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Example dSPE Cleanup: PAHs in Infant Formula
Analyzing polycyclic aromatic hydrocarbons (PAHs) in infant formula can be difficult as both the target
analytes and certain matrix elements are lipophilic in nature and difficult to separate. Proper sorbent
choice is critical to removing matrix interferences, while assuring good PAH recoveries. When choos-
ing a sorbent, target analyte and matrix component chemistry must be considered. PAHs are relatively
nonpolar, planar compounds with no pH-dependent functional groups. Infant formula typically contains
significant amount of sugars and can be fortified with fatty acids.
Here, PSA was chosen for dSPE cleanup since both sugars and fatty acids can be removed through hydro-
gen bonding. Using PSA to remove these matrix compounds is optimal, because it will not bind to the
relatively nonpolar PAHs, thus ensuring they remain available for analysis. GCB is not recommended
here because it also can bind planar PAHs. (Note: GCB is not needed since infant formula does not con-
tain pigments.) Based on the chemical structure of the analytes of interest, as well as the most dominant
matrix compounds, PSA is the best choice when analyzing PAHs in infant formula.
Chrysene
Phenanthrene
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visit
www.restek.com/quechersFigure 3:
PSA is ideal for removing matrix sugars and fatty acids, while leaving PAHs behind for analysis.
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14 Time(min)
Scan Mode
A. Q-sep™ QuEChERS cleanup
B. No extract cleanup
GC_FF01122
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18 19 20
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Compound list and ions monitored (SIMmode)
Compound
m/z
1. decafluorobiphenyl (SS)
265
2. Naphthalene
128
3. 2-Methylnaphthalene
142
4. 1-Methylnaphthalene
142
5. Acenaphthylene
152
6. Acenaphthene
152
7. Fluorene
166
8. Phenanthrene-d10 (IS)
188
9. Phenanthrene
178
10. Anthracene
178
11. Fluoranthene
202
12. Pyrene
202
13. Benzo[a]anthracene
228
14. Chrysene
228
15. Benzo[b]fluoranthene
252
16. Benzo[k]fluoranthene
252
17. Benzo[a]pyrene
252
18. Indeno[1,2,3-cd]pyrene
276
19. Dibenz[a,h]anthracene
278
20. Benzo[ghi]perylene
276
Q-sep™ QuEChERS
cleanup SIM Mode
Scan Mode
B. No extract cleanup
A. Q-sep™ QuEChERS cleanup
GC_FF01123
Column
Rxi®-5Sil MS, 30 m, 0.25 mm ID, 0.25 μm (cat.# 13623)
Sample
See notes
Injection
Inj. Vol.:
1 μL splitless (hold 0.15 min)
Liner:
3.5 mm Gooseneck Splitless w/Wool (cat.# 22286-200.1)
Inj. Temp.:
300 °C
Oven
Oven Temp: 50 °C (hold 0.5 min) to 290 °C at 25 °C/min to 320 °C at
5 °C/min (hold 5 min)
Carrier Gas
He, constant flow
Flow Rate:
1.4 mL/min
Detector
MS
Mode:
Scan
Transfer Line Temp.: 290 °C
Analyzer Type:
Quadrupole
Ionization Mode:
EI
Scan Range:
100-350 amu
Instrument
Shimadzu 2010 GC & QP2010+ MS
Notes
Sample Details:
Liquid infant formula spiked at 1 μg/mL with decafluorobiphenyl (cat.#
31842) and EPA Method 8310 PAH mixture (cat.# 31841) and at 0.5
μg/mL with internal standard phenanthrene-d10 (cat.# 31045), then
extracted with acetonitrile and Q-sep™ QuEChERS extraction salts.
A. Extract with cleanup using Q-sep™ QuEChERS dSPE cleanup tube
(cat.# 26215)
B. Extract without dSPE cleanup