Odours from Food Packagingan Analytical Challenge?

Transcription

1 1 S C I E N C E P A S S I O N T E C H N O L O G Y Odours from Food Packagingan Analytical Challenge? Erich Leitner, Institute of Analytical Chemistry and Food Chemistry RAFA u

2 2 Content General Aspects of Odour Active Substances Analytical Considerations Example 1 Derivatization of Phenols (GC-MS) Example 2 Aldehydes in Polyolefin (GCxGC-MS) Example 3 TCA and TBA in Recycled Board (GC-MS/MS)

3 3 Perception of Smell Odour activity is strongly linked to volatility. Only volatiles show odour activity BUT not all volatiles smell. Compounds with a molecular weight above 400 Dalton do NOT smell. In contrary to the basic taste sensation one single component can bind to different types of receptors resulting in a much more complicated scenario. Several thousand impressions can be distinguished There is a difference between the nasal and the retronasal odour impression (Flavour release, Temperature )

4 4 RAFA 2015 Sensory thresholds Substance Smell impression Sensory threshold [mg/l] Ethanol alcoholic 100 Vanilline vanilla 0.02 Hexanal cut grass Methylthiole roasty, sulphur ,4,6-Tribromoanisol musty, mouldy pg/l (!!!)

5 5 Analytical Methods There is a strong need to develop analytical methods for the identification and quantification of odour active compounds. Due to the fact that only volatile substances can be odour active, capillary gas chromatography with different detector systems is the preferred analytical method. For the determination of relevant substances methods must be used which are able to reach detection limits which are in the range of the sensory threshold!!!!!

6 6 Gas Chromatography-Olfactometry (GC-O)

7 7 RAFA 2015 GC-O Result strong medicinal, chemical smell bad good NO smell

8 8 Halophenols Halophenols can be found in recycling paper products They show odor activity (upper ng-µg/kg) and are the precursors of micobiologically formed Haloanisoles Sometimes causing problems in drinking water due to chlorination and due to hygienic actions

9 9 Nasty Behaviour of Phenols new column used column Loss of peak shape Retention time shift Loss of sensitivity

10 10 Derivatization Reaction in Aqueous Media Sample plus K 2 CO 3 to adjust ph Addition of 50 µl Acetanhydride Reacts in a few minutes at room temperature Erich Leitner, Institut für Analytische Chemie und Lebensmittelchemie

11 11 Mass Spectra Derivatized compounds show a very similar fragmentation pattern to the underivatized phenols +42 amu Erich Leitner, Institut für Analytische Chemie und Lebensmittelchemie

12 12 Method Shimadzu QP-2010 Ultra Temp programme: 45 C (1 C/min to 230 C/min to 290 C Sample volume 5 ml aqueous solution Compound Target Qualifier 2,4-Dichlorophenol Target ,6-Dichlorophenol Target ,4,6-Trichlorophenol Target ,3,4-Trichlorphenol Target ,6-Dibromophenol Target ,4,6-Tribromophenol Target Phenylphenol-d9 ISTD Pentachlorophenol Target Calibration range: µg/l Erich Leitner, Institut für Analytische Chemie und Lebensmittelchemie

13 13 2,6-Dibromophenol at 50 ng/l Erich Leitner, Institut für Analytische Chemie und Lebensmittelchemie

14 14 Food Packaging (Polyolefin) Odor Causing Substances Substance Sensory Threshold [µg/kg] Odor Heptanal 3 Tallowy, fishy Octanal 0.4 Fatty, Orange Nonanal 2.5 Card board, Orange Decanal 0.1 Fatty Undecanal 5 Waxy, floral 2-Heptenal (E) 13 Tallowy, fishy 2-Octenal (E) 0.2 fatty, rancid 2-Nonenal (E) 0.08 Card board 2-Decenal (E) 0.4 burnt plastic

15 15 Heavy Interferences from Alkanes/Alkenes Ion Ion

16 16 Comprehensive GCxGC Comprehensive chromatography in combination with mass spectrometry / Editor L. Mondello., ISBN , John Wiley & Sons 2010

17 17 GCxGC-MS To get rid of the interferences a GCxGC-MS method was developed Shimadzu QP 2010 Ultra with Zoex Modulator & OPTIC IV Injector Column 1: 30 m HP-5MS*0.25 mm id*0.25 µm df Column 2: 2.5 m BPX-50, 0.15 mm id*0.15 µm df Cryogenic Modulation: 8 s, hot jet 350 msec, 280 C Temperature programme: 35 C (1 2 C/min to 240 C Scan: amu, 50 scans/s C6 C7 C8 C9 C10 C11 C12 Aldehydes

18 18 Improving Resolution by Column Combination Column 1: 30 m ZB1HT*0.25 mm id*0.25 µm df Column 2: 2.5 m BPX-50, 0.15 mm id*0.15 µm df

19 19 2,4,6-Trichloroanisole & 2,4,6-Tribromoanisole 2,4,6-TCA Odor: musty, mouldy 2,4,6-TBA Odor: earthy, musty Odor Threshold: Water: 0.03 ng/l 1 Beer: 0.09 ng/l 2 Wine: 1-30 ng/l 3 Odor Threshold: Water: 0.02 ng/l 4 Ref.: 1) N. Griffith & R. Fenwick, Chem Senses and Flavor (1977) 2) M. J. McGarrity et al., MBAA TQ ( 2003) 3) H. Tanner & C. Zanier, Schweiz. Z. Obst- Weinbau (1981) 4) F. B. Whitfield et al., J. Agric. Food Chem. (1997)

20 20 Triple-Quadrupole-GC-MS 1.50 (x100,000) (x100,000) :215 TCA d5 2:210 TCA :215>197 TCA d5 2:210>195 TCA

21 21 Method Sample preparation: 100 mg recycled card board cut in small pieces 20 ml HS vial Glass coated magnetic stir bar Internal standards: 2,4,6-TCA-d5 10 pg (= 100 ng/kg sample) 2,4,6-TBA-d5 10 pg (= 100 ng/kg sample) SPME 2 cm 50/30 µm DVB/Carboxen/PDMS 100 C, 20 min Column: BPX5, 30 m*0.25 mm id * 0.25 µm df Temperature programme: 60 C (1 10 C/min to C/min to 310 C

22 22 MS/MS Parameter Shimadzu TQ8040 Compound Start Time End Time Event time Transition CE Transition CE Q1 Res Q2 Res 2,4,6-TCA-d > > Unit Unit 2,4,6-TCA > > Unit Unit 2,4,6-TBA-d > > Unit Unit 2,4,6-TBA > > Unit Unit Multiplier 2 kv Collision gas: Argon 200 kpa

23 23 Recycled Cardboard Samples 65 ng TCA ng TBA Depending on the sample size and the matrix low ng/kg quantification limits can be achieved

24 24 Thank you for your kind attention.