Search results for "Detection limit"
showing 10 items of 810 documents
Fluxapyroxad Haptens and Antibodies for Highly Sensitive Immunoanalysis of Food Samples
2017
Fluxapyroxad is a new-generation carboxamide fungicide, with residues increasingly being found in food samples. Immunochemical assays have gained acceptance in food quality control as rapid, cost-effective, sensitive, and selective methods for large sample throughput and in situ applications. In the present study, immunoreagents to fluxapyroxad were obtained for the first time, and competitive immunoassays were developed for the sensitive and specific determination of fluxapyroxad residues in food samples. Two carboxyl-functionalized analogues of fluxapyroxad were prepared, and antibodies with IC50 values in the low nanomolar range were generated from both haptens, though a dissimilar respo…
Ion-pair in-tube solid-phase microextraction and capillary liquid chromatography using a titania-based column: application to the specific lauralkoni…
2012
Abstract A quick, miniaturized and on-line method has been developed for the determination in water of the predominant homologue of benzalkonium chloride, dodecyl dimethyl benzyl ammonium chloride or lauralkonium chloride (C 12 -BAK). The method is based on the formation of an ion-pair in both in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography. The IT-SPME optimization required the study of the length and nature of the stationary phase of capillary and the processed sample volume. Because to the surfactant character of the analyte both, the extracting and replacing solvents, have played a decisive role in the IT-SPME optimized procedure. Conditioning the capil…
Quantitative Analysis of Terpenic Compounds in Microsamples of Resins by Capillary Liquid Chromatography
2019
A method has been developed for the separation and quantification of terpenic compounds typically used as markers in the chemical characterization of resins based on capillary liquid chromatography coupled to UV detection. The sample treatment, separation and detection conditions have been optimized in order to analyze compounds of different polarities and volatilities in a single chromatographic run. The monoterpene limonene and the triterpenes lupeol, lupenone, &beta
Application of the 6-aminoquinolyl-N-hydroxysccinimidyl carbamate (AQC) reagent to the RP-HPLC determination of amino acids in infant foods.
2005
The validation of a pre-column derivatization procedure with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) to the determination of the amino acid content by RP-HPLC with fluorescence detection (lambda excitation 250 nm, lambda emission 395 nm) in milk-cereal based infant foods was carried out. The analytical parameters: linearity (0.0025-0.2mM), precision of the method (0.2-3.5% variation coefficients), accuracy (derivatization: 86-106% average recovery and method: 88.3-118.2% average recovery) and the limits of detection (0.016-0.367 microM) and quantification (0.044-1.073 microM) were determined. Glutamic acid, proline and leucine were the most abundant amino acid whereas the lowe…
Antibody generation and immunoassay development in diverse formats for pyrimethanil specific and sensitive analysis
2012
Immunochemical techniques are complementary tools to modern analytical requirements. These methods rely on the production of immunoreagents with adequate binding properties. In the present study, a rationally designed and functionalized derivative of pyrimethanil-a modern anilinopyrimidine fungicide-was synthesized in order to generate for the first time high-affinity and selective antibodies to this xenobiotic. A single coupling procedure-based on hapten activation using N,N′-disuccinimidyl carbonate and purification of the active ester-was followed to prepare both immunizing and assay conjugates. Polyclonal antibodies were produced and characterized by enzyme-linked immunosorbent assay (E…
Amperometric detection of extended-spectrum β-lactamase activity : application to the characterization of resistant E.coli strains
2015
EA MERS CT3; International audience; The amperometric detection of extended-spectrum β-lactamase (ESBL) with carbon screen-printed sensors was investigated in the presence of the Nitrocefin, a commercially-available β-lactamase chromogenic cephalosporin substrate. Using an ESBL isolated from a clinical sample, it was shown for the first time that the intensity of a specific anodic pic current (EP = [similar]+0.3 V vs. Ag/AgCl) resulting from the catalytic hydrolysis of the β-lactam ring was proportional to the amount of ESBL. The proof-of-principle of a novel susceptibility assay for the rapid and accurate identification of ESBL- producing bacteria was then demonstrated. The detection schem…
The presence of KCl in the exposure medium strongly influences the mutagenicity of metabolites of polycyclic aromatic hydrocarbons in Escherichia col…
1994
Abstract Previous studies demonstrated that the ion composition of the exposure medium may strongly influence the mutagenicity of many compounds in the liquid preincubation modification of the reversion assay with his − Salmonella typhimurium strains. Similar influences were now observed in the reversion assay with trp − Escherichia coli strain WP2 uvrA . The exposure medium was 8 mM sodium phosphate buffer (pH 7.4), containing no other ions or 125 mM KCl. Omission of KCl resulted in an about 10-fold enhancement of the mutagenic activity of 7-methylbenz[ a ]anthracene 5,6-oxide, but in a strong decrease in the mutagenicity of 1-hydroxymethylpyrene sulphate, close to the limit of detection. …
FI-chemiluminometric study of thiazides by on-line photochemical reaction
2004
The present manuscript deals with a simple and sensitive flow-injection method for the chemiluminescent determination of thiazides. The method is based on the on-line photodegradation and chemiluminescent determination of the resulting photo-fragments. The on-line photodegradation is performed in basic medium by using a photoreactor consisting of a 550 cm long x 0.8 mm ID piece of PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. The determination of the photo-irradiated thiazides is performed by a chemiluminescent oxidative reaction with Ce(IV) in sulphuric acid medium. A heterogeneous group of thiazides (indapamide, metolazone, hydroflumethiazide, chlorthalidone and be…
On-line gradient liquid chromatography–Fourier transform infrared spectrometry determination of sugars in beverages using chemometric background corr…
2008
Abstract An on-line gradient reversed phase liquid chromatography–Fourier transform infrared spectrometry (LC–FTIR) method was developed for the determination of fructose, glucose, sucrose and maltose in beverages. Improved chromatographic resolution was obtained using a linear gradient from 75 to 55% (v/v) acetonitrile in water in 15 min. Changes in the background spectra were corrected employing “univariate background correction based on the use of a reference spectra matrix” (UBC-RSM) and using the ratio of absorbance (AR) at 2256 and 2253 cm −1 for the identification of the eluent spectra within the RSM. The method provided limits of detection in the order of 0.75 mg ml −1 . The precisi…
An in-tube SPME device for the selective determination of chlorophyll a in aquatic systems.
2010
We report a new device for the estimation of the content of chlorophyll a pigment in water samples as an indicator of water quality. The extraction of the pigment from water was also optimized. 10 mL of water was filtered through a nylon filter (45m pore size and 13 mm of diameter), after the chlorophylls were dissolved by immersing the filter in 1 mL of a low non-hazardous solvent as ethanol. An in-valve in-tube SPME device coupled to capillary liquid chromatography with diode array detection was designed. A capillary column of 70 cm in length (0.32 mm i.d. coated with 5% diphenyl–95% polydimethylsiloxane, 3m coating thickness) was used as the loop of the injection valve for preconcentrati…