Sensitivity is one of the key parameters characterizing the analytical method
for the determination of synthetic pyrethroid metabolites in the general population
not exposed occupationally, since average concentrations are well below 1 ng/mL.
Metabolites other than 3PBA are detected much less frequently and even in lower
concentrations. In general, methods based on gas chromatography are more sensitive
than methods based on liquid chromatography. Chromatographic methods in combination with mass spectrometry with different types of analyzers are used exclusively in HBM, as only advanced systems allow reliable detection of low
concentrations resulting from environmental exposure.
3 Separation Techniques
3.1 Sample Preparation
From a practical point of view, the fewer the stages of sample preparation for the
analysis, the lower the probability of making a mistake, but also the smaller
workload and consequently the unit cost of the analysis. Very low levels of synthetic
pyrethroid metabolites that are found in urine samples from non-occupationally
exposed subjects require the use of analytical methods characterized by high sensitivity of the instrument or advanced technique of extraction and purification of the
sample before instrumental analysis or the combination of both. Dilute-and-shoot
technique which is the simplest way of biological sample preparation for LC-MS/
MS was never used for the analysis of synthetic pyrethroid metabolites in human
urine.
In general, sample preparation steps include (a) internal standard addition,
(b) hydrolysis, (c) sample extraction and cleanup, (d) derivatization (only in GCMS-based methods), and (e) instrumental analysis.
The better sensitivity of GC-MS over LC-MS mentioned earlier is associated
however with a much greater effort at the stage of sample preparation for analysis,
whereas in the case of LC-MS, the hydrolyzed sample is only subjected to extraction
and possibly enrichment (solvent evaporation) before instrumental analysis. In the
case of GC-MS, the extracts are practically always subjected to additional cleanup,
concentration, and derivatization.
The vast majority of the immunological methods described do not require
advanced sample preparation for analysis. Usually, dilution of the urine sample or
simple SPE extraction is sufficient.
3.1.1 Hydrolysis
As mentioned earlier, all of the end products of pyrethroid metabolism when
excreted in urine are present as conjugates. No analytical method that was published
up to date dealt with determination of conjugated forms or only free form, but in all
52
B. Wielgomas et al.
for the determination of synthetic pyrethroid metabolites in the general population
not exposed occupationally, since average concentrations are well below 1 ng/mL.
Metabolites other than 3PBA are detected much less frequently and even in lower
concentrations. In general, methods based on gas chromatography are more sensitive
than methods based on liquid chromatography. Chromatographic methods in combination with mass spectrometry with different types of analyzers are used exclusively in HBM, as only advanced systems allow reliable detection of low
concentrations resulting from environmental exposure.
3 Separation Techniques
3.1 Sample Preparation
From a practical point of view, the fewer the stages of sample preparation for the
analysis, the lower the probability of making a mistake, but also the smaller
workload and consequently the unit cost of the analysis. Very low levels of synthetic
pyrethroid metabolites that are found in urine samples from non-occupationally
exposed subjects require the use of analytical methods characterized by high sensitivity of the instrument or advanced technique of extraction and purification of the
sample before instrumental analysis or the combination of both. Dilute-and-shoot
technique which is the simplest way of biological sample preparation for LC-MS/
MS was never used for the analysis of synthetic pyrethroid metabolites in human
urine.
In general, sample preparation steps include (a) internal standard addition,
(b) hydrolysis, (c) sample extraction and cleanup, (d) derivatization (only in GCMS-based methods), and (e) instrumental analysis.
The better sensitivity of GC-MS over LC-MS mentioned earlier is associated
however with a much greater effort at the stage of sample preparation for analysis,
whereas in the case of LC-MS, the hydrolyzed sample is only subjected to extraction
and possibly enrichment (solvent evaporation) before instrumental analysis. In the
case of GC-MS, the extracts are practically always subjected to additional cleanup,
concentration, and derivatization.
The vast majority of the immunological methods described do not require
advanced sample preparation for analysis. Usually, dilution of the urine sample or
simple SPE extraction is sufficient.
3.1.1 Hydrolysis
As mentioned earlier, all of the end products of pyrethroid metabolism when
excreted in urine are present as conjugates. No analytical method that was published
up to date dealt with determination of conjugated forms or only free form, but in all
52
B. Wielgomas et al.