Guidance in selecting analytical techniques for identification and quantification of non-intentionally added substances (NIAS) in food contact materials (FCMS)

Figures & data

Figure 1. Classification of NIAS, adapted from Geueke (2013). A more detailed description of potential sources of NIAS is described in (Koster et al. 2015).

Table 1. Examples of extraction for food contact materials (FCM). Solubility of the substance should also be considered when choosing an extraction solvent

FCM	Extraction solvent
	Extraction	Dissolution/Precipitation
Polyolefin	Dichloromethane, isooctane	Hot xylene/methanol
Polystyrene	95% ethanol	Dichloromethane /methanol Dimethylacetamide (for headspace analysis)
Polyester (PET) PEN	Acetonitrile/ Dichloromethane	Hexafluorisopropanol or trifluoroethanol or Dichloracetic acid/Methanol
Polyamide	Acetonitrile/ Dichloromethane, 95 % ethanol,	Hexafluorisopropanol or trifluoroethanol or Dichloracetic acid/Methanol
Multilayer films	Depending on material of food contact side
Paper	Water, ethanol, acidic medium
PVC	Acetonitrile/ Dichloromethane	Tetrahydrofurane/methanol

Figure 2. Screening procedure for sample preparation and analytical techniques for identification of NIAS in polymers. GC: gas chromatography; MS: mass spectroscopy; LC: liquid chromatography; HS: headspace; TD: thermal desorption.

Figure 3. Screening procedure for identification of NIAS in simulants. HS: headspace; TD: thermal desorption from FCM or adsorbent (e.g. MPPO), purge and trap or dynamic headspace; SBSE: stir bar sorptive extraction; SPME: solid-phase microextraction.

Figure 4. Schematic for analytical approaches for analysing NIAS.

Table 2. Overview of strengths and Limitations of different analytical techniques for analysing migrants either in FCMs or in simulants after migration tests, as well as approaches for sample preparation

