A new method was proposed for the determination of underivatized biogenic amines based on ion-exchange chromatography coupled with mass spectrometry detection. The method was applied to the analysis of 10 biogenic amines in fresh and processed fish products. The amines were extracted from muscle tissue with water without any additional derivative step or sample clean-up. Separation of biogenic amines was done by the IonPac (4 × 50 mm) column, applying a gradient eluent by mixing formic acid (2 mol L⁻¹) and Milli-Q water (formic acid concentration from 400 mM to 2 M). The results demonstrated a linear response in the range of 0.01 to 10 mg L⁻¹. The detection limits for the fish products ranged from 20 ng/g up to around 400 ng/g for histamine and putrescine, respectively. Spermidine and spermine showed significantly higher detection limits. This current method can be used for the determination of biogenic amines in both fresh and processed fish products for regulatory purposes and monitoring food-safety issues relating to these amines, particularly histamine. It is also a useful method for evaluation of other commercial analytical test kits and commonly used methods that are possibly affected by the food matrix due to processing or other drawbacks arising from the derivatization process.

In this study, comparative analyses were carried out with ion chromatography mass-spectrometry (IC-MS/MS) which has no derivatization step, high-performance liquid chromatography (HPLC) technique, as well as two quantitative and two semi-quantitative immunoassays. The results demonstrated that HPLC and quantitative immunoassay methods were well-correlated with IC-MS/MS in determining histamine in various types of fish products. The best correlation was observed with the HistaSure ELISA Fast Track kit (R² = 0.9903). More than half of the values (68%) obtained by two methods were also statistically similar. The results of semi-quantitative test kits also supported histamine values estimated by quantitative methods, with some exceptions. The best results were found for HistaSure Lateral Flow in supporting the quantitative techniques. Therefore, these methods are found suitable for monitoring histamine in fish products in terms of food safety. Good correlations were also observed HPLC and IC-MS/MS in determining cadaverine, putrescine, and tyramine with the highest value observed for tyramine as R² = 0.9785. However, no correlation was observed for other biogenic amines, and the majority of the results were significantly different from each other for these amines (p < 0.05). The differences may be caused by the drawbacks reported previously for HPLC. However, further studies are required to confirm the possible effects. This study provides a comparative evaluation of several methods in terms of their suitability in determining biogenic amines in fish products for both monitoring and regulatory purposes.

A partial distance-weighted variable anti-connectivity topological index was introduced for modelling pK _a values of 31 aliphatic carboxylic acids and haloalkyl-carboxylic acids. The partial distance-weighted variable anti-connectivity index showed superior modelling capabilities compared with the index calculated from the complete graph, because it is capable of accounting correctly for the intramolecular interactions of unconnected vertices to specific bond strengths (active site), thereby improving the RMS_CV error by about 30% (0.221 pK _a units).

This study demonstrates the effects of the freezing and frozen storage of anchovies prior to brining and dry-salting on quality changes and food safety during refrigerated storage (4 ± 1 °C). Fresh anchovies were divided into two groups, one of which was used as a control representing fresh raw material; the other was the experimental group and consisted of frozen and thawed anchovies stored at −18 °C for a year. Five different salt concentrations were used for brining (10, 15, 20, 25 and 30%) in addition to the dry-salting method. Microbiological, chemical, physical and sensory analyses were carried out during storage. Salt concentration and salting method had significant effects on the shelf-life of salted anchovy products, with the highest shelf-life corresponding to dry-salted anchovies (p < 0.05). The effect of using frozen and thawed raw materials for salting on the shelf-life depended on the processing method since the experimental dry-salted group had a shelf-life one month longer than that of the control group, while the opposite situation occurred for the brined samples, with one exception. Strong correlations were usually found between sensory values and chemical quality parameters (R²: 0.83–0.99 for the control group and 0.63–0.99 for the experimental group). The results demonstrated that the experimental group, with some exceptions, had better values for most quality and food safety parameters in comparison to the control group, indicating the advantage of using frozen and thawed raw materials before salting to prevent spoilage and enhance food safety. Considering that the experimental group was produced from one-year-stored raw material compared to the control group, the advantage of the freezing and frozen storage of anchovies can be accepted as much higher versus when freezing is not implemented. The positive effect is due to the fact that frozen anchovies absorb salt faster after thawing, especially in groups with high salt concentrations. Therefore, it can be concluded that frozen salted anchovies can be utilized for longer as they have a longer shelf-life, particularly when using either the 30% brining or dry-salting method.

The glycosylation process plays a crucial role in the structural integrity and biological activity of glycoproteins, where glycans are attached to a protein backbone. There are many kinds of glycans, the most common being N-glycans, which can be arranged into three classes, that is, complex, hybrid, and high mannoses, forming a structurally very diverse set of polar compounds that are difficult to detect and separate. Most commonly, N-glycans are labeled before separation by charged or fluorescence tags for better MS or fluorescence detection, respectively. This study examines the influence of ionic strength and organic modifier selection on the separation of fluorescently labeled dextran ladders in Hydrophilic Interaction Liquid Chromatography (HILIC). Using a Glycan BEH Amide column and varying the ammonium formate buffer concentration along with acetonitrile and methanol ratios, we investigated analyte retention, separation efficiency, and post-column conductivity changes. Our findings reveal that changes in the ionic strength of the mobile phase do not contribute to changes in selectivity, neither when acetonitrile nor methanol were used as organic modifiers to the mobile phase. However, the addition of methanol significantly changes the separation mechanism where two different prevailing separations mechanisms can be identified. It was assumed that the addition of methanol influences the folding pattern of dextrans around the permanent positive charge on the added tag, which influences the changes of separation selectivity. This work presents a systematic approach to altering mobile phase composition (buffer concentration, organic modifier type) to control retention and selectivity in complex glycan analysis. The discovery that methanol significantly alters separation behavior provides a potential new method for refining HILIC separations of polar compounds.