Ask the Experts: Practical Answers to Today’s Biggest MOSH/MOAH Analysis Questions

Introduction

MOSH and MOAH analysis remains one of the most challenging and closely scrutinized areas in food and packaging safety testing. With evolving regulations, updated standards such as ISO 20122:2024, and increasing expectations for data quality and throughput, laboratories are under constant pressure to deliver accurate, reproducible, and compliant results.

To help laboratories navigate this complexity, Thermo Fisher Scientific and SampleQ hosted an Ask the Experts session focused entirely on MOSH/MOAH analysis using LC-GC-FID and GC×GC-FID/MS workflows. Analytical specialists addressed real-world questions from scientists and lab managers—covering sample preparation, quality control, internal standards, data processing, and system selection.

Assorted bottles of cooking oils with olives and herbs on a wooden surface.

This blog brings together the most important expert insights and practical guidance from that session, providing a valuable reference for anyone responsible for MOSH/MOAH testing.

Why MOSH/MOAH analysis is so challenging

Mineral Oil Saturated Hydrocarbons (MOSH) and Mineral Oil Aromatic Hydrocarbons (MOAH) are complex mixtures rather than single compounds. Their broad carbon number distribution, co-elution with natural matrix components, and sensitivity to sample preparation steps make analysis technically demanding.

At the same time, regulatory scrutiny continues to increase, particularly for MOAH due to potential carcinogenicity. Laboratories must therefore balance:

Regulatory compliance
Robust quantification
Reliable identification of markers
High sample throughput

The Ask the Experts session focused on how modern, integrated workflows can help labs meet all these demands.

Are MOSH/MOAH sample preparation steps matrix dependent?

One of the most common questions from laboratories is whether MOSH/MOAH sample preparation can be standardized across all matrices.

The expert answer: it depends on the matrix—and validation is essential.

For fats and oils, certain steps are always required:

Saponification
Epoxidation

However, alumina (Alox) clean-up is matrix dependent. Practical comparisons show that:

Some matrices benefit from Alox clean-up
Others may suffer from analyte loss if Alox is applied unnecessarily

For non-fat matrices, sample preparation must be carefully selected, and method validation is critical to ensure accuracy and recovery.

Key takeaway: There is no universal sample prep recipe for MOSH/MOAH. Laboratories must adapt workflows to their matrices while staying aligned with ISO 20122 guidance.

Managing multiple sample prep options in a busy lab

Many labs analyze a wide variety of matrices daily. Running different sample prep workflows manually can be time-consuming and error-prone.

Experts highlighted how software-driven workflows help solve this challenge:

Multiple sample prep methods can run in the same sequence
Optional steps (such as Alox clean-up) can be toggled per sample
Overlapping methods maximize instrument utilization
Analysts only need to weigh samples and load reagents—automation handles the rest

E-workflows simplify method selection and ensure the correct prep is applied every time, reducing training requirements and minimizing human error.

For lab managers, this translates into:

Higher throughput
More consistent results
Less hands-on time for skilled analysts

Which internal standard is best for MOAH quantification?

Internal standard selection is critical for reliable MOAH quantification. The experts addressed this directly, referencing extensive comparative studies.

Three candidates were evaluated:

1-Methylnaphthalene (1-MN)
2-Methylnaphthalene (2-MN)
Tert-butylbenzene (TBB)

Based on repeatability, reproducibility, recovery, and accuracy, TBB emerged as the clear winner and is now specified in ISO 20122.

Why TBB?

More stable behavior across sample prep steps
Better overall performance in routine analysis
Improved consistency between laboratories

For labs updating or validating MOSH/MOAH methods, aligning internal standards with ISO recommendations is strongly advised.

How should ISO criteria for internal standard recovery be interpreted?

A frequent point of confusion is how to interpret internal standard recovery limits defined in ISO methods.

