Determination of glyceryl linoleate in malt and rice for brewing by gas chromatography-tandem mass spectrometer with simultaneous transesterification and solid-phase micro-extraction

A method based on solid-phase micro-extraction (SPME) with simultaneous transesterification coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of glyceryl linoleate in raw materials (malt and rice) for beer. The impact of different factors on transesterification and extraction was investigated. The results showed that a 85μm Polyacrylate fiber extracting for 60min at 65℃ after adding 0.75 mL 10.7mmol/L KOH/CH3 OH and 1g NaCl in sample diluents was the best choice. The matrix effect was reduced by spiking glyceryl trilinoleate as an external standard in malt and rice, respectively. The limitations of detection of the method were 0.132μg/g in malt and 0.579μg/g in rice. The recoveries of glyceryl trilinoleate were found to be 116% and 114% at the spike levels of 5.0mg/g and 1.0mg/g in malt and rice matrices, respectively. Comparing to traditional way, the advantages of this method were less sample needed, accuracy simple operation process and suitability for routine analysis of glyceryl linoleate in raw materials for beer.