Activated aluminum oxide selectively retaining long chain n-alkanes: Part II. Integration into an on-line high performance liquid chromatography-liquid chromatography-gas chromatography-flame ionization detection method to remove plant paraffins for the determination of mineral paraffins in foods and environmental samples.
Aluminum oxide activated by heating to 300-400 degrees C retains n-alkanes with more than about 20 carbon atoms, whereas iso-alkanes largely pass non-retained (with characteristics described in more detail in Part I). This property is useful for the analysis of mineral oil contamination of foods and other matrices: it enables the removal of plant n-alkanes, typically ranging from C(23) to C(33), when they disturb the analysis of mineral paraffins (usually almost exclusively consisting of iso-alkanes). An on-line HPLC-LC-GC-FID method is proposed in which a first silica gel HPLC column isolates the paraffins from the bulk of edible oils or extracts and is backflushed with dichloromethane. In a second separation step, a 10 cm x 2 mm i.d. column packed with activated aluminum oxide separates the long chain n-alkanes from the fraction of the iso-alkanes which is transferred to GC-FID by the on-column interface and the retention gap technique. The retained n-alkanes are removed by flushing with iso-octane.
Fiselier
Katell
K
Official Food Control Authority of the Canton of Zurich, P.O. Box, CH-8032 Zurich, Switzerland.
Fiorini
Dennis
D
Grob
Koni
K
D000473:Alkanes / Q000032:analysis; D000537:Aluminum Oxide / Q000737:chemistry*; D002849:Chromatography, Gas / Q000379:methods*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003314:Corn Oil / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D005410:Flame Ionization / Q000379:methods*; D005504:Food Analysis / Q000379:methods; D008899:Mineral Oil / Q000032:analysis; D010232:Paraffin / Q000032:analysis*
D000473:Alkanes; D003314:Corn Oil; D010232:Paraffin; D008899:Mineral Oil; D000537:Aluminum Oxide