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Ohmic potential
VoltammetryVoltammetry techniques measure current as a
function of applied potential under conditions that
promote polarization of a working electrode. Polarography: Invented by J. Heyrovsky (Nobel
Prize 1959). Differs from voltammetry in that it
employs a dropping mercury electrode (DME) to
continuously renew the electrode surface. Amperometry: current proportional to analyte
concentration is monitored at a fixed potential
Classical and Thermal MethodsAldehydes and Ketones
– Form acetals and ketals respectively with normal
methanol-containing reagents
– Water formed in this reaction will then be titrated to give
erroneously high water results
– With aldehydes a second side reaction can take place,
consuming water, which can lead to sample water
content being underestimated
– Replacing methanol with another solvent can solve the
difficulties (commercial reagents are widely available)
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Electronic Spectroscopy 2 UV-Visible spectra can be
interpreted to help determine
molecular structure, but this
is presently confined to the
analysis of electron behavior
in known compounds.
Information from other
techniques (NMR, MS, IR) is
usually far more useful for
structural analysis
However, UV-Vis evidence
should not be ignored!
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Intro to Electroanalytical Chemistry Matched against a wide range of spectroscopic
and chromatographic techniques, the techniques
of electroanalytical chemistry find an important
role for several reasons:
– Electroanalytical methods are often specific for a
particular oxidation state of an element
– Electrochemical instrumentation is relatively
inexpensive and can be miniaturized
– Electroanalytical methods provide information about
activities (rather than concentration)
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Introduction to Separations Science IUPAC Definition: chromatography is a physical method of
separation in which the components to be separated are
distributed between two phases, one of which is stationary
while the other moves in a definite direction
Stationary phase (SP): common name for the column
packing material in any type of chromatography
Mobile phase (MP): liquid media that continuously flows
through the column and carries the analytes
Analyte: the chemical species being investigated (detected
and quantitatively measured) by an analytical method...
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Introduction to SpectroscopyThe velocity at which radiation travels (or propagates)
through a medium is dependent on the medium itself
When radiation travels through a medium and does not
undergo a frequency change, it cannot be undergoing a
permanent energy transfer
However, radiation can still interact with the medium
– Radiation, an EM field, polarizes the electron clouds of
atoms in the medium
– Polarization is a temporary deformation of the electron
clouds
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