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23.1 Introduction
Until a few decades ago, sample preparation was carried out using traditional techniques, such as liquid-liquid extraction (LLE) and solid-liquid extraction (SLE),
which use large volumes of organic solvents. Although with the advent of solidphase extraction (SPE) much less solvent has been used compared to LLE, the volume can still be significant. However, this approach is not applicable to solid
matrices for which the Soxhlet extraction is still the most used technique in the
official methods of analysis. These preparation methods are expensive, timeconsuming and environmentally unfriendly. Since some years, a great effort has
been made to develop alternative and high-throughput analytical methods for the
pollutant extraction from solid matrices. Among these approaches, one of the most
interesting is the microwave-assisted extraction (MAE). In recent years this methodology has attracted growing interest as it allows for the rapid extractions of target
molecules from solid matrices, with extraction efficiency comparable to that of the
classical techniques [1]. In addition, compared to other extraction techniques, optimization of MAE experimental conditions is rather easy owing to the low number
of influential parameters (i.e. matrix moisture, nature of the solvent, time, power,
and temperature in closed vessels) [2].
The analysis of toxic agents in solid matrices is usually carried out by combining
the extraction step, often followed by a clean-up and pre-concentration procedure,
with a final determination using gas or liquid chromatography coupled to suitable
detection system such as tandem mass spectrometry. In this respect, although the
modern and advanced analytical techniques allow for the analysis of a broad range
of organic compounds, to maximize the method performance in terms of sensitivity,
specificity, and robustness, a proper sample preparation step is mandatory [3–6].
In this chapter, we focus our attention on a combined strategy for the analysis of
toxic chemical compounds in solid matrices. This new approach provides for the
use of MAE for the extraction of the target molecules followed by a solid-phase
microextraction (SPME) analysis. The key point of the method is the use of an ecocompatible hydroalcoholic mixture, instead of the traditional organic solvents,
which is compatible with the use of solid-phase microextraction in direct immersion
mode (DI-SPME) and can be analyzed without any other clean-up step. SPME is an
established sample preparation technique that has many advantages over the traditional approaches including the simultaneous extraction, pre-concentration, and
direct introduction of analytes into the gas chromatographic system [7]. As a result,
SPME has demonstrated to be a simple, solvent-free, reliable and flexible tool to
analyze molecules with different physicochemical properties in various matrices [5,
8, 9]. As a case study, we present the application of the proposed approach to the
analysis of organophosphate esters (OPEs) from airborne particulate matter (PM)
[10]. OPEs are synthetic derivatives of phosphoric acid with a wide range of
physical- chemical properties and several applications that in recent years led to a
sharp increase in global consumption. OPEs are relatively stable toward biodegradation, and several studies report that once in the environment, OPEs may undergo
A. Naccarato et al.
23.1 Introduction
Until a few decades ago, sample preparation was carried out using traditional techniques, such as liquid-liquid extraction (LLE) and solid-liquid extraction (SLE),
which use large volumes of organic solvents. Although with the advent of solidphase extraction (SPE) much less solvent has been used compared to LLE, the volume can still be significant. However, this approach is not applicable to solid
matrices for which the Soxhlet extraction is still the most used technique in the
official methods of analysis. These preparation methods are expensive, timeconsuming and environmentally unfriendly. Since some years, a great effort has
been made to develop alternative and high-throughput analytical methods for the
pollutant extraction from solid matrices. Among these approaches, one of the most
interesting is the microwave-assisted extraction (MAE). In recent years this methodology has attracted growing interest as it allows for the rapid extractions of target
molecules from solid matrices, with extraction efficiency comparable to that of the
classical techniques [1]. In addition, compared to other extraction techniques, optimization of MAE experimental conditions is rather easy owing to the low number
of influential parameters (i.e. matrix moisture, nature of the solvent, time, power,
and temperature in closed vessels) [2].
The analysis of toxic agents in solid matrices is usually carried out by combining
the extraction step, often followed by a clean-up and pre-concentration procedure,
with a final determination using gas or liquid chromatography coupled to suitable
detection system such as tandem mass spectrometry. In this respect, although the
modern and advanced analytical techniques allow for the analysis of a broad range
of organic compounds, to maximize the method performance in terms of sensitivity,
specificity, and robustness, a proper sample preparation step is mandatory [3–6].
In this chapter, we focus our attention on a combined strategy for the analysis of
toxic chemical compounds in solid matrices. This new approach provides for the
use of MAE for the extraction of the target molecules followed by a solid-phase
microextraction (SPME) analysis. The key point of the method is the use of an ecocompatible hydroalcoholic mixture, instead of the traditional organic solvents,
which is compatible with the use of solid-phase microextraction in direct immersion
mode (DI-SPME) and can be analyzed without any other clean-up step. SPME is an
established sample preparation technique that has many advantages over the traditional approaches including the simultaneous extraction, pre-concentration, and
direct introduction of analytes into the gas chromatographic system [7]. As a result,
SPME has demonstrated to be a simple, solvent-free, reliable and flexible tool to
analyze molecules with different physicochemical properties in various matrices [5,
8, 9]. As a case study, we present the application of the proposed approach to the
analysis of organophosphate esters (OPEs) from airborne particulate matter (PM)
[10]. OPEs are synthetic derivatives of phosphoric acid with a wide range of
physical- chemical properties and several applications that in recent years led to a
sharp increase in global consumption. OPEs are relatively stable toward biodegradation, and several studies report that once in the environment, OPEs may undergo
A. Naccarato et al.