Browsing by Subject "Dispersive liquid-liquid microextraction"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Restricted
    Degradation of imidacloprid in water by photo-Fenton process using UV-LED lamps at neutral pH: Study of intermediate products by liquid chromatography mass spectrometry after dispersive liquid–liquid microextraction
    (Elsevier, 2024-03-01) Martínez Escudero, Carmen Maria; Garrido, Isabel; Contreras, Fulgencio; Hellín, Pilar; Flores, Pilar; Arroyo Manzanares, Natalia; Campillo Seva, Natalia; Pastor Belda, Marta; Viñas López-Pelegrin, Pilar; Fenoll, José; León Morán, Lixy Olinda; Química Analítica
    In the present study, a suitable analytical method to determine imidacloprid (IMI) and its main transformation products (TPs) in water by means of dispersive liquid–liquid microextraction (DLLME) combined with liquid chromatography coupled to mass spectrometry (LC-MS), using both quadrupole-time-of-flight (QTOF) and triple quadrupole (QqQ) analysers, has been developed. In addition, the structures of major products formed when IMI is photo-oxidized using ultraviolet A (UVA) irradiation with light emitting diode (LED) lamps were established. Finally, the behaviour of IMI and its main TPs generated in water during photo-Fenton processes at neutral pH using two ferric iron complexes, with ethylenediamine-N,N-disuccinic acid (EDDS) and nitrilotriacetic acid (NTA) as chelating agents, was studied. DLLME was found to efficiently preconcentrate IMI and IMI TPs from the water matrix using chloroform (as extractant solvent) and acetonitrile (as dispersant solvent) in a simple step. The selectivity of the used techniques provided unequivocal identification of IMI and its TPs and their quantification with high sensitivity during the photo-Fenton treatments. In addition, the photo-Fenton treatment using EDDS exhibited higher degradation rate than photo-Fenton treatment using NTA.
  • Thumbnail Image
    Publication
    Restricted
    Non-chromatographic speciation of arsenic by successive dispersive liquidliquid microextraction and in situ formation of an ionic liquid in water samples
    (Elsevier, 2020-05-30) Vicente Martínez, Yésica; Química Analítica
    Arsenic is an element present in waters in its different species which can cause a serious risk to human health due to the consumption of these waters. However, the toxicity of each species is very different. Because of that, in analytical chemistry there is a great interest in developing methods that allow the quantification of low concentrations and speciation of arsenic. Accordingly, this work introduces a novel method applied to determine very low concentrations of arsenic species (As (III), As (V), monomethylarsonic acid (MA), dimethylarsinic acid (DMA) and arsenobetaine (AB)) in water samples. The procedure provides high enrichment factors and great sensitivity in a simple and non-chromatographic way using electrothermal atomic absorption spectrometry. The in-situ formation of an ionic liquid (IL) results in a dispersion through the formation of a cloud of IL droplets that allows the instantaneous extraction of the arsenic species. After centrifugation, they can be quantified by direct injection of the extract (IL+arsenic species) into the detector. The different experimental conditions such as pH and the use of complexing agents allow the selective extraction of each species. An enrichment factor of 295 is obtained by using this procedure. Additionally, high sensitivity and a low detection limit (0.02 μg L−1) for all species are achieved, enabling the method as an alternative for the chromatographic techniques.
  • Thumbnail Image
    Publication
    Open Access
    Targeted and untargeted approaches using liquid chromatography with high-resolution mass spectrometry for the determination of lipophilic marine biotoxins in seawater and mussel samples
    (Elsevier, 2025-09-12) Pastor Belda, Marta; Arroyo Manzanares, Natalia; Viñas López-Pelegrin, Pilar; Sánchez Fernández, Olga; Pérez Ruzafa, Ángel; Campillo Seva, Natalia; León Morán, Lixy Olinda; Química Analítica
    Marine biotoxins are naturally occurring compounds produced around the world by various species of microalgae, whose presence increases significantly due to harmful algal blooms. This phenomenon is a major public health concern, as a large amount of marine fauna is exposed to these biotoxins. The aim of this study was the improvement and application of dispersive liquid-liquid microextraction and liquid chromatography coupled to high-resolution mass spectrometry for the determination of eight lipophilic marine biotoxins, okadaic acid (OA), dinophysistoxin 1 (DTX-1), dinophysistoxin 2 (DTX-2), 16:0 7-O-acyl okadaic acid (DTX-3a), gambierone (GAM), 44-methylgambierone (44-GAM), yessotoxin (YTX), and homoyessotoxin (hYTX), and their derivatives in seawaters and mussels by targeted and untargeted approaches. The proposed method provided detection limits ranging from 0.0004 to 1.7 ng mL-1 in seawater and 0.06 to 119 ng g-1 in mussel samples, depending on the biotoxin. A total of 23 seawater samples collected in the Mar Menor lagoon between 2021 and 2023 were analyzed and several of them were found to contain OA and DTX-3a at concentration levels in the 0.006–1.5 ng mL-1 range. OA and DTX-2 were also found at maximum levels of 8.0 and 1.2 ng g-1, respectively, in several mussel samples from commercial origin. In addition, a suspect screening was developed in the untargeted approach to investigate the presence of other derivatives of the target marine biotoxins in the samples using a home-made database covering 93 compounds. An unsaturated ester derivative of OA/DTX-2 was detected in the seawater samples collected during a red tide.