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Photothermal lens technique: a comparison between conventional and self-mixing schemes
John Fredy Barrera Ramírez, Dorota Korte, Jose Juan Suárez-Vargas, Jehan Akbar, Evelio E. Ramírez-Miquet, Fatima Matroodi, Imrana Ashraf, Humberto Cabrera, Hanna Budasheva, Joseph J. Niemela, 2019, original scientific article

Abstract: This work focuses on assessing the analytical capabilities of a new photothermal lens method based on the self-mixing effect to reliably measure metallic traces in water-ethanol solutions. We compare it with the conventional thermal lens scheme, considering the low detection limit and versatility. A theoretical model is presented to describe the laser power variations as a function of the photothermal parameters of the analyzed sample. The experimental results demonstrate that the laser intensity variations, induced by the external optical feedback, are governed by the photothermal lens effect. Measurements of Fe(II)-1,10-phenanthroline in water–ethanol solutions show a favourable correspondence and agreement with the theory. The low detection limits obtained by the two analytic techniques also agree very well. Nevertheless, our instrument presents advantages regarding compactness and simplicity, suggesting that this platform could be potentially useful as a robust analytical tool for metallic trace detection. In addition, calibration of the method is performed by measuring the so-called self-mixing constant.
Found in: osebi
Keywords: thermal lens, photothermal spectroscopy, self-mixing effect, trace detection
Published: 05.04.2019; Views: 2307; Downloads: 0
.pdf Fulltext (715,09 KB)

Modulation of Pinot Noir wine colour by yeast selection
Dorota Korte, Lorena Butinar, Jelena Topić Božič, Branka Mozetič Vodopivec, 2019, published scientific conference contribution abstract

Found in: osebi
Keywords: yeast, HCDC activity, wine colour, Pinot Noir, pyranoanthocyanins
Published: 27.05.2019; Views: 2239; Downloads: 0
.pdf Fulltext (157,36 KB)

Determination of biogenic amine-forming potential of naturally occuring lactic acid bacteria (LAB) strains isolated from the grapes of Vitis vinifera cv. Refošk grape variety
Dorota Korte, Branka Mozetič Vodopivec, Lorena Butinar, Martina Bergant Marušič, Jelena Topić, 2020, published scientific conference contribution abstract

Abstract: Biogenic amines are naturally occurring compounds that have been reported in variety of food, such as fish, meat, cheese, vegetables, and wines. When biogenic amines are formed by microorganisms such as lactic acid bacteria (LAB) they may have adverse effect on human health. The most common biogenic amines found in foodstuff are histamine, tyramine, putrescine and cadaverine. LAB are used as starters in the production of several foods and beverages. In wines they are used in malolactic fermentation, where the conversion of malic acid to lactic acid occurs. The aim of this work was to determine biogenic amine-forming capacity of indigenous LAB strains isolated from grapes which were PCR positive and screening medium positive for biogenic amines. Three methods for the confirmation of LAB biogenic amine-forming potential were developed and compared: HPLC-DAD and TLC methods both using derivatization agent dansyl chloride and enzymatic method using horseradish peroxidase (HRP) and diamine oxidase (DAO) enzymes. The applicability of methods was tested on the three known biogenic amine-producing LAB strains: 0006, 9809, 9906 (IOEB, France). The limit of detection (LOD) of the methods was <1 mg/L for HPLC-DAD, 5 mg/L for TLC and 25 mg/L for enzymatic method. Although the LODs between the proposed methods differed, all of the three methods confirmed BA-forming potential of the three strains. Furthermore, the proposed methods were applied for the analysis of three indigenous strains: MKBT-282 (BA+), MKBT-307 (BA-) and MKBT-325 (BA+). The positive or negative BA-forming potential was confirmed with all of the three proposed methods.
Found in: osebi
Keywords: lactic acid bacteria, biogenic amines, histamine, grape
Published: 10.07.2020; Views: 1697; Downloads: 0
.pdf Fulltext (225,99 KB)

Determination of Dissolved Iron Redox Species in Freshwater Sediment using DGT Technique Coupled to BDS
Yue Gao, Arne Bratkič, Dorota Korte, Aleksander Kravos, Hanna Budasheva, Mladen Franko, 2019, original scientific article

Abstract: In this work we have developed a novel method for determination of iron redox species by the use of diffusive gradients in thin-film (DGT) technique coupled to photothermal beam deflection spectroscopy (BDS). The combination of both methods achieved low limit of detection (LOD) of 0.14 μM for Fe (II) ions. The total Fe concentration determined in the Vrtojbica river sediment (Slovenia, Rožna Dolina, 5000 Nova Gorica) was 49.3 μgL–1. The Fe (II) and Fe (III) concentra- tion amounted to 12.8 μgL–1 and 39.9 μgL–1, respectively. Such an approach opens new opportunities for monitoring the content of iron species in natural waters and sediments and provides highly sensitive chemical analysis and an accurate qualitative and quantitative characteristic of the materials under study.
Found in: osebi
Keywords: Beam deflection spectroscopy, diffusive gradients in thin-film technique, iron redox species, photothermal techniques, sediment
Published: 26.02.2019; Views: 2472; Downloads: 91
.pdf Fulltext (452,58 KB)

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