Search results for "Specificity."
showing 10 items of 2232 documents
Validated, non-destructive and environmentally friendly determination of cocaine in euro bank notes.
2005
A non-destructive, fast and environmentally friendly procedure has been developed for cocaine determination in euro bank notes. Cocaine was extracted with 15 ml methanol by vortex agitation during 5 min. The extract was evaporated and reconstituted in 0.5 ml methanol. GC-MS-MS analysis was performed using as precursor ion m/z 182.2, with an excitation energy voltage of 1.60 eV, being the product ions measured m/z 150.2 and 82.0. A limit of detection of 0.15 ng per note and a repeatability of 6%, established from the relative standard deviation, of a 1 ng ml(-1) level, were achieved. Recoveries of 101+/-2 and 98+/-3% were obtained for samples spiked with 100 and 10 microg respectively. Resul…
Determination of abamectin in citrus fruits by liquid chromatography-electrospray ionization mass spectrometry.
2000
Liquid chromatography coupled to electrospray mass spectrometry (LC-ES-MS) with positive ion detection was used to determine abamectin in oranges. MS conditions were optimized to achieve maximum sensitivity. The main ion for abamectin was [M+Na]+ at a fragmentor voltage of 180 V. Abundant structural information can be obtained at different fragmentor voltages. The detection limit for the standard solution was 12 pg injected, and good linearity and reproducibility were observed. Abamectin residues were extracted using matrix solid-phase dispersion. Orange samples were homogenized with C18 bonded silica placed onto a glass column and eluted with dichloromethane. Recoveries of the abamectin fr…
Automated trace enrichment for screening and/or determination of primary, secondary and tertiary amphetamines in biological samples by liquid chromat…
1999
A rapid and simple liquid chromatographic method for the automated determination of amphetamines in biological fluids was developed. The proposed procedure is based on the injection of 250 microL of sample into a 20 x 2.1 mm id precolumn (packed with a 30 microns Hypersil C18 stationary phase) for enrichment and purification of the analytes. Next, the analytes are transferred to a 5 microns LiChrospher 100 RP18, 125 x 4 mm id analytical column for their separation under reversed-phase conditions. Water was used to eliminate the matrix components from the precolumn and a 0.2 M phosphate buffer (pH 3) containing 2% triethylamine was the mobile phase for the resolution of the amphetamines. The…
Quantitative analysis of six pesticides in fruits by capillary electrophoresis-electrospray-mass spectrometry.
2005
A method to identify and quantify six pesticide residues - dinoseb, pirimicarb, procymidone, pyrifenox, pyrimethanil, and thiabendazole - in peaches and nectarines using capillary electrophoresis-electrospray ionization-quadrupole ion trap-tandem mass spectrometry (CE-ESI-MS/MS) is described. Separation was carried out using a buffer of 0.3 M ammonium acetate at pH 4 with 10% methanol. Pesticide residues present in peach and nectarine samples were preconcentrated by solid-phase extraction using C(18), eluted with CH(2)Cl(2), concentrated to dryness, and redissolved in buffer to obtain lower detection limits. The recoveries of the analytes ranged from 58 to 99% and the relative standard devi…
Analysis of thiabendazole and procymidone in fruits and vegetables by capillary electrophoresis–electrospray mass spectrometry
2002
Abstract A capillary electrophoresis–mass spectrometry method for determining procymidone and thiabendazole in apples, grapes, oranges, pears, strawberries and tomatoes is described. Separation is achieved using a buffer of formic acid–ammonium formate at pH 3.5 with 2% of methanol. Fungicide residues present in the sample are preconcentrated by both solid-phase extraction and injection of large sample volumes into the capillary by a stacking technique, to obtain lower detection limits. Ionization is performed at atmospheric pressure in an electrospray type source and detection is carried out using positive ionization and selected ion monitoring modes. The quantitation limits are 0.005 and …
Arsenic content of Spanish cows' milk determined by dry ashing hydride generation atomic absorption spectrometry.
1994
SummaryThe arsenic content of cows' milk consumed in Spain was determined. A procedure using dry ashing hydride generation atomic absorption spectrometry was developed for the purpose. Experimental conditions for the destruction of organic matter were established and an interference study was carried out. The method developed has a detection limit of 0·1 ng/g, a relative SD of 5%, and a recovery (mean ± CSI) of 100 ± 4%. The accuracy of the method was checked by analysis of a certified sample of IAEA milk powder (mean ± CSI: certified, 4·85 ± 0·32 ng/g; found, 5·04 ± 0·81 ng/g). The proposed procedure was used to analyse cows' milk samples. The extremely low arsenic levels found do not pres…
Imaging techniques for the vulnerable coronary plaque
2007
The goal of this article is to illustrate the main invasive and noninvasive diagnostic modalities to image the vulnerable coronary plaque, which is responsible for acute coronary syndrome. The main epidemiologic and histological issues are briefly discussed in order to provide an adequate background. Comprehensive coronary atherosclerosis imaging should involve visualization of the entire coronary artery tree and plaque characterization, including three-dimensional morphology, relationship with the lumen, composition, vascular remodelling and presence of inflammation. No single technique provides such a comprehensive description, and no available modality extensively identifies the vulnerab…
Imaging techniques in inflammatory bowel disease: recent trends, questions and answers
2009
Summary Imaging techniques have undergone substantial progress in recent years and contribute significantly in the diagnosis of inflammatory bowel diseases in conjunction with patient history, clinical and laboratory examination. Modern cross-sectional imaging modalities such as computed tomography and magnetic resonance imaging allow an evaluation not only of the complete bowel wall of the small intestine, but also of extraluminal structures. They constitute a major diagnostic component in the initial workup, in stricturing or fistulizing disease and in suspected abscess. Transabdominal ultrasonography has been re-appreciated in these settings as an easy- and ready-to-use tool yielding rea…
A method for the determination of dimethylamine in air by collection on solid support sorbent with subsequent derivatization and spectrophotometric a…
2005
A new method for dimethylamine determination in air is reported. The proposed assay is based on the employment of C18-packed solid phase extraction cartridges for sampling. The retained amine is then derivatized inside the cartridges with the reagent 1,2-naphthoquinone-4-sulfonate. By observing the coloured area of the cartridge, a semiquantitative estimation of the amine can be made. It was also possible to distinguish between primary and secondary amines by visual inspection. Quantitative tests entailed desorption from the cartridges of the derivatives formed, and measurement of the absorbance of the collected extracts. The selected conditions were applied to quantify dimethylamine up to …
Sensitive determination of aliphatic amines in water by high-performance liquid chromatography with chemiluminescence detection.
2004
A sensitive method has been developed for liquid chromatographic determination of short aliphatic amines in water samples. Analytes are preconcentrated and dansylated on solid sorbents (C18 solid-phase extraction cartridges). The dansyl derivatives are chromatographed and post-column mixed with peroxyoxalate (TCPO) and H2O2 in order to perform chemiluminescence detection. Optimal results have been obtained using a sample volume of 5 ml. The method has been applied to the quantification or screening of several aliphatic amines: methylamine, ethylamine, butylamine, diethylamine, pentylamine and hexylamine. The screening procedure has been developed including also polyamines (putrescine, cadav…