Chemiluminescence measurement of tertiary amines using the continuous-addition-of-reagent technique. Determination of trimethylamine in fish samples

The continuous-addition-of-reagent technique was used as an effective means for enhancing the performance of energy transfer chemiluminescence-based determinations. For this purpose, the reaction between tertiary aliphatic amines and sodium hypochlorite in alkaline medium containing fluorescein as sensitizer was chosen. The influence of experimental variables such as the addition rate and sodium hypochlorite concentration, pH and fluorescein concentration on the maximum reaction rate was assessed and compared with that observed when using Rhodamine B as sensitizer. The method based on fluorescein exhibited the better analytical features (e.g. calibration graph for trimethylamine was linear over a wide such range as 10–2500 nmol, with relative standard deviation of 2.6%). The proposed method allows the indirect determination of primary amines (viz. methyl- and ethylamine) and compares favourably with recent alternatives to the determination of trimethylamine in fish tissue (mean recovery 101.0% and standard deviation 2.7). Some aspects on the degradation during storage of fish samples are discussed.