28
1 Introduction to Analytical Chemistry
Nore:The heading"Problem"here encompasses the two types of problem (viz. the information
needed and the analytical problem involved) included in the definition of Analytical
Chemistry given in Sect. 1.1.
Box 1.13
One should avoid using the words analysis, determination and measurement indifferently as
they refer to different types of actions.
Thus, it is correct to speak of the following:
• Determination of cadmium in toys.
• Determination of hydrides in waste water.
• Analysis of a lunar rock.
• Measurement of the absorbance at 540 nm of the copper-cuproin complex.
However, it is incorrect to refer to the following:
• Analysis of cadmium in toys.
• Measurement of copper in sea water.
• Analysis of pesticides in milk.
I 1.7 Classifications
The intrinsic contents and scope of Analytical Chemistry have promoted the
development of classifications according to the different criteria outlined in the
previous sections. The most salient of such classifications are schematically
depicted in Fig. 1.19.
According to purpose and type of information required, Analytical Chemistry can be classified as follows:
• Qualitative analysis, which is concerned with the identification of analytes
(ions, molecules, atoms or chemical groups) present in a sample being
subjected to an analytical process. It produces a yes/no binary response (e.g.
to the presence or absence of aromatic hydrocarbons in the atmosphere,
pesticides in foods, drugs and their metabolites in blood) that is of a high
analytical value. Uncertainty is substantially diminished when the qualitative
response is obtained. However, one should be aware of the inability to
detect very low concentrations of some analytes - below their limits of
detection. As a result, a theoretically ideal, categorical yes/no response is in
fact an actual reply to a more specific question: is the analyte sought present
at a concentration above the limit of detection of the analytical process used?
Qualitative analysis therefore possesses quantitative connotations. A more
detailed description is provided in Chap. 5 .
• Quantitative analysis aims to determine the amounts or proportions of analytes,
atoms or chemical groups in the materials studied. It produces a numerical
response suited to the particular purpose. This information is subject to the
uncertainty inherent in experimental measurements (see first example in Box
1.4). Chapter 6 deals more extensively with this analytical concept.
1 Introduction to Analytical Chemistry
Nore:The heading"Problem"here encompasses the two types of problem (viz. the information
needed and the analytical problem involved) included in the definition of Analytical
Chemistry given in Sect. 1.1.
Box 1.13
One should avoid using the words analysis, determination and measurement indifferently as
they refer to different types of actions.
Thus, it is correct to speak of the following:
• Determination of cadmium in toys.
• Determination of hydrides in waste water.
• Analysis of a lunar rock.
• Measurement of the absorbance at 540 nm of the copper-cuproin complex.
However, it is incorrect to refer to the following:
• Analysis of cadmium in toys.
• Measurement of copper in sea water.
• Analysis of pesticides in milk.
I 1.7 Classifications
The intrinsic contents and scope of Analytical Chemistry have promoted the
development of classifications according to the different criteria outlined in the
previous sections. The most salient of such classifications are schematically
depicted in Fig. 1.19.
According to purpose and type of information required, Analytical Chemistry can be classified as follows:
• Qualitative analysis, which is concerned with the identification of analytes
(ions, molecules, atoms or chemical groups) present in a sample being
subjected to an analytical process. It produces a yes/no binary response (e.g.
to the presence or absence of aromatic hydrocarbons in the atmosphere,
pesticides in foods, drugs and their metabolites in blood) that is of a high
analytical value. Uncertainty is substantially diminished when the qualitative
response is obtained. However, one should be aware of the inability to
detect very low concentrations of some analytes - below their limits of
detection. As a result, a theoretically ideal, categorical yes/no response is in
fact an actual reply to a more specific question: is the analyte sought present
at a concentration above the limit of detection of the analytical process used?
Qualitative analysis therefore possesses quantitative connotations. A more
detailed description is provided in Chap. 5 .
• Quantitative analysis aims to determine the amounts or proportions of analytes,
atoms or chemical groups in the materials studied. It produces a numerical
response suited to the particular purpose. This information is subject to the
uncertainty inherent in experimental measurements (see first example in Box
1.4). Chapter 6 deals more extensively with this analytical concept.