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Applying Principles of High Speed Gas Chromatography to Reduce Analysis Times in the Speciation of Fats by GC Using EZGC Online Software
Jaap de Zeeuw, Rebecca Stevens*, Jennifer Rutherford, & Linx Waclaski.
Overview Determination of fat content in food is achieved through GC
analysis of the corresponding fatty acid methyl esters (FAMES)
Speciation of fats into saturated, monounsaturated, polyunsaturated, and trans categories is required for
nutritional labeling
A growing body of research has implicated elevated trans fat intake with cardiovascular disease, FDA recently determined that partially hydrogenated vegetable oils (PHVO’s) are no
longer generally recognized as safe (GRAS)
The separation of positional and geometric isomers (cis/trans) of unsaturated FAMES is challenging, standard
approaches involve 100m x 0.25mm ID capillary GC columns containing 90+% bis-cyanopropylpolysiloxane, analysis times
routinely exceed 1 hour
High Speed GC and Method Translation
Method translation is used to calculate new method parameters for different columns, carrier gases, and outlet
pressures. The elution temperature of each analyte is unchanged from the original method so that the
chromatographic profile is maintained
Software for performing method translation is freely available at http://www.restek.com/ezgc-mtfc
Separations and Calibration Analysis of PHVO’s in CandyFAME Peak # Alias
C4:0 1C6:0 2C8:0 3C10:0 4C11:0 5C12:0 6C13:0 7C14:0 8C14:1 (t9) 9C14:1 (c9) 10 MyristoleicC15:0 11C15:1 (t10) 12C15:1 (c10) 13C16:0 14C16:1 (t9) 15C16:1 (c9) 16 PalmitoleicC17:0 17C17:1 (t10) 18C17:1 (c10) 19C18:0 20C18:1 (t6) 21C18:1 (t9) 22 ElaidicC18:1 (t11) 23 VaccenicC18:1 (c6) 24C18:1 (c9) 25 OleicC18:1 (c11) 26C18:2(t9,t12) 27C19:1 (t7) 28C19:1 (t10) 29C18:2(c9,c12) 30 LinoleicC20:0 31C20:1T (t11) 32C18:3(c6,c9,c12) 33 γ-LinolenicC20:1 (c11) 34 EicosenoicC18:3(c9,c12,c15) 35 α-LinolenicC21:0 36C20:2 (c11,c14) 37C22:0 38C22:1T (t13) 39C20:3 (c8,c11,c14) 40 DGLAC22:1 (c13) 41 ErucicC20:3(c11,c14,c17) 42C23:0 43C20:4 (c5,c8,c11,c14) 44 ArachidonicC22:2 (c13,c16) 45C24:0 46C20:5 (c5,c8,c11,c14,c17) 47 EPAC24:1 (C15) 48 NervonicC22:6 (c4,c7,c10,c13,c16,c19) 49 DHAC18:1 (t9, OH-12) 50
A 50 component mix of FAMES in hexane at 0.90 mg/mL was used for evaluation of different high speed GC
configurations
FAMES spanned a range of 1-10 % w/w and are representative of major fatty acids found in meat, fish, dairy,
and vegetable oils
A shorter 70m x 0.18mm x 0.18mm bis-cyanopropylsiloxane column was employed as well as hydrogen carrier gas to
reduce analysis time while maintaining high peak capacity
Complex FAME separations are very sensitive to column loading, carrier gas flow, and oven temperature program
A commercial caramel candy listing partially hydrogenated soybean oil and cream as ingredients was chosen to
highlight a complex mixture of FAMES
A 2.16 g sample of candy was subjected to hydrolytic extraction and BF3-MeOH transmethylation according to AOAC method 996.06 followed by both high speed and
standard GC determination
The combination of dairy fat and PHVO gave a complex mixture of 18:1 and 18:2 trans isomers, several unknown isomers were observed but their area not peak summed.
Detailed separation of positional isomers is traded for speed on shorter, wider bore columns. Sample loading capacity was
acceptable for both 0.25mm ID and 0.18mm ID columns
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60Minutes
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Overall Profile
100m x 0.25mm, He 60 min analysis
100m x 0.25mm, H2 36 min analysis
70m x 0.18mm, H2 19 min analysis
AOAC 996.06100m x 0.25mm, He
12 14Minutes
70m x 0.18mm, H2
GC Method Total Fat (mg)
Sat.(%)
MUFA(%)
PUFA(%)
Trans (%)
100m x 0.25mm, He 243.2 2.8 4.4 0.8 2.3
100m x 0.25mm, H2 236.2 2.8 4.2 0.8 2.2
70m x 0.18mm, H2 216.9 2.4 3.8 0.7 2.3
4x dilution, 50:1 split
4x dilution, 75:1 split
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* Pharmasol Corporation, One Norfolk Avenue, South Easton, MA 02375