Search results for "ample"
showing 10 items of 2398 documents
Determination of hydroxytyrosol and tyrosol by liquid chromatography for the quality control of cosmetic products based on olive extracts
2014
An analytical method for the simultaneous determination of hydroxytyrosol and tyrosol in different types of olive extract raw materials and cosmetic cream samples has been developed. The determination was performed by liquid chromatography with UV spectrophotometric detection. Different chromatographic parameters, such as mobile phase pH and composition, oven temperature and different sample preparation variables were studied. The best chromatographic separation was obtained under the following conditions: C18 column set at 35°C and isocratic elution of a mixture ethanol: 1% acetic acid solution at pH 5 (5:95, v/v) as mobile phase pumped at 1 mL min(-1). The detection wavelength was set at …
Improving analysis of apolar organic compounds by the use of a capillary titania-based column: Application to the direct determination of faecal ster…
2010
This article reports a new procedure for the direct determination of faecal sterols coprostanol and cholesterol in wastewater samples as tracers of human sewage contamination. The method combines in-tube solid-phase microextraction (IT-SPME) for analyte enrichment and capillary liquid chromatography (LC) for separation with diode array detection for identification and quantification. A titania-based polymeric capillary column and a conventional octadecyl silica (ODS) capillary column were evaluated and compared for their ability to separate the analytes. The titania-based column allowed the separation of the analytes in much shorter chromatographic times and with better chromatographic prof…
Determination of alternative preservatives in cosmetic products by chromophoric derivatization followed by vortex-assisted liquid-liquid semimicroext…
2016
An analytical method for the simultaneous determination of phenethyl alcohol, methylpropanediol, phenylpropanol, caprylyl glycol, and ethylhexylglycerin, which are used as alternative preservatives in cosmetic products, has been developed. The method is based on liquid chromatography with UV spectrophotometric detection after chromophoric derivatization with benzoyl chloride and vortex-assisted liquid-liquid semimicroextraction. Different chromatographic parameters, derivatization conditions, and sample preparation variables were studied. Under optimized conditions, the limits of detection values for the analytes ranged from 0.02 to 0.06µgmL(-1). The method was validated with good recovery …
A new selective method for dimethylamine in water analysis by liquid chromatography using solid-phase microextraction and two-stage derivatization wi…
2005
Abstract A new method is presented for the determination of DMA in water as its 9-fluorenylmethyl chloroformate (FMOC) derivative using solid-phase microextraction (SPME) and liquid chromatography. The method is based on the employment of SPME fibres coated with carbowax-templated resin (CW-TR) for analyte extraction and derivatization. The fibres were successively immersed in the samples, in a solution of o -phthalaldialdehyde and N -acethyl- l -cysteine (OPA–NAC) and finally, in a solution of FMOC. OPA–NAC reacted on the fibre with possible primary aliphatic amines present in the samples, particularly with PA which is a direct interferent in the determination of DMA with FMOC. In such a w…
Method and apparatus using selected superparamagnetic labels for rapid quantification of immunochromatographic tests
2009
Mika PA Laitinen1, Jari Salmela2, Leona Gilbert1, Risto Kaivola1, Topi Tikkala2, Christian Oker-Blom1, Jukka Pekola3, Matti Vuento11Department of Biological and Environmental Science; 2Department of Physics, University of Jyväskylä, Jyväskylä, Finland; 3Low Temperature Laboratory, Helsinki University of Technology, Helsinki, FinlandAbstract: A rapid method and instrumentation for quantification of immunochromatographic tests (ICT) are described. The principle and performance of the method was demonstrated by measuring the levels of human chorionic gonadotropin (hCG) present in urine. The test format was a sandwich assay using two distinct monoclonal antib…
On-line bidirectional electrostacking of chromium(III) and chromium(VI) for flame atomic absorption spectrometry determination
2000
Abstract An on-line bidirectional electrostacking-flow injection-flame atomic absorption spectrometry method has been developed for the simultaneous separation, pre-concentration and determination of Cr(III) and Cr(VI). The electrostacking-flow injection unit was established, the pH and components of the support buffer and sample medium were investigated. Results indicated that the ionic mobility, electric field strength and sample area cross-section are the main influence factors on the electrostacking. The calibration range for both, Cr(III) and Cr(VI), was from 20 to 400 μg l −1 . The limit of detection was 7 μg l −1 for three-times the standard deviation of blank values using a electros…
Fourier-transform infrared determination of nicotine in tobacco samples by transmittance measurements after leaching with CHCl3
1998
Abstract A new procedure is proposed for the FT-IR spectrometric determination of nicotine in tobacco. The method is based on the extraction of nicotine in CHCl 3 from tobacco samples, wetted with an aqueous solution of NH 3 (0.1 M), and the measurement of absorbance in the stopped-flow mode at 1316 cm −1 , using a spectral baseline correction established from 1334 to 1300 cm −1 . The procedure developed does not requires a complex sample preparation, and provides a limit of detection of 0.045 mg ml −1 nicotine, a sampling frequency of 3.3 h −1 and a coefficient of variation of 0.3% for five independent measurements of a tobacco sample with a nicotine content of 1.5% w/w. The accuracy of th…
Determination of 129I/127I isotope ratios in liquid solutions and environmental soil samples by ICP-MS with hexapole collision cell
2003
The determination of I-129 in environmental samples at ultratrace levels is very difficult by ICP-MS due to a high noise caused by Xe impurities in argon plasma gas (interference of Xe-129(+)), possible (IH2+)-I-127 interference and an insufficient abundance ratio sensitivity of the ICP mass spectrometer for I-129/I-127 isotope ratio measurement. A sensitive, powerful and fast analytical technique for iodine isotope ratio measurements in aqueous solutions and contaminated soil samples directly without sample preparation using ICP-MS with a hexapole collision cell (ICP-CC-QMS) was developed. Oxygen is used as reaction and carrier gas for iodine thermal desorption via the gas phase from solid…
Flow injection flame atomic absorption analysis of Fe and Mn in cement samples
1993
A new procedure has been developed for the determination of Fe and Mn in cements. It consists in dispersing 50 mg of the solid sample in 25 ml of 0.15 mol/l HNO3 and 0.12 mol/l HCl solution. Acid slurries are heated at 50°C for 10 min and then different volumes of the slurry are injected into a water carrier stream. This previous acid treatment leaches the elements to be determined and permits the use of acid solutions as standards. For the Mn determination, the use of a single line flow injection manifold provides a limit of detection of 0.03 mgl−1 and a dynamic range up to 6 mgl−1. For the determination of Fe, the on-line dispersion of samples, using a well stirred mixing chamber, increas…
Optimization of a microwave-assisted extraction large-volume injection and gas chromatography–ion trap mass spectrometry procedure for the determinat…
2006
Abstract A sensitive and rapid method for the determination of polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and polychlorinated naphthalenes (PCNs) in sediment samples is proposed. The method involving microwave-assisted extraction (MAE) and large-volume injection (LVI) gas chromatography (GC)–ion trap mass spectrometry (ITMS), and the experimental conditions were optimized using the statistical design of experiments (DOE). A Plackett–Burman (P–B) design was chosen to estimate the influence of five factors, such as resonance excitation voltage (EV), isolation time (IT), excitation time (ET), ion source temperature (IST) and electron energy (EE) on the analytical r…