Search results for "Elution"
showing 10 items of 337 documents
Determination of the new psychoactive substance dichloropane in saliva by microextraction by packed sorbent – Ion mobility spectrometry
2018
Abstract A simple procedure based on microextraction by packed sorbent (MEPS) has been proposed for the extraction of dichloropane in oral fluids and its determination by ion mobility spectrometry (IMS). Extraction conditions such as type of sorbent (octyl and octadecyl silica), sample pH, number of sample loadings, and elution volume were evaluated to obtain the most appropriate values. Dichloropane was extracted from saliva samples using C8 MEPS, loading with 100 μL sample (adjusted to pH 7) in 4 cycles, washing with 100 μL deionized water, and eluting with 50 μL 2-propanol in 10 cycles. The proposed MEPS procedure has been validated in terms of linearity, accuracy, and precision. A limit…
Determinación de residuos de paraquat en lechuga y repollo cultivados en Lepaterique mediante HPLC-DAD
2018
La determinación de residuos del herbicida paraquat en lechuga (Lactuca sativa) y repollo (Brassica oleracea) producidos en la comunidad de La Brea, Lepaterique y comercializados en la ciudad de Tegucigalpa fue llevada a cabo en los meses de octubre y noviembre de 2017, mediante la aplicación de cromatografía líquida de elevada resolución con detector de arreglo de diodos (HPLC-DAD) en menos de 6 minutos, con un mecanismo de separación de fase reversa empleando una columna superficialmente porosa C18 y una mezcla de ácido orto fosfórico al 0.1 M (pH 3,0) con acetonitrilo en proporción de 3:1 como fase móvil. El método se basa en la extracción con baño ultrasónico utilizando agua como solven…
Carbon fibers as green and sustainable sorbent for the extraction of isoflavones from environmental waters.
2021
Abstract Isoflavones are a group of phytoestrogens of important environmental concern due to their endocrine disrupting effects. This article presents a rapid, green, and sustainable method for determining four isoflavones (daidzein, genistein, formononetin, and biochanin A) in environmental waters complying with current trends in Analytical Chemistry. The method consists of in-syringe dispersive solid-phase extraction (DSPE) as the extraction approach, using carbon fibers as extraction material. The synthesis of carbon fibers is simple and sustainable, since it only requires a natural product such as raw cotton as precursor, which is thermally treated (600 °C for 30 min) in an inert (Ar) a…
Application of stable isotopes and AF4/ICP-SFMS for simultaneous tracing and quantification of iron oxide nanoparticles in a sediment–slurry matrix
2016
One major challenge in nanomaterial analysis, especially in complex environmental matrices, is the unambiguous differentiation between natural and engineered nanomaterials (ENMs). Particularly with regard to the investigation of ENM's/engineered nanoparticle's (ENPs) fate, analytical methods are needed allowing for tracing and sensitive quantification. Several ENPs are metal-based and contain elements being omnipresent in environmental matrices (e.g., Al, Ti, Zn, Fe and non-metal Si) – hence, high background levels of these elements are expected, compromising sensitive detection. In this work we developed successfully a combined approach of stable isotope labeling (tracing) and reverse post…
Comparison of different sorbents for on-line liquid-solid extraction followed by high-performance liquid chromatographic determination of nitrogen-co…
1998
Abstract LiChrolut EN [poly(styrene-divinylbenzene), PSDVB], Carbograph (graphitized carbon black, GCB), Isolute CN (cyanopropylsilica), Isolute C 2 (ethylsilica), and LiChrospher RP18 (octadecylsilica) were studied for on-line solid-phase extraction of twelve nitrogen containing pesticides from water. Determination (UV 210 nm) was performed with a Spherisorb C 8 analytical column and an acetonitrile-water gradient. The mean recoveries from 50 ml ranged from 83% for RP18 to 44% for GCB, and decreased in the following order: RP18, CN, LiChrolut EN, C 2 , and GCB. GCB showed poor recoveries due to incomplete desorption with the acetonitrile-water gradient used, and memory effects were detecte…
