Self-assembled polydiacetylene (PDA) vesicles, with the distinct advantages of low-cost materials, simple preparation, and excellent chromatic properties, can be perfectly combined with a colorimetric strip for on-site inspection. Herein, without involving expensive reagents and instruments, a visual colorimetric strip based on well-prepared PDA vesicles was developed to analyze and monitor histamine in deep-sea fish and its canned food. The standard calorimetric card for semiquantitative detection of histamine was successfully prepared and the quantitative detection can be further realized by analyzing the gray value using ImageJ and “Color Grab” in a smart phone. After optimizing the assembly conditions, this assay exhibited a linear response to histamine within the range from 70 to 2240 ppm. With excellent stability and sensitivity, this strip can be used to monitor the quality change of canned fish at different temperatures, so that people can avoid suffering from histamine poisoning, suggesting that it holds great potential in the intelligent system for on-site detection and real-time monitoring.

A sensitive and easy analytical method for catecholamine metabolites including 4-hydroxy-3-methoxyphenylglycol sulfate (HMPG sulfate), vanillylmandelic acid (VMA) and homovanillic acid (HVA) determination was developed based on liquid chromatography-tandem mass spectrometry in a negative multiple reaction monitoring mode. The analytes were rapidly separated on a reversed-phase Waters Xbridge C18 column (150 × 2.1 mm i.d.) with the mobile phase of 15% (v/v) acetonitrile containing 2 mM ammonium formate and 85% (v/v) formic acid solution (0.05%, v/v). Mass spectrometric conditions, such as characteristic fragmentations and quantification ion transitions, both with chromatographic conditions including separation column type and mobile phase composition, were systematically investigated to get optimal sensitivity and specificity. The limits of detection were in the range of 0.03-0.7 ng/mL for the targets. Recovery rates of spiked urine samples with three different concentration levels (low, middle and high) were above 86% with precisions less than 5.7%. For serum analysis, acetonitrile chosen both as protein precipitation reagent and extraction solvent facilitates to reduce matrix effects. Recovery rates of spiked serum sample were in the range of 90.6% to 111.1% for three targets. The intra-day and inter-day precisions were satisfactory less than 8.7%. This proposed method was successfully applied to determine HMPG sulfate, HVA and VMA present in human urine and serum.

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