The usage of Reference Standards in MOSH/MOAH Analysis

Abstract

The unintended migration of mineral oil compounds into food, e.g from packing materials or from production processes are a raising topic in industry and scientific discussions. For a first screening, an LC-GC/FID method was established in the last years. In collaboration with Axel Semrau, Restek has developed ready to use standards for quantification and and identification of the different fractions to be controlled. Saturated Hydrocarbons and Aromatic Hydrocarbons have to be cut of from LC fraction before transferred into the GC and the different areas which have to be taken into consideration have to be identified properly. The Blog entry gives an overview about how to use the different available standards correctly.

MOSH/MOAH

Food may be contaminated with mineral oil compounds by unintended migration from different sources. One of the most common sources for such an unintended contamination is coming out of recycled paperboards, but also during production processes such a failure may occure.

Due to their different toxicological capability, mineral oil compounds are subdivided into two fractions:

  • MOSH: Mineral Oil Saturated Hydrocarbons
    -saturated hydrocarbons
    -paraffines & naphthenes (cyclic)
    -highly alkylated
  • MOAH: Mineral Oil Aromatic Hydrocarbons
    -highly alkylated mono- and polyaromatic compounds
    -also saturated ring linked to aromatic rings
    consistence often unknown

The toxicity of both groups are described as follows:

  • MOSH:
    –accumulated in Human Tissue
    –toxicological relevance unknown
  • MOAH
    -most substances unknown and toxicological nonvaluated
    -carcinogenic potential can not be excluded
    -unaccepted risk
    -unaccepted in food

The different toxicological risks have found its expressions in different legal restrictions, as to be found in the EU Commission  Recommendation (EU) 2017/84 of 16 January 2017 or in the German Mineral Oil Regulation, wherein the concentration in food contact material (recycling paper & cardboard) is limited for MOAH to 6 mg/kg or, if limits in the material does not comply, it has to be verified that limits in the food comply to MOAH C16-C35  less than  0,5 mg/kg.

For the MOSH fraction the ALARA Principle has to be applied.

  • ALARA Principle
    –In Europe the ALARA principle is regulated by the European Food Safety Agency EFSA and translates to “As Low As Reasonably Achievable”

Analytical Aspects

In both fractions, MOSH and MOAH, a tremendous amount of different compounds have to be covered with an analytical method. Therefore both fractions can only be described as a sum parameter method.

Due to EFSA “Currently, the most efficient methods for analysis of MOSH and MOAH in food and feed comprise extraction followed by pre-separation by high performance liquid chromatography (HPLC) on-line coupled to GC with flame ionisation detection (FID).” – EFSA Journal, 2012, 10(6):2704, is the best choice for this analysis.

This method was first described by K. Grob and M. Biedermann from the Kantonales Labor Zurich. (BIEDERMANN M., GROB K. On-line coupled high performance liquid chromatography-gas chromatography (HPLC-GC) for the analysis of mineral oil: Part 1: method of analysis. J. Chromatogr. A. 2012, 1255 pp. 56–75)  and has found its way into a European norm via EN 16995:2017 (Foodstuffs – Vegetable oils and foodstuff on basis of vegetable oils – Determination of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) with on­line HPLC­GC­FID analysis).

Restek is accompanying the development of an automated system for the analysis of MOSH and MOAH of the German company Axel Semrau GmbH since years, adding our knowledge in separation science as well as in LC and GC but also by preparing the needed reference materials.

The method uses a “Normal Phase” HPLC with a Silica column to separate both fractions, MOSH and MOAH, from sample matrix, than transfers either the MOSH or the MOAH fraction as a large volume injection onto a 7 to 10 m retention gap, which uses solvent focusing and a solvent vapor vent to get rid of most of the used solvent. This approach delivers both fractions, MOSH and MOAH as a chromatographic hump, as shown in the chromatograms below. Both chromatograms were provided by Axel Semrau GmbH

 

Sunflower Oil MOSH Fraction

 

Sunflower Oil MOAH Fraction

Reference Standards

For quantification, to prevent losses of low boiling compounds and to make sure that the complete fraction was transferred to the GC, an internal standard (IS) is used. (Restek cat. No. #31070). The 9 compounds included are used as shown in the chromatograms below.

Sunflower Oil MOSH fraction, spiked with IS, courtesy of Axel Semrau GmbH

CyCy: Cyclohexyl Cyclohexane, standard for Quantification, not present in mineral oil products
C13: Tridecane, proves no coelution with CyCy. Peak Identification. Has to be a peak pair with CyCy.
C11: Undecane, detection of losses of volatile compounds
Cho: Cholestane, end of MOSH Fraction

Sunflower Oil MOAH Fraction, spiked with IS, courtesy of Axel Semrau GmbH

2-MN, 1-MN: 1-/2-Methylnaphtalene: standard for Quantification, peak pair for better identification
5B: n-Pentylbezene: detection of losses of volatile compounds
TBB: Tri-tert.-butylbenzene: start of MOAH Fraction
PER: Perylene: end of MOAH fraction. Can be determined also with UV detection in automated approaches

Different regulations are looking for different integration limits for the detection of the two fractions. Restek therefore has developed a Retention Time Standard (Restek cat. No. #31076), This standard has to be run before and after every Sequenz to avoid retention time shifts and therefore wrong results by using the wrong integration limits.

The compounds are used as follows:

  • C10 = lowest boiling compound to be detected
    C11 = Marker out of Restek-Mix #31070 – retention time stability
    C13 = Internal Standard out of Restek-Mix #31070 – ret. Time stability
    C16 = requested boiling point limit for fraction quantification
    C20 = requested boiling point limit for fraction quantification
    C24 = nowadays requested boiling point limit for fraction
    quantification
    C25 = New supposed requested boiling point limit for fraction
    quantification. If C24 or C25 will be used is not yet fully
    determined (both included gives future proof)
    C35 = requested boiling point limit for fraction quantification
    C40 = todays detection limit
    C50 = desired new detection limit

 

MOSH/MOAH Analysis helps to improve our Food Quality

 

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