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Edible oil GC and GC-MS applications

Updated: Apr 13



Fats and oils are among the most popular ingredients in cooking.

Variety of products and tastes, value or potential threat to health, branding of high-quality products are all criteria that stimulate great interest into the research of edible oils composition.

Free fatty acid determination by GC; Fatty Acid Methyl Ethers (FAME) key compounds determination in order to identify source of origin or possible adulterations by GC or GC-MS technique; Trans isomers analysis by GC-FID provides determination of monounsaturated and polyunsaturated FAMEs Triglycerides analysis using high temperature GC-FID


Analysis methods

1. ISO 15304:2002. Animal and vegetable fats and oils -- Determination of the content of trans fatty acid isomers of vegetable fats and oils -- Gas chromatographic method
2. ISO 12966:2014. Animal and vegetable fats and oils -- Gas chromatography of fatty acid methyl esters.
3. ISO 17678:2010 (IDF 202: 2010). Milk and milk products -- Determination of milk fat purity by gas chromatographic analysis of triglycerides (Reference method


 


Free Fatty Acid determination


Volatile fatty acids containing short hydrocarbon chain (C2-C7) are usually analysed by GC in free form. Though high polarity of carboxyl group brings no advantage in comparison with methyl esterified form, easy sample preparation makes free fatty acids determination is preferable method.

Instrument configuration

Split splitless inlet (SSI)
Column BP-21 (FFAP) 30 m × 0.25 mm 0.25 µm film, Cat.
FID detector
Carrier-gas – helium

Operating mode

Chromatograph Analysis time 8 min
Column Carrier-gas flow 1.6 ml/min Flow split 1:50
Column temperature 145 °С Inlet Inlet temperature 230 °С
FID detector Hydrogen flow rate 25 ml/min Air flow rate 250 ml/min Make up gas flow 20 ml/min Detector temperature 250 °С
Sample volume 0.5 µL



 


FAME analysis


Methyl ethers of fatty acids are convenient compounds for GC separation and quantification, providing excellent stability and minimum undesirable adsorption activity in comparison with underivatized fatty acids. Qualitative and quantitative analysis of FAME structural isomers is mainly applied for confirmation/determination of Fats & Oils source by pattern profile describable to reference samples. This analysis is also very important for detection of samples adulterated with low-cost oils. Another major demand to quantify trans-isomers as an indicator of synthetic additives or hydrogenating processes exposed to foods. A column of high polarity liquid phase can be applied for both FAME distribution analysis and separation of cis/trans-C18 isomers in the same analysis cycle.

Instrument configuration

Split splitless inlet (SSI). Optionally Programmable split/splitless inlet (PSSI) can be used.
Column RTX-2330, 105 m × 0.25 mm 0.2 µm film,
FID detector. Optionally MSD detector can be used for approved identification.
Carrier-gas – helium



Operating mode

Chromatograph Analysis time 60 min
Column Carrier-gas flow 1.9 ml/min Flow split 1:40
Column temperature Isotherm 1: 140 °С 0 min 3 °С/min Isotherm 2: 200 °С 15 min 4 °С/min Isotherm 3: 240 °С
Inlet Inlet temperature 230 °С
FID detector Hydrogen flow rate 25 ml/min Air flow rate 250 ml/min Make up gas flow 20 ml/min Detector temperature 250 °С
Sample volume 0.2 µL





 


Triglycerides analysis


Triglycerides are the underivatized components of fats and oils. Chromatographic analysis of triglycerides can be successfully used as additional test method to FAME analysis to detect falsifications. This measurement provides analyst with comprehensive data about native triglycerides and fatty acids as constituent parts of molecules. Chromatec Crystal 9000 Gas chromatograph intended for triglycerides analysis offers hightemperature programming in conjunction with highly inert system required to eliminate sorption of polar analytes.

Instrument configuration

Programmable Split-Splitless Inlet (PSSI)
Column CP-TAP CB for Triglycerides, 25 m × 0.25 mm, 0.1 µm film,
FID detector
Carrier-gas – helium Operating mode Chromatograph Analysis time 40 min
Column Carrier-gas flow 2.5 ml/min
Injection On-column
Column temperature Isotherm 1: 100 °С 1 min 10 °С/min Isotherm 2: 355 °С Inlet Temperature 100 °С 1 min 10 °С/min 355 °С
FID detector Hydrogen flow rate 25 ml/min Air flow rate 250 ml/min Make up gas flow 20 ml/min Detector temperature 370 °С
Sample Butter oil triglycerides in hexane
Sample volume 0.2 µL





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