Method	Strengthts	Limitations
Static headspace (HS)	Equilibrium conditions needed for reproducibility. Direct analysis for solid samples. Good for the most volatile compounds. Clean chromatograms without solvent delay in MS.	Sensitivity decreases with increasing boiling point. Dependence of partitioning equilibrium on substance and matrix (reference substances needed for quantification). Solution: Multiple headspace extraction allows extrapolation to quantitative transfer into the gas phase under the applied equilibrium conditions
Dynamic headspace (Purge & Trap)	For the most volatile compounds. Very sensitive. Clean chromatograms without solvent delay in MS.	Many interferences. Only suitable for volatiles. Requires specific instrument. Care is required with the moisture content of the sample. The adsorbent must be chosen with respect to the analytes that should be covered. Many parameters (time and temperature of purge, trap, temperature and desorption time) to optimize.
Liquid-liquid microextraction	High concentration rate.	Difficult handling unless automatic device is available. Careful selection of extraction solvent is required. Cannot cover all substances with one solvent
Solvent extraction either from solid FCM or from food simulant, including Tenax, Accelerated Solvent extraction (ASE), Microwave-assisted extraction (MAE) and ultrasonic extraction (USE).	Versatile. High concentration rate is possible.	Compatibility with the subsequent analytical technique is required. Optimization of solvent, volume and conditions are required. Solvent delay required in MS. (some substances will be not detected.
Thermal desorption	High concentration rate. High sensitivity; either direct from the material or from a solid sorbent such as the simulant Tenax®	Requires specific injection port in GC and device for automatic analysis (desorption). In case a sorbent is used it must be chosen with respect to the analytes that should be covered.
SPME/HS or immersion mode	High concentration of analytes. Clean chromatograms without solvent delay in MS. Automatic or manual. Very sensitive. Available for volatile and semi-volatile compounds. Can be applied to aqueous and solid samples.	Requires careful optimization (fibre, time, temperature) as there are several SPME fibres. Important to work under equilibrium conditions for reproducibility. Reference substances needed for quantification. Maximum concentration of organic solvents in aqueous solutions is 10%.
SBSE	High concentration of analytes. Clean chromatograms without solvent delay in MS. Automatic or manual. Very sensitive. Available for volatile and semi-volatile compounds.	Requires special equipment for automatic thermal desorption. Cannot cover all substances with one SBSE phase. SBSE is only useful for extraction of components, when the partitioning between SBSE and FCM/or food simulant allows it.
Low polarity GC column (DB5 or similar)	Quite universal for many low polar volatile and semivolatile organic substances Kovats Indices available in NIST database to support identification	Size and thickness of stationary phase of the GC column need to be selected according to the analytes
Polar GC column (carbowax, polyethylenglycol or similar)	For polar and volatile substances (ketones, aldehydes, etc.) Kovats Indices available in NIST database to support identification	Size and thickness of stationary phase of the GC column need to be selected according to the analytes Restricted temperature resistance of the columns compared to others.
RP-LC (C18 and modified phases) for non-volatile and low polarity substances,	Quite universal. There are more specific modified phases for groups of substances. Different size and thickness available	No suitable for very polar substances. No compatible with organic solvents
HILIC-LC (non-volatile and very polar substances)	Good separation for very polar and/or ionic substances	Careful optimization of mobile phase is required
GC-FID	Can be used for quantification, suitable for volatile and semi-volatile substances Mol wt upper limit ~ 800 Daltons applicable for a wide range of substances.	Non-specific detector, not applicable for identification unless pure standards were used. The response depends on the number of carbons and the chemical structure.
GC-MS (direct injection) Several injection modes are available: on-column, split/split-less, PTV…	Libraries available to assist identification. Suitable for volatile and semi-volatile substances Mol Wt upper limit ~ 800 Daltons.	Solvent delay prevents the analysis of the most volatile components. Special care should be taken to avoid new NIAS produced in the injection port
GCxGC-MS or GCxGC-FID	2D separation of overlapped compounds in the first GC.	Expensive equipment that requires specific training. No common in many labs.
LC-MS-triple Quad or ion trap (MS-MS).	Very good for target analysis and for quantification. Widely available. Very sensitive (if the substances are ionisable) for quantification of non-volatiles. Wide range of substances depending on the LC column used and ionisation source.	Limited accuracy of masses of substances. Limited identification. It requires confirmation by pure standards. Targeted analysis.
LC-HRMS various techniques	Very good for untargeted analysis and screening, providing the compounds are ionisable. Accurate molecular mass and mass fragments, essential for identification. Quantification is possible.	No wide libraries commercially available yet, as the spectrum depends on experimental conditions used. Adducts formed, which make identification more difficult. Software required to help with identification. Ionisation and therefore detection depend on the substance, the ionisation technique, solvents, and apparatus settings
LC-IM-HRMS	Accurate molecular mass and mass fragments. Additional separation based on IM that provide CCS values for identification. Values of CCS from IM do not depend on chromatography. Isomers can be separated Quantification is possible.	No commercial libraries are available yet. Some are in process.
NMR	Useful for elucidation of the chemical structure and purity of a reference substance Quantitative NMR can be used to determine the amount of certain functional groups in a migrate (e.g. oxirane moieties) or even the amount of certain substance group (dimethylsiloxane in food; Helling et al. 2010).	Limited sensitivity, need for isolated compounds and not being readily coupled to LC. Not readily available to many companies or laboratories.
UV/DAD/fluorescence (coupled to LC)	Needs a suitable chromophore (selectivity). Very sensitive depending on the chromophore (fluorescence) Very specific (fluorescence)	Reference standard is needed. DAD is not substance specific but tentative identification of the chromophore by UV-spectra (DAD) can be achieved.
HPLCxGC	Provides the separation of one or more pre-separated fractions (2D). Can be also applied off-line	Specific devices for coupling both equipments (LC and GC) is required. Experience required for processing the data and interpreting the results
TGA-GC-MS	-Analysis of decomposition products at high temperature conditions-compositional analysis of polymer blends	Not available in most of the labs

Table 3. Information to include in the analysis report

Information about the sample

1. Include the picture of the sample if relevant 2. Add information on the sample (type, sample point, time of sampling) 3. Amount of sample taken 4. End use for product if known

