Search results for "Detection limit"
showing 10 items of 810 documents
Determination of type A trichothecenes by high-performance liquid chromatography with coumarin-3-carbonyl chloride derivatisation and fluorescence de…
2000
A method for the analysis of type A trichothecenes T-2 toxin, HT-2 toxin, neosolaniol and diacetoxyscirpenol by high-performance liquid chromatography with fluorescence detection using coumarin-3-carbonyl chloride has been developed. Different parameters concerning the analytical procedure such as stability of both the reagent and derivatised analytes, time and temperature of the derivatisation reaction, were studied and optimised. Three different clean-up procedures (solid-phase extraction with silica gel or C-18 cartridges, and liquid-liquid partition between toluene and dihydrogen phosphate buffer) were tested in order to remove the excess reagent peaks. The last procedure gave the best …
Direct determination of oleic acid in soybean oil by capacitively coupled contactless conductivity detection capillary electrophoresis in an oil-misc…
2014
Este trabalho teve por objetivo desenvolver um método analítico direto e rápido para a determinação de ácido oleico em óleo de soja por eletroforese capilar com detecção condutométrica sem contato. O eletrólito de corrida empregado foi uma mistura metanol/1-propanol (1:6 v/v) contendo 4 × 10-2 mol L-1 de KOH e 10% (v/v) em etileno glicol. As amostras foram preparadas pela solubilização de 50 g L-1 de óleo de soja e 1,33 × 10-3 de ácido salicílico (padrão interno) no eletrólito de corrida. Os ensaios quantitativos foram realizados adicionando ácido oleico puro às amostras, na faixa entre 0,53 e 2,13 × 10-3 mol L-1. Sob polaridade negativa, os solutos aniônicos deslocaram-se mais rapidamente …
Development and Validation of a Reversed-Phase Liquid Chromatography Method for the Simultaneous Determination of Indole-3-Acetic Acid, Indole-3-Pyru…
2011
A simple, sensitive, precise, and specific reverse HPLC method was developed and validated for the determination of plant hormones in barley (Hordeum vulgareL.). The method includes extraction in aqueous organic solvent followed by solid-phase extraction, sample evaporation, and reversed-phase HPLC analysis in a general purpose UV-visible (abscisic acid (ABA)) and fluorescence detection (indole-3-acetic acid (IAA) and indole-3-pyruvic acid (IPA)), high-performance liquid chromatography system. The separation was carried out on Zorbax Eclipse XDB C8 column (150 × 4.6 mm I.D) with a mobile phase composed of methanol and 1% acetic acid (60 : 40 v/v) in isocratic mode at a flow rate of 1 ml min…
A clean method for flow injection spectrophotometric determination of cyclamate in table sweeteners
2005
Abstract A flow system based on the multicommutation is proposed for fast and clean determination of cyclamate. The procedure exploits the reaction of cyclamate with nitrite in acidic medium and the spectrophotometric determination of the excess of nitrite by iodometry. The flow system was designed with a set of solenoid micro-pumps to minimize reagent consumption and waste generation. The detection limit was estimated as 30 μmol L −1 (99.7% confidence level) with linear response ranging up to 3.0 mmol L −1 . The coefficient of variation was estimated as 1.7% for a solution containing 2.0 mmol L −1 cyclamate ( n = 20). About 60 samples can be analyzed per hour, consuming only 3 mg KI and 1…
An environmentally friendly multicommutated alternative to the reference method for anionic surfactant determination in water
2004
Abstract It has been developed a fully mechanized procedure for the spectrophotometric determination of anionic surfactants in water expressed in terms of SDS concentration. The reference method, based on the reaction of SDS with methylene blue (MB) followed by extraction in chloroform, was mechanized in order to reduce the consumption of organic solvents. The system was based on the multicommutation approach and provided a 35 times reduction of the waste production without sacrificing the figures of merit of the method in terms of sensitivity and repeatability, for a dynamic linear range from 0.2 to 1.7 mg l−1. Results obtained for washing water samples were comparable with those obtained …
Flow analysis-spectrophotometric determination of ?-dopa in pharmaceutical formulations by reaction with p-Aminophenol
1994
Abstract A new method has been developed for the spectrophotometric determination of l -dopa in pharmaceutical formulations. The method is based on the reaction between the open-chain quinone of l -dopa, obtained in NaOH, and the benzoqinoneimine form of p-aminophenol, in the presence of KIO4. The reaction product is determined at 574 nm by using both alternately procedures, one based on the stopped-flow and another on a flow injection approach. Under the best experimental conditions L-dopa can be determined with a limit of detection of 52 ng/ml and a relative standard deviation of 0.2% for three replicate measurements of a solution containing 4 μg/ml.
Direct derivative spectrophotometric determination of carbaryl and carbofuran in water samples
1990
Abstract Derivative absorption spectrophotometry has been applied to the direct determination of carbaryl and carbofuran in water samples. The use of the third derivative for carbaryl and the fourth derivative for carbofuran reduces the matrix effect and the seventh derivative provides, in both cases, accurate results for the determination of these pesticides, even working at low dilution levels of the samples. A limit of detection of 4 ppb and a variation coefficient of 0.1% have been obtained for the determination of carbaryl. Carbofuran can be determined with a limit of detection of 5 ppb and a variation coefficient of 0.02%.
Spectrophotometric flow injection determination of formetanate and m-aminophenol in water after reaction with p-aminophenol
1992
Abstract An automated procedure has been developed for the determination of formetanate and its metabolite m -aminophenol (MAP) in water samples. MAP can be selectively determined in the presence of formetanate by direct on-line reaction with p -aminophenol and spectrophotometric measurement of the absorbance at 576 nm in the presence of KIO 4 , as oxidizing agent. The method has a limit of detection of 5 × 10 −7 M , it provides a recovery percentage from 95 to 104% and permits one to carry out 120 measurements/hr. The spectrophotometric determination of formetanate must be carried out after a previous hydrolysis to MAP. To determine formetanate in the presence of MAP, two steps are necessa…
Automated Determination of Trimipramine and N-Desmethyl-Trimipramine in Human Plasma or Serum by HPLC With On-Line Solid Phase Extraction
1995
A fully automated method including column-switching and isocratic high performance liquid chromatography (HPLC) was developed for determination of the tricyclic antidepressant trimipramine (T) and its N-demethylated metabolite N-desmethyltrimipramine (DT). The limit of quantification was below 10 ng/ml for T and DT. The assay revealed linearity between detector response and drug concentration in a therapeutically relevant range of 10 to 500 ng/ml. The mean intra- and interassay variabilities were 6.2 and 12.3%, respectively, for T and 4.7 and 8.7% respectively, for DT. The method can be applied to therapeutic drug monitoring of patients under T therapy and may be useful for pharmacokinetic …
Spectrophotometric determination of phenol and resorcinol by reaction with p-aminophenol
1993
Abstract Based on the reaction with p-aminophenol, a series of procedures have been developed for the spectrophotometric determination of phenol and resorcinol. Three basic approaches have been studied: (i) a batch procedure, using the dissolved oxygen as oxidant, (ii) a stopped-flow procedure by use of KIO4 as oxidant and (iii) a flow injection (FI) procedure developed in the presence of KIO4. Phenol can be accurately determined at 626 nm, in the stopped-flow mode, after a reaction time of 45 min in 0.005M NaOH, 0.004M KIO4 and 500 μg/ml of PAP. The development of a manifold, which incorporates a sample parking, is a convenient approach which makes it possible to measure, in the stopped-fl…