2003) applied hollow fiber membrane liquid–liquid microextraction for the extraction of six phthalates, including dimethyl phthalate, diethyl phthalate, dinbutyl
phthalate, benzyl butyl phthalate, di(2-ethylhexyl) phthalate, and dioctyl phthalate,
in water samples. They used toluene as the extraction solvent, because it can provide
high solubility for the target phthalates and compatible with the gas chromatographic
system. Furthermore, it has a low solubility in water to prevent solvent dissolution
during extraction, and it has a polarity matching that of the hollow fiber material, so
it could impregnate and become immobilized within the pores of the hollow fiber.
The method had linear ranges of 0.02–10 μg/L for most target phthalates with the
limits of detection of 0.005–0.1 μg/L. The relative standard deviations of the method
varied between 4% and 11%. Vortex solvent bar microextraction, an improved
hollow fiber solvent bar microextraction method, has been proposed for the extraction of nine phthalates in bottled mineral water samples. It used 2 cm length Q3/2
hollow fibers immobilized with xylene (extraction solvent) as the solvent bar, which
was then thrown into the stirring water sample and stirred around the bottom of the
vortex during extraction. After extraction, the fibers were vortex eluted with microamount of acetone, and the eluent was applied to gas chromatography–mass spectrometric analysis. The vortex solvent bar microextraction gave enrichment factors
over 1500, with the relative standard deviations of less than 7.1% (Huang et al.
2012). Yang et al. (2018a) extracted four phthalates in water using hollow fiber
liquid-phase microextraction and determined the phthalates by high performance
liquid chromatography. An ionic liquid, i.e. [BMIm]PF6, was used as extractant, and
dodecanol was used as the supporting membrane. The detection limits of the method
were 1.67–7.38 μg/L with the relative standard deviations of 2.1% À5.7%.
Dispersive Liquid–Liquid Microextraction
Dispersive liquid–liquid microextraction, developed by Rezaee and coworkers in
2006 (Rezaee et al. 2006), is that the water-insoluble extractant is dispersed into the
aqueous phase to form a cloud-like solution, and the contact area between the
aqueous phase and the extraction phase increases tremendously, so that the analytes
can be quickly transferred from the aqueous phase into the extraction phase. The
extraction solvent is reaggregated by centrifugation, and then it is withdrawn for
subsequent analysis.
Dispersive liquid–liquid microextraction is much time-saving, and a very small
amount of organic solvents is needed compared with other extraction methods.
Furthermore, it does not need a special device and is easy to operate (Viñas et al.
2015). Based on the density of the extraction solvent, this technique can be divided
into a high-density solvent dispersive liquid–liquid microextraction and a low
density solvent dispersive liquid–liquid microextraction.
Dispersive liquid–liquid microextraction requires an organic dispersant which
has to be fully soluble with the aqueous phase. For this purpose, acetone, acetonitrile, and methanol are usually used. The extraction solvent should have satisfactory
extraction efficiency for the analytes. Also, the extraction solvent has to be soluble in
the dispersant, but it is insoluble in the aqueous phase. Furthermore, the density of
15 Analytical Methods for Phthalates in Water Samples
549
phthalate, benzyl butyl phthalate, di(2-ethylhexyl) phthalate, and dioctyl phthalate,
in water samples. They used toluene as the extraction solvent, because it can provide
high solubility for the target phthalates and compatible with the gas chromatographic
system. Furthermore, it has a low solubility in water to prevent solvent dissolution
during extraction, and it has a polarity matching that of the hollow fiber material, so
it could impregnate and become immobilized within the pores of the hollow fiber.
The method had linear ranges of 0.02–10 μg/L for most target phthalates with the
limits of detection of 0.005–0.1 μg/L. The relative standard deviations of the method
varied between 4% and 11%. Vortex solvent bar microextraction, an improved
hollow fiber solvent bar microextraction method, has been proposed for the extraction of nine phthalates in bottled mineral water samples. It used 2 cm length Q3/2
hollow fibers immobilized with xylene (extraction solvent) as the solvent bar, which
was then thrown into the stirring water sample and stirred around the bottom of the
vortex during extraction. After extraction, the fibers were vortex eluted with microamount of acetone, and the eluent was applied to gas chromatography–mass spectrometric analysis. The vortex solvent bar microextraction gave enrichment factors
over 1500, with the relative standard deviations of less than 7.1% (Huang et al.
2012). Yang et al. (2018a) extracted four phthalates in water using hollow fiber
liquid-phase microextraction and determined the phthalates by high performance
liquid chromatography. An ionic liquid, i.e. [BMIm]PF6, was used as extractant, and
dodecanol was used as the supporting membrane. The detection limits of the method
were 1.67–7.38 μg/L with the relative standard deviations of 2.1% À5.7%.
Dispersive Liquid–Liquid Microextraction
Dispersive liquid–liquid microextraction, developed by Rezaee and coworkers in
2006 (Rezaee et al. 2006), is that the water-insoluble extractant is dispersed into the
aqueous phase to form a cloud-like solution, and the contact area between the
aqueous phase and the extraction phase increases tremendously, so that the analytes
can be quickly transferred from the aqueous phase into the extraction phase. The
extraction solvent is reaggregated by centrifugation, and then it is withdrawn for
subsequent analysis.
Dispersive liquid–liquid microextraction is much time-saving, and a very small
amount of organic solvents is needed compared with other extraction methods.
Furthermore, it does not need a special device and is easy to operate (Viñas et al.
2015). Based on the density of the extraction solvent, this technique can be divided
into a high-density solvent dispersive liquid–liquid microextraction and a low
density solvent dispersive liquid–liquid microextraction.
Dispersive liquid–liquid microextraction requires an organic dispersant which
has to be fully soluble with the aqueous phase. For this purpose, acetone, acetonitrile, and methanol are usually used. The extraction solvent should have satisfactory
extraction efficiency for the analytes. Also, the extraction solvent has to be soluble in
the dispersant, but it is insoluble in the aqueous phase. Furthermore, the density of
15 Analytical Methods for Phthalates in Water Samples
549