2
Sample Preparation
Herbal and tea samples were extracted with an
accelerated solvent extraction method using the
Thermo Scientific Dionex ASE 350 Accelerated Solvent
Extractor. The ASE method used is described in an official
pesticide standard method [3]. The collected extracts were
concentrated using a rotary evaporator (Rotavap) and
further cleaned up via gel permeation chromatography
(GPC). The GPC step used a polystyrene gel
(Bio-Beads
®
S-X3) with an ethylacetate/cyclohexane
mobile phase. After additional concentration by the
Rotavap, the extracts were ready for GC injection using
ethylacetate as the main solvent.
Method Setup
The analytical method comprised sample handling and
injection using the Thermo Scientific TriPlus RSH liquid
autosampler, TRACE GC 1310 gas chromatograph
equipped with an instant connect, temperature
programmable PTV injection system, and the TSQ
™
8000
triple quadrupole GC-MS/MS detection system. The MRM
detection method was taken from a routinely employed
Thermo Scientific TSQ Quantum XLS GC-MS/MS
method without any further optimization on the
TSQ 8000 GC-MS/MS system [4]. The TSQ 8000 system
automatically optimized acquisition windows and
optimized instrument duty cycle using timed-SRM
(t-SRM) for maximum sensitivity. This enabled the
avoidance of lengthy manual set-ups usually required
when adopting new instrumentation (Figure 1).
ASE
™
350 Accelerated Solvent Extraction
Sample weight
10 g
Extraction solvent
Ethylacetate/cyclo-Hexane 1:1,
same as GPC solvent
Temperature
120 °C
Pressure
100 bar
Extraction time
5 min, 1 cycle
Flushing with solvent
60% of cell volume
Flushing with nitrogen
100 s
TriPlus
™
RSH Autosampler
Syringe
10 µL
Injection volume
1 µL
Injection type
Fast liquid band injection,
100 ms injection time
Washing cycles
3 x 10 µL, solvent ethylacetate
TRACE
™
1310 Gas Chromatograph
Injector PTV
Splitless mode
Base temperature
50 °C
Transfer
10 °C/s to 250 °C, until end of run
Flow
Constant flow, 1.2 mL/min, helium
Analytical column
40 m, ID 0.18 mm, 0.18 µm film,
5%-phenyl phase (5MS type)
Pre-column
5 m, ID 0.18 mm, empty deactivated,
no backflush
Column oven
Temperature programmed
Start
70 °C, for 1.50 min
Ramp 1
15 °C/min to 190 °C
Ramp 2
7 °C/min to 290 °C, 12 min
Transfer line
250 °C
TSQ 8000 Mass Spectrometer
Ion source temperature
220 °C
MRM Detection
Timed SRM mode (see Appendix)
Figure 1. Screenshot of a section of the analytical run showing the “acquisition map” automatically created by the TSQ 8000 system
using t-SRM. This mode ensures the instrument only monitors for compounds when they elute to optimize sensitivity.
