The branch of chemistry that deals with
the separations, identification and
determination of components in a
It also traditionally includes coverage of
chemical equilibrium and stastistical
treatment of data.
Analytical chemistry can be broken down into
two general areas of analysis :
1. Qualitative analysis – attempting to identify
what materials are present in a sample.
2. Quantitative analysis – determining how
much of a material is present in a sample.
Example : GC/MS – this method includes both
a separation tool(GC) and a spectral
method(MSpectrometry). The combination is a
very powerful method.
Type of methods
The are many approaches can and have
1. gravimetry – methods based on a
2. titrimetry - methods based on a
3. electrochemical – approaches that
rely on measurement of potential,
current, resistance, charge, etc
Type of methods
4. spectral methods – interaction of an
analyte with electromagnetic radiation.
5. Chromatography – separation of a
material due to its interaction with two
6. chemometrics – the statistical
treatment of data.
We need to review the general steps that
are taken for any quantitative methods.
These steps are taken to ensure an
accurate and reliable answer.
What type of information do we need?
Complete analysis – the goal is to
determine the amount of each
component in a sample.
ultimate analysis – the amount of each
element present without regard to
partial analysis – determining one or a
limited number of species sample. This
is the most common approach.
Iron in an ore sample
Electrolyte level in blood
Presence of lead in a water sample
Basic steps in an analysis
technique to be used
sampling and sample preparation
proper application of the method
data analysis and reporting
Factor to consider
1. accuracy and sensitivity
3. number of sample to be assayed
4. number of components in a sample
The approach we taken, must produce
the result you require in a timely, cost
effect manner – primarily determined
by the type of sample you have.
Must be representative.
Steps must be taken to ensure that your
results reflect average composition.
Example – determination of iron in an
- Minerals and ores are
heterogeneous. To assay single
sample may not yield results for
an entire sample lot.
Proper sample selection and preparation
can help minimize this problem.
Require some knowledge as to sample
source and history.
One common approach is to select
several random samples for analysis.
-Powder the samples
-Blend the powders
-Select a fraction for assay
One must then convert the sample to a
suitable form for the method of analysis.
Based on the method, this may include :
Drying to ensure an accurate weight.
Elimination or masking of potential
Conversion of analyte to a single or
All methods have errors associated with
Using multiple samples and replicates
helps track and identify this error.
- Identically prepared from another
- used to verify if your sampling was
splits of the same sample.
Helps track and identify errors in
For most methods, we measure a
response that is proportional to the
concentration of our analyte.
Gravimetric – weight of a precipitate.
Titration - volume of a titrant.
Spectrophotometric – light absorbed.
Chromatographic – peak area.
Once your response has been obtained, the
final steps is to calculate your results.
This will include
Application of your standard
Estimation of error based on
Reporting in a standard, usable