6 Gas Chromatography Columns Using Ionic Liquids …
149
6.5 Analysis of Environmental Pollutants
Phthalates or phthalic acid esters (PAEs) and adipates or adipic acid esters are mainly
used as plasticizers in the manufacturing of plastic products [107, 108]. Phthalates
are not biodegradable, and they have adverse effects on humans as they lead to congenital disabilities, heart diseases, and respiratory problems and they are endocrine
disruptors [109–112]. In addition to humans, they cause reproductive and fertility
problems in wildlife [113]. The Environmental Protection Agency (EPA) demands
strict control of the use and monitoring of toxic phthalates. GC-MS is a widely utilized technique for the analysis of PAEs as lower sensitivity is obtained with LC-MS
[113]. Chromatographic separation of phthalates is important because identification
and quantification by MS can be difficult due to the structural similarity of phthalates
(most phthalates have a common base peak ion at m/z 149) [114].
IL stationary phases have broad selectivity toward a variety of compounds and
were evaluated for the separation of phthalates. Three toxic adipates and eight phthalates were analyzed on the commercial SLB-IL59, SLB-IL76, SLB-IL82, SLBIL100, and SLB-IL111 GC columns [115]. All plasticizers were completely separated
on the SLB-IL59, SLB-IL76, and SLB-IL111 columns, while diethylbutyl phthalate
and diethylhexyl adipate coeluted on SLB-IL82 and SLB-IL100. All the IL columns
showed the same retention order except diethylhexyl adipate, which was less retained
on the SLB-IL 111 column compared to other columns. Symmetric peak shapes and
narrow peak widths were observed for plasticizers compared to the 5% phenyl-95%
methylpolysiloxane column. When non-commercial phosphonium-based dicationic
ILs with aromatic substituents were used to analyze twelve regulated phthalates,
complimentary selectivities were observed for most of the phthalates with respect to
the 5% phenyl polydimethylsiloxane (PDMS) phase [19]. Phthalates with benzene
and cyclohexyl ring substituents were observed to retain longer on the studied phosphonium ILs compared to the 5% PDMS phase. Three pairs of compounds (bis(4methyl-2-pentyl) phthalate/bis(2-ethoxyethyl) phthalate, di-n-hexyl phthalate/butyl
benzyl phthalate, and dicyclohexyl phthalate/bis(2-ethylhexyl) phthalate) were difficult to separate on the 5% phenyl column. However, they were well separated on
the phosphonium dicationic IL GC stationary phases studied [19].
Polychlorinated biphenyls (PCBs) are toxic environmental pollutants, and they
have adverse effects on humans. Use of PCBs is currently banned, but due to their
persistent nature and widespread use in the last century, they are present in the
environment at low concentrations. There are 209 possible congeners of PCBs, and
they cannot be separated chromatographically by using any single column [116,
117] (PCB nomenclature with numbers is reported in the literature [118]). Hence,
research is targeted toward the development of new stationary phases for the effective
separation of PCB congeners. The PCBs are classified into two main categories:
planar and non-planar. Non- and mono-ortho-substituted PCBs are planar, while
other ortho-substituted PCBs are non-planar. Planar PCBs are more toxic compared
to non-planar PCBs and should be effectively separated from each other for better
quantification.
149
6.5 Analysis of Environmental Pollutants
Phthalates or phthalic acid esters (PAEs) and adipates or adipic acid esters are mainly
used as plasticizers in the manufacturing of plastic products [107, 108]. Phthalates
are not biodegradable, and they have adverse effects on humans as they lead to congenital disabilities, heart diseases, and respiratory problems and they are endocrine
disruptors [109–112]. In addition to humans, they cause reproductive and fertility
problems in wildlife [113]. The Environmental Protection Agency (EPA) demands
strict control of the use and monitoring of toxic phthalates. GC-MS is a widely utilized technique for the analysis of PAEs as lower sensitivity is obtained with LC-MS
[113]. Chromatographic separation of phthalates is important because identification
and quantification by MS can be difficult due to the structural similarity of phthalates
(most phthalates have a common base peak ion at m/z 149) [114].
IL stationary phases have broad selectivity toward a variety of compounds and
were evaluated for the separation of phthalates. Three toxic adipates and eight phthalates were analyzed on the commercial SLB-IL59, SLB-IL76, SLB-IL82, SLBIL100, and SLB-IL111 GC columns [115]. All plasticizers were completely separated
on the SLB-IL59, SLB-IL76, and SLB-IL111 columns, while diethylbutyl phthalate
and diethylhexyl adipate coeluted on SLB-IL82 and SLB-IL100. All the IL columns
showed the same retention order except diethylhexyl adipate, which was less retained
on the SLB-IL 111 column compared to other columns. Symmetric peak shapes and
narrow peak widths were observed for plasticizers compared to the 5% phenyl-95%
methylpolysiloxane column. When non-commercial phosphonium-based dicationic
ILs with aromatic substituents were used to analyze twelve regulated phthalates,
complimentary selectivities were observed for most of the phthalates with respect to
the 5% phenyl polydimethylsiloxane (PDMS) phase [19]. Phthalates with benzene
and cyclohexyl ring substituents were observed to retain longer on the studied phosphonium ILs compared to the 5% PDMS phase. Three pairs of compounds (bis(4methyl-2-pentyl) phthalate/bis(2-ethoxyethyl) phthalate, di-n-hexyl phthalate/butyl
benzyl phthalate, and dicyclohexyl phthalate/bis(2-ethylhexyl) phthalate) were difficult to separate on the 5% phenyl column. However, they were well separated on
the phosphonium dicationic IL GC stationary phases studied [19].
Polychlorinated biphenyls (PCBs) are toxic environmental pollutants, and they
have adverse effects on humans. Use of PCBs is currently banned, but due to their
persistent nature and widespread use in the last century, they are present in the
environment at low concentrations. There are 209 possible congeners of PCBs, and
they cannot be separated chromatographically by using any single column [116,
117] (PCB nomenclature with numbers is reported in the literature [118]). Hence,
research is targeted toward the development of new stationary phases for the effective
separation of PCB congeners. The PCBs are classified into two main categories:
planar and non-planar. Non- and mono-ortho-substituted PCBs are planar, while
other ortho-substituted PCBs are non-planar. Planar PCBs are more toxic compared
to non-planar PCBs and should be effectively separated from each other for better
quantification.