Analytica Chimica Acta 580 (2006) 216–222 Seafood freshness determination through vapour phase Fourier transform infrared spectroscopy S. Armenta a , N.M.M. Coelho b , R. Roda a , S. Garrigues a,∗ , M. de la Guardia a a Department of Analytical Chemistry, Universitat de Val` encia, Edifici Jeroni Mu˜ noz, 50th Dr. Moliner, 46100 Burjassot, Val` encia, Spain b Institute of Chemistry, University of Uberlˆ andia, Av. Jo˜ ao Naves de ´ Avila, 2160, Campus Santa M ˆ onica, CEP 38.408.110, Uberl ˆ andia, MG, Brazil Received 14 May 2006; received in revised form 20 July 2006; accepted 28 July 2006 Available online 2 August 2006 Abstract A new vapour-phase manifold has been developed to determine trimethylamine (TMA) in fish and cephalopod samples by Fourier transform infrared (FT-IR) spectroscopy. Samples were treated off-line for 1h with trichloroacetic acid (TCA), filtered and washed. The obtained extracts were aspirated and alkalinized with NaOH 2.0 M, in an on-line system. TMA was separated from the solution in a gas phase separator and then transported by means of a nitrogen carrier into a home made 10cm pathlength IR gas cell, where the corresponding FT-IR spectra were acquired by accumulating 30 scans per spectrum with 2 cm -1 nominal resolution. The method was applied to the determination of TMA in natural samples providing concentration values statistically comparables with those obtained by a head space gas chromatography (HS-GC) reference procedure. The sample throughput by FT-IR is increased by a factor of 6 as compared with HS-GC. © 2006 Elsevier B.V. All rights reserved. Keywords: Vapour phase; Fourier transform infrared spectroscopy; Trimethylamine; Fish and cephalopod samples 1. Introduction The quality of fish products can be evaluated by different approaches. Typical methods include sensory like odour, taste, texture; microbiological expressed as total viable count (TVC); physical, based on texture and electrical properties and chemical, from the determination of volatile compounds such as (CH 3 ) 3 N (trimethylamine or TMA), (CH 3 ) 2 NH (dimethylamine or DMA) and NH 3 (ammonia); which are products of microbial degra- dation [1]. Ammonia and amines can be collectively distilled and measured as total volatile basic nitrogen (TVB-N), and this parameter could be used as a marker of the fish spoilage [2]. The fish industry and retailers are interested in methods that are cost effective, rapid, reliable and non-destructive. The stan- dard EU method for determination of TVB-N levels in fish tissue samples consist of extraction of volatile bases by a perchloric acid solution followed by steam distillation of the extract which is then collected in boric acid and titrated against standard HCl [3]. Although, this method is accurate when performed by expe- ∗ Corresponding author. Tel.: +34 963543158; fax: +34 963544838. E-mail address: salvador.garrigues@uv.es (S. Garrigues). rienced analysts, the reference method is nonetheless destructive and time-consuming. On the other hand, the AOAC International recommends a method for the determination of trimethylamine based on extraction of the amine in toluene and subsequent reac- tions with picric acid. Involving several time-consuming steps, the method is rather complex and hazardous [4]. Most of the methods described in the literature for the deter- mination of the aliphatic amines involve gas-chromatography with flame ionization detection (FID) [5] or mass spectrom- etry (MS) [6] and solid phase micro-extraction (SPME) [7] or head-space (HS) [8] as sampling technique. Alternatively, ion exchange chromatography [9], and capillary electrophore- sis with indirect UV detection [10] have been used for alky- lamine determination in foods. Other methods developed for TMA determination were based on an ammonia ion selective electrode [11], a chemiluminescence reaction [12] and a gas biosensor system [13]. The pervaporation of the TMA through a polytetrafluorethylene (PTFE) membrane has been successfully employed with photometric [14] and potentiometric detection [15]. On the other hand, it has been evidenced that Fourier trans- form infrared (FT-IR) spectrometry is an exceptionally tool for the quantitative determination of volatile or semivolatile com- 0003-2670/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2006.07.070