Automated derivatization and fluorimetric determination of biogenic amines in milk by zone fluidics coupled to liquid chromatography

Ammonium determination by merging-zone flow injection analysis and a naphthalene-based fluorescent probe

This paper discusses the first-time study of a naphthalene-based fluorescent probe-naphthalene-2,3-dicarboxaldehyde (NDA), in combination with merging-zone flow injection analysis for the automated fluorescence determination of ammonium. The determination was contingent on detecting the fluorescent product of NDA-SO₃^2--NH₄⁺, which has maximum excitation and emission wavelengths of 508 nm and 564 nm, respectively. And the possible sensing mechanism of NDA-NH₄⁺ was proposed. The effects of the reaction parameters, including reagent concentrations, reaction flow rate, coil length, reaction temperature, and pH were optimized. Under optimal conditions, this method afforded a sampling rate of 8 h^-1, a limit of detection of 0.045 μmol L^-1, and RSD of 3.68% (n = 14) with 1.50 μmol L^-1 ammonium, and the calibration range was 0.045-6.00 μmol L^-1. Examination of the organic nitrogen interference confirmed that the method attracts minimal interference from organic nitrogen, and the stability of the NDA reagent facilitates its field application. Other exhibited advantages include low reagent consumption and high automation; the method has been utilized in the successful determination of ammonium in freshwater and rainwater. The development of NDA applications for ammonium determination also provides more options for fluorometric determination of ammonium.

Recent Developments in Isoindole Chemistry

Isoindoles are highly reactive aromatic heterocycles that have a variety of important applications in areas such as medicine, analytical detection, and solar energy. Due to their highly reactive nature, isoindoles can be used to access their derivatives, which possess a diverse array of biological activities. However, their reactivity also makes isoindoles unstable and thus, difficult to prepare. Consequently, there has been a need for the development of novel methods that address some of the synthetic challenges and limitations, as well as reactions that utilize isoindoles to access potentially useful compounds. This review will give an overview of the novel reactions reported within the past decade (2012 to 2022) that involve 2H- and 1H-isoindoles and fused isoindoles as reactants, key intermediates, or products. This review is divided into two parts, with the first part focusing on the synthesis of isoindoles and the second part focusing on reactions of isoindoles. The scopes and limitations of the methods described therein will be discussed and the significance of their contributions to the literature will be highlighted. Similar reactions will also be compared.

1 Introduction

2 Synthesis of Isoindoles

2.1 Synthesis of 2H-Isoindoles

2.2 Synthesis of 1H-Isoindoles

3 Reactions of Isoindoles

3.1 Reactions of 2H-Isoindoles

3.2 Reactions of 1H-Isoindoles

4 Conclusions

Analytical strategies for the determination of biogenic amines in dairy products

Biogenic amines (BA) are mainly produced by the decarboxylation of amino acids by enzymes from microorganisms that emerge during food fermentation or due to incorrectly applied preservation processes. The presence of these compounds in food can lead to a series of negative effects on human health. To prevent the ingestion of high amounts of BA, their concentration in certain foods needs to be controlled. Although maximum legal levels have not yet been established for dairy products, potential adverse effects have given rise to a substantial number of analytical and microbiological studies: they report concentrations ranging from a few mg/kg to several g/kg. This article provides an overview of the analytical methods for the determination of biogenic amines in dairy products, with particular focus on the most recent and/or most promising advances in this field. We not only provide a summary of analytical techniques but also list the required sample pretreatments. Since high performance liquid chromatography with derivatization is the most widely used method, we describe it in greater detail, including a comparison of derivatizing agents. Further alternative techniques for the determination of BA are likewise described. The use of biosensors for BA in dairy products is emerging, and current results are promising; this paper thus also features a section on the subject. This review can serve as a helpful guideline for choosing the best option to determine BA in dairy products, especially for beginners in the field.