Bio-metal-organic frameworks for molecular recognition and sorbent extraction of hydrophilic vitamins followed by their determination using HPLC-UV
2020
A bio-metal-organic framework (bio-MOF) derived from the amino acid L-serine has been prepared in bulk form and evaluated as sorbent for the molecular recognition and extraction of B-vitamins. The functional pores of bio-MOF exhibit high amounts of hydroxyl groups jointly directing other supramolecular host-guest interactions thus providing the recognition of B-vitamins in fruit juices and energy drinks. Single-crystal X-ray diffraction studies reveal the specific B-vitamin binding sites and the existence of multiple hydrogen bonds between these target molecules and the framework. It offered unique snapshots to accomplish an efficient capture of these solutes in complex aqueous matrices. Fo…
Online Solid-Phase Extraction LC-MS/MS: A Rapid and Valid Method for the Determination of Perfluorinated Compounds at Sub ng·L-1Level in Natural Water
2018
In this research paper, we report a method able to detect perfluorinated compound at pg·L−1 levels in superficial and underground water samples. An online solid phase extraction HPLC-MS/MS method was developed for the analysis of 12 perfluoroalkyl acids (PFASs). The method is based on injection of 5000 µL of water sample in SPE online WAX column followed by chromatography separation and mass spectrometry determination. SPE online elution was performed by water + 0.05% NH4OH and methanol + 0.05% NH4OH, while separation of target compounds was achieved within 10 min by Gemini chromatographic column operating from 1 to 12 pH range and using a mixture of water-methanol + 0.05% NH4OH. Sub ng·L−1…
Chromatographic Separation of Cresol Isomers by a β‐Cyclodextrin: Application for the Determination of Volatile Phenols in Alcoholic Beverages
2006
Abstract The chromatographic separation of o‐cresol, m‐cresol, and p‐cresol by using β‐cyclodextrin as a chiral reagent has been studied. Conditions for the chromatographic separation of these isomers by using the cyclodextrin in the mobile phase or bonded in the stationary phase were optimized, and both procedures provided good results for the resolution of the chromatographic peaks. The use of fluorimetric detection (λexc 275 nm λem 300 nm) allows detection and quantification limits of the µg/L for eight studied phenols by using both procedures. The determination of volatile phenols in alcoholic beverages must be carried out using the cyclodextrin in the mobile phase because of the co‐elu…
Determination of sulfide in waters by flow-injection solid phase spectrophotometry
2000
A highly sensitive flow injection solid-phase spectrophotometric method was developed for the determination of sulfide in waters. The method is based on the formation of Methylene Blue (MB) by reaction between sulfide and N,N-dimethyl-p-phenylenediamine chloride in presence of Fe(III) in acidic medium. The MB formed was adsorbed on C18 bonded silica, located inside a laboratory-made flow cell, which was placed in the optical path of the spectrophotometer. Analyte retention and detection at 666 nm were performed simultaneously, followed by elution with a mixture of methanol and hydrochloric acid. Several variables of the system, such as amine concentration, acidity of the reaction medium, re…
Spectrophotometric determination of carbaryl by on-line elution after its preconcentration onto polyurethane foam.
2000
Abstract An analytical methodology has been developed for the UV-spectrophotometric determination of carbaryl in waters after its preconcentration onto a polyether type polyurethane foam followed by on-line elution. The aforementioned strategy offers an easy way for in-field sampling and to improve the analytical sensitivity. Several chemical and flow variables (mass of sorbent, sample flow rate, sample volume and carrier flow rate) were studied to ensure the best performance of the system. Recovery studies, carried out on natural water samples spiked with known amounts of carbaryl at concentration levels between 250 and 500 μg l−1, provided recovery percentages between 94 and 105%. A detec…