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4
Results and Discussion
Sensitivity for PCDD/F Analysis
The prerequisites for a technique to be applicable to low
level PCDD/F determinations is sensitivity and selectivity.
The concentration levels where these substances are
required to be measured often exceed the performance
capability of bench-top GC-MS systems. In order to test
the sensitivity of the TSQ Quantum XLS Ultra for this
application, a serial dilution of commonly used EPA
1613B CS1 standard was performed, and increasingly
low levels were injected onto the system. The limit of
detection (LOD) was then calculated using statistical
methods. Figure 2 shows the lowest level CS1 dilution
(x10 – vial concentrations given in Table 4) used for this
study. Quantitative SRM ions are clearly detected along
with the confirmatory SRM ions for all PCDD/Fs tested
within the QC ion ratio criteria. Precision studies at this
level enabled an LOD to be calculated for the methodology.
Table 4 gives the precision data obtained and calculated
LOD at 99 % confidence limits. The LOD obtained from
the TSQ Quantum XLS Ultra was found at a level that is
highly applicable for environmental dioxins analysis in a
range of sample types.
Table 4. Instrumental LOD (pg/µL) given to 2 d.p. (99% confidence) and
precision data (n=10) for PCDD/Fs from GC-MS/MS analysis of a ten times
diluted EPA 1613 CS1.
Figure 2. SRM chromatograms of PCDD/Fs after injection of a 10x diluted EPA1613B CS1 standard. (TCDD/F 0.05 pg/µL, PeCDD/F thru HpCDD/F 0.25 pg/µL,
OCDD/F 0.5 pg/µL)
Concentration
pg/µL
RSD
%
LOD
(99)
pg/µL
2,3,7,8 TCDF
0.05
6.2
0.01
2,3,7,8 TCDD
0.05
11.1
0.01
1,2,3,7,8 PeCDF
0.25
6.0
0.03
2,3,4,7,8-PeCDF
0.25
4.6
0.03
1,2,3,7,8 PeCDD
0.25
9.2
0.05
1,2,3,4,7,8-HxCDF
0.25
7.7
0.04
1,2,3,6,7,8-HxCDF
0.25
4.7
0.03
2,3,4,6,7,8-HxCDF
0.25
4.1
0.02
1,2,3,4,7,8-HxCDD
0.25
7.7
0.04
1,2,3,6,7,8-HxCDD
0.25
6.1
0.03
1,2,3,7,8,9-HxCDD
0.25
5.0
0.03
1,2,3,7,8,9-HxCDF
0.25
4.9
0.03
1,2,3,4,6,7,8-HpCDF
0.25
5.2
0.03
1,2,3,4,6,7,8-HpCDD
0.25
6.8
0.04
1,2,3,4,7,8,9-HpCDF
0.25
5.7
0.03
OCDD
0.5
7.9
0.09
OCDF
0.5
4.8
0.05
32.5 33.0 33.5 34.0 34.5 35.0
40.0
41.0
42.0
43.0
36.0 36.5 37.0 37.5 38.0
39.0
38.5
39.5
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
44.0
45.0
46.0
47.0
48.0 49.5
50.5
51.5
52.5
53.5
TCDD/F
HxCDD/F
HpCDD/F
PeCDD/F
OCDD/F
Minutes
Minutes
Minutes
RT: 46.79
RT: 32.70
303.90 > 240.94
305.90 > 242.94
331.94 > 267.97
333.93 > 269.97
371.82 > 308.86
373.82 > 310.86
387.82 > 324.86
389.82 > 326.85
351.90 > 287.93
353.90 > 289.93
367.90 > 303.93
369.89 > 305.89
407.78 > 344.82
441.76 > 378.80
443.76 > 380.79
457.74 > 394.77
459.74 > 396.77
409.78 > 346.82
423.78 > 360.81
425.77 > 362.81
RT: 32.70
RT: 33.31
RT: 33.31
RT: 36.37
RT: 37.30
RT: 36.67
RT: 36.63
RT: 37.30
RT: 37.59
RT: 37.59
RT: 40.29
RT: 41.08
RT: 42.15
RT: 40.44
RT: 41.08
RT: 42.16
RT: 41.27
RT: 41.72
RT: 41.38
RT: 41.72
RT: 44.17
RT: 44.17
RT: 46.79
RT: 45.88
RT: 45.88
RT: 52.05
RT: 52.04
RT: 51.65
RT: 51.66