Numerous analytical approaches have been developed to determine histamine levels in food samples due to its health consequences. Consuming histamine over the Food and Drug Administration (FDA)-regulated 50 mg kg^-1 limit would result in chronic toxicity. Consequently, the present study discusses a novel electrochemical approach to evaluate histamine levels in fish products via a molecularly imprinted polymer (MIP) on an electrode surface. The film was produced with electropolymerized polyurethane (PU), which maintained the histamine compound. Fourier-transform infrared (FTIR) spectroscopy was applied to verify the MIP manufactured in this study. The capability of the polymer was measured by assessing its electron shifts with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Differential pulse voltammetry (DPV) was also employed to validate the sensing method. The MIP/screen-printed electrode (SPE) and non-imprinted polymer (NIP)/SPE recorded a linear response ranging from 1 to 1000 nmol L^-1 at the 1.765 and 709 nmol L^-1 detection limits. The sensing technique was subsequently utilized to determine the histamine levels in selected samples at room temperature (25 °C). Generally, the sensor allowed the accurate and precise detection of histamine in the fish samples. Furthermore, the approach could be categorized as a simple technique that is low-cost and suitable for on-site detections.

Polyurethane (PU) is a unique polymer that has versatile processing methods and mechanical properties upon the inclusion of selected additives. In this study, a freestanding bio-based polyurethane film the screen-printed electrode (SPE) was prepared by the solution casting technique, using acetone as solvent. It was a one-pot synthesis between major reactants, namely, palm kernel oil-based polyol and 4,4-methylene diisocyanate. The PU has strong adhesion on the SPE surface. The synthesized bio-based polyurethane was characterized using thermogravimetry analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy (FTIR), surface area analysis by field emission scanning electron microscope, and cyclic voltammetry. Cyclic voltammetry was employed to study electrocatalytic properties of SPE-polyurethane towards oxidation of PU. Remarkably, SPE-PU exhibited improved anodic peak current as compared to SPE itself using the differential pulse voltammetry method. Furthermore, the formation of urethane linkages (-NHC(O) backbone) after polymerization was analyzed using FTIR and confirmed by the absence of peak at 2241cm^-1 attributed to the sp-hydridized carbons atoms of CC bonds. The glass transition temperature of the polyurethane was detected at 78.1C.

Histamine is an important substance that can be applied as a parameter for allergic reactions and food freshness. This study develops a method to produce a histamine sensor based on electrodes modified using polyurethane-LiClO₄. A sensor method was developed where this sensor was produced from polyurethane. The application of 4,4′-diphenylmethane diisocyanate (hard compound) and palm kernel oil-based monoester polyol (soft compound) to produce polyurethane (PU) based on bio-polyol. The addition of lithium perchlorate (LiClO₄) was done in order to increase the conductivity of PU. The oxidation process was detected using cyclic voltammetry, whereas the electrochemical impedance spectroscopy was used to analyze the conductivity of the polymer. The polyurethane-LiClO₄ was attached on a screen-printed electrode (SPE) within 45 min. Moreover, the 1% LiClO₄-PU-SPE presented satisfactory selectivity for the detection of histamine in the pH 7.5 solution. The LiClO₄-PU-SPE presented a good correlation coefficient (R = 0.9991) in the range 0.015–1 mmol·L^–1. The detection limit was 0.17 mmol·L^–1. Moreover, the histamine concentration of mackerel samples was detected by the PU-SEP-LiClO₄. Several amine compounds were chosen to study the selectivity of histamine detection using SPE-PU-LiClO₄. The interference was from several major interfering compounds such as aniline, cadaverine, hexamine, putrescine, and xanthine. The technique showed a satisfactory selective analysis compared to the other amines. A satisfactory recovery performance toward varying concentrations of histamine was obtained at 94 and 103% for histamine at 0.01 and 0.1 mmol·L^–1, respectively. The application of PU-SEP-LiClO₄ as an electrochemical sensor has a great prospect to analyze histamine content in fish mackerel as a consequence of PU-SEP-LiClO₄ having good selectivity and simplicity.

The toxicity of histamine has attracted numerous researchers to develop a method for histamine determination purposes. The Food and Drug Administration (FDA) unequivocally prohibits the consumption of histamine above 50mg·kg⁻¹. Thus, an innovation in histamine detection in fish has been developed in this research. The investigation of the histamine level in fish has been conducted by using an electrochemical sensor approach and producing a polymer via molecularly imprinted polymer (MIP) on a screen-printed electrode. The technique was validated by assessing the shifts in electron shifting using the cyclic voltammetry (CV) approach and electrochemical impedance spectroscopy (EIS), whereas differential pulse voltammetry (DPV) was applied to validate the sensor method. The instruments showed a linear response ranging from 11000nmol·L⁻¹, with a detection limit of MIP/SPE at 1.765nmol·L⁻¹ and 709nmol·L⁻¹ for the NIP/SPE, respectively. The sensing technique was employed to determine the histamine level in selected samples at room temperature (25°C). The outcomes of this study indicated that the validated chemical sensor allowed accurate and precise detection of fish samples and can be categorized as a simple approach. The instrument is inexpensive and suitable for on-site detection.

Determination of five biogenic amines (heptylamine, histamine, tyramine, cadaverine and spermidine) in fish was optimised and validated using gas chromatography – flame ionisation detector (GC-FID) followed by confirmation using mass spectrometry (MS). The biogenic amines were derivatised using BSA (N, O-bis (trimethylsilyl) acetamide) + TMCS (trimethylchlorosilane) as a derivatisation agent. The linear working range was between 0.9995 – 0.9999. The limit of detection (LODs) were in the range of 1.20 – 2.90 μg/mL. The efficiency of recovery for every biogenic amines, which ranged between 98.41 – 116.39%, indicated that analytical procedure can be used to extract biogenic amines in fish. Using GC-FID, the concentration of five biogenic amines were simultaneously determined in fresh and salted fish samples such as mackerel (Scomberomorus guttatus), sardine (Sardinella gibbosa), whiptail (Himantura walga), gourami (Trichogaster pectoralis) and toli shad (Tenualosa toli). Histamine is found in fresh mackerel (S. guttatus) and sardine (S. gibbosa) at concentration of 5.96 and 2.69 mg/kg, respectively. Salted sardine (S. gibbosa) has histamine concentration of 8.95 mg/kg. All histamine concentrations detected were below 50 mg/kg (FDA regulation) which is below the permissible threshold associated with scombroid poisoning. Cadaverine was detected in fresh sardine (S. gibbosa), whiptail stingray (H. walga) and salted gourami (T. pectoralis) with concentration of 4.96, 146.39 and 18.80 mg/kg, respectively. None of them has biogenic amines, and histamine within FDA regulation levels (below 50 mg/kg).