toxic and environmentally hazardous reagents
(e. g. mercury salts) and solvents (e. q. chlorofluorocarbons). This entails the use of new
materials (e. q. novel chemicals of decreased toxicity relative to traditional reagents) and
methodologies (e. g. supercritical fluid extraction instead of conventiona l solvent extraction).
(b) By developing new sub-steps for inclusion in the first or second step of the CMP in order
to destroy or inactivate harmful materials.
Both strategies are hot topics in current analytical resea rch, which must respond to the
increasing need to manage laboratory waste in a cost-effective, environmentally friendly
manner.
4.3.2 Sub-steps
Each CMP must be consistent with the analytical problem addressed. Preliminary operations are the greatest source of variability in number and nature
of CMP sub-steps. Figure 4.9 shows some of the more common sub-steps involved in such operations. The sequence of this scheme is not always followed in
PRELIMINARY
OPE RATIONS
Box 4.5
4 The Measurement Process in Chemistry
Fig. 4.8. Direct and indirect
effects of preliminary operations of a CMP on the
different types of analytical
properties
"Clean methods" are CMPs where the potential adverse effects of the analytical tools to be
used in the preliminary operations on laboratory personnel and the environment have been
considered. This approach, which is becoming increasingly popular and endorsed in Analytical Chemistry, can be real ized in two different ways, namely:
(a) By minimizing or avoiding the use of toxic and environmentally hazardous reagents
(e. g. mercury salts) and solvents (e. q. chlorofluorocarbons). This entails the use of new
materials (e. q. novel chemicals of decreased toxicity relative to traditional reagents) and
methodologies (e. g. supercritical fluid extraction instead of conventiona l solvent extraction).
(b) By developing new sub-steps for inclusion in the first or second step of the CMP in order
to destroy or inactivate harmful materials.
Both strategies are hot topics in current analytical resea rch, which must respond to the
increasing need to manage laboratory waste in a cost-effective, environmentally friendly
manner.
4.3.2 Sub-steps
Each CMP must be consistent with the analytical problem addressed. Preliminary operations are the greatest source of variability in number and nature
of CMP sub-steps. Figure 4.9 shows some of the more common sub-steps involved in such operations. The sequence of this scheme is not always followed in