Search results for "ample"
showing 10 items of 2398 documents
Optimization of clean-up procedure for patulin determination in apple juice and apple purees by liquid chromatography
2009
Patulin (PAT) is a mycotoxin produced in fruits, mainly in apples, by several fungal species that can be carried into industrial apple juice by-products during factory processing. An analytical method for determination of PAT in apple juice and another one for determination of this compound in apple purees and apple compotes by liquid chromatography are proposed in the present paper. These methods have better precision and sensitivity than previously reported methods and focus mainly on extraction and clean-up. To accomplish analytical methods with higher accuracy, lower limits of detection and simpler procedures for application in quality control of the goods, different extraction and clea…
Calibration of LA-ICP-MS via standard addition using dried picoliter droplets
2020
A novel microanalytical calibration approach for quantitative spatially resolved analysis of thin layered materials with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is presented. This method relies on standard addition via the generation of dried pL-droplet residues. Therefore, a drop on demand dosing device based on a modified commercial ink cartridge and a dosing interface, both accessible via a self-constructed microcontroller, were developed. This dosing device enables the precise deposition of pL-droplets onto solid samples for the generation of residues with dimensions in the low μm-range. The LA-ICP-MS analysis of such residues allows calibration over at l…
GFAAS determination of selenium in infant formulas using a microwave digestion method.
1994
A method for determining the selenium content of infant formulas is proposed. It includes wet digestion with nitric acid and hydrogen peroxide in medium pressure teflon bombs in a microwave oven and determination by graphite furnace atomic absorption spectrometry (GFAAS). The absence of interferences is checked. Values obtained for the limit of detection (19.4 ng/g), precision (RSD = 2.2%) and accuracy by analysis of a reference material show that the method is reliable.
Optimization of Matrix Solid-Phase Dispersion method for simultaneous extraction of aflatoxins and OTA in cereals and its application to commercial s…
2010
Abstract A method based on Matrix Solid-Phase Dispersion (MSPD) has been developed for the determination of 5 mycotoxins (ochratoxin A and aflatoxins B and G) in different cereals. Several dispersants, eluents and ratios were tested during the optimization of the process in order to obtain the best results. Finally, samples were blended with C 18 and the mycotoxins were extracted with acetonitrile. Regarding to matrix effects, the results clearly demonstrated the necessity to use a matrix-matched calibration to validate the method. Analyses were performed by liquid chromatography–triple quadrupole-tandem mass spectrometry (LC–QqQ-MS/MS). The recoveries of the extraction process ranged from …
Extraction and analysis of ochratoxin A in bread using pressurised liquid extraction and liquid chromatography.
2005
A pressurised liquid extraction (PLE) method for the analysis of ochratoxin A (OTA) in bread samples is given. Parameters such as solvent, temperature, pressure and time were investigated thoroughly. The optimized PLE conditions were: methanol as extraction solvent, 80 degrees C, 2000 psi and a 5-min cycle. OTA was determined by liquid chromatography coupled with fluorescence detection and confirmed by methyl ester derivatization. Under these conditions OTA recovery is 92.3% with a RSD of 5%. Limits of detection and quantification were 0.02 and 0.06 microg/kg, respectively. The proposed method was applied to 20 bread samples, finding two positive samples with OTA levels below the maximum pe…
Determination of ochratoxin A in maize bread samples by LC with fluorescence detection.
2007
Ochratoxin A (OTA) is a secondary fungal metabolite produced by several moulds, mainly by Aspergillus ochraceus, A. carbonarius, A. niger and by Penicillium verrucosum. The present work shows the results of comparative studies using different procedures for the analysis of OTA in maize bread samples. The studied analytical methods involved extraction with different volumes of PBS/methanol, different extraction apparatus, and clean-up through immunoaffinity columns. The separation and identification were carried out by high-performance liquid chromatography with fluorescence detection. The optimized method for analysis of OTA in maize bread involved extraction with PBS:methanol (50:50), and …
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 PENTOBARBITAL IN BIOLOGICAL SAMPLES BY MICELLAR LIQUID CHROMATOGRAPHY
1999
A liquid chromatographic procedure for the determination of pentobarbital in urine and plasma samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C18 analytical column, a guard column of similar characteristics, and a 0.02 M CTAB-15% 1-propanol at pH 7.5 mobile phase. The UV detector was set at 250 nm. Pentobarbital was isolated from urine and plasma samples by using a single solid phase extraction procedure with LMS cartridges. Mephobarbital was used as internal standard. Limits of detection were 0.53 μg/mL and 0.60 μg/mL in urine and plasma samples respectively. In both cases the coefficients of variation were lower than 6.5%, and the recoveries ranged betwe…
Green, rapid and simultaneous determination of ‘alternative preservatives’ in cosmetic formulations by gas chromatography-mass spectrometry
2022
Abstract Some hydroxylated compounds commonly used in cosmetic formulations including short chain glycols, benzylic alcohols, and organic acids show antimicrobial activity, although they are not considered as preservatives according to the existing European legislation. These ‘alternative preservatives’ are not exempt of potential side-effects for cosmetics users. The aim of this work is to develop a simple and affordable analytical method useful for the simultaneous and green determination of fourteen compounds used as ‘alternative preservatives’ in cosmetic samples with different matrices. The proposed method allows a rapid sample preparation by simple dissolution or dispersion of the sam…
Derivatization techniques for automated chromatographic analysis of amphetamine usingo-phthaldialdehyde: A comparative study
2000
The potential of different chromatographic systems for automated, on-line analysis of amphetamine in biological fluids is illustrated. The various systems integrate analyte purification and enrichment, separation, derivatization in different derivatization modes witho-phthaldialdehyde (OPA) and N-acetyl-L-cysteine (NAC), and fluorimetric detection. The reliability of the systems has been tested by analysing urine and plasma samples containing amphetamine in the 0.1–20.0 μg mL−1 range. Pre, on and post-column derivatization strategies are compared in terms of their instrumental requirements, selectivity, sensitivity, linearity and reproducibility.