Analysis of food packaging contaminants by LC-MS

Transcription

1 Analysis of food packaging contaminants by LC-MS Ludwig Gruber Martin Schlummer Fraunhofer IVV Giggenhauser Str Freising, Germany

2 Topics Compliance of Packaging Materials: general remarks Analytical techniques: GC versus LC LC-MS instrumentation: HPLC Analyzer types Ionization types (APCI, APPI, ESI) and some analytical examples (PFC, isomeric plasticizers, printing inks, additives) The CAD: an universal detector for HPLC and its use for the screening of unknown substances Conclusions

3 Compliance of Packaging Materials ur work Analysis and evaluation of plastics, paper, and metals with regard to relevant directives and regulations: Framework regulation 1935/2004, Plastics Directive 72/2002/EC and amendments, Recycling Regulation 282/2008, Active Packaging Regulation 450/2009, PIM Regulation 11/2011 Execution of approval procedures (EFSA, FDA, BfR) Identification of the causes of offodors in packaged foods Development of physical-chemical analysis methods, in particular for trace and ultra-trace analysis Development of material-specific permeation measurement techniques for organic substances

4 Compliance of Packaging Materials Migration recent developments The new European Plastics Implementing Measure (PIM) and other recent developments in legislation make the analysis of food contaminants and chemical migration from food contact materials more complex. Important changes in the last years were Expansion with plastics layers in multi materials in the PIM Separate sets of standard test conditions for overall and for specific migration testing and last but not least an implicit Non detectable migration limit for non-evaluated substances ( -> 10 ppb detection limit )

5 Compliance of Packaging Materials Migration - Fundamental Question How can I Packaging Food quickly, reliably and at favorable cost C t=0 Migration??? C Food,t??? determine at C Food,t? Diffusion Distribution Diffusion

6 Migration testing: analytical techniques GC versus HPLC MS Traditional methods of analysis like GC-FID or HPLC are often hampered by limitations like the achievable detection limit, specific matrix effects and a restricted number of analytes. GC/EI-MS, LC-MS and other advanced analytical techniques can be used to avoid a number of these problems, but provide other challenges for the analyst. Whereas GC/EI-MS is a relatively easy-to-handle tool, LC-MS is much more sophisticated especially for the analysis of unknowns. Source conditions are often very specific for individual compounds, and ion suppression occurs due to the presence of less volatile compounds that change the efficiency of droplet formation or droplet evaporation.

7 Migration testing: analytical techniques Adapting an HPLC Method for MS Detection Most HPLC methods can be coupled with MS detection, but: Typical MS interfaces accept flows of up to 1 ml/min, but performs best at lower flow rates. Mobile phase should contain only volatile components. Inorganic salts have to be replaced with volatile additives. Water is difficult to evaporate in the interface, so higher concentrations of organic solvents are beneficial. HPLC/MS allows the use of isotope labeled internal standards.

8 Migration testing: analytical techniques HPLC-MS Analyzers Single quadrupole MS cheap, but not very capable More sophisticated analyzers that allow MS/MS experiments and/or high mass resolution are: Triple quad MS MS/MS experiments possible, wide quantitation range TF (Time of flight) high resolution possible, QTF allows also MS/MS Ion-trap MS n experiments possible, quantitation range poor rbitrap high resolution, combination with ion-trap or quadrupole possible

9 HPLC-MS: Ionization techniques Common types of ion sources Molecular size APPI ESI APCI Polarity

10 ESI: Electrospray ionization Ion source techniques for HPLC MS Spray needle / capillary 4000 V Nitrogen (Drying Gas) Taylor cone Solvent spray Multiply charged droplet Transfer capillary Ions: [MH], [MNa], [MNH 4 ], [MX - ], [M-H] -, [M-X ] - Ionization by formation of adducts Evaporation of solvent Rayleigh Limit reached Coulombic Explosion Desolvatisation Analyte ion

