The availability of different columns played an important role in multiresidue
separation in one single injection. However, the reversed phase (RP) C18 and C8
columns are dominantly used for pharmaceutical separation for LC [72, 197], while
fused silica capillary and DB5 columns are commonly used for GC [80, 92].
For GC-MS, helium is always used as carrier gas, and 1–2 μL of samples are
injected in split/splitless mode, while the column temperature is programmed from
50 to 300
C, EI ionization temperature is between 200 and 250
C, and finally the
standard ionization energy of 70 eV is always used. The traditional ionization mode,
electronic impact (EI), was always used as ionization source coupled with GC.
LC chromatography techniques are available as high-performance LC (HPLC)
and ultrahigh-performance LC (UHPLC). The latter has a higher sensitivity with 2–3
orders of magnitude compared to HPLC, since it uses columns with particles of
smaller dimensions (<2 μm), with consequent better chromatographic separation,
better resolution, narrow peak shapes, and a reduced chromatographic run. However,
UHPLC is used in only a few numbers of studies [53, 77, 95, 154, 159]. The
composition of the mobile phase is an equally important factor for obtaining good
ionization and separation efficiencies, reproducible retention times, and peak shapes
[198]. Generally, the methanol/water or acetonitrile/water mixtures, at different pH
values, are commonly used for the separation of pharmaceutical products under
gradient elution. For better ionization and separation of pharmaceutical products,
some modifiers are added to the mobile phases. Formic acid, acetic acid, ammonium
acetate, and ammonium formate are the modifiers commonly used in the positive/
negative ionization modes [58, 74].
When the mass spectrometer is coupled to LC, electrospray ionization (ESI) is
always the most used ionization source for PhACs. It is a soft atmospheric ionization
technique, easily coupled to LC. The analytes are dissolved in an organic solvent and
introduced into the ionization chamber through a fine needle in the form of a spray. A
high electrical potential is applied to the needle, resulting in the formation of charged
droplets. The droplets are then vaporized by introducing neutral gas (generally
nitrogen). Under these conditions, the charged droplets decrease in size as they
move inside the source, the droplet of the solvent evaporates, and the charged
analytes pass through the ionization chamber toward the analyzer. Therefore, ESI
is the atmospheric pressure ionization technique mostly preferred and used since it is
excellent with polar and non-polar compounds and for compounds with low thermal
stability [199].
Advances and developments in mass spectrometry allow the detection of pharmaceutical by target analysis (using reference standards) with consequent quantification at the trace and ultra-trace levels or by providing the possibility to perform
suspect or non-target screening. Additionally, the use of tandem MS/MS offers
higher specificity, provided with MS
2 of compounds, thus reducing co-elution
problems of matrix interferences. Therefore, it is preferred in the analysis of solid
complex matrices. Mass spectrometers with single (MS) or multiple analyzers
(MS/MS tandem) are both highly used. Single quadrupole (Q) [54], Orbitrap [74],
and ion trap (IT) [59] are used as single MS, while triple quadrupole (QqQ) [58],
quadrupole-time of flight (QTOF) [123, 156], and triple quadrupole-linear ion trap
Development of Methods for the Determination of PhACs in Soil/Earthworm/Crop. . .
477
separation in one single injection. However, the reversed phase (RP) C18 and C8
columns are dominantly used for pharmaceutical separation for LC [72, 197], while
fused silica capillary and DB5 columns are commonly used for GC [80, 92].
For GC-MS, helium is always used as carrier gas, and 1–2 μL of samples are
injected in split/splitless mode, while the column temperature is programmed from
50 to 300
C, EI ionization temperature is between 200 and 250
C, and finally the
standard ionization energy of 70 eV is always used. The traditional ionization mode,
electronic impact (EI), was always used as ionization source coupled with GC.
LC chromatography techniques are available as high-performance LC (HPLC)
and ultrahigh-performance LC (UHPLC). The latter has a higher sensitivity with 2–3
orders of magnitude compared to HPLC, since it uses columns with particles of
smaller dimensions (<2 μm), with consequent better chromatographic separation,
better resolution, narrow peak shapes, and a reduced chromatographic run. However,
UHPLC is used in only a few numbers of studies [53, 77, 95, 154, 159]. The
composition of the mobile phase is an equally important factor for obtaining good
ionization and separation efficiencies, reproducible retention times, and peak shapes
[198]. Generally, the methanol/water or acetonitrile/water mixtures, at different pH
values, are commonly used for the separation of pharmaceutical products under
gradient elution. For better ionization and separation of pharmaceutical products,
some modifiers are added to the mobile phases. Formic acid, acetic acid, ammonium
acetate, and ammonium formate are the modifiers commonly used in the positive/
negative ionization modes [58, 74].
When the mass spectrometer is coupled to LC, electrospray ionization (ESI) is
always the most used ionization source for PhACs. It is a soft atmospheric ionization
technique, easily coupled to LC. The analytes are dissolved in an organic solvent and
introduced into the ionization chamber through a fine needle in the form of a spray. A
high electrical potential is applied to the needle, resulting in the formation of charged
droplets. The droplets are then vaporized by introducing neutral gas (generally
nitrogen). Under these conditions, the charged droplets decrease in size as they
move inside the source, the droplet of the solvent evaporates, and the charged
analytes pass through the ionization chamber toward the analyzer. Therefore, ESI
is the atmospheric pressure ionization technique mostly preferred and used since it is
excellent with polar and non-polar compounds and for compounds with low thermal
stability [199].
Advances and developments in mass spectrometry allow the detection of pharmaceutical by target analysis (using reference standards) with consequent quantification at the trace and ultra-trace levels or by providing the possibility to perform
suspect or non-target screening. Additionally, the use of tandem MS/MS offers
higher specificity, provided with MS
2 of compounds, thus reducing co-elution
problems of matrix interferences. Therefore, it is preferred in the analysis of solid
complex matrices. Mass spectrometers with single (MS) or multiple analyzers
(MS/MS tandem) are both highly used. Single quadrupole (Q) [54], Orbitrap [74],
and ion trap (IT) [59] are used as single MS, while triple quadrupole (QqQ) [58],
quadrupole-time of flight (QTOF) [123, 156], and triple quadrupole-linear ion trap
Development of Methods for the Determination of PhACs in Soil/Earthworm/Crop. . .
477