Determination of Polycyclic Aromatic Hydrocarbons (PAH) in Food with GC-MS/MS

Transcription

1 Determination of Polycyclic Aromatic Hydrocarbons (PAH) in Food with GC-MS/MS Thorsten Bernsmann, Peter Fürst Chemical and Veterinary Analytical Institute Münsterland-Emscher-Lippe Joseph-König-Str. 40, Münster/Germany 24 th CRC; Melbourne

2 Outline background/ legislation sample preparation GC-MSD versus GC-MS/MS / PAH source results conclusion / 2

3 EU data collection on PAH in food PAH concentration (µg/kg) in 9,714 food products PAH N >LOD Concentration in µg/kg P05 Median Mean P95 Maximum LB UB LB UB LB UB LB UB LB UB BaP % BaA % BbFA % BkFA % BghiP % CHR % DBahA % IP % BjFA % CPP % DBaeP % DBahP % DBaiP % DBalP % MCH % BcFL % / 3

4 Opinion on PAH of the European Food Safety Authority (EFSA) Opinion on PAH in food adopted on 9 June In this opinion EFSA concluded that benzo[a]pyrene is not a suitable marker for the occurrence of PAH in food and that a system of four specific PAH would be the most suitable indicators of PAH in food. Benz[a]anthracene Benzo[b]fluoranthene Benzo[a]pyrene Chrysene / 4

5 EU maximum levels for PAH in food Regulation (EC) No 1881/2006 (EC No 835/2011) / 5

6 Requirements for PAH analysis: Regulation (EC) No 333/2007 (836/2011) / 6

7 Performance criteria for methods of analysis for PAH: Regulation (EC) 333/2007 (836/2011) table 7 METHOD VALIDATION AND QUALITY CONTROL PROCEDURES FOR PESTICIDE RESIDUES ANALYSIS IN FOOD AND FEED SANCO/12495/2011 Limit of detection (LOD) will be defined by the lowest trace / 7

8 Determination of PAH Nowadays there are the two main analytical techniques to determine PAH in foods: HPLC FLD GC-MS They are sticky, not active Difficult to vaporize and keep from depositing high temperatures are important Minimize surface contact Tailing peaks Subject to desublimation (deposition) LODs and recoveries for PAH are compound, food matrix and method dependent. The LODs for PAH typically range from 0.1 to 1 µg/kg / 8

9 Method used at the * * German Research Foundation 2 g fat or 2-4 g solid food matrix extraction and saponification with potassium hydroxide in methanol liquid/liquid extraction with cyclohexane liquid/liquid extraction with dimethylformamide liquid/liquid extraction: dimethylformamid + NaCl + water/ cyclohexane Other method: Clean up with florisil, phenyl-spe MIP(molecule imprinted polymer) -SPE GPC silica gel clean up / 9

10 GC-MS/MS Method 7890 / 7000B GC-MS/MS System / 10

11 GC- Configuration for PAH 2 ul splitless injection Multi Mode Inlet 7000B TQ 30 m x 0.25 mm ID x 0.15 µm Agilent Select PAH Helium MS-Tee 2.0 ml/min Constant flow 7890A Option: Select PAH 15 m x 0.15 mm ID (0,10 µm) note: temperature between 180 and 230 C is important for the separation Inlet temp program : 80 (0.5) 400 C/min 330 C! Oven temp program : 80 (0.5) (0) 40 C/min 180 (0) 3 C/min 280(0) 330 (10) C / 11

12 PAH product ion scan Benzo(b)fluoranthene CID CID CID CID V30 V V PAH were destroyed only by high CE energy not enough product ions with a necessary response use of [M]+ as precursor and quantifier: [M]+ -> [M]+ [M]+ -> [M-2]+ as qualifier ion the collision energy is used to destroy matrix/interfering ions M+ M-2 M / 12

13 Compounds /Triphenylene / 13

14 Multiple reaction monitoring (MRM) EI: 70 ev; Dwell 50 msec.; Q1 and Q2 resolution: unit / 14 [M]+ -> [M]+ [M]+ -> [M-2]+