11 ESI: Electrospray ionization Analysis of perfluorinated compounds with ESI I Weak anion exchange SPE cartridges were preconditioned with 2 ml of methanol and water, respectively, and the extracts were passed through the preconditioned cartridges. The cartridges were then washed with methanol/water (1/1; v/v) and eluted with 1% NH4H in methanol. SPE eluates were evaporated under a gentle stream of nitrogen and diluted with water to a final volume of 1 ml. HPLC-ESI-MS/MS: Surveyor Plus HPLC connected to a Quantum Ultra AM mass spectrometer (both Thermo). Chromatographic separation is achieved by a Luna PFP phase (150 x 4.6 mm, 5 µm, Phenomenex). Gradient HPLC was performed with methanol and 5mM ammonia acetate in water (ph 3.5), increasing methanol from 20 to 100% within 10 minutes. Mass spectrometry is performed by electron spray ionisation (ESI) in the negative ion mode and subsequent single reaction monitoring. For PFS and PFA the following MS/MS transitions (MRM) are monitored: PFS (499 99), 13 C 4 -PFS (503 99), PFA ( ), 13 C 4 -PFA ( ) Note: The use of isotope labeled standards is mandatory! ( ion supression effects )

12 ESI: Electrospray ionization Analysis of perfluorinated compounds with ESI - II HPLC-ESI-MS/MS interferences can disturb the quantification of PFS significantly. Taurodeoxycholate, which coelutes with PFS isomers, produces significant interference on the most sensitive MS/MS transition of PFS, ,22 Relative Abundance 4,0 3,8 3,6 3,4 3,2 3,0 2,8 2,6 2,4 2,2 2,0 1,8 1,6 1,4 1,2 1,0 0,8 0,6 0,4 0,2 0,0 79,82 106,83 123,85 - NH taurodeoxycholate S CH 3 H CH 3 373,23 433,25 331,08 164,90 187,12 218,19 276,17 469,09 481, m /z H H H CH 3 H H The interference can be avoided by monitoring the more specific transition

13 APCI: Atmospheric Pressure Chemical Ionisation Ionization techniques for HPLC MS Spray needle/ capillary Nitrogen Heater (450 C) solvent- vapor Corona-Needle Transfer capillary 5 12 µa N 2 2 N e - 2 N SolventH N 2 2 [SolventH] [SolventH] M Solvent [MH] Ionization by formation of adducts Negative-mode for substances with acidic proton

14 APCI: Atmospheric Pressure Chemical Ionisation Analysis of isomeric plasticizers with APCI

15 APPI: Atmospheric Pressure Photoionization Ionization techniques for HPLC MS Spray needle/ capillary Nitrogen Heater (450 C) solvent- vapor UV-Lamp (10 ev) Transfer capillary N 2 2 N e - 2 N Solvent H N 2 2 [Solvent H] [Solvent H] M Solvent [M H] Direct ionization and formation of adducts Negative-mode for substances with acidic proton Use of dopant (e.g. toluene) recommendable

16 APPI: Atmospheric Pressure Photoionisation Example for an APCI/APPI ion source

17 APPI: Atmospheric Pressure Photoionisation Analysis of printing inks with APPI - I CH 3 Signalintensität Irgacure 379 TP-L TP CPTX H 3 C P H 3 C H 3 C H 3 C Cl CH 3 H 3 C C H 3 CH 3 CH 3 P N CH H 3 C 3 N 0 S Retentionszeit [min] Esacure 1001M H 3 C H 3 C S CH 3 CH 3 S

18 APPI: Atmospheric Pressure Photoionisation Analysis of printing inks with APPI- II Calibration curve and standard addition of Esacure Irgacure 379 Area APCI Irgacure 379 Area APPI Wurst Irgacure 379 Aufstockung Area APCI Wurst Irgacure 379 Aufstockung Area APPI Konzentration in ppb Konzentration in ppb

