Experimental and quantum-chemical studies of histamine complexes with copper(II) ion

In situ synthesis of luminescent dsDNA-Cu NCs stained with a dsDNA-lighted fluorophore for rapid and stable detection of histamine in food

Poisonous histamine is accumulated in stale meat and fermented foods. The rapid and stable detection of histamine is essential for food safety. Herein, a ratiometric fluorometric method for histamine detection was designed through in situ preparing double-stranded DNA‑copper nanoclusters (dsDNA-Cu NCs) stained with 4',6-diamidino-2-phenylindole (DAPI). dsDNA-Cu NCs with red emission were rapidly synthesized via mixing Cu2+, ascorbate and dsDNA at room temperature for 5 min. When DAPI was added during preparation, DAPI coordinated with the Cu element accompanied by the quenched red emission of dsDNA-Cu NCs, and DAPI bound to dsDNA together with the enhanced blue emission of DAPI. Upon adding DAPI and histamine simultaneously, the coordination of histamine with the Cu element further decreased the red emission of dsDNA-Cu NCs, and drove the movement of DAPI from the Cu element to dsDNA along with the enhanced blue emission of DAPI. Significantly, ratiometric fluorescence was insensitive to variations in instrument and environment, causing stable measurement. Meanwhile, in situ synthesis integrated probe preparation with analyte detection, reducing time consumption. Additionally, this method quantified histamine in the concentration range of 7-50 μM with a detection limit of 3.6 μM. It was applied to determining histamine in food with satisfactory accuracy and precision.

Crystal structure of 2-(1H-imidazol-4-yl)ethanaminium chloride

The title mol­ecular salt, C₅H₁₀N₃⁺·Cl⁻, was obtained as by-product in the attempted synthesis of a histamine derivative. The terminal amino group of the starting material is protonated. The C_imidazole—C—C—N(H₃)⁺ group in the cation is in an anti conformation with a torsion angle of 176.22 (10)°. In the crystal, cations and anions are linked via N—H⋯N and N—H—Cl hydrogen bonds, forming a two-dimensional network parallel to (10-1). A single weak C—H⋯Cl hydrogen bond completes a three-dimensional network.

Quantification of histamine in various fish samples using square wave stripping voltammetric method

The objective of this study was to describe a new and simple method for the determination of histamine so that it can be used in routine food analysis. A square wave stripping voltammetric (SWSV) method has been used for the indirect determination of histamine. The method is based on accumulation copper (II) - histamine complex onto a hanging mercury drop electrode and reduction of complex. The optimum conditions include an accumulation potential of -420 mV (versus Ag/AgCl), an accumulation time of 10 s. Two linear calibration graphs were obtained with slopes of 0.078 (μM/μA) and 0.014 (μM/μA), respectively. The detection limits were found to be 3 × 10(-7) and 1 × 10(-5) M for histamine (S/N = 3), respectively. The validated SWSV method showed good linearity as well as satisfactory repeatability and immediate precision values, for both instrument and method. The effect of common excipients and metal ions on the peak height of Cu-histamine complex peak was studied. The method was successfully, applied to the determination of histamine in canned anchovy (Engraulis encrasicholus), frozen Tinca tinca (L.) and Cyprinus carpio fish samples.