Search results for "Detection limit"
showing 10 items of 810 documents
Gas chromatographic analysis of resveratrol in plasma, lipoproteins and cells after in vitro incubations
1998
Resveratrol is a trihydroxystilbene present in certain red wines. It may play a role in the inhibition of lipoprotein oxidation and platelet activity. We have developed the first method to measure resveratrol in animal and human samples and to study its incorporation in vitro. After adding epicoprostanol as an internal standard, samples are subjected to lipid extraction in the presence of antioxidant and under dim light to minimize both denaturation and isomerization of the trans-resveratrol to the cis-form. Extracts were purified by cold acetone precipitation and the resveratrol-containing acetone phase was evaporated under nitrogen. The resveratrol was analyzed as a trimethylsilyl derivat…
Determination of organochlorine pesticide residues in honey from the central zone of Portugal and the Valencian community of Spain
2004
In this study nine organochlorine pesticide residues ([alpha]-, [beta]-, and [gamma]-hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), aldrin, p,p'-DDE, p,p'-DDD, o,p'-DDT, and p,p'-DDT) in forty nine samples of honey collected from markets of Portugal and Spain during 2001 and 2002, respectively, were evaluated. For this evaluation, three analytical procedures were studied. The analytical procedure, based on LLE extraction with ethyl acetate followed by gas chromatography-electron-capture detection (GC-ECD) for quantification, and mass spectrometry (GC-MS) for confirmation, has been selected. Recoveries of spiked samples ranged from 68%, for [beta]-HCH, and 126% for p,p'-DDT, for forti…
Determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in goat milk and tissues by glass capillary gas chromatography and medium resolution mass fragme…
1981
Abstract An analytical method has been developed for the study of the elimination of 2,3,7,8-tetrachlodoribenzo-p-dioxin (TCDD) by lactation and its determination in various tissues of goat. The method is based on the alkaline hydrolysis of milk, liver, fat, muscle, blood, faeces and urine samples, extraction with n-hexane, treatment with sulphuric acid-saturated silica gel, chromatographic clean-up on silica gel and alumina micro-columns, and glass capillary gas chromatography—medium resolution mass fragmenography (resolution 2000). 1,2,3,4-Tetrachlorodibenzo-p-dioxin is used as the internal standard, the concentration of TCDD being determined from the calibration curve calculated from the…
A new selective fluorogenic probe for trivalent cations.
2012
[EN] A new selective chromo-fluorogenic probe for Fe 3+, Cr 3+ and Al 3+ is reported. Detection limits are in the ¿M range and the fluorogenic sensing ability could be observed by the naked eye when illuminated with UV-light. No response is observed with divalent cations. © 2012 The Royal Society of Chemistry.
Extraction of polycyclic aromatic hydrocarbons from cookies: a comparative study of ultrasound and microwave-assisted procedures.
2008
The chromatographic determination of 15 polycyclic aromatic hydrocarbons (PAHs) in cookies has been improved in order to obtain a fast method with a low limit of detection through the combination of microwave-assisted extraction (MAE), oil saponification and solid-phase extraction clean-up before the injection of purified extracts in a C18 201TP52 (5 microm, 250 x 2.1 mm) column. Using acetonitrile-water as mobile phase, with a 50% to 95% w/w acetonitrile gradient for a fixed flow of 0.250 ml min(-1), 15 PAHs were separated in 45 min. The column temperature was maintained at 15 degrees C; and fluorimetric detection was made at a fixed excitation wavelength of 264 nm and emission measurement…
Liquid chromatography/atmospheric pressure chemical ionization-mass spectrometric analysis of benzoylurea insecticides in citrus fruits.
2000
A liquid chromatography (LC) method for the quantitative determination of three benzoylurea insecticide residues (diflubenzuron, flufenoxuron and hexaflumuron) in citrus fruits is described. Residues were successfully separated on a C18 column by methanol/water gradient elution. Detection was by negative-ion, selected-ion monitoring atmospheric pressure chemical ionization-mass spectrometry (APCI-MS); the main ions were [M - H]-, and the secondary fragment ions were [M - H - HF]-. Useful confirmatory information can thus be obtained at low extraction voltages from losses of HF. Detection limits for standard solutions were 10 fg injected and good linearity and reproducibility were obtained. …
Development and validation of a micellar liquid chromatographic method to determine three antitumorals in plasma
2017
Aim: A micellar liquid chromatographic method to determine several anticancer drugs (pazopanib, dabrafenib and regorafenib) in plasma was developed and validated by the guidelines of the EMA. Experimental: Plasma samples were directly injected, after a 1/5-dilution in a micellar solution. The drugs were resolved in <18 min using a C18 column. The mobile phase was an aqueous solution of 0.12 M SDS – 2% 1-pentanol, buffered at pH 7. The detection was performed by absorbance at 260 nm. Results: The values of the main validation parameters were: LOD (0.1–1 mg/l), calibration range (0.2–2 to 80 mg/l), accuracy (-12.5 to +11.7%) and precision (<11.9%). Conclusion: The procedure was conduct…
In situ generation of Co(II) by use of a solid-phase reactor in an FIA assembly for the spectrophotometric determination of penicillamine
2005
[EN] A flow injection analysis (FIA) manifold for the determination of penicillamine in pharmaceutical preparations is proposed. The manifold includes a solid-phase reactor for the in situ production of the derivatizing reagent, Co(II) ion, which forms a coloured complex with penicillamine in an alkaline medium. The reactor is prepared by natural immobilization of cobalt carbonate on a polymer matrix, which endows it with a high mechanical and microbiological stability. The cobalt released by passage of a 5 x 10(-4) Mol l(-1) sulphuric acid stream at a flow-rate of 2.3 ml min(-1) is merged with a volume of 314 mu l of sample containing penicillamine in ammonium-ammonia buffer at pH 9.5 to m…
Portable low-cost open-source wireless spectrophotometer for fast and reliable measurements
2020
This article is based upon COST Action CA16215 and supported by the ERDF , European-Union Project No.1.1.1.2/16/I/001.
A glassy carbon electrode modified by a triply-fused-like Co( ii ) polyporphine and its ability for sulphite oxidation and detection
2018
This article presents a Co(II) polyporphine conductive polymer easily and rapidly obtained (less than 2 h 30 min) on the surface of a glassy carbon electrode from the transformation of an initial Mg(II) porphine solution in a four-step process (including electrochemical and chemical stages). The intimate molecular structure is argued on the basis of the electrochemical response of the modified electrode, as well as its surface characterization. Owing to its apparent stability in water over potential cycling and its high density in active Co(II) centers, the electrosynthesized film shows its ability to catalyze sulphite oxidation in aqueous solutions. The mechanism of this molecular catalysi…