Evaluation of chemical indicators for monitoring freshness of food and determination of volatile amines in fish by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A headspace solid-phase microextraction and gas chromatography-mass spectrometric (HS-SPME-GC-MS) method was developed to monitor methylamine (MA), dimethylamine (DMA) and trimethylamine (TMA) in fish. The alkylamines were extracted using carboxen/divinylbenzene/polydimethylsiloxane (CAR/DVB/ PDMS) fibres at 25 degrees C and exposure time of 5 min. Calibration curves showed good linearity in the concentration range of 0.5-10 mu g ml(-1) and the corresponding coefficients of correlation were all above 0.99. Detection limits were estimated to be 0.10 mu g ml(-1) for MA and DMA; and 0.15 mu g ml(-1) for TMA. Intra-day and inter-day variation of spike samples at 2.0 mu g g(-1) were 4.3-6.2% and 5.4-10%, respectively. Recovery of the method for TMA was found to be comparable to that of a standard titration method with the mean deviation of the two methods being 6.7%. The validated method was applied to study the decay profiles of the concerned alkylamines in two fish species that were stored at 0 and -20 degrees C; and the results obtained were compared with that obtained by using the classical parameter of total volatile basic nitrogen (TVBN).