150
M. Talebi et al.
Recently commercialized IL stationary phases were evaluated for the separation
of PCB congeners, and their performance was compared to the 5%-phenyl/95%methyl polysiloxane (DB-5MS) column [116]. The number of coelutions on the
IL columns and DB-5MS were not much different, while the important difference
observed was in the elution order of the PCBs. More polar mono-ortho-substituted
PCBs were retained longer compared to the less polar di-ortho-substituted PCBs
on the IL columns. The SLB-IL111 column showed the highest deviation in the
elution order compared to the DB-5MS column. Trichlorobiphenyls (28 and 30)
were retained longer than tetrachlorobiphenyls (47, 49, and 52) on the SLB-IL111
column, while the opposite elution order was observed on the DB-5MS column and
all other IL columns. PCBs 28 and 30 were partially separated on the SLB-IL59,
but they could not be separated on all the other columns evaluated in the study.
This separation was important as PCB 28 is one of the so-called indicator PCBs.
Seven indicator PCBs 28, 52, 101, 118, 138, 153, and 180 were best separated on
the DB-5MS column compared to all the commercialized IL columns.
In a separate study, a total of 69 PCBs were investigated on the IL columns, and
the separation performances were assessed based on the polarity of IL stationary
phases [119]. The extremely polar stationary phase SLB-IL111 showed the highest number of coelutions, that is, 31 congeners. Among three IL columns (SLBIL100, SLB-IL82, and SLB-IL76), the number of coelutions increased with the
polarity of the IL stationary phase. Between SLB-IL59 and SLB-IL61, SLB-IL59
showed better performance in the separation of PCBs. Moreover, more symmetrical and narrower peak shapes were obtained with SLB-IL59. The phosphoniumbased IL stationary phases SLB-IL59 and SLB-IL76 performed better compared
to the imidazolium-based IL stationary phases in the separation of PCBs. SLBIL61 containing a triflate anion and the same phosphonium dication as SLBIL59 performed poorly compared to the SLB-IL59. Non-commercial phosphonium ILs with aromatic substituents were shown to be effective in the separation of toxic planar PCBs. A dicationic IL stationary phase, 1,9-bis(diphenylo-tolyl-phosphonium)nonane bis(trifluoromethanesulfonyl)imide, effectively separated twelve tetra- to hepta-chloro-substituted toxic PCB congeners [19]. The same
IL stationary phase also showed a baseline separation of the most toxic 2,3,7,8tetrachlorodibenzodioxin (TCDD) isomer from the other five TCDD isomers when
compared to the commercial SLB-5MS and SP-2331 columns [19].
Polycyclic aromatic compounds (PACs) are common environmental pollutants
comprised of condensed multiring benzenoid compounds [120]. Polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic sulfur heterocycles (PASHs)
are classes of PACs and have carcinogenic and mutagenic activities. Gas chromatography is the preferred technique for the separation and determination of PACs [121].
Many of the PAHs and PASHs are structural isomers, and their chromatographic
separation is essential as they generate the same mass spectra. The structural isomers
can have different toxicities, and their separation is important for quantification.
PASHs are a dominant part of fossil fuel-based pollutants and coal tar. Their analyses are mainly done by using moderate- to nonpolar columns in GC or GC × GC
M. Talebi et al.
Recently commercialized IL stationary phases were evaluated for the separation
of PCB congeners, and their performance was compared to the 5%-phenyl/95%methyl polysiloxane (DB-5MS) column [116]. The number of coelutions on the
IL columns and DB-5MS were not much different, while the important difference
observed was in the elution order of the PCBs. More polar mono-ortho-substituted
PCBs were retained longer compared to the less polar di-ortho-substituted PCBs
on the IL columns. The SLB-IL111 column showed the highest deviation in the
elution order compared to the DB-5MS column. Trichlorobiphenyls (28 and 30)
were retained longer than tetrachlorobiphenyls (47, 49, and 52) on the SLB-IL111
column, while the opposite elution order was observed on the DB-5MS column and
all other IL columns. PCBs 28 and 30 were partially separated on the SLB-IL59,
but they could not be separated on all the other columns evaluated in the study.
This separation was important as PCB 28 is one of the so-called indicator PCBs.
Seven indicator PCBs 28, 52, 101, 118, 138, 153, and 180 were best separated on
the DB-5MS column compared to all the commercialized IL columns.
In a separate study, a total of 69 PCBs were investigated on the IL columns, and
the separation performances were assessed based on the polarity of IL stationary
phases [119]. The extremely polar stationary phase SLB-IL111 showed the highest number of coelutions, that is, 31 congeners. Among three IL columns (SLBIL100, SLB-IL82, and SLB-IL76), the number of coelutions increased with the
polarity of the IL stationary phase. Between SLB-IL59 and SLB-IL61, SLB-IL59
showed better performance in the separation of PCBs. Moreover, more symmetrical and narrower peak shapes were obtained with SLB-IL59. The phosphoniumbased IL stationary phases SLB-IL59 and SLB-IL76 performed better compared
to the imidazolium-based IL stationary phases in the separation of PCBs. SLBIL61 containing a triflate anion and the same phosphonium dication as SLBIL59 performed poorly compared to the SLB-IL59. Non-commercial phosphonium ILs with aromatic substituents were shown to be effective in the separation of toxic planar PCBs. A dicationic IL stationary phase, 1,9-bis(diphenylo-tolyl-phosphonium)nonane bis(trifluoromethanesulfonyl)imide, effectively separated twelve tetra- to hepta-chloro-substituted toxic PCB congeners [19]. The same
IL stationary phase also showed a baseline separation of the most toxic 2,3,7,8tetrachlorodibenzodioxin (TCDD) isomer from the other five TCDD isomers when
compared to the commercial SLB-5MS and SP-2331 columns [19].
Polycyclic aromatic compounds (PACs) are common environmental pollutants
comprised of condensed multiring benzenoid compounds [120]. Polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic sulfur heterocycles (PASHs)
are classes of PACs and have carcinogenic and mutagenic activities. Gas chromatography is the preferred technique for the separation and determination of PACs [121].
Many of the PAHs and PASHs are structural isomers, and their chromatographic
separation is essential as they generate the same mass spectra. The structural isomers
can have different toxicities, and their separation is important for quantification.
PASHs are a dominant part of fossil fuel-based pollutants and coal tar. Their analyses are mainly done by using moderate- to nonpolar columns in GC or GC × GC