19 APPI: Atmospheric Pressure Photoionisation Analysis of printing inks with APPI- III Signal to noise ratio, sausage extracted, addtion of 5 ppb TP-L APPI - S/N = 244 APCI - S/N = 55

20 Screening for not known non-evaluated substances General remarks The importance of analyzing non-intentionally added substances (NIAS), not clearly defined small oligomers or other target compounds increase more and more in terms of compliance evaluations. A real challenge is the non detectable migration limit (10 ppb) for non-evaluated substances. There are some approaches: GC-FID in combination with GC/MS is a valuable tool. It combines identification (MS) with standardless semiquantification via FID, but many compounds can not analyzed by GC. LC-MS can be also a choice for analytical screening method, but needs a backup by an universal HPLC-detector like the CAD (Charged Aerosol Detector)

21 Screening for not known non-evaluated substances CAD: Charged aerosol detector * * Courtesy of Dionex Corp.

22 Screening for not known non-evaluated substances CAD: Charged aerosol detector The CAD provides nearly universal detection independent of chemical structure for non- and some semi-volatile analytes. The advantages are: High sensitivity Response independent of chemical structure Wide dynamic range The combination of CAD and MS is a valuable tool for the screening of unknown substances.

23 Screening for not known non-evaluated substances CAD: Relative Response Factors for additives 3.00 Gradient condition A BADGE TEGDB DEGDB Irganox 245 Benzoflex 284 DPGDB Irganox MD 1024 Irganox 1098 BDBP Phosflex 362 Benzoflex 354 Irganox 3052 Irganox 1081 Irganox 1035 Chimasorb 81 DEHP DEHA Irganox 3114 Uvitex B Tinuvin 327 Ultranox 626 Irganox 1010 Irganox 1330 Irganox 565 Irganox PS 800 Irganox 1076 Irgafos 168 RRF rganic solvent content (%) Retention time (min.)

24 Screening for not known non-evaluated substances CAD: Relationship between molecular weight and RRF* mv 1 2, , IS 12 14, 15 0,1 5,0 10,0 15,0 20,0 25,0 30,0 35,0 40,0 45,0 50,3 1. Bisphenol A 5. Propylene glycol dibenzoate 9. 2-Ethylhexyl diphenyl phosphate 2. Diethylene glycol dibenzoate 6. Dipropylene glycol dibenzoate 10. 2,2,4-Trimethyl-1,3- pentanediol dibenzoate Figure 1 : Representative chromatograms of the adhesive related substances detected on HPLC-CAD by using gradient condition B (standard solution containing 50 µg/ml) Triethylene glycol dibenzoate 7. 4,4 -Bis(diethylamino) benzophenone BADGE Gradient B Irganox Irganox Chimasorb Irganox Diethylhexyl adipate 15. Diethylhexyl phthalate 16. Irganox Uvitex B 18. Irganox Irganox Irganox PS Irganox Irgafos 168 IS : Tinuvin 234 * Chan-Suk Yoon et al.: Poster ILSI Conf min RRF (w/w) RRF (mol/mol) 1.8 Gradient B Molecular weight more than 400 g/mol Molecular weight (g/mol) Figure 2 : Relationship between molecular weight and RRF (W/W) of the substances detected on HPLC-CAD by using gradient condition B. 3.2 Gradient B y = x R 2 = Molecular weight (g/mol) Figure 3 : Relationship between molecular weight and RRF (mol/mol) of the substances detected on HPLC-CAD by using gradient condition B.

25 Conclusions Pros and Cons of HPLC/MS PRs Most HPLC methods can be adapted Very sensitive and selective Intense molecular ion, fragmentation for identification purposes possible Use of labeled standards possible Wide mass range Wide range of analyzable substances MS/MS and high resolution options available CNs Method development needs time and experienced personal Expensive equipment Screening for not known substances is difficult because of selective sources and ph, polarity and buffer dependency of response Cleanup for dirty samples recommended Ion suppression possible, use of internal standards necessary

26 Fraunhofer IVV Thank you for your attention!