Search results for "REAGENT"
showing 10 items of 699 documents
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 …
Solid-phase FT-Raman determination of caffeine in energy drinks
2005
Abstract A solid-phase vibrational spectrometry-based methodology (solid-phase Fourier transform-Raman spectrometry, SP-FT-Raman) has been developed for caffeine determination in commercial energy drink samples. The Raman spectra of caffeine, fixed on a C18 solid phase packed into a glass tube of 5 mm i.d., was obtained directly between 3500 and 70 cm −1 . In order to quantify caffeine, Raman intensity between 573 and 542 cm −1 corrected using a baseline defined between 580 and 540 cm −1 was used. A repeatability of 3%, as relative standard deviation of five analysis of a 200 mg l −1 concentration, and a limit of detection of 18 mg l −1 were obtained. The SP-FT-Raman procedure provides a sa…
Spectrofluorimetric Determination of Iproniazid and Isoniazid in a FIA System Provided with a Solid-Phase Reactor
1998
Abstract A FIA assembly is proposed for the fluorimetric determination of iproniazid and isoniazid. The oxidation of both drugs is carried out by H2O2. The excess of reagent is destroyed and removed from the flow-injection manifold by means of a metallic copper reactor which acts as catalyst in the decomposition of H2O2 and a home made debubbler. The calibration graphs were linear up to 14 μg ml−1 and 10 μg ml−1 (n=6) for iproniazid and isoniazid, respectively, with limits of detection of 0.008 μg ml−1 and 0.005 μg ml−1. The sample throughput was 24 h−1 for both drugs. The influence of foreign compounds was studied and the procedure was applied to determination of iproniazid and isoniazid i…
A microanalytical method for ammonium and short-chain primary aliphatic amines using precolumn derivatization and capillary liquid chromatography.
2007
Abstract A new microscale method is presented for the determination of ammonium and primary short-chain aliphatic amines (methylamine, ethylamine, propylamine, n -butylamine and n -pentylamine) in water. The assay uses precolumn derivatization with the reagent o -phthaldialdehyde (OPA) in combination with the thiol N -acetyl- l -cysteine (NAC), and capillary liquid chromatography with UV detection at 330 nm. The described method is very simple and rapid as no preconcentration of the analytes is necessary, and the volume of sample required is only 0.1 mL. Under the proposed conditions good linearity has been obtained up to a concentration of the analytes of 10.0 mg L −1 , the limits of detec…
A Fully Automated Assembly Using Solenoid Valves for the Photodegradation and Chemiluminometric Determination of the Herbicide Chlorsulfuron
2005
Abstract This paper presents a new photochemiluminescent system for the determination of chlorsulfuron in water samples. The light from a low‐pressure mercury lamp is used as a clean, reproducible, and inexpensive “reagent” for the derivation of the pesticide, performed in glycine buffer at pH 9.5. Then, the photo‐products from irradiation are oxidized by permanganate in sulfuric acid solution. The oxidation reaction was favored by using high temperatures. A comparative study and discussion about the use of polyphosphoric acid instead of sulfuric acid in the oxidation reaction is also presented. The use of solenoid valves allows for the easy, complete automation of the process with low samp…
Chiral separation of bupivacaine enantiomers by capillary electrophoresis partial-filling technique with human serum albumin as chiral selector
2004
Abstract Capillary electrophoresis (CE) is a powerful technique for enantiomer separations due to its intrinsic high separation efficiencies, speed of analysis, low reagent consumption and small sample requirements. However, some chiral selectors present strong background UV absorption providing high detection limits. The present paper deals with the application of the partial-filling technique to the separation of bupivacaine enantiomers by capillary electrophoresis using human serum albumin (HSA) as chiral selector. In this procedure the cationic surfactant cetyltrimethylammonium bromide (CTAB) was used as a dinamic capillary coating in order to reduce the electro-osmotic flow and detect …
Sequential injection spectrophotometric determination of oxybenzone in lipsticks
2001
A sequential injection (SI) procedure for the spectrophotometric determination of oxybenzone in lipsticks is reported. The colorimetric reaction between nickel and oxybenzone was used. SI parameters such as sample solution volume, reagent solution volume, propulsion flow rate and reaction coil length were studied. The limit of detection was 3 microg ml(-1). The sensitivity was 0.0108+/-0.0002 ml microg(-1). The relative standard deviations of the results were between 6 and 12%. The real concentrations of samples and the values obtained by HPLC were comparable. Microwave sample pre-treatment allowed the extraction of oxybenzone with ethanol, thus avoiding the use of toxic organic solvents. E…
Near infrared determination of Diuron in pesticide formulations
2005
Abstract A simple, fast and environmentally friendly near infrared (NIR)-based methodology was developed for Diuron determination in pesticide formulations. This methodology was based on the pesticide extraction with acetonitrile and subsequent transmittance measurement determination by peak area measurement between 2021 and 2047 nm, corrected with a single point baseline established at 2071 nm. The repeatability, as relative standard deviation of five independent analysis of a 15.3 mg g −1 Diuron standard was 0.03% and the limit of detection 0.013 mg g −1 . The reagent consumption was clearly reduced in front of a chromatographic reference procedure from 39.1 ml acetonitrile per sample, re…
Solid-Phase Microextraction Liquid Chromatography/Tandem Mass Spectrometry To Determine Postharvest Fungicides in Fruits
2003
A method to determine five postharvest fungicides (dichloran, flutriafol, o-phenylphenol, prochloraz, tolclofos methyl) in fruits (cherries, lemons, oranges, peaches) has been developed using solid-phase microextraction (SPME) coupled to liquid chromatography (LC) with photodiode array (DAD), mass spectrometry (MS), or tandem mass spectrometry (MS/MS) with ion trap detection. Extraction involved sample homogenization with an acetone/water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. The pesticides were isolated with a fused-silica fiber coated with 50-microm Carbowax/template resin. The effects of pH, ion strength, sample volume, and extraction time were in…
Quantitative determination of moniliformin in vegetable foods and feeds
1984
A suitable and simple method for the quantitative determination of moniliformin in vegetable foods and feeds is described. The mycotoxin was extracted by Soxhlet extraction with methanol from mouldy maize, rice, rye, oats, wheat and barley samples. Moniliformin was determined by thin-layer chromatography (TLC) using N-methylbenzthiazolon-2-hydrazone (MBTH) as a new derivatization reagent for this mycotoxin. The moniliformin derivative was assayed at 518 nm. Quantification could be performed after calibration. A linear relationship between mycotoxin amount and peak area was found from 100 to 400 ng/spot. The detection limit is 75 ng/spot.