Methyl (9Z,12E)-octadeca-9,12-dienoate: Properties & Lab Guide

Methyl (9Z,12E)-octadeca-9,12-dienoate is a geometric isomer of linoleic acid methyl ester featuring a cis double bond at C-9 and a trans double bond at C-12, making it a valuable reference standard and biochemical probe in lipid research.

Chemical Name

Methyl (9Z,12E)-octadeca-9,12-dienoate

SKU

M1539317

Molecular Formula

C19H34O2

Molecular Weight

294.47 g/mol

Double Bond Geometry

Δ9 cis (Z), Δ12 trans (E)

Recommended Storage

–20 °C, under inert atmosphere, protected from light

Chemical Identity and Structure

Methyl (9Z,12E)-octadeca-9,12-dienoate is an 18-carbon fatty acid methyl ester (FAME) bearing two conjugated-geometry double bonds: a cis (Z) bond at the Δ9 position and a trans (E) bond at the Δ12 position. Its molecular formula is C₁₉H₃₄O₂ with a molecular weight of approximately 294.47 g/mol. This compound is a geometric isomer of methyl linoleate (all-cis 9,12-octadecadienoate), differing by the configuration at the C-12 double bond. The mixed Z/E geometry confers distinct physical and biochemical properties relative to both fully cis and fully trans isomers, making it useful as a stereospecific reference material in fatty acid analysis.

Research Applications

This compound serves several roles in lipid biochemistry and analytical chemistry:

• Chromatographic reference standard: Due to its defined stereochemistry, it is used as an authentic standard for GC-FID and GC-MS quantification of geometric fatty acid isomers in food, biological, and clinical samples.
• Lipidomics and metabolomics: Researchers employ this FAME to calibrate retention-time libraries for untargeted lipidomic workflows, aiding in the discrimination of cis/trans isomers that co-elute on non-polar columns but are resolved on silver-ion or highly polar (e.g., CP-Sil 88, SP-2560) stationary phases.
• Biochemical probe: As a structural analog of conjugated linoleic acid (CLA) methyl esters, it assists in studying isomer-specific effects on membrane fluidity, enzyme activity (e.g., desaturases, cyclooxygenases), and cellular lipid metabolism.
• Method development and validation: Suitable for spike-and-recovery experiments and proficiency testing in official methods (e.g., AOAC, ISO) for trans-fatty acid determination.

Handling, Storage, and Stability

Storage: Store at –20 °C in a tightly sealed vial under an inert gas atmosphere (nitrogen or argon), protected from light. Cold-chain shipping is recommended to maintain integrity during transit.

Handling precautions: Unsaturated fatty acid esters are susceptible to autoxidation at bis-allylic and allylic positions. Always work in a low-oxygen environment when weighing or diluting the compound. Use amber glassware or foil-wrapped vessels to minimize photodegradation. Avoid repeated freeze-thaw cycles; consider preparing single-use aliquots in inert-gas-purged vials.

Solubility: Readily soluble in common organic solvents including hexane, chloroform, diethyl ether, ethyl acetate, and methanol. Not appreciably soluble in water.

Stability indicators: Monitor solutions periodically by GC or UV absorbance. Formation of conjugated diene absorption around 230–235 nm is an early indicator of oxidative degradation. Discard solutions showing visible discoloration or off-odor.

Quality and Purity Considerations

For use as a quantitative analytical standard, the purity and isomeric integrity of Methyl (9Z,12E)-octadeca-9,12-dienoate are critical. Key quality parameters to verify upon receipt include:

• Isomeric purity: Confirm the Z/E configuration ratio by silver-ion HPLC or high-resolution capillary GC on a polar stationary phase. Co-elution of the 9Z,12Z isomer on standard columns requires careful chromatographic method selection.
• Chemical purity: GC-FID area-percent purity should be assessed relative to a certified reference material where possible. Typical research-grade FAMEs are supplied at ≥95–98% purity; verify the certificate of analysis (CoA) provided by Aladdin Scientific for the specific lot.
• Peroxide value: An initial peroxide value check is advisable for solutions prepared from stock, especially if the material has been stored for extended periods.

Always request the lot-specific CoA from Aladdin Scientific to confirm purity, isomeric composition, and any spectral data (NMR, MS) prior to critical experiments.

Frequently asked questions

What distinguishes Methyl (9Z,12E)-octadeca-9,12-dienoate from methyl linoleate?

Methyl linoleate (methyl 9Z,12Z-octadecadienoate) carries two cis double bonds, whereas Methyl (9Z,12E)-octadeca-9,12-dienoate has a cis bond at Δ9 and a trans bond at Δ12. This single geometric difference alters the molecule's three-dimensional shape, melting point, chromatographic retention, and biological activity, making the two isomers distinct entities requiring separate analytical standards.

Which chromatographic columns are recommended for resolving this isomer from related fatty acid methyl esters?

Highly polar capillary GC columns such as CP-Sil 88 (100 m), SP-2560, or equivalent cyanopropyl-polysiloxane phases are the industry standard for resolving geometric FAME isomers. Silver-ion (Ag-ion) HPLC provides complementary separation based on double-bond geometry and degree of unsaturation. Standard non-polar or mid-polarity columns are generally insufficient to separate 9Z,12E from 9Z,12Z isomers.

How should working solutions of this compound be prepared to minimize oxidation?

Prepare working solutions under nitrogen or argon by dissolving the neat compound in degassed hexane or chloroform at concentrations appropriate for your assay. Transfer to pre-purged amber vials, seal with PTFE-lined caps, and store at –20 °C. Prepare fresh dilutions on the day of analysis when possible, and discard any solution showing UV absorbance increases at 230–235 nm indicative of conjugated diene formation.

Is this compound suitable for use as a certified reference standard in regulated testing?

Methyl (9Z,12E)-octadeca-9,12-dienoate from Aladdin Scientific (SKU M1539317) is supplied as a research-grade reagent. For regulated or accredited laboratory testing requiring traceable certified reference materials (CRMs), users should verify whether the specific lot meets the metrological requirements of their regulatory framework (e.g., ISO 17025). Contact Aladdin Scientific for available documentation including CoA and purity data.

References

1. Christie, W.W. and Han, X. (2010) Lipid Analysis: Isolation, Separation, Identification and Lipidomic Analysis, 4th ed. Woodhead Publishing.
2. Destaillats, F. and Angers, P. (2002) One-step methodology for the synthesis of FA methyl esters from complex lipid matrices. JAOCS.
3. AOCS Official Method Ce 1h-05: Determination of cis-, trans-, Saturated, Monounsaturated, and Polyunsaturated Fatty Acids in Vegetable or Non-Ruminant Animal Oils and Fats by Capillary GLC. AOCS Press.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.