8 / 302
4
Compund CAS Number
Formula
Molecular
Weight
Chemical Structure
Tefluthrin
79538-32-2
C
17
H
14
ClF
7
O
2
418.7
Terbufos
13071-79-9
C
9
H
21
O
2
PS
3
288.4
Terbutryn
886-50-0
C
10
H
19
N
5
S
241.3
Trichlorfon
66758-31-4
C
4
H
8
Cl
3
O
4
P
257.4
Direct Analysis in Real Time (DART)
A DART source with a Standardized Voltage and Pressure
(SVP) controller (IonSense
™
, MA, USA) was used as the
ionization source. The ionization mechanism in DART is
Penning ionization.
8
It relies upon fundamental principles
of atmospheric pressure chemical ionization (APCI).
Excited-state helium atoms produce reactive species for
analyte ionization.
1
Figure 1 shows a schematic diagram
of DART technology.
The operating temperature range of the DART-SVP source
is 50–500 °C, and the optimal temperature for the studied
compounds was found to be 300 °C. The ionization and
instrumental analysis time was set to 30 sec. The DART
operating conditions are summarized in Table 2.
Figure 1. DART technology
Samples were loaded onto a strip that contained 10 spots
for sample deposition. Each sample was individually
deposited on a metal mesh and allowed to dry before the
strip was fitted on the DART source. The strip was then
set to run and each sample was presented in front of the
mass spectrometer for analysis. Hot helium gas flowed
through the sample/mesh, ionizing the sample by an
atmospheric pressure chemical ionization (APCI) -like
mechanism.