A new spectrofluorimetric method was developed in this study for simple determination of cadaverine (CD) (1,5-diaminopentane) in flesh of mackerel fish. This method required homogenization of the flesh, solid phase extraction (SPE) with 0.4M HCl/methanol or water/methanol (25/75v/v), centrifugation and derivation with orthophthalaldehyde (OPA). Physico-chemical parameters that affected the sensitivity of the fluorescence signal of the cadaverine-dihydrochloride/orthophthalaldehyde complex (CD/OPA), were optimised; these included reaction time, temperature, solvent system, pH and reactants concentrations (OPA/CD). The study was conducted in acetate buffer (pH 3.5 and 7) and showed low limits of detection (LOD), 0.6 and 25.5 ng. mL -1 respectively. The limits of quantification (LOQ) obtained were 3.5 ngmL -1 (pH 3.5) and 122 ngmL -1 (pH 7). The sensitivity of the results allowed its satisfactory application for quantification of cadaverine in fish.

In this work, a spectrofluorimetric method was developed to determine the rate of agmatine (AGM) in shrimp using orthophthalaldehyde (OPA) as derivatization agent. To optimize analytical results, the stoichiometry of the orthophthalaldehyde-agmatine complex (OPA-AGM) was determined. The effects of agitation and temperature on the fluorescence spectra of the complex in alkaline medium (pH 13) were then studied. We obtained in all media satisfactory analytical performances with very low detection limits (DL) ranging from 0.36 to 2.52 ng/mL and a quantification limit (QL) oF 1.62 to 8.40 ng/mL The relative standard deviations (RSD) obtained ranged from 0.08 to 1.5%, which shows the excellent replicability of measurements. In addition, recovery rates found in shrimp extract, between 96.3% and 103.4%, show the accuracy of measurements. Lastly, the interference effects on the determination of agmatine rate with biogenic amines and some metal ions likely to be present in shrimp were studied.

This paper concerns spectrofluorometric analysis of putrescine using orthophthaladehyde as a fluorophore in aqueous alkaline medium. Wavelengths of excitation and emission in acid, neutral, and alkaline media were different. There is a maximum intensity of fluorescence in alkaline medium 24 h after complexation compared with other media. Putrescine and orthophthaladehyde are used at an equimolar ratio, and the product is kinetically stable in alkaline medium. Calibration curves obtained gave limits of detection and quantification of 39 and 65 ng/mL, respectively. The correlation coefficient obtained in alkaline medium was 0.992 at pH 12. Results obtained largely showed a good reproducibility of our method.

The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.