Chapter 6
Analytical Quality Control
Outlook
The final step of analysis is the evaluation of the obtained results by quality
control. For quantitative data three parameters are important, the sensitivity,
the accuracy and the reducibility. These aspects will be discussed in detail in
this chapter.
All analytical data obtained need to be validated or evaluated. The quality control in
qualitative analyses, that means the criteria for an unambiguous identification in
Organic Geochemistry, have been already introduced in detail in Sect. 5.1. However,
one aspect needs to be mentioned additionally. In order to avoid false positive
detection as the result of laboratory contamination, the preparation and analyses of
so-called blanks is recommended (see Fig. 6.2). These blanks are executed by
using the whole laboratory working steps (extraction, evaporation, fractionation,
filtration, . . .) but without any sample matrix. Analyses of such blanks always reveal
substances normally at very low concentration levels that derive e.g. from the used
materials (plasticizers, . . .), laboratory air (PCBs, solvents, . . .) or laboratory stuff
(e.g. fragrances of perfumes, UV protectors, . . .). Substances identified in the blanks
should be compared with the results of the original samples. All compounds detected
in the blanks should not be considered as identified in the real samples except for
significant differences in concentrations (e.g. magnitudes higher signals). However,
the latter case needs to be checked very carefully.
Following the quality parameter for quantitative analyses are discussed in more
detail. Reliable quantitative data are assessed by three parameters, the sensitivity of
the analyses as well as their accuracy and reproducibility. Accuracy and reproducibility are often combined to the parameter precision. The sensitivity of an analysis
can be expressed by two different values, the limit of detection LOD and the limit of
quantitation LOQ. It has to be considered, for which analytical steps sensitivity has
© Springer Nature Switzerland AG 2020
J. Schwarzbauer, B. Jovančićević, Introduction to Analytical Methods in Organic
Geochemistry, Fundamentals in Organic Geochemistry,
https://doi.org/10.1007/978-3-030-38592-7_6
129
Analytical Quality Control
Outlook
The final step of analysis is the evaluation of the obtained results by quality
control. For quantitative data three parameters are important, the sensitivity,
the accuracy and the reducibility. These aspects will be discussed in detail in
this chapter.
All analytical data obtained need to be validated or evaluated. The quality control in
qualitative analyses, that means the criteria for an unambiguous identification in
Organic Geochemistry, have been already introduced in detail in Sect. 5.1. However,
one aspect needs to be mentioned additionally. In order to avoid false positive
detection as the result of laboratory contamination, the preparation and analyses of
so-called blanks is recommended (see Fig. 6.2). These blanks are executed by
using the whole laboratory working steps (extraction, evaporation, fractionation,
filtration, . . .) but without any sample matrix. Analyses of such blanks always reveal
substances normally at very low concentration levels that derive e.g. from the used
materials (plasticizers, . . .), laboratory air (PCBs, solvents, . . .) or laboratory stuff
(e.g. fragrances of perfumes, UV protectors, . . .). Substances identified in the blanks
should be compared with the results of the original samples. All compounds detected
in the blanks should not be considered as identified in the real samples except for
significant differences in concentrations (e.g. magnitudes higher signals). However,
the latter case needs to be checked very carefully.
Following the quality parameter for quantitative analyses are discussed in more
detail. Reliable quantitative data are assessed by three parameters, the sensitivity of
the analyses as well as their accuracy and reproducibility. Accuracy and reproducibility are often combined to the parameter precision. The sensitivity of an analysis
can be expressed by two different values, the limit of detection LOD and the limit of
quantitation LOQ. It has to be considered, for which analytical steps sensitivity has
© Springer Nature Switzerland AG 2020
J. Schwarzbauer, B. Jovančićević, Introduction to Analytical Methods in Organic
Geochemistry, Fundamentals in Organic Geochemistry,
https://doi.org/10.1007/978-3-030-38592-7_6
129