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1.
Determination of biogenic amines by thermal lens microscopic detection of enzymatically released ammonium
Mladen Franko, Mojca Žorž, 2016, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Biogenic amines (BAs) are organic amines present in meat, fish, dairy produce and wine due to the breakdown of amino acids, catalysed by microbial decarboxylases. BAs determination in food is important not only because of possible toxicological effects such as nausea, sweating and headache but also due to their possible role as indicators of food spoilage. Chromatographic methods are traditionally applied for determination of BAs in food [1], which usually require preliminary operations for sample pre-treatment that are laborious and difficult to automate. On the other hand, screening analytical systems provide simple, low cost and rapid analysis with the possibility of subjecting high number of samples to the screening system in a short time [2]. In this work we present a novel method for screening determination of BAs using a microfluidic system with the detection by highly sensitive thermal lens microscope (μFIA-TLM). Four biogenic amines (putrescine, cadaverine, histamine and tyramine) were subjected to enzymatic catalysis by transglutaminase, where ammonia was released as a product of acyl transfer reaction between the peptide bound glutamine (Gln) and the amino group of BAs. Ammonia was further transformed into indophenol blue by the Berthelot reaction. The coloured product was detected in batch (static) mode in a 100 μm sample cell or in μFIA (flowing) mode in a microchip with the same optical path length. The detection was performed on a TLM system applying a solid-state diode as an excitation source (660 nm). Organic solvents were tested for signal enhancement. For evaluation of the sensitivity and determination of LOD values (S/N = 3 basis), the NH4Cl standard solution was applied in Berthelot reaction with further detection on TLM system. The LODs for NH4+ in batch mode and in μFIA were 24 μg/L and 109 μg/L, respectively. Both LOD values are lower than the LOD achieved with conventional spectrophotometry (180 μg/L). When mixtures of the indophenol standard solutions and EtOH in the ratio of 1:1 were prepared the LOD in batch mode was improved to 3 μg/L, achieving 60-times improvement compared to spectrophotometry.
Najdeno v: osebi
Ključne besede: Biogenic amines, Thermal lens microscopy, microfluidics, translgutaminase
Objavljeno: 05.07.2016; Ogledov: 865; Prenosov: 0
.pdf Polno besedilo (74,85 KB)

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Determination of bioactive compounds in food samples by thermal lens microscopy
Mladen Franko, Dorota Korte Kobylinska, Branka Mozetič Vodopivec, Valeria Guzsvány, Mojca Žorž, Jelena Topič, 2016, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: osebi
Ključne besede: thermal lens microscopy, food samples, bioactive compounds
Objavljeno: 08.11.2016; Ogledov: 713; Prenosov: 0
.pdf Polno besedilo (516,89 KB)

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NOVEL APPROACHES FOR THE DETERMINATION OF BIOGENIC AMINES IN FOOD SAMPLES
Sara Budal, Mitja Martelanc, Mojca Žorž, Mladen Franko, 2017, izvirni znanstveni članek

Opis: In this work, new analytical approaches for determination of biogenic amines in wines were developed. For the first time, we studied the derivatization of BAs in wines with naphthalene- 2,3-dicarboxaldehyde (NDA) and with dabsyl chloride (DBS) and analysis of derivatized BAs by HPLC coupled to fluorescence (HPLC-NDA-FL) and thermal lens spectrometry (HPLC-DBS-TLS) detectors. The sensitivity of the two methods (LODs HPLC-NDA-FL in the range 27-73 μg/L; LODs HPLC-DBS-TLS in the range 3.4-11 μg/L) was higher than that of the official method for biogenic amines in wines, OIV-MA-AS315-18 (60-77 μg/L). For its best performances, the HPLC-DBS-TLS technique was applied to the analysis of putrescine, cadaverine, histamine and tyramine in two white wine samples. Additionally, exploiting the Berthelot reaction, the TLS fast screening of biogenic amines in wines, following the release of ammonia by transglutaminase, was also proposed. This approach allowed us to determine total biogenic amount content in concentrations below 0.1 mg/L, expressed as equivalents of histamine.
Najdeno v: osebi
Ključne besede: biogenic amines, NDA, liquid chromatography, TLS, fluorescence, wine
Objavljeno: 02.11.2017; Ogledov: 83; Prenosov: 2
.pdf Polno besedilo (441,06 KB)

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