Search results for "Detection limit"
showing 10 items of 810 documents
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…
Use of gold nanoparticle-coated sorbent materials for the selective preconcentration of sulfonylurea herbicides in water samples and determination by…
2012
Abstract Two new gold nanoparticle (NP) coated materials (silica supported on gold NP with and without ionic liquid) were synthesized for solid phase extraction of sulfonylurea herbicides (SUHs), such as bensulfuron-methyl (BSM), metsulfuron-methyl (MSM), pyrazosulfuron-methyl (PSM), thifensulfuron-methyl (TFM) and triasulfuron (TS), from water samples, followed by capillary liquid chromatography coupled to diode array detection (CLC–DAD). Several factors influencing the preconcentration efficiency of SUHs and its subsequent determination, such as pH of the sample, eluent and reusability of sorbents, have been investigated. Under the optimum conditions, the developed method allowed the dete…
Polydopamine-coated magnetic nanoparticles for the determination of nitro musks in environmental water samples by stir bar sorptive-dispersive microe…
2021
Magnetic-based microextraction approaches have gained popularity in recent years due to the magnetic properties of the extraction phases allowing to handle them easier and more efficiently. This work describes a magnetic-based analytical method for the determination of the family of nitro musks in environmental water samples. These compounds have been of great concern due to their environmental impacts and potential health effects. The method is based on stir bar sorptive-dispersive microextraction (SBSDME) as extraction approach, prior to thermal desorption coupled to gas chromatography-mass spectrometry analysis (TD-GC-MS). For this purpose, polydopamine-coated cobalt ferrite magnetic nan…
Development of stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles and its analytical application to the determination of…
2014
A novel microextraction technique combining the principles of stir bar sorptive extraction (SBSE) and dispersive micro-solid phase extraction (DμSPE) is presented. The main feature of the method is the use of a neodymium-core stirring bar physically coated with a hydrophobic magnetic nanosorbent. Depending on stirring speed, the magnetic sorbent either acts as a coating material to the stir bar, thus affording extraction alike SBSE, or as a dispersed nanosorbent medium for the collection and extraction of the target analytes, in close analogy to DμSPE. Once the stirring process is finished, the strong magnetic field of the stir bar prevails again and rapidly retrieves the dispersed MNPs. Al…
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…
Selective solid-phase extraction of organophosphorus pesticides and their oxon-derivatives from water samples using molecularly imprinted polymer fol…
2020
Abstract A molecularly imprinted polymer was synthesized and characterized to be used as solid-phase extraction sorbent for simultaneous chlorpyrifos and diazinon and their oxon derivatives. Several imprinted polymers were prepared and evaluated in a retention study of these analytes compared with a non-printed polymer. Several parameters affecting the extraction of imprinted polymer such as washing solvent, composition and volume of the eluting solvent and sample volume, were also investigated. Under the optimum conditions, the developed method provided satisfactory limits of detection ranging between 0.07 µg L−1 to 0.12 µg L−1 and the material showed an excellent reusability (> 50 reuses)…
Determination of ultraviolet filters in bathing waters by stir bar sorptive–dispersive microextraction coupled to thermal desorption–gas chromatograp…
2015
In this work, a new approach that combines the advantages of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE), i.e. stir bar sorptive-dispersive microextraction (SBSDµE), is employed as enrichment and clean-up technique for the sensitive determination of eight lipophilic UV filters in water samples. The extraction is accomplished using a neodymium stir bar magnetically coated with oleic acid-coated cobalt ferrite magnetic nanoparticles (MNPs) as sorbent material, which are detached and dispersed into the solution at high stirring rate. When stirring is stopped, MNPs are magnetically retrieved onto the stir bar, which is subjected to thermal desorption (TD) to…
Some observations on the sensitivity of flow-injection techniques for atomic absorption spectrophotometry
1989
Abstract Different strategies for coupling flow-injection manifolds to atomic absorption spectrometers in order to obtain better sensitivity are compared. Using a T-connector interface, different carriers and flow compensation solvents have been assayed in an attempt to improve the sensitivity of flow-injection analysis. Manganese and copper determinations in sewage sludge have been used as a test system and the analytical parameters of both batch and flow-injection methods are compared.
Multi-pumping mechanised determination of selenium in natural waters by light emitting diode (LED) spectrometry
2009
It has been developed a fully mechanised procedure for the determination of selenium in waters employing a LED based spectrometer and solenoid multi-pumps as solution propelling devices. The proposed method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine, which oxidizes Variamine Blue to form a violet-colour species which absorb at 530 nm. The system was mechanised using the multicommutation process and a stopped flow strategy in the final step reaction. The analytical curve was linear between 0.010 and 0.500 mg L-1, with an equation ΔA = 0.501 (± 0.004) C and r = 0.999. The limit of detection (3σ/S) obtained for the proposed method was 0.00…
Development of a method for the analysis of seven banned azo-dyes in chilli and hot chilli food samples by pressurised liquid extraction and liquid c…
2008
An automated, confirmatory and sensitive procedure has been developed and validated for the determination of Sudan (I-IV), Sudan Orange G, Sudan Red 7B and Para Red in hot chilli food samples. The proposed method includes pressurised liquid extraction (PLE) with acetone, gel permeation chromatography (GPC) clean-up and detection by liquid chromatography (LC) coupled to electrospray ionization in positive mode tandem mass spectrometry (ESI-MS-MS). The main parameters affecting the performance of the different ionization sources and PLE parameters were previously optimised using statistical design of experiments (DOE). The method was in-house validated on chilli powder and chilli meat. Linear…