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advantage@restek.com15
Figure 2:
The Rxi®-PAH column separates isobaric PAHs,
allowing unbiased quantification of critical compounds
that coelute on most GC columns.
1,020
1,030
1,040
1,050
1,060
Time (sec)
= m/z 228
= m/z 226
1
2
3
4
1,020
1,030
1,040
1,050
1,060
Time (sec)
= m/z 228
= m/z 226
1
2
3
4
among the most difficult PAHs to separate. Other notable PAHs that
coelute on most GC columns include benzo[b]fluoranthene/benzo[j]
fluoranthene and dibenz[a,c]anthracene/dibenz[a,h]anthracene; all
these compounds were separated and accurately reported using an
Rxi®-PAH column and the Restek® methodology described here.
Visit
www.restek.com/ADV1514for a complete presentation of
the data summarized here.
References
[1] A.P. Dasanayake, A.J. Silverman, S. Warnakulasuriya,
Mate Drinking and Oral and Oro-pharyngeal
Cancer: A Systematic Review and Meta-analysis,
Oral Oncol 46 (2010) 82.
[2] D. Loria, E. Barrios, R. Zanetti,
Cancer and Yerba Mate Consumption: A Review of Possible
Associations,
Rev Panam Salud Publica 25 (2009) 530.
Fast, Simple Sample Preparation
for PAHs in Mate Tea
Modified QuEChERS Extraction
1. Homogenize dry tea into a powder.
2. Soak 1 g tea powder in 10 mL water for 10 min in an FEP centrifuge tube.
3. Add 10 mL hexane:acetone (1:1) and vortex 30 min.
4. Add Q-sep® QuEChERS unbuffered salts (cat.# 23991), shake 1 min, and then spin for
5 min in a Q-sep® 3000 centrifuge.
5. Evaporate 2 mL of extract down to 1 mL, then adjust final volume to 2 mL with hexane.
Perform this step twice.
Silica SPE Cleanup
1. Rinse Resprep® SPE cartridges (3 mL, 0.5 g silica; cat.# 24036) with 3 mL methanol
followed by 3 mL acetone.
2. Condition cartridges with 3 mL hexane:methylene chloride (1:1), followed by 6 mL hexane.
3. Load 1 mL of extract onto cartridge and elute with 5 mL hexane:methylene chloride (7:3).
4. Evaporate to 1 mL.
Figure 1:
Chlorophyll and other nonvolatiles will quickly
foul GC inlets and columns, but they can be removed eas-
ily and reliably with this modified QuEChERS method.
After Cleanup
Before Cleanup
Report more accurate results with the
separating power of an Rxi®-PAH column.
Table I:
The simplified PAH method developed by Restek
produced good quantitative results for both fortified and
unfortified tea samples.
PAH
% Recovery
(500 ng/g
Fortified Tea)
Unfortified Tea
Sample (ng/g)
Naphthalene
90
93
Acenaphthylene
110
42
Acenaphthene
99
8
Fluorene
110
25
Phenanthrene
81
540
Anthracene
130
58
Fluoranthene
72
270
Pyrene
74
290
Benzo[c]phenanthrene
75
14
Benz[a]anthracene
81
66
Triphenylene
80
28
Chrysene
82
120
5-Methylchrysene
76
ND
Benzo[b]fluoranthene
92
49
Benzo[k]fluoranthene
96
21
Benzo[j]fluoranthene
89
25
Benzo[a]fluoranthene
97
11
Benzo[e]pyrene
89
44
Benzo[a]pyrene
100
55
Perylene
94
14
Dibenz[a,c]anthracene
100
7
Indeno[1,2,3-cd]pyrene
110
52
Dibenz[a,h]anthracene
98
12
Benzo[ghi]perylene
88
94
Dibenzo[a,e]pyrene
93
ND
Coronene
86
130
ND = not detected
Peaks
t
R
(sec)
1. Benz[a]anthracene
1,028.4
2. Cyclopenta[cd]pyrene 1,044.0
3. Triphenylene
1,050.0
4. Chrysene
1,054.8
1,400
1,420
1,440
1,460
1,480
Time (sec)
= m/z 252
1,500
1
2
3
4
5
6
7
Benzofluoranthenes
[b]
[k}
[j]
Column
: Rxi®-PAH, 60 m, 0.25 mm ID, 0.10 µm (cat.#
49317);
Injection:
Inj. Vol.: 2.5 µL splitless (hold 1 min);
Liner: Sky® 4 mm single taper w/wool (cat.# 23303.5);
Inj. Temp.: 275 °C; Purge Flow: 40 mL/min;
Oven:
Oven
Temp.: 80 °C (hold 1 min) to 210 °C at 40 °C/min to 260
°C at 3 °C/min to 350 °C at 11.5 °C/min (hold 6.25 min);
Carrier Gas
: H
2
, constant flow; Flow Rate: 2.4 mL/min;
Detector:
TOFMS; Transfer Line Temp.: 320 °C; Analyzer
Type: TOF; Source Temp.: 300 °C; Electron Energy: 70 eV;
Mass Defect: 0 mu/100 u; Solvent Delay; Time: 3.67 min;
Tune Type: PFTBA; Ionization Mode: EI; Acquisition Range:
45-550 amu; Spectral Acquisition Rate: 5 spectra/sec;
Instrument:
LECO Pegasus 4D GCxGC-TOFMS
GC_FF1244
GC_FF1245