Information about the analysis performed

1. Description of the sample preparation Migration/extraction preparation Migration/extraction conditions (time, temperature, solvent, surface to volume ration, single sided migration versus total immersion Solvent(s) or food simulants used, applied t/T (time/temperature) conditions, experimental surface to volume ratio and rationale for the test conditions selected. Include a picture of the sample before and after the analysis if relevant (e.g. in case of delamination, physical damage or swelling). 2. Description of the measurement techniques used and why they collectively provide adequate coverage for all/any migrants from that FCM Indication of the internal standard(s) used. Performance of the migration/extraction (recovery data obtained by spikes, multiple extractions in a row) Indication of the technique used and the experimental conditions applied, including type of injection (PTV, cold-splitless…), injection volume, column used, ionization mode, temperature program, mobile phase solvent, gradient, internal standard(s) used for quantification or semi-quantification. ionization mode, internal standard(s) used for (semi-) quantification. Standards used for calibration plot (quantitative purpose). Limits of detection. Limits of quantification. Confidence level in the identification and quantification 3. Migration modelling If modelling is used rather than analysis, it is necessary to obtain a Cp0. This is normally done by analysis. The techniques used and model used with assumptions should be listed

Results

1. Information about the S/V ratio used for calculation 2. Example of calculation 3. For each technique, summary of all detected substances such as: name of the semi-quantified substances CAS numbers, if available MS spectrum when using MS as a detector Residual concentration in mg/kg material or mg/dm² material (depending on the technique used) concentration in mg/kg food using either 6 dm²/kg or the actual ratio. SML if existing Limits of detection Limits of quantification confidence level in the identification

Table

NIAS	Non-intentionally added substances
APCI	Atmospheric pressure chemical ionization
APGC	Atmospheric pressure gas chromatography
APPI	Atmospheric pressure photoionization
BADGE	Bisphenol A diglycidyl ether
BPA	Bisphenol A
CAD	Charged aerosol detector
CLND	Chemiluminescent nitrogen detector
CSS	Collision cross section
EI	Electron ionization
ESI	Electrospray ionization
FCMs	Food contact materials
FID	Flame ionization detector
GC	Gas chromatography
GC x GC	Multidimensional gas chromatography
GC-MS	Gas chromatography–mass spectrometry
HPLC	High-performance liquid chromatography
HRMS	High resolution mass spectroscopy
HS	Headspace
IAS	Intentionally added substances
IM	Ion mobility
IT	Ion trap
LC	Liquid chromatography
LC-MS	Liquid chromatography–mass spectrometry
LDPE	Low density polyethylene
LLME	Liquid-liquid microextraction
MPPO	Poly(2,6-diphenyl-p-phenylene oxide) Tenax®
MS	Mass spectroscopy
MS^n	Multi-stage mass spectroscopy
NMR	Nuclear magnetic resonance
P&T	Purge and trap
PAAs	Primary aromatic amines
PET	Polyethylene terephthalate
QqQ	Triple-quadrupole mass spectrometer
QTOF	Quadrupole time of flight
QuEChERS	Quick, Easy, Cheap, Effective, Rugged & Safe
RT	Retention time
SBSE	Stir bar sorptive extraction
SML	Specific migration limit
SOP	Standard operating procedure
SPE	Solid phase extraction
SPME	Solid phase microextraction
TD	Thermal desorption
TTC	Threshold of toxicological concern

Geueke B. 2013. FPF Dossier: Non-intentionally added substances (NIAS). Zenodo. https://doi.org/http://doi.org/10.5281/zenodo.33514|

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Koster S, Bani-Estivals M, Bonuomo M, Bradley E, Chagnon M, Garcia M, Godts F, Gude T, Helling R, Paseiro-Losada P, et al. 2015. Guidance on BEST practices on the risk assessment of non intentionally added substances (NIAS) in food contact materials and articles. ILSI Eur Rep Ser. 2015:1–70. https://ilsi.org/europe/wp-content/uploads/sites/3/2016/04/2015-NIAS_version-January-2016.pdf .

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