Search results for "Chloroform"
showing 10 items of 414 documents
Comparative study of the determination of trimethylamine in water and air by combining liquid chromatography and solid-phase microextraction with on-…
2005
This work describes a new approach for the determination of trimethylamine (TMA) in water and air by liquid chromatography (LC). The assay is based on the employment of a solid-phase microextraction (SPME) fiber for sampling and for derivatization of the analyte with the fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC). The fiber, with a Carbowax-templated resin -50mum coating, was first immersed into a solution of the reagent. Once loaded with the reagent, the fiber was immersed into the water samples or exposed to the air samples in order to extract and to derivatize the analyte. Finally, the fiber was placed into a HPLC-SPME interface to desorb and transfer the TMA-FMOC derivat…
Determination of sertraline in rat plasma by HPLC and fluorescence detection and its application toin vivopharmacokinetic studies
2012
A simple, rapid, and sensitive HPLC method based on 9H-fluoren-9-ylmethyl chloroformate derivatization for the quantification of sertraline in rat plasma has been developed, requiring a plasma sample of only 0.1 mL, which was deproteinized and derivatized for 5 min in two single steps. The obtained derivative was stable at room temperature and was determined by HPLC using a fluorescence detector. The analytical column was a C(18) column and the mobile phase was acetonitrile and water (80:20, v/v). Calibration curves were linear in the range of 10-500 ng/mL. The limit of detection was approximately 3 ng/mL, and the lower limit of quantification was established at 10 ng/mL. The bias of the me…
Derivatization of amines in solid-phase extraction supports with 9-fluorenylmethyl chloroformate for liquid chromatography
1997
Abstract A new method based on reaction in solid-phase extraction cartridges with 9-fluorenylmethyl chloroformate is described for improved derivatization of amines prior to liquid chromatography. The effects of the reaction conditions, the kinetics of the reaction and the kind of packing material on the derivatization have been evaluated. The reliability of the described approach has been tested by derivatizing propylamine, diethylamine, diethanolamine, glycine, glutamic acid, p-aminobenzoic acid and β-phenylethylamine. Reaction yields compared with those of the analogous solution derivatizations were in the 44–169% range, and satisfactory linearity was achieved at concentrations of the am…
Impact of the ΔPhe configuration on the Boc-Gly-ΔPhe-NHMe conformation: experiment and theory
2019
Conformational propensities of N-t-butoxycarbonyl-glycine-(E/Z)-dehydrophenylalanine N′-methylamides (Boc-Gly-(E/Z)-ΔPhe-NHMe) in chloroform were investigated by NMR and IR techniques. The low-temperature crystal structure of the E isomer was determined by single crystal X-ray diffraction and the experimental data were elaborated by theoretical calculations using DFT (B3LYP, M06-2X) and MP2 approaches. The β-turn tendencies for both isomers were determined in the gas phase and in the presence of solvent. The obtained results reveal that the configuration of ΔPhe residue significantly affects the conformations of the studied dehydropeptides. The tendency to adopt β-turn conformations is sign…
CCDC 724470: Experimental Crystal Structure Determination
2010
Related Article: E.Nauha, H.Saxell, M.Nissinen, E.Kolehmainen, A.Schafer, R.Schlecker|2009|CrystEngComm|11|2536|doi:10.1039/b905511h
Chlorinated short chain aliphatic hydrocarbons in pine needles by purge and trap gas chromatography/mass spectrometry
1995
The concentrations of volatile chlorinated short chain aliphatic hydrocarbons in pine needles have been measured using purge and trap GC/MS. The concentrations of dichloromethane, chloroform, dichloroethene and tetrachloroethene in the needles were calculated. The concentrations of dichloromethane and tetrachloroethene were highest. As a rule the concentrations were higher in the older needles. The needle samples were collected from five sampling points in an area situated in the Southern Finland in the vicinity of a metal scrab plant. Reference needles were collected in the Central Finland. Needles originated from years 1991, 1992 and 1993.
Fourier transform infrared spectrometric strategies for the determination of Buprofezin in pesticide formulations
2002
Abstract Two different strategies for Buprofezin determination, an off-line extraction and stopped-flow determination and an automated procedure, based on the on-line extraction of Buprofezin samples with chloroform and flowing action analysis–fourier transform infrared (FIA–FT-IR) spectrometric measurement of the extracts, have been developed. For the treatment of the off-line extraction mode, data a three-factor partial least squares (PLSs) calibration was developed, using the region from 1465.7 to 1342.3 cm−1 with a single point baseline defined at 2051.9 cm−1 and based on the use of chloroform solutions of Buprofezin. The method provides a R.S.D. On the other hand, the recommended FIA m…
FTIR approaches for diuron determination in commercial pesticide formulations.
2005
Two strategies have been developed for Diuron determination by FTIR spectrometry, an off-line extraction and stopped-flow determination and a fully mechanized procedure, based on the on-line extraction of Diuron and FIA-FTIR measurement of the extracts. The aforementioned procedures have been compared with a reference chromatographic method. The off-line FTIR spectra were obtained at a nominal resolution of 4 cm(-1) from 4000 to 900 cm(-1) by accumulating 25 scans. Diuron was determined using peak height measurements at 1582 cm(-1) corrected using a baseline defined between 1562 and 1614 cm(-1). The waste generation of the off-line procedure was 3.4 mL chloroform for each sample, and the me…
An evaluation of solid phase microextraction for aliphatic amines using derivatization with 9-fluorenylmethyl chloroformate and liquid chromatography
2005
The reliability of SPME combined with a chemical reaction for the analysis of short-chain aliphatic amines by liquid chromatography has been investigated. Different options to couple SPME and derivatization have been tested and compared: (i) derivatization of the analytes in solution followed by the extraction of the derivatives, (ii) extraction of the analytes and subsequent derivatization by immersing the SPME fibre onto a solution of the reagent, and (iii) extraction/derivatization of the analytes using fibres previously coated with the reagent. Methylamine (MA), dimethylamine (DMA) and trimethylamine (TMA) have been selected as a model of primary, secondary and tertiary amines, respecti…
Estimation of formamide harmonic and anharmonic modes in the Kohn-Sham limit using the polarization consistent basis sets.
2010
Formamide harmonic and anharmonic frequencies of fundamental vibrations in the gas phase and in several solvents were successfully estimated in the B3LYP Kohn-Sham complete basis set limit (KS CBS). CBS results were obtained by extrapolating a power function (two-parameter formula) to the results calculated with polarization-consistent basis sets. Anharmonic corrections using the second order perturbation treatment (PT2) and hybrid B3LYP functional combined with polarization consistent pc-n (n = 0, 1, 2, 3, 4) and several Pople’s basis sets were analyzed for all fundamental formamide vibrational modes in the gas phase and solution. Solvent effects were modeled within a PCM method. The anhar…