G000507

GC Analysis of Volatiles in Milk (Before and After Exposure to Sunlight) on Supel-Q PLOT after SPME using a 75 μm PDMS/Carboxen Fiber

suitable for GC, application for SPME

Properties

• technique(s): gas chromatography (GC): suitable; solid phase microextraction (SPME): suitable
• test parameters: sample/matrix: 3 g of 2% milk + 10 μL internal standard solution (20 μg/mL 4-methyl-2-pentanone) (9 mL GC vial); SPME fiber: PDMS/Carboxen, 75 μm (57318); extraction: headspace, 15 min with constant stirring at 45 °C; desorption process: 5 min, 250 °C; column: Supel-Q PLOT, 30 m × 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); inj. temp.: 250 °C; detector: GC-MS ion trap, m/z = 33-300; carrier gas: helium, 35 cm/sec; injection: splitless, closed 2 min; liner: 0.75 mm liner; sample: Milk
• suitability: application for SPME
• application(s): food and beverages

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.

Legal Information

Analyte

4-Methyl-2-pentanone
Dimethyl disulfide
Hexanal
3-Methylpentane
Acetone