Corey Chromatography Solves the Challenge of Isomer Separation: Accurate Separation of Acetaldehyde and Ethylene Oxide in Food-Grade Carbon Dioxide

 

According to the internal quality requirements issued by The Coca-Cola Company for its carbon dioxide suppliers, ethylene oxide testing has been added, and the annual testing program conducted by third-party laboratories must include ethylene oxide. EO).

This change imposes new technical requirements on food-grade carbon dioxide suppliers and third-party testing laboratories: they must not only be capable of detecting trace amounts of ethylene oxide, but also eliminate interference from coexisting compounds such as acetaldehyde in their analytical results.

Among them, a long-standing technical challenge in the detection of food-grade carbon dioxide is:

Acetaldehyde and ethylene oxide are structural isomers, sharing the same molecular formula and molecular weight; conventional gas chromatographic methods struggle to achieve their effective separation.

If acetaldehyde and ethylene oxide cannot be separated, the two components may exhibit peak overlap, compromising the qualitative and quantitative analysis of ethylene oxide and even posing a risk of misinterpretation. To address this critical challenge, Core Chromatography has developed a food-grade carbon dioxide–specific gas chromatography method that achieves clear separation of acetaldehyde and ethylene oxide, with an ethylene oxide detection limit reaching… 0.04 ppm. This means the system can not only detect EO but also accurately distinguish it from acetaldehyde, which has similar chemical properties, thereby providing a reliable analytical basis for quality control of food-grade carbon dioxide.

Why is it difficult to separate acetaldehyde from ethylene oxide?

Acetaldehyde and ethylene oxide are typical constitutional isomers.

Project	Acetaldehyde	Ethylene oxide
English name	Acetaldehyde	Ethylene Oxide
Common abbreviations	AA	EO
Molecular formula	C₂H₄O	C₂H₄O
Relative molecular mass	44.05	44.05
Chemical category	Aldehydes	Cyclic ethers
Challenges in Detection	Easy to confuse with EO peak elution is approaching.	Prone to interference from the acetaldehyde peak.

Although the two compounds have different structures, they share identical molecular formulas and molecular weights, and their physicochemical properties are also quite similar. Under conventional chromatographic column conditions and standard analytical procedures, acetaldehyde and ethylene oxide may exhibit the following behaviors:

Retention times are similar;

Partial overlap of chromatographic peaks;

The two components co-elute;

The qualitative determination of ethylene oxide is interfered with by acetaldehyde.

The quantitative results for ethylene oxide show deviations.

This is also the core challenge in food-grade carbon dioxide and ethylene oxide detection: a response from the instrument does not necessarily mean that ethylene oxide has been accurately identified.

If the chromatographic system cannot resolve acetaldehyde from ethylene oxide, it becomes difficult to reliably determine whether the detected response originates solely from acetaldehyde, ethylene oxide, or a combined contribution of both.

Therefore, when evaluating an ethylene oxide detection protocol, one cannot rely solely on “Is there a peak?” or “What is the limit of detection?” must also be carefully verified:

Can acetaldehyde and ethylene oxide each elute as separate peaks?

Whether effective chromatographic separation has been achieved between the two components;

Does the qualitative analysis of ethylene oxide suffer interference from acetaldehyde?

Can it maintain stable separation in a food-grade carbon dioxide matrix?

Can the method detection limit meet the enterprise’s quality control requirements?

Liaoning Kerui’s technological breakthrough: truly separating acetaldehyde from ethylene oxide.

To address the challenge of separating acetaldehyde from ethylene oxide, Core Chromatography did not simply enhance detector sensitivity; instead, it adopted a systematic design approach encompassing column selection, valve‑switching flow paths, analytical conditions, and detection channels.

The Corei Chromatography food-grade carbon dioxide analysis solution employs:

Double FID detector + 2 valves, 3 columns

By employing a dedicated chromatographic column configuration and optimizing the flow path, the retention behavior of acetaldehyde and ethylene oxide within the system was altered. In the actual test chromatograms, acetaldehyde and ethylene oxide elute as distinct peaks, yielding two well-resolved, independently identifiable chromatographic peaks.

This technology does not address a simple… “Whether there is a response,” but rather two more critical questions:

1. Can it be confirmed that what was detected is indeed ethylene oxide?

After acetaldehyde and ethylene oxide are separated, they can be qualitatively identified based on their respective retention times, thereby reducing the risk of misidentifying acetaldehyde as ethylene oxide.

2. Can the ethylene oxide content be accurately determined?

When two chromatographic peaks overlap, the peak area may include the combined response of both components. After achieving effective separation, the peaks can be integrated individually, thereby enhancing the reliability of the quantitative results for ethylene oxide.

The core advantage of the Corei chromatographic solution lies not only in detecting ethylene oxide, but also in its ability to separate acetaldehyde, which is easily confused with it.

