Assuming that the measurements are carried
out using standard 1-cm pathlength spectrophotometer cuvettes, with a maximum working volume
of 4 ml, then for the optimum analytical accuracy
the mixtures should of 2 mL DPPH solution and 2
mL of the reductant, unless the amounts available
preclude this. The common practice of using smaller
volumes in either case (such as 0.1 mL plus 3.9
mL, or vice versa) reduces the accuracy of the
relative volumes. Since the absorption is well into
the visible region ( 5) then it is possible to use
cheap plastic “disposable” cuvettes, which are not
attacked by the solvents most commonly used
here (methanol or ethanol) (Bondet et al., 1997).
Numbers of reactions, representing the points
along the titration plot (Figure 1), can thus be
carried out in parallel. This enables the progress ofthe reaction to be followed, and allows adequate
time for the overall reaction to go to completion
in each individual reaction mixture ( 6).
Assuming that the measurements are carried
out using standard 1-cm pathlength spectrophotometer cuvettes, with a maximum working volume
of 4 ml, then for the optimum analytical accuracy
the mixtures should of 2 mL DPPH solution and 2
mL of the reductant, unless the amounts available
preclude this. The common practice of using smaller
volumes in either case (such as 0.1 mL plus 3.9
mL, or vice versa) reduces the accuracy of the
relative volumes. Since the absorption is well into
the visible region ( 5) then it is possible to use
cheap plastic “disposable” cuvettes, which are not
attacked by the solvents most commonly used
here (methanol or ethanol) (Bondet et al., 1997).
Numbers of reactions, representing the points
along the titration plot (Figure 1), can thus be
carried out in parallel. This enables the progress ofthe reaction to be followed, and allows adequate
time for the overall reaction to go to completion
in each individual reaction mixture ( 6).
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