Shimadzu GCMS PAH-PCB App Note
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Title
Shimadzu GCMS PAH-PCB App Note
Keywords
Shimadzu, GCMS, PAH,-PCB, App, Note
Product Range
*None
Language
UK English
Company Brand
Peak Scientific
Extracted text
Your local gas generation partner
GC-MS/MS analysis pf PAH and
PCB in enviroment samples
Dr Stephan Schroder
Product Specialist GC/GC-MS Shimadzu Germany
The polychlorinated biphenyls (PCB)
and polyaromatic hydrocarbons
(PAH) are among the most commonly
analysed compound classes in
environmental analysis. This article
demonstrates how hydrogen carrier
gas can be used in place of helium
for CC-MS/MS analysis of these
compounds.
Analysis of polyaromatic
hydrocarbons (PAH) is typically
conducted using HPLC with
UV- and fluorescence detection.
Polychlorinated biphenyls (PCB)
are usually analysed using GC-ECD
(electron capture detection). The
analysis run-times are typically
around 30 minutes for HPLC
and 60 minutes for GC methods.
Environmental contaminants such
as PCBs and PAHs are present
in a variety of matrices. These
compounds are usually of industrial
origin and they are typically
monitored in soil, sewage sludge and
drainage water.
Regulations for waste disposal allow
waste class O (non-harmful waste,
mineral waste) to be analysed by
GC-MS according to DIN ISO 18287.
DIN EN 15308 recommends PCB
analysis to be conducted by GC-ECD
or GC-MS. Regulations for disposal
of sludge mandate that there should
be no interference between PCB
101 and o,p'-DDE or a-Endosulphan
as well as PCB 138 and p,p'-DDT.
One critical separation within this
analysis is that of PCB 28 and PCB
31. Otherwise there is no reason why
both classes of compound cannot be
analysed using just one GC analysis.
This would be advantageous since
both analyses combined would offer
much shorter analysis time than two
separate analyses and would result
in reduced costs for the lab user.
Additionally, hydrogen carrier gas can
be used in place of helium, offering
further reduction in time and costs.
Migrating all analyses to GC-MS
obviously requires optimization and
validation of the method.
Here we present a comparison of
the results of individual analyses of
PCBs and PAHs from soil samples
with single-quadrupole GC-MS and
a triple-quadrupole GC-MS (TQ-GC
MS). The use of hydrogen carrier gas
is, however, still a work in progress
for the multiple reaction monitoring
(MRM) optimization for the TQ-GC
MS.
Sample Preparation
Soil samples underwent separate
extraction for PCBs and PAHs and
were mixed 1:1 prior to analysis.
The dilutions for calibration were
prepared in cyclohexane. PAH
samples were prepared according to
technical bulletin number 1 from the
German Federal Environment Agency
NRW (LUA-merkblatt Nr. 1 NRW). For
PCB analysis, the methods in DIN 38
414-20 were followed. For GC-MS/MS
analyses, samples were diluted 1:100
in cyclohexane.
Analysis of the PCB/PAH mixture
Standards of 18 polycylic aromatics
were mixed 1:1. Figure 1 shows the
full-scan chromatogram of the
standard mixture. The requirement
for separation of PCB 28 and PCB 31
(Peaks 10 and 11 in Figures 1 and 2)
were achieved with a resolution of
greater than 0.9.
Samples were analysed using a
Shimadzu GC-MS/MS Triple
Quadrupole. The instrument ran as a
singlequadrupole MS for SIM
detection and as a triple-quadrupole
MS for the MRM analyses with argon
serving as collision gas. A hydrogen
generator from Peak Scientific
(Precision Hydrogen Trace 500cc)
supplied the high-purity carrier gas.
The column used was a Restek
Rxi-XLB (20m x 0.18mm x 0.18 µm).
Samples were injected using pulsedsplitless injection at 150 kPa for 0.5
min into a hot split/splitless inlet
(280 °C). The carrier gas flowed at a
constant linear velocity of 80 cms-1
The oven temperature ramp rate was
set so that the sample could be
separated in around 11 minutes.
Optimization of Multiple Reactions
Monitoring transitions
Calibration curves were established
in the range of 0.5 - SO pg µL-1 for
PCBs and from s - SOD pg µL-1 for
PAHs. Multiple reaction monitoring
transitions for PCB congeners are
relatively simple to optimize owing
to their fragment stability and allow
high sensitivity. Analysis of PAHs
with triple-quadrupole MS detectors
offers only slightly greater sensitivity
than instruments employing SIM
detection owing to the high stability
of the molecule.
