A new method for the rapid determination of volatile substances:: the SPME-direct method -: Part II. Determination of the freshness of fish

A rapid method for determining the freshness of the harvested fish is presented. The volatile amines, which are liberated during the storage of the tish have been quantified using a SPME direct method. This new method consist of an injection port of a gas-chromatograph linked by a short capillary to a detector. We have utilized standard chromatographic detectors, either FID or NPD. The volatile compound are adsorbed on a SPME-fiber and desorbed in the injector. The peaks are evaluated either by their area or the height. We have monitored the storage of salmon and whiting over a period of 20 days. Two different methods for preparing the fish samples have been evaluated: (1) the basification of a minced sample of fish directly in the vial without other preparation, (2) the standard TVB extraction procedure followed by basification in a head space vial. The response of the detector was standardized using aqueous trimethylamine solutions. The results show a good correlation between the time of conservation on ice of the fish and the measured signal either with the FID or with the NPD detector. The method allows a high throughput of samples with minimal manipulation. (C) 2001 Elsevier Science B.V. All rights reserved.