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Merck

Milk sample off-flavors

Milk sample off-flavors suitable for GC, application for SPME

Materiales

Estándar

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4-Methyl-2-pentanone

analytical standard

Hexanal

analytical standard

Dimethyl disulfide

analytical standard

Fibra para SPME

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Fibra de carboxeno/polidimetilsiloxano (DVB/CAR/PDMS) de SPME

df 75 μm(CAR/PDMS, for use with manual holder, needle size 24 ga

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columna analítica

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Columna capilar para GC Supel-Q PLOT

L × I.D. 30 m × 0.32 mm, average thickness 15 μm

CONDITIONS

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

Descripción

Nota de análisis

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.

Información legal

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