Pseudo-MRM transitions have
proven to be advantageous for PAH
analysis. Thereby, the mother and
daughter ions are set to the same
masses in both quadrupole 1 and
quadrupole 3. This results in a double
filtering of the interfering ions. This
double filtering increases sensitivity,
at a collision energy that allows the
target analytes to survive intact
whilst eliminating matrix noise.
The optimization of the collision
energies for pseudo-MRM gave
differing values in standards and
samples. Where S V was the optimal
energy for standard samples, 10V
was found to be optimal in soil
samples. This phenomenon can
only be explained whereby the
higher energy fragments the matrix
components more strongly without
reducing the detector signal. An
increase in collision energy above this
level leads to a reduction in signal
strength of pseudo-MRM transitions
for fluoranthene.
Comparison of real soil samples
A prepared soil sample was analysed
using the traditional methods of
HPLC-UV/Fluorescence and GCECD. The HPLC analysis gave a total
content of PAHs in the sample of
7.71 mg kg-1 . PAH analysis by GC-MS
in SIM mode gave a value of 7.03
mg kg-1 whereas analysis in MRM
mode the content was calculated
to be 8.08 mg kg-1 . Using the GC
MS, simultaneous analysis of the
complete PCB content of samples
could be conducted. Results showed
a content of 31 µg kg-1 detected in
SIM mode and 45 µg kg 1 detected
in MRM, compared with 24 µg kg-1
detected by the GC-ECD.
For PCB components, the GCMS triple quadruple gave better
precision and was even capable of
detecting PCB 28 and PCB 52, which
were undetected using the GC-ECD.
Quantitative analysis showed results
in the same order of magnitude,
however TO -GC-MS detection
was found to give more sensitive
results than GC-ECD detection and
compounds previously below the
limit of detection were detectable
using TO -GC-MS. With a total run
time of 11 minutes, the combined
analysis is at least twice as fast as
classical analyses. Hydrogen carrier
gas gives improved chromatographic
separation at higher linear velocities.
References:
1. Lin, Y.P. Talanta 9/2013, 113:41-48
(x 1 00.000.000)
1,3
1,2
TIC (1,00)
1,1
1,0
0,9
0,8
0,7
0,6
'::'..._rvi
r-
.,...
0,5
;; �';:!
-
�
�
0
N
ffi
!;:'
NM
£::!.._N
;:::;
...
N
.,... "'
"'
C:!-
"' r-
0,4
�
0,3
r
0,2
0,1
3,0
3,5
4,0
4,5
5,0
5,5
6,0
�L----""
6,5
7,0
7,5
8,0
Naphthalene
1-methyl-Naphthalene
2-methyl-Naphthalene
Biphenyl
Acenaphthalene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
PCB 31 (TriCB)
PCB 28 (TriCB)
PCB 52 (TetraCB)
Fluoranthene
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
PCB 101 (PentaCB)
Pyrene
PCB 153 (HexaCB)
PCB 138 (HexaCB)
PCB 180 (HeptaCB)
Benz(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
PCB 209 (DecaCB)
Benzo(a)pyrene
lndeno(l,2,3-cd)pyrene
Dibenz(a,h)anthracene
Benzo(ghi)perylene
�
..
T
0,0
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
8,5
9,0
I'-'---
9,5 10,0 10,5
Figure 1. Gas chromatogram of PCB and PAH standard mixture at a concentration of 5 ng µ1- 1
per component. The full list of compounds can be seen on the right.
8,0
7,0
6,0
(x 1.000.000)
(x 10.000)
4,5
256,00 > 186,00
258,00 > 185,90
4,0
3,5
3,0
5,0
2,5
4,0
2,0
3,0
2,0
1,0
0,0
202, 10 > 199,90
202, 10 > 202, 10
6,30
6,35
6,40
)
1,5
1,0
0,5
6,45
6,50
Figure 2. The critical separation of PCB 28 and PCB 31 achieved
with the MRM. Compound concentration on column was 5 pg.
Chromatographic resolution between peaks was R> 0.94 min.
6,55
6,60
10,8 10,9
11,0
11,1
11,2
11,3
Figure 3. MRM signal for Fluoranthen. The
pseudo-transition 202.1>202.1 (red) shows
a better sensitivity than the SRM transition
202.1>199.9 (black).