Chemistry Reference
In-Depth Information
60 days. The cartridges loaded with the organotin compounds, after drying under nitrogen stream, can be
stored at room temperature in the dark, which reduce the space needed for storage [35].
Other examples of on-line in-field sampling and monitoring is the use of ion-pair solid-phase extraction for
determination of benzene- and naphthalenesulfonates in waste water [36] and a novel solid phase-extraction
device integrated onto a centrifugal microfluidic platform has also been developed for organic pollutants in
aqueous samples [37].
Another alternative for in-field sampling is SFE (supercritical fluid extraction). The main advantages of
SFE are high preconcentration rates, cleanliness and safety, quantitative capability, possibility for in-field
sampling, on-line coupling with hyphenated techniques and automation [33].
The solvents used in the analytical techniques for sampling and analysis should be eco-friendly such as
supercritical fluids or ionic liquids. However, supercritical fluids are not in widespread use due to the lack of
standard procedures and the scarcity of studies about the handling of liquid samples. In the case of ionic
liquids, there are few data on toxicity (bioaccumulation and biodegradability), few data on physical properties
and not clear understanding of solvent/material properties with regards to the structural features of ionic
liquids. Also there are not official analytical methods where ionic liquids are involved; they are expensive and
not commercially available.
Nevertheless, the ideal green analysis would run in situ integrating sampling and analysis, with real time
measurement techniques that do not use reagents for preservatives or extractions or that use small amount of
them. The 'Triad approach' is promoted by the US EPA for decision making that proactively exploits new
characterization and treatment tools [38]. The goal of the Triad approach is to assure that project decisions
about contaminant presence, location, fate, exposure, and risk reduction choices and design, are made
correctly and cost-effectively. 'Correct' decisions are defined as the decisions that would be made if fully
completely accurate knowledge of contamination nature and extent and receptor exposure were available to
decision-makers. The foundation for site-related decisions that are both correct and optimized (from a cost-
benefit standpoint) is the conceptual site model (CSM). A CSM uses all available historical and current
information to estimate [39]:
1.
where contamination is (or might be) located,
2.
how much is (or might be) there,
3.
how variable concentrations may be and how much spatial patterning may be present,
4.
what is happening to contaminants as far as fate and migration,
5.
who might be exposed to contaminants or harmful degradation products, and
6.
what might be done to manage risk by mitigating exposure.
The triad refers to three primary components; systematic planning, dynamic work strategies, and real
time measurement systems. The most important component for Green Analytical Chemistry is real time
measurement systems such as X-ray fluorescence spectrometry (XRF) [40], attenuated total reflectance
infrared spectroscopy, lab-on-a-chip technology, field sensors or microfluidic devices [38]. Also in the
literature are some examples of capillary electrophoresis microchips [41], single-drop biosensors [42],
microfluidic SPE for sample preconcentration [43] and membrane implanted analysis for cholesterol [44].
In field determination of metals can be also performed by a spectrophotometric analysis system [45], by
electrochemical stripping 46] or by a miniaturized stripping-based carbon modified sensor [47]. In-field
determination of arsenic in natural waters can be performed by a bacteria based bioassay with biosensor-
reporter strains as elements for the detection [48].
The liquid-phase microextraction techniques can also be used for in-field sampling in the framework of
Green Analytical Chemistry using less toxic extractant phases and new materials (nanomaterials, monolithic
silica, etc.) [49].
