GC Analysis of Volatiles in Milk on Supel-Q™ PLOT after SPME using a 75 µm PDMS/Carboxen Fiber

Conditions

sample/matrix	3 g of 2% milk + 10 µL internal standard solution (20 µg/mL 4-methyl-2-pentanone) (9 mL GC vial)
desorption process	5 min, 250 °C
extraction	headspace, 15 min with constant stirring at 45 °C
SPME fiber	PDMS/Carboxen, 75 µm (57318)
column	Supel-Q PLOT, 30 m x 0.32 mm I.D. (24242)
oven	70 °C (2 min) to 140 °C at 6 C/min (2 min hold) then to 220 °C at 6 C/min (5 min hold)
carrier gas	helium, 35 cm/sec
sample	Milk
injection	splitless, closed 2 min
liner	0.75 mm liner
inj. temp.	250 °C
detector	GC-MS ion trap, m/z = 33-300

Description

Analysis Note	In this study, SPME was used for the analysis of volatiles in milk using a headspace method. Light can catalyze the formation of peroxides that can cleave double bonds in fatty acids. The cleaved by-products form aldehydes that can give the food a pungent off flavor. Dr. Ray Marsili investigated the feasibility of using SPME as a substitute sample preparation device prior to GC/MS analysis. The Carboxen/PDMS fiber was evaluated for the extraction of low ppb levels of pentanal, hexanal, and dimethyldisulfide. The results of the comparison of SPME to dynamic headspace analysis indicate that SPME-GC/MS is more accurate and precise while providing sensitivities equivalent to DH-GC/MS. The GC column used, Supel-Q PLOT, operates via gas-solid chromatography with a DVB adsorbent and permits the separation of a wide range of analytes.
Categories	Analytical Chromatography, Food & Beverage Analysis, SPME Applications, GC Applications, Foods, Flavors & Fragrances, Beverage Testing, Milk, Volatiles
Featured Industry	Food and Beverages
Legal Information	Supel-Q is a trademark of Sigma-Aldrich Co. LLC
Other Notes	Complementary products: Syringes Vials Gas Purification and Gas Management Inlet Liners, Glass Wool, and Specialized Hand Tools Septa and Specialized Hand Tools Column Ferrules, Nuts, and Specialized Hand Tools
suitability	application for SPME, application for GC

Analyte

• 2-Butanone
• 3-Methylpentane
• Acetone
• Dimethyl disulfide
• Hexanal
• Pentanal