Figure 1. Chromatogram of acetaldehyde and ethylene oxide separation in the Kerei chromatography food-grade carbon dioxide analysis system

The experimental results show that the Core Chromatography method achieves a detection limit for ethylene oxide of:

Project	Indicator or requirement
Ethylene Oxide Control Standards	0.2 ppm
ISBT reference values	0.1 ppm
Core Chromatography EO detection limit	0.04 ppm
Separation capability	Acetaldehyde and ethylene oxide elute at separate retention times.

The detection limit of 0.04 ppm is lower than both the control threshold of 0.2 ppm and the reference value of 0.1 ppm specified by ISBT (International Society of Beverage Technologists), thereby providing a robust analytical foundation for the identification and quality control of trace amounts of ethylene oxide.

A single system covers food-grade applications. Six key organic impurities of CO₂

In addition to focusing on resolving the separation of acetaldehyde and ethylene oxide, Core Chromatography’s dual… The FID, two-valve, three-column analytical system can also detect multiple key organic impurities in food-grade carbon dioxide.

Test Items	Detection limit ( ppm)	Primary detection targets
Benzene	0.0034	Monitoring trace aromatic hydrocarbon pollution
Total hydrocarbons	0.0295	Assessment of the overall level of organic impurities
Methanol	0.02	Monitoring oxygen-containing organic compounds
Acetaldehyde	0.05	Monitor flavor and organic impurities while excluding them. EO jamming
Vinyl chloride	0.04	Monitoring trace-level chlorinated organic compounds
Ethylene oxide	0.04	Meet the requirements for new testing and quality control.

Multi-valve, multi-column, and dual-detector systems can allocate analytical channels based on the retention characteristics of different components, enabling both multi‑component analysis and the separation of critical constituents on a single instrument. For carbon dioxide suppliers and quality‑control laboratories, this approach helps minimize equipment switching between different analytical methods, thereby enhancing food‑grade compliance. Efficiency of multi-component CO₂ analysis.

Why Is “separation efficiency” more important than simply observing a chromatographic peak?

In practical testing, ethylene oxide analysis typically comprises three levels.

Level 1: The instrument responds.

Once the sample enters the chromatographic system, the detector generates a signal. However, this only indicates the presence of a detectable component in the sample and does not, by itself, confirm that the response corresponds to ethylene oxide.

Second level: The system can detect low concentrations.

By optimizing the injection and detection conditions, the system can lower the limit of detection. However, if acetaldehyde and ethylene oxide continue to co‑elute, even a sufficiently strong response may still fail to accurately quantify the individual concentrations of the two components.

Third layer: both sensitive and selective.

First, separate acetaldehyde from ethylene oxide using a chromatographic system, and then perform qualitative and quantitative analyses on each compound separately; this constitutes a more reliable analytical approach.

Therefore, food-grade carbon dioxide EO testing should not be based solely on limit of detection comparisons; it is also necessary to examine the actual chromatograms, retention time stability, and chromatographic resolution.

The technical value of the Core Chromatography solution lies in its simultaneous resolution of The two issues of “cannot be separated” and “cannot be measured as low.”

Which enterprises and laboratories is the plan applicable to?

Food-grade carbon dioxide production enterprise;

Carbon dioxide suppliers and related supply-chain enterprises;

Carbonated beverage manufacturing enterprise;

Beer and other food-grade products CO₂ enterprises;

Industrial Gas Quality Control Laboratory;

Third-party testing agency for food and gases;

Laboratories required to add ethylene oxide as an annual testing item;

Users who need to address the separation of acetaldehyde and ethylene oxide;

Enterprises that need to upgrade their existing gas chromatography analysis systems.

For laboratories already equipped with gas chromatographs, Corei can assess suitable valve systems, chromatographic columns, and analytical flow‑path configurations—along with potential upgrades—based on the existing instrument model, detector setup, target analytes, and required detection limits.

Conclusion: In ethylene oxide testing, the key is to achieve both low detection limits and effective separation.

With the addition of an ethylene oxide testing item to the food-grade carbon dioxide analysis, the laboratory faces not merely the introduction of a new test name, but also the need to address a fundamental technical challenge: how to confirm that the detected chromatographic peak originates specifically from ethylene oxide, rather than from acetaldehyde or other coexisting components.

Acetaldehyde and ethylene oxide have identical molecular formulas and molecular weights, making them a pair of isomers that are difficult to separate under conventional chromatographic conditions. Inadequate separation can compromise the qualitative and quantitative analysis of ethylene oxide. Core Chromatography employs a dual… The FID+2 valve‑3‑column dedicated gas chromatography system achieves separate peak resolution of acetaldehyde and ethylene oxide in food‑grade carbon dioxide, with a detection limit for ethylene oxide as low as 0.04 ppm.

Only by clearly distinguishing can one accurately identify; only by detecting at low levels can one effectively control. This is precisely the core technical value of Liaoning Kerui Chromatography Technology Co., Ltd.’s analytical solution for food-grade carbon dioxide and ethylene oxide.