AI10382-GC-MS-Food Safety-Analysis - page 150

The collision cell (Q2) gas pressure and collision
energy were optimized for PCDD/F measurement. The
monitored SRM transitions as well as the GC conditions
are given below in Table 3.
The results of the GC-MS/MS measurements were
compared with routine GC-HRMS measurements using
the DFS High Resolution MS (Thermo Scientific, Bremen,
Germany).
Results and Discussion
Selectivity, Sensitivity and Quantitative Performance
In order for a screening technique to be truly efficient it
needs to be able to perform at a level that closely
correlates with high resolution confirmatory techniques.
The first prerequisite of any such technique is sensitivity
and selectivity. Figure 2 shows an overlay of 2,3,7,8-TCDD
target ions for five injections of a mixed animal fat sample
at 0.13 pg/g fat. The sensitivity and selectivity obtained
was high enough to allow comfortable, precise detection
with all ion ratio integrity maintained. Figure 3 shows
overlay of 1,2,3,7,8-PeCDF (0.4 ng/kg 88% dry weight)
and 2,3,4,7,8-PeCDF (3.4 ng/kg 88% dry weight) for four
injections of grass meal (animal feed) sample. Figure 4
shown native PCDD/Fs SRM chromatograms for the
bottom calibration level for this methodology.
PTV Injection (PCDD/Fs)
Injected Volume 5 µL (toluene)
Injection Speed 5 µL/s
Liner Open Silcosteel® liner (Restek ®)
Injection Temperature 100 °C
Vent Flow 20 mL/min
Transfer Rate 13.3 °C/s
Final Transfer Temperature 340 °C
GC Programme (PCDD/Fs)
GC Column DB-5MS (60 m, 0.25 µm, 0.25 mm)
Initial Temperature 120 °C
Rate 1 17 °C/min to 250 °C
Rate 2 2.5 °C/min to 285 °C
Final Temperature 285 °C for 13 min
Table 4: GC and injector conditions
PCDD/F Precursor Product
TCDF 303.90 240.94
TCDF 305.90 242.94
13C TCDF ISTD 315.94 251.97
13C TCDF ISTD 317.94 253.97
TCDD 319.90 256.90
TCDD 321.89 258.89
13C TCDD ISTD 331.94 267.97
13C TCDD ISTD 333.93 269.97
PeCDF 339.86 276.90
PeCDF 341.86 278.89
13C PeCDF ISTD 351.90 287.93
13C PeCDF ISTD 353.90 289.93
PeCDD 355.85 292.85
PeCDD 357.85 294.85
13C PeCDD ISTD 367.90 303.90
13C PeCDD ISTD 369.89 305.89
HxCDF 371.82 308.86
HxCDF 373.82 310.86
13C HxCDF ISTD 383.86 319.90
13C HxCDF ISTD 385.86 321.89
HxCDD 387.82 324.82
HxCDD 389.82 326.82
13C HxCDD ISTD 399.86 335.86
13C HxCDD ISTD 401.86 337.86
HpCDF 407.78 344.82
HpCDF 409.78 346.82
13C HpCDF ISTD 419.82 355.86
13C HpCDF ISTD 421.82 357.85
HpCDD 423.78 360.78
HpCDD 425.77 362.77
13C HpCDD ISTD 435.82 371.82
13C HpCDD ISTD 437.81 373.81
OCDF 441.76 378.80
OCDF 443.76 380.79
13C OCDF ISTD 453.78 389.82
13C OCDF ISTD 455.78 391.81
OCDD 457.74 394.74
OCDD 459.74 396.74
13C OCDD ISTD 469.78 405.78
13C OCDD ISTD 471.78 407.78
Table 3: Target congener groups SRM transitions
Figure 2: Overlay of 2,3,7,8-TCDD target ions for five injections of a mixed
animal fat sample at 0.13 pg 2,3,7,8-TCDD/g fat. 12% CV was achieved on
the real calculated amount.