Rapid detection of vegetable oils in milk fat by on-line LC-GC analysis of β-sitosterol as marker

Abstract

On-line liquid chromatography-gas chromatography (LC-GC) has been applied to the detection of vegetable oils in milk fat using β-sitosterol as marker. The method involves transesterification of the fat, pre-separation of the sterol fraction from other lipid constituents and on-line transfer to the capillary GC system. The on-line approach avoids time-consuming sample preparation steps prior to GC analysis. The suitability of this analytical approach was tested with model mixtures of milk fat with cotton and rapeseed oil. The method allows the detection of adulterations at low levels. Simultaneous quantification of cholesterol in milk fat is also possible. Considering the rapid sample preparation, the described method can be applied for screening of large sample numbers.