Validation of a flow-injection-gas diffusion method for total volatile basic nitrogen determination in seafood products

A potentiometric flow-injection method, using a gas-diffusion cell, is described for the determination of total volatile basic nitrogen (TVB-N) in seafood products. The method was based on the change of the potential of a tungsten oxide electrode when volatile basic compounds, liberated from the fish extract sample, diffuses via a permeable membrane into a phosphate buffer acceptor stream and locally shifts the pH. After being optimized the method was validated in terms of linearity, precision sensitivity and recovery. calibration graph was obtained in the range 1–20 mg of N per L with a detection limit (S/N = 3) of 0.02 mg N per L. The precision (relative standard deviation, n = 10) of this method for within and between-days is better than 1.2% and 2.2%, respectively. The method was applied for the analysis of TVB-N in four fish species (sardine, red mullet, mackerel and hake) and gave results in close agreement with those obtained by the official method. Comparison of the results using student t-test and variance ratio F-test showed there was no significant difference between the methods compared. Thus the proposed method is simple, easy to handle and reliable instrument for quality control of seafood products with a high throughput (40 samples h−1).