Search results for "aqueous solution"
showing 10 items of 1610 documents
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…
Development of a gas chromatography-mass spectrometry method for the determination of ultraviolet filters in beach sand samples
2014
An analytical method for the determination of eight fat-soluble ultraviolet (UV) filters in beach sand samples is presented for the first time. The method is based on a leaching process of the target compounds from sand samples using vortex mixer agitation and further centrifugation, followed by dispersive liquid–liquid microextraction (DLLME) of the supernatant and gas chromatography-mass spectrometry (GC-MS) analysis of the DLLME extract. The variables involved in the leaching and in the DLLME processes were studied to provide the best enrichment factors. In the first case, the leaching solvent type and volume, and the vortex mixer agitation time were studied. In the case of the DLLME, th…
Ion mobility spectrometry as a fast analytical tool in benzalkonium chloride homologs determination.
2017
Abstract A novel procedure is proposed for the determination by ion mobility spectrometry (IMS) of C 12 , C 14 and C 16 benzalkonium chloride (BAC) homologs. The proposed method requires minimum sample treatment and the measurement was made in less than one minute. A high sensitivity was obtained for BAC determination by IMS with limit of detection values from 37 to 69 µg L −1 . Accuracy of the proposed methodology was evaluated through the analysis of aqueous and alcoholic samples spiked with BAC at concentration levels from 0.002% to 20% (w/v), providing recovery values from 91% to 104%. BAC was determined in sanitary alcohols, nasal sprays, postharvest products, algaecides, and treated s…
Sequential injection analysis for benzophenone-4 and phenylbenzimidazole sulphonic acid in sunscreen sprays by solid-phase extraction coupled with ul…
2002
Abstract A sequential injection UV method was developed to determine benzophenone-4 (BZ4) and phenylbenzimidazole sulphonic acid (PBS) simultaneously, these being the most commonly used UV-filters in aqueous formulations used as sunscreen sprays. The selective elution of both was performed by on-line solid-phase extraction, by retention on a SAX microcolumn and separation by varying the pH of elution. The sensitivity obtained was 0.042±0.001 ml μg −1 for PBS and 0.0159±0.0003 ml μg −1 for BZ4. The limit of detection was 1.6 μg ml −1 for PBS and 0.6 μg ml −1 for BZ4. The R.S.D. of the results was 1–6% for PBS and 1–12% for BZ4. The method was validated using commercial sunscreen formulations…
New flow-multicommutation method for the photo-chemiluminometric determination of the carbamate pesticide asulam
2004
This paper deals with a straightforward automated method for the determination of asulam in water based on the use of a flow manifold including three computer-controlled solenoid valves. The method involves irradiating on an aqueous solution of asulam in glycine buffer at pH 8.3 with UV light during 90 s, then follows the oxidation with potassium permanganate in a sulphuric medium and chemiluminescence-based detection of the resulting photoproducts. The limit of detection thus achieved is 40 mug l(-1). The detector response is linear up to a 5 mg l(-1) asulam concentration and the throughput is 30 samples h(-1). In parallel tests, oxidation with alkaline ferricyanide was also assessed and t…
A simple novel configuration for in-vial microporous membrane liquid–liquid extraction
2009
Abstract A novel arrangement for microporous membrane liquid–liquid extraction from the aqueous donor phase to the organic acceptor phase within a micro-vial, which is compatible with the chromatograph autosampler is presented. The device consisted of a stoppered glass micro-vial containing the organic solvent where the septum of the screw stopper was replaced by a sized piece of membrane which is hermetically assembled to the volumetric flask containing the aqueous donor solution. The placement of the membrane in alternative contact with the solutions was achieved by orbital agitation. As a preliminary study, 2-ethylhexyl 4-(dimethylamino)benzoate has been determined (limit of quantificati…
Determination of water-soluble UV-filters in sunscreen sprays by liquid chromatography.
2002
Abstract Liquid chromatography was used for the determination of the three most used water-soluble UV filters, benzophenone-4 (BZ4), terephthalylidene dicamphor sulfonic acid (TDS), and phenylbenzimidazole sulphonic acid (PBS), in aqueous sunscreen sprays. A C 18 stationary phase and an isocratic mobile phase of EtOH–20 m M sodium acetate buffer of pH 4.6 (30:70, v/v) were used at a flow-rate of 0.5 ml min −1 . Mobile phase was also used as solvent for samples and standards. UV detection was at 313 nm. The analytical run took 5.5 min. The limits of detection were 0.5, 0.9 and 2 μg ml −1 for BZ4, TDS and PBS, respectively. The proposed method does not involve highly toxic solvents.
On-line removal of mass interferences in palladium determination by ICP-MS using modified capillaries coupled to micro-flow nebulizers
2001
This paper describes a novel approach developed for on-line removal of interferences within modified capillaries coupled to micro-flow nebulizers, for palladium determination by inductively coupled plasma mass spectrometry (ICP-MS). A strong cation exchanger [2-(4-chlorosulfophenyl)ethyltrichlorosilane)] was covalently bound to the silica capillary that was coupled to a microconcentric nebulizer (MCN) or to a direct injection nebulizer (DIN). The modified surface of the capillary was able to selectively retain copper and yttrium from aqueous samples at pH 7.5 during the sample introduction step, while Pd was not retained and 105Pd could be determined in the absence of interferent elements. …
Determination of atranol and chloroatranol in perfumes using simultaneous derivatization and dispersive liquid-liquid microextraction followed by gas…
2013
Abstract A new analytical method based on simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–mass spectrometry (GC–MS), for the determination of the allergenic compounds atranol and chloroatranol in perfumes, is presented. Derivatization of the target analytes by means of acetylation with anhydride acetic in carbonate buffer was carried out. Thereby volatility and detectability were increased for improved GC–MS sensitivity. In addition, extractability by DLLME was also enhanced due to a less polar character of the solutes. A liquid–liquid extraction was performed before DLLME to clean up the sample and to obtain an aqueous sample …
Determination of Parabens in Cosmetics without Previous Extraction by Micellar Liquid Chromatography
1999
A simple and rapid micellar liquid chromatography method for the determination of p-hydroxybenzoic acid esters (methyl-, ethyl-, n-propyl-, and n-butylparaben) in cosmetics (bath foam, milk lotion, hand cream, cream base, and shampoo) is described. The samples are solved with n-propanol, further diluted with more n-propanol or with an aqueous sodium dodecyl sulphate (SDS) micellar solution, and injected. Separations are performed with a micellar mobile phase containing 0.1M SDS, 2.5% n-propanol, 10mM phosphate (pH 3), and with an octadecyl silica column (C 18 ). Calibrations are linear (correlation coefficient r > 0.999) and the limits of detection range from 0.03 to 0.3 ng paraben. The det…