15 How does it work? Comparison between MS and MS/MS GC-MSD SIM chromatogram of a 1 µg/l standard solution: Benzo[a]pyrene / 15

16 Comparison between MS and MS/MS GC-MS/MS chromatogram of a 1 µg/l standard solution: Benzo[a]pyrene Benzo[a]pyrene > Benzo[a]pyrene > C 4 -Benzo[a]pyrene (ISTD) / 16

17 Benzo[a]pyrene in a food sample: 0.03 µg/kg Benzo[a]pyrene > Benzo[a]pyrene > C 4 -Benzo[a]pyrene (ISTD) / 17

18 Benzo[b/k/j]fluoranthene Concentrations in a food sample: b: 0.09 µg/kg; k: µg/kg; j: µg/kg > b > b k j k j b k ISTD / 18

19 GC-MSD: matrix interference food sample spiked with 1 µg/kg TIC TIC MSD Important compounds like: Benzo[c]fluorene, Benzo[a]anthracene, Cyclopenta[c,d]pyrene, Chrysene, Methylchrysene, Benzo[b,k,j]fluoranthene eluted in this region / 19

20 Benzo[a]anthracene SIM-chromatogram:benzo[a]anthracene (food sample spiked with 1 µg/kg) the matrix interference suppressed the signal of benzo[a]anthracene (spiked with 1 µg/kg) completely Only the compounds which eluted after 25 min, such as benzo[a]pyrene can be determined reliably / 20

21 GC-MS/MS: matrix interference food sample spiked with 1 µg/kg TIC-MRM Important compounds like: Benzo[c]fluorene, Benzo[a]anthracene, Cyclopenta[c,d]pyrene, Chrysene, Methylchrysene, Benzo[b,k,j]fluoranthene eluted in this region / 21

22 Benzo[a]anthracene/Chrysene in a food sample (spiked with 1 µg/kg) normalized chromatogram of the different MRM Benzo[a]anthracene Chrysene 13 C 6 -Benzo[a]anthracene 13 C 6 -Chrysene ISTD / 22

23 Chrysene Triphenylene critical pair C 18 H 12 : same elemental formula; same transition separation mandatory for GC-MS/MS Benz(a)anthracene Triphenylene Chrysene / 23

24 Chrysene/triphenylene in a food sample: conc. (chrysene) = 0.5 µg/kg ratio between chrysene and triphenylene in all samples analysed so far range from 0.1 up to / 24

25 PAH analyzer PAH Automated Offline Source Cleaning Offline Cleaning Mode: 0.4 ml/min, Source 350C, Filament On Page /

26 PAH analyzer Automated Continuous Source Cleaning Continuous Cleaning Mode: ml/min during acquisition Page /

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28 7000B MS/MS systems, stock configuration Dibenzo(a,l)pyrene, a late eluter Optimized PAH Analyzer Page /

29 Standard solution: blue without H 2 cleaning; green with H 2 cleaning Standard solution: black with H 2 cleaning; red without H 2 cleaning and green H 2 cleaning before and after the run / 29

30 Standard solution 1; the lowest calibration point without H 2 : Cal 1: 0.5 pg/µl; injection 1 µl Continuous Cleaning Mode H 2 : Cal 1: 0.5 pg/µl; injection 1 µl / 30

31 conclusion: GC-MS/MS: LODs of 0.01 µg/kg were reached which is 20 times lower than with our single quadrupole and without changing the sample preparation and the sample concentration with selective GC columns like Select PAH it is possible to separate critical pairs, such as chrysene/triphenylene or benzo[b,k,j]fluoranthenes analyze larger amounts of sample without losing sensitivity due to increased interference from matrix use of 13C-labelled PAH as internal standard possible and advisable PAH analyzer improved peak shapes, less tailing, higher sensitivity; Source stays clean / 31

32 Many thanks to the people behind the work and you for your attention! / 32