The experts clarified an important distinction:

Recovery criteria apply to direct injections of internal standards
All components should fall within 90–110% of the quantification standard
Perylene is allowed a slightly broader range (80–100%)

In real samples, internal standard recoveries can vary due to legitimate chemical effects:

Epoxidation may reduce perylene
Alox clean-up can reduce cholestane
Saponification may affect methylnaphthalenes
Some hydrocarbons may be naturally present in the matrix

Bottom line: Deviations in sample recoveries do not automatically indicate method failure. Understanding the chemistry behind each step is key to correct interpretation.

Do you still need LC-GC-FID if you have GC×GC-MS?

As GC×GC-MS becomes more accessible, many labs ask whether it can replace LC-GC-FID entirely.

According to current EURL guidance:

GC×GC is primarily intended for identification, not quantification
Quantification using GC×GC-FID is technically possible but not yet recommended
LC-GC-FID remains the reference technique for MOSH/MOAH quantification

GC×GC-MS plays a complementary role by:

Confirming the presence of aromatic markers and MOSH markers like hopanes, steranes and particular naphthenes
Differentiating mineral oil components from biogenic interferences
Supporting risk assessment and regulatory discussions

For now, the most robust approach is a combined workflow:

LC-GC-FID for quantification
GC×GC-FID/MS for confirmation and identification

Using specific ion masses for marker identification in GC×GC

GC×GC-MS offers powerful identification capabilities when used correctly.

Experts highlighted that:

The EURL provides recommended ion masses for key MOAH subgroups
Selective ion chromatograms (SICs) can be generated for markers such as:
- Naphthalenes
- Hopanes
- Steranes
- DIPNs

Using multiple SIC views alongside total ion chromatograms (TICs) allows:

Faster confirmation of markers
Clear differentiation from interferences
More confident reporting of MOAH presence

This approach significantly improves interpretability compared to relying on TICs alone.

How is GC×GC-MS data processed efficiently?

One concern with GC×GC-MS is the perceived complexity of data handling.

The experts demonstrated a streamlined workflow:

Instrument control and acquisition remain in Chromeleon S/W
Raw data are automatically exported for GC×GC processing
Templates are applied to identify known marker regions
Results are organized by vial, run, and detector channel

This structured approach ensures:

Consistent marker identification
Reduced manual data handling
Faster reporting despite large data volumes

For labs new to GC×GC, standardized templates and automated processing significantly reduce the learning curve.

Comparing FID and MS chromatograms: why it matters

Accurate comparison between FID and MS data is critical when combining quantification and identification.

Thanks to synchronized acquisition:

FID and MS chromatograms are recorded simultaneously
First-dimension retention times are identical
Second-dimension alignment is highly accurate

This enables:

Direct correlation of quantified FID regions with identified MS markers
Greater confidence in results
Stronger defensibility during audits and regulatory review

Why use a single quadrupole MS instead of TOF-MS?

Time-of-flight MS is often associated with GC×GC due to its high scan speed. However, experts explained why single quadrupole MS can be a practical alternative.

By optimizing scan speed:

Single quadrupole MS can capture sufficient data points
Complexity and cost are reduced
Compliance with EURL guidance is maintained

For many routine MOSH/MOAH applications, this offers an excellent balance between performance and operational efficiency.

Is offline sample preparation better for GC×GC?

There is no universal answer—workflow design depends on laboratory needs.

Integrated systems offer:

Minimal user intervention
Reduced risk of contamination
Streamlined operation

Separate systems allow:

Parallel operation
Higher overall throughput in some labs

The best choice depends on sample volume, staffing, and analytical priorities.

Final thoughts: Building a future-proof MOSH/MOAH workflow

MOSH/MOAH analysis is evolving rapidly, but some principles remain constant:

Robust quantification still relies on LC-GC-FID
GC×GC-FID/MS adds critical confirmation power
Automation and software workflows reduce complexity
Alignment with ISO and EURL guidance ensures defensibility

By combining expert knowledge with integrated technology, laboratories can confidently meet today’s regulatory requirements—while preparing for what comes next.

If you’re looking to optimize or future-proof your MOSH/MOAH analysis, the insights from this Ask the Experts session provide a strong foundation for success.

Watch the free webinar on demand: Talk to an expert about our barrier-free analysis of MOSH/MOAH

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