Search results for "Spectroscopy"
showing 10 items of 10293 documents
Spectrofluorimetric determination of emetine by flow injection using barium peroxide and UV derivatization
1993
Abstract The flow-injection spectrofluorimetric determination of emetine was carried out by photoderivatization in the presence of barium peroxide, in a flow-injection assembly in which the PTFE tubing in the injection valve is helically coiled around the lamp. The sample solution merges with a barium peroxidephosphoric acid solution and then the resulting mixture is irradiated; pure distilled water is used as a carrier stream. The calibration graph is linear over the range 0.05–50 μ g ml −1 of emetine dihydrochloride. The influence of foreign compounds was studied and the method was applied to the determination of emetine in injection and human urine samples.
Continuous flow-injection-atomic absorption spectrometric method for the determination of Ondansetron
1995
Abstract A flow-injection procedure for the indirect determination of the new drug Ondansetron is proposed. The method is based on the reaction of the drug in an oxidative solid-phase reactor included in the flow assembly. The reactor was made by lead dioxide physically entrapped by polymerization; the released lead(II) was monitored by atomic absorption spectrometry at 217.0 nm. The procedure gave a linear calibration graph up to 20 μg ml−1 of Ondansetron with a sample throughput of 338 samples h−1.
Direct determination of Mancozeb by photoacoustic spectrometry
2006
Abstract A solvent free, fast and environmentally friendly photoacoustic-infrared-based methodology (PAS-FTIR) was developed for the determination of Mancozeb in agrochemicals. This methodology was based on the direct measurement of the transmittance spectra of solid samples and a multivariate calibration model to determine the active ingredient concentration. The proposed partial least squares (PLS) model was made using nine standards prepared by mixing different amounts of kaolin and Mancozeb, with concentrations between 5.43 and 88.10% (w/w). A hierarchical cluster analysis was made in order to classify the samples in terms of similarity in the PAS-FTIR spectra. From their spectra differ…
Synthesis and characterization of diatomaceous earth chemically modified with γ-aminopropyltrimethoxysilane
2003
A stationary phase for thin-layer chromatography has been prepared by bonding purified diatomaceous earth (rich in silica) with γ-aminopropyltrimethoxysilane. The phase has been characterized by elemental analysis, measurement of the specific surface area, IR spectroscopy, thermal analysis, and chromatographic testing.
Univariate method for background correction in liquid chromatography–Fourier transform infrared spectrometry
2007
An univariate method is proposed for background correction in on-line gradient liquid chromatography-Fourier transform infrared (LC-FTIR) spectrometry using acetonitrile:water as mobile phase components. The method is based on the calculation of the ratio of absorbances (AR) at two characteristic wavenumbers for each spectrum. This parameter is subsequently used to locate the most appropriated eluent spectrum within a reference spectra matrix (RSM) to be subtracted from each spectrum included in the sample chromatogram. To correct minor changes in eluent spectra intensity during the elution of analytes, a correction factor (Kf), defined as the ratio of the absorbance of the sample and the s…
Procedures of Separation and Pre‐concentration for Molybdenum Determination Using Atomic Spectrometry—a Review
2004
Abstract The literature concerning the improvement of atomic and ionic procedures for molybdenum determination through separation and pre‐concentration were updated. Analytical procedures based on flame atomic absorption spectrometry (AAAS), electrothermal or graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma optical emission spectrometry (ICP‐OES), and inductively coupled plasma mass spectrometry were reviewed taking into consideration the preliminary steps, which can enhance the selectivity and sensitivity based on co‐precipitation, solvent extraction, and solid‐phase extraction. Both in‐batch and on‐line procedures were considered.
Microwave-assisted extraction of polybrominated diphenyl ethers and polychlorinated naphthalenes concentrated on semipermeable membrane devices
2006
Abstract Microwave-assisted extraction (MAE) has been evaluated as an alternative to dialysis for the extraction of polybrominated diphenyl ethers (PBDEs) and polychlorinated naphthalenes (PCNs) sampled by semipermeable membrane devices (SPMDs), using gas chromatography coupled to tandem mass spectrometry (GC–MS–MS). For MAE optimization a two level full factorial design 2 3 , plus a centre point, which involves 11 randomized runs was used. The results showed that the temperature had a significant influence on the extraction of the nine PBDEs and four PCNs tested. Also, the solvent volume had a positive influence on the extraction of PBDEs and PCNs, but only in latter compounds, it achieves…
Samplers for VOCs in air based on cyclodextrin–silica hybrid microporous solid phases
2012
Samplers for VOCs in air based on cyclodextrin-silica hybrid microporous solid phases are proposed. The solid phase preparation is very easy and inexpensive. Proposed samplers compared with other solid phases present the advantages of a wider range of operative conditions for VOCs desorption. Samplers are tested based on results for the determination of benzene, toluene, ethylbenzene and o-xylene, m-xylene and p-xylene (BTEX) in air. Operational parameters are optimized and quantitative recovery is obtained using a solid phase from 2-hydroxypropyl-β-cyclodextrin and acetonitrile as the extraction solvent. The recoveries obtained are 89 ± 4%, 90 ± 6%, 91 ± 2%, 87.0 ± 0.9%, 88 ± 4%, and 88 ± …
A new derivatization procedure for the determination of cephalexin with 1,2-naphthoquinone 4-sulphonate in pharmaceutical and urine samples using sol…
1998
Abstract The present report shows how to derivatize cephalexin with 1,2-naphthoquinone-4-sulphonate (NQS) into solid-phase extraction cartridges (C18) using UV–visible detection. Optimum conditions for this new procedure are: hydrogen carbonate/carbonate buffer pH=10.5, 5 min reaction time at 25°C and NQS concentration of 7.1×10−3 mol l−1. The accuracy and the precision of the method were tested. The procedure was used to measure cephalexin in pharmaceutical and urine samples. The results obtained were contrasted with those reported by UV-spectrophotometric and HPLC methods for pharmaceutical samples and with HPLC method for urine samples. The H-point standard additions method was used to m…
Determination of busulfan in human plasma using high-performance liquid chromatography with pre-column derivatization and fluorescence detection.
1999
A rapid, sensitive and reproducible high-performance liquid chromatographic assay for busulfan in human plasma was developed. After extraction of plasma samples with acetonitrile and methylene chloride, busulfan and the internal standard [1,5-bis(methanesulfonyloxy)pentane] were derivatized with 8-mercaptoquinoline to yield fluorescent compounds which were detected with a fluorescence detector equipped with filters of 360 nm (excitation) and 425 nm (emission). Calibration graphs showed a linear correlation (r>0.9990) over the concentration range of 20-2000 ng/ml. The recovery of busulfan from plasma standards was 70+/-5%. The detection and quantification limits for busulfan in plasma sample…