analytical methodologies. Extraction and cleanup steps have presented a high
improved, especially in terms of automation reducing the sample manipulation and
the time of analysis. Sample preparation methods for pyrethroids are well established
for environmental and food samples, with acceptable recoveries and good
reproducibilities. Regarding instrumental determination, developed methodologies
are based on the use of gas chromatography (GC) coupled to mass spectrometry
(MS). However, in order to achieve limits of detection adequate for the
determination at environmentally relevant concentrations, the use of tandem
mass spectrometry (MS-MS) seems mandatory. Moreover, it is important to
guarantee the quality of analytical data in the analysis of pollutants, such as
pyrethroids, in complex matrices. These quality parameters must be tested through
the performance of interlaboratory tests and combined, if it is possible and
available, with the use of reference materials. However, these have not yet been
treated in the case of pyrethroids, and future works must be done in this sense.
Regarding enantiomeric separation, beta-cyclodextrin-based columns were
usually applied due to its excellent enantioselectivity. However, the enantiomeric
analysis is a complicated task. Different works achieved the separation of some
enantiomeric pairs, especially for cis enantiomers. However, the separation of trans
enantiomers still remains an unsolved task. Research is necessary into development
of new chiral columns able to achieve this separation between trans enantiomers.
Another challenge in chiral analysis is the lack of standards to enable quantification
of individual enantiomers.
Chapter “Analytical Methods for Determination Urinary Metabolites of Synthetic
Pyrethroids” summarizes the analytical work carried out for the analysis of
pyrethroid metabolites in human samples. Urine, as a major route of elimination
of pyrethroid metabolites, is considered the most appropriate matrix for the
assessment of pyrethroid exposure. In general, sample preparation steps include
a hydrolysis step before sample extraction. This step could be an acidic or an
enzymatic hydrolysis. However, enzymatic hydrolysis has some disadvantages: is
time consuming since it is usually performed overnight, and sample should be
acidified before extraction. In contrast, after acidic hydrolysis, no pH adjustment
is needed before extraction. New research is focused on the development of
analytical methods for the metabolite determination of new pyrethroids and
those less frequently used. The main problem is the lack of commercial availability
of reference substances and relevant isotopically labeled internal standards.
The market of MS is extremely dynamic and manufacturers invest into
the development of new technologies. Actually, ultrahigh resolving power analyzers
(>100,000), such as Orbitrap-type systems, are increasing their use to identify
non-target compounds. This opens the opportunity for the identification of new
pyrethroids as well as their metabolites that are not currently included in traditional
target methodologies. The analysis strategy is based on a “scan” in full-scan mode
in an integrated (non-specific) way and with the help of software, such as SIEVE and
ExactFinder, to identify the presence of potential unknowns. Once identified,
and if commercial analytical standards are available, a definitive and unambiguous
confirmation of the compounds could be done, as well as their quantitative analysis.
308
E. Eljarrat
improved, especially in terms of automation reducing the sample manipulation and
the time of analysis. Sample preparation methods for pyrethroids are well established
for environmental and food samples, with acceptable recoveries and good
reproducibilities. Regarding instrumental determination, developed methodologies
are based on the use of gas chromatography (GC) coupled to mass spectrometry
(MS). However, in order to achieve limits of detection adequate for the
determination at environmentally relevant concentrations, the use of tandem
mass spectrometry (MS-MS) seems mandatory. Moreover, it is important to
guarantee the quality of analytical data in the analysis of pollutants, such as
pyrethroids, in complex matrices. These quality parameters must be tested through
the performance of interlaboratory tests and combined, if it is possible and
available, with the use of reference materials. However, these have not yet been
treated in the case of pyrethroids, and future works must be done in this sense.
Regarding enantiomeric separation, beta-cyclodextrin-based columns were
usually applied due to its excellent enantioselectivity. However, the enantiomeric
analysis is a complicated task. Different works achieved the separation of some
enantiomeric pairs, especially for cis enantiomers. However, the separation of trans
enantiomers still remains an unsolved task. Research is necessary into development
of new chiral columns able to achieve this separation between trans enantiomers.
Another challenge in chiral analysis is the lack of standards to enable quantification
of individual enantiomers.
Chapter “Analytical Methods for Determination Urinary Metabolites of Synthetic
Pyrethroids” summarizes the analytical work carried out for the analysis of
pyrethroid metabolites in human samples. Urine, as a major route of elimination
of pyrethroid metabolites, is considered the most appropriate matrix for the
assessment of pyrethroid exposure. In general, sample preparation steps include
a hydrolysis step before sample extraction. This step could be an acidic or an
enzymatic hydrolysis. However, enzymatic hydrolysis has some disadvantages: is
time consuming since it is usually performed overnight, and sample should be
acidified before extraction. In contrast, after acidic hydrolysis, no pH adjustment
is needed before extraction. New research is focused on the development of
analytical methods for the metabolite determination of new pyrethroids and
those less frequently used. The main problem is the lack of commercial availability
of reference substances and relevant isotopically labeled internal standards.
The market of MS is extremely dynamic and manufacturers invest into
the development of new technologies. Actually, ultrahigh resolving power analyzers
(>100,000), such as Orbitrap-type systems, are increasing their use to identify
non-target compounds. This opens the opportunity for the identification of new
pyrethroids as well as their metabolites that are not currently included in traditional
target methodologies. The analysis strategy is based on a “scan” in full-scan mode
in an integrated (non-specific) way and with the help of software, such as SIEVE and
ExactFinder, to identify the presence of potential unknowns. Once identified,
and if commercial analytical standards are available, a definitive and unambiguous
confirmation of the compounds could be done, as well as their quantitative analysis.
308
E. Eljarrat