Search results for "liquid chromatography"
showing 10 items of 942 documents
Identification of lipid binders in old oil paintings by separation of 4-bromomethyl-7-methoxycoumarin derivatives of fatty acids by liquid chromatogr…
2005
A HPLC-fluorescence method for identification of drying oils from binding media or protective film used in pictorial works of art prior to conservation or restoration is proposed. Fluorescence derivatization of fatty acids released by hydrolysis of structural drying oils is studied. The derivatization reagent was 4-(bromomethyl)-7-methoxycoumarin with 18-crown-6 as catalyst. Mobile phase was programmed from methanol-water (90:10 v/v) to methanol-water (100:0 v/v) in 25 min. The excitation and emission wavelengths were 325 and 395 nm, respectively. Under these chromatographic conditions, coumarin derivatives of myristic, palmitic, oleic and stearic acids were satisfactorily resolved. The met…
Rapid and sensitive ultra-high-pressure liquid chromatography-quadrupole time-of-flight mass spectrometry for the quantification of amitraz and ident…
2008
Liquid chromatography under high pressure in combination with quadrupole time-of-flight mass spectrometry (QqTOF-MS and MS/MS) has been used to detect amitraz degradation products in pears, to characterize their structures, and to evaluate their occurrences in samples of different origins. Using the proposed approach, the parent pesticide and four degradation products were identified. To this end, pear samples were extracted with ethyl acetate and anhydrous sodium sulphate. Amitraz was found to be rapidly decomposed into four related compounds, of which N-(2,4-dimethylphenyl)formamidine (DMPF) was the most abundant and persistent. N,N'-bisdimethylphenylformamidine (BDMPF), 2,4-dimethylforma…
Automated on-line in-tube solid-phase microextraction-assisted derivatization coupled to liquid chromatography for quantifying residual dimethylamine…
2008
Abstract A method for the analysis of dimethylamine (DMA) by automated in-tube solid-phase microextraction (IT-SPME)-supported chemical derivatization coupled with high-performance liquid chromatography was developed. Extraction, derivatization and desorption were studied by using a capillary coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane. Solution derivatization and automated IT-SPME derivatization using 9-fluorenylmethyl chloroformate (FMOC) were compared. The proposed procedure provided adequate linearity, accuracy and precision in the 0.2–2.0 μg/mL concentration interval, and the limit of detection (LOD) was 50 ng/mL. The main advantages of the proposed procedure are: …
Simultaneous detection of hazardous skin whitening agents in Indian cosmetic products using a green chromatographic technique
2021
The present work mainly highlights the simultaneous detection of four skin whitening agents i.e. hydroquinone (HQ), resorcinol (RS), catechol (CC) and 3,3′-dichlorobenzidine (DCB) in facial creams and body lotion. Among these, the first three are positional isomers of dihydroxybenzene so simultaneous separation is difficult with the conventional reverse-phase high-performance liquid chromatographic technique (RP-HPLC). The selected skin whitening agents were detected in facial cream and body lotion using micellar liquid chromatography coupled to a photodiode array detector (MLC-PDA). In the present study, optimization of the method was accomplished using response surface methodology (RSM) w…
An Infrared Method, with Reduced Solvent Consumption, for the Determination of Chlorsulfuron in Pesticide Formulations
2003
A simple method has been developed for the determination of Chlorsulfuron in pesticide formulations by Fourier Transform Infrared (FTIR). Samples were diluted with CHCl3− , and the FTIR spectra of the samples and standards were obtained at a nominal resolution of 4 cm− 1 from 4000 to 900 cm− 1 with the accumulation of 25 scans. Chlorsulfuron determination was based on the measurement of peak area values from 1373 to 1363 cm− 1 which were corrected by use of a two points baseline defined from 1401 to 1302 cm− 1. The limit of detection achieved, which was of the order of 6 µg g− 1, was appropriate for the determination of Chlorsulfuron in commercially available formulations. FTIR results were…
Amphetamine and methamphetamine determination in urine by reversed-phase high-performance liquid chromatography with sodium 1,2-napthoquinone 4-sulfo…
1995
A rapid method is described for the identification and determination of amphetamine and methamphetamine in human urine samples by liquid chromatography with UV-Vis detection. The samples were transferred onto a C18 solid-phase extraction column and chromatographed on a Hypersil ODS RP C18, 5 microns (250 x 4 mm I.D.) with an acetonitrile-water elution gradient containing propylamine. Under these conditions, the amines are eluted with a short retention time. The procedure has been applied to the determination of amphetamine and methamphetamine in the range 0.3-4.0 micrograms/ml in spiked urine samples. The detection limits at 280 nm were 4 and 2 ng/ml for amphetamine and methamphetamine, res…
Analysis of T-2 toxin by HPLC and GC in samples of corn and oats
1984
HPLC is the only physico-chemical method for the analysis of trichothecenes for which no derivatization is necessary. Hence a combination of different methods can be performed. For exclusion of any faulty interpretation of data and in order to decrease the detection limit HPLC should be followed by GC.
Determination of UV-filters in sunscreens by HPLC.
2001
Simultaneous determination of six internationally authorised organic UV-filters in sunscreen formulations was performed by HPLC with UV spectrophotometric detection. The filters determined were: sulisobenzone, oxybenzone, octyl dimethyl PABA, octyl methoxycinnamate, octyl salicylate and homosalate. A C18 stationary phase and a mobile phase of ethanol water acetic acid (70 : 29.5 : 0.5) were used with a flow rate of 0.5 mL/min. UV measurements were carried out at 313 nm. The time required for the analysis was 25 min and the limits of detection were between 0.2 and 2 mg/L, except for sulisobenzone, which gave a limit of detection of 20 mg/L. The procedure proposed provides an accurate, fast a…
A rapid HPLC assay for zearalenone in laboratory cultures ofFusarium graminearum
1993
A high pressure liquid chromatographic (HPLC) method to determine zearalenone in corn contaminated withFusarium graminearum is described. After extraction with methanol-water and solvent partition, samples were cleaned up by applying the extract to a disposable silica cartridge and by eluting the toxin with a mixture of hexane/dry ethyl ether (5/5). Separation was achieved by a reverse phase μBondapak C18 column followed by fluorescence detection using an excitation wavelength at 274 nm and an emission wavelength at 440 nm. Detection limit was about 5 ng. Recoveries ranging from 85.37 to 100.97%, in standard solutions range 30–0.5 µg/ml, were found.
Determination of type A trichothecenes by high-performance liquid chromatography with coumarin-3-carbonyl chloride derivatisation and fluorescence de…
2000
A method for the analysis of type A trichothecenes T-2 toxin, HT-2 toxin, neosolaniol and diacetoxyscirpenol by high-performance liquid chromatography with fluorescence detection using coumarin-3-carbonyl chloride has been developed. Different parameters concerning the analytical procedure such as stability of both the reagent and derivatised analytes, time and temperature of the derivatisation reaction, were studied and optimised. Three different clean-up procedures (solid-phase extraction with silica gel or C-18 cartridges, and liquid-liquid partition between toluene and dihydrogen phosphate buffer) were tested in order to remove the excess reagent peaks. The last procedure gave the best …