4
Broad Scope Pesticide Screening in Food Using Triple Quadrupole GC-MS
ides in lettuce matrix during the
he compounds was R
2
> 0.98.
eFinder™ software. Ten
alyzed. To test screening
he 40 ppb spike which had not
gh the use of this method.
andard are given in Table 2.
s of the compounds in the 40
alibration. This demonstrates
targeted compounds in
A second method was generated that targeted only the 52 compounds and contained
only 104 transitions. Ten replicates of a 5 ppb and 10 ppb standard were analyzed to
determine the MDLs for the two instrument methods, one with 1300+ transitions, and
the other containing only 104 transitions. The results of compounds with MRLs for
lettuce are shown in Figure 3. Although lower detection limits result from longer dwell
times in the method with 104 transitions, the screening method that scans for 600
compounds is still capable of reaching the limits in lettuce set by the EU for the
compounds requiring a targeted analysis in our list.
ix.
FIGURE 2. Pesticides Identified by Ion Ratio Not in the Targeted Calibration
Curve. First Peak is the Quan Peak, and the Others are for Confirmation.
FIGURE 5. Close-up View o
was performed using the
. After retention times were
lected reaction monitoring
single injection. Over 1,300
8000 Pesticide Analyzer
th the processing and
hod Synch. The transfer line
Figure 1 demonstrates timed-
pesticides and provides for
Avg %RSD
35.1
6.0
45.5
9.8
62.4
4.4
45.6
3.5
47.2
9.2
43.9
2.3
47.1
2.9
38.8
8.3
58.7
4.0
46.2
6.0
41.4
4.6
e
42.6
2.0
26.6 16.5
55.9
6.5
40.2
1.7
eak 1
43.7 18.5
eak 2
49.3
6.0
46.9
2.1
39.0
1.4
37.5 15.3
62.8
6.0
52.3
7.0
49.6
9.9
46.7
4.3
48.5 14.3
58.6
4.3
FIGURE 3. Comparison of MDLs: 52 Compounds vs. 600 Compounds.
0
20
40
60
80
100
Bendiocarb
Isoprocarb
Oxadixyl
Acibenzolar-S-methyl
Fenamidone
Spiromesifen
Benalaxyl
Carbaryl
Diethofencarb
Ethofumesate
Flonicamid
Fuberidazol
Propham
Pyrimethanil
Methiocarb
Triflumizole
Pirimicarb
Parts per billion
50 Pesticides Method
LOD
600 Pesticides Method
LOD
EU MRL
Method 2 – Alternating SRM/FS
Sample Preparation and Gas Chromatography
The sample preparation and GC parameters remained the same as in the first study.
Mass Spectrometry
The scanning of 147 compounds was performed using the TSQ 8000 triple
quadrupole MS. After retention times were determined in full scan, a timed-SRM
method using selected reaction monitoring (SRM) was constructed to analyze all
147 compounds in a single injection. A second method was constructed, adding full
scan to the analysis.
Results
A sample of fruit drink was ex
cleanup. The extract was co
extract to produce calibration
were constructed using Trac
SRM/full scan for 147 pestici
0.98 for both methods of anal
fruit juice extract were analyz
methods, SRM only and alter
methods are shown in Figure
the instrument method, but v
FIGURE 4. Comparison of
Fruit drink was spiked at 100
This extract was also spiked
chromatogram shows several
retention times of 9.29, 9.73,
minutes. A close-up view of t
displays the NIST library mat
3-Hydroxycarbofuran
Dicrotophos
Improvalicarb
Myclobutanil
