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E. Apparatus and Conditions
(
a
)
GC-MS analysis.—
(
1
)
GC-MS system
.—Model 7890A gas chromatograph connected to a Model 5975C
mass selective detector with electron ionization (EI) source and equipped with a Model 7683
autosampler and Chemstation data processing software system (Agilent Technologies, Wilmington, DE,
USA), or equivalent.
(
2
)
Column
.--DB-1701 capillary column (30 m × 0.25 mm × 0.25 μm), or equivalent.
(
3
)
Column temperature
.—40°C hold 1 min, at 30°C/min to 130°C, at 5°C/min to 250°C, at 10°C/min to
300°C, hold 5 min.
(
4
)
Carrier gas
.--Helium, purity ≥99.999%, flow rate 1.2 mL/min.
(
5
)
Injection port temperature
.--290°C.
(
6
)
Injection volume
.--1 μL.
(
7
)
Injection mode
.--Splitless, purge on after 1.5 min.
(
8
)
Ionization mode
.—EI.
(
9
)
Ion source polarity
.--Positive ion.
(
10
)
Ionization voltage
.--70 eV.
(
11
)
Ion source temperature
.--230°C.
(
12
)
GC-MS interface temperature
.--280°C.
(
13
)
Solvent delay
.--14 min.
(
14
)
Ion monitoring mode
.--Selected ion monitoring (SIM), one quantifying ion and two qualifying ions
are selected for each compound. The retention times, quantifying ions, qualifying ions, and the expected
ion abundances for each of the 20 pesticides included in the study and heptachlor epoxide are listed in
Table
2014.09A
. SIM acquisition parameters for ions monitored by GC-MS are shown in Table
2014.09B
.
(
b
)
GC-MS/MS analysis.--
(
1
)
GC-MS/MS system
.—Model 7890A gas chromatograph connected to a
Model 7000B triple quadrupole mass spectrometer with EI source and equipped with a Model 7693
autosampler and Mass Hunter data processing software system (Agilent Technologies), or equivalent.
(
2
) Operating conditions are the same as for GC-MS with the exception that the ion monitoring mode is
by selected reaction monitoring (SRM) and monitoring one precursor ion and two product ion
transitions.
(
3
) The monitored ion transitions and the collision energies for the 20 pesticides of interest in the study
and heptachlor epoxide are shown in Table
2014.09C
. The SRM acquisition partameters for the precursor
Candidates for 2016 Method of the Year
275