Showing papers on "Derivatization published in 2005"
TL;DR: The potential of derivatization for metabolic profiling in LC/MS is demonstrated by the enhanced analysis of plant extracts, including the potential to measure volatile acids such as formic acid, difficult to achieve by GC/MS.
Abstract: An overview is presented of gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS), the two major hyphenated techniques employed in metabolic profiling that complement direct 'fingerprinting' methods such as atmospheric pressure ionization (API) quadrupole time-of-flight MS, API Fourier transform MS, and NMR. In GC/MS, the analytes are normally derivatized prior to analysis in order to reduce their polarity and facilitate chromatographic separation. The electron ionization mass spectra obtained are reproducible and suitable for library matching, mass spectral collections being readily available. In LC/MS, derivatization and library matching are at an early stage of development and mini-reviews are provided. Chemical derivatization can dramatically increase the sensitivity and specificity of LC/MS methods for less polar compounds and provides additional structural information. The potential of derivatization for metabolic profiling in LC/MS is demonstrated by the enhanced analysis of plant extracts, including the potential to measure volatile acids such as formic acid, difficult to achieve by GC/MS. The important role of mass spectral library creation and usage in these techniques is discussed and illustrated by examples.
680 citations
TL;DR: This deposition method, which involves simple reagents and does not require the isolation and purification of the diazonium salt, enabled the grafting of covalently bounded layers which exhibited properties very similar to those of layers obtained by the classical derivatization method involving isolated diaz onium salt dissolved in acetonitrile or aqueous acid solution.
Abstract: The derivatization of a glassy carbon electrode surface was achieved by electrochemical reduction of several in situ generated diazonium cations. The diazonium cations were synthesized in the electrochemical cell by reaction of the corresponding amines with NaNO2 in aqueous HCl. The versatility of the method was demonstrated by using six diazonium cations. This deposition method, which involves simple reagents and does not require the isolation and purification of the diazonium salt, enabled the grafting of covalently bounded layers which exhibited properties very similar to those of layers obtained by the classical derivatization method involving isolated diazonium salt dissolved in acetonitrile or aqueous acid solution. Cyclic voltammetry and electrochemical impedance spectroscopy carried out in aqueous solutions containing electroactive redox probe molecules such as Fe(CN)63-/4- and Ru(NH3)63+ confirmed the barrier properties of the deposited layers. The chemical composition of the grafted layers was d...
370 citations
TL;DR: In this paper, the authors discuss detection-oriented derivatization as well as the application of mobile phase additives to enhance the sensitivity of detection in liquid chromatograph/atmospheric ionization/mass spectrometry (LC/API/MS), focusing in particular on the applications involving small molecules in bio-matrices.
232 citations
TL;DR: Reversed-phase liquid chromatography (RPLC) separation on different C18 columns using various perfluorinated carboxylic acids as ion-pairing agents has been found suitable for coupling with MS/MS, and for the separation of AA.
Abstract: Seventy-six molecules of biological interest for the diagnosis of inherited disorders of amino acids (AA) metabolism have previously been demonstrated to be detectable in electrospray ionization tandem mass spectrometry (ESI-MS/MS) positive mode without derivatization. Reversed-phase liquid chromatography (RPLC) separation on different C18 columns using various perfluorinated carboxylic acids as ion-pairing agents has been found suitable for coupling with MS/MS, and for the separation of AA. A new procedure was optimized in order to replace the usual ion-exchange chromatographic, post-column ninhydrin derivatization, time-consuming routine method. This procedure allowed an adequate separation of all the molecules from other known interfering compounds, and a throughput of two samples per hour. Quantification limits for each molecule were found to be compatible with their measurement in plasma and urine. We validated the qualitative part of the method by analyzing plasma and urine samples from patients affected with several inherited disorders of AA metabolism. We validated the quantification of 16 AA using their stable isotopes as internal standard. The calibration curves were linear over the range 0-3 mM. The quantitative results obtained with the new method on 105 plasma and 99 urine samples were in good agreement with those obtained by the established routine method. Spiking experiments and precision results were also satisfactory.
185 citations
TL;DR: It is the authors' conclusion that strategies such as chemical derivatization and on-line H/D exchange should be used more routinely in drug metabolism studies in order to facilitate metabolite identification.
171 citations
TL;DR: Compared to other reported methods for glyphosate and phosphate, the developed IC-ICP-MS method is sensitive and simple, and does not require any chemical derivatization, sample preconcentration and mobile phase conductivity suppression.
147 citations
TL;DR: A highly selective and sensitive LC-MS/MS technique capable of reliable detection of less than 50 fmol of the derivatives of S1P and DHS1P without significant sample carryover was developed.
146 citations
TL;DR: In this paper, the authors used enzyme-linked immunosorbent assay (ELISA), high-performance liquid chromatography with UV detector (HPLC-UVD) and gas chromatography in combination with electronic capture detector (GC-ECD) and mass spectrometry detector(GC-MS) in both electronic ionisation mode (EI) and the negative ion chemical ionization mode (NCI) with selected-ion monitoring (SIM) acquisition method (GCMS-NCI-
134 citations
TL;DR: The results suggest that the application of SLM extraction as a method for glyphosate and AMPA enrichment from complicated liquid matrices may be useful mean of routine analysis.
128 citations
TL;DR: Analytical parameters, such as enrichment factor, precision, linearity and detection limits were determined and the influence of derivatizing reagent volume, derivatization time and temperature on the yield of the in-syringe silylation was investigated.
124 citations
TL;DR: The influence of various parameters in each step of derivatization reactions was studied, using both cod liver oil and microalgal biomass as model systems, and Polarity of the reaction medium was found to be of the utmost importance in the process.
Abstract: Assays for fatty acid composition in biological materials are commonly carried out by gas chromatography, after conversion of the lipid material into the corresponding methyl esters (FAME) via suitable derivatization reactions. Quantitative derivatization depends on the type of catalyst and processing conditions employed, as well as the solubility of said sample in the reaction medium. Most literature pertinent to derivatization has focused on differential comparison between alternative methods; although useful to find out the best method for a particular sample, additional studies on factors that may affect each step of FAME preparation are urged. In this work, the influence of various parameters in each step of derivatization reactions was studied, using both cod liver oil and microalgal biomass as model systems. The accuracies of said methodologies were tested via comparison with the AOCS standard method, whereas their reproducibility was assessed by analysis of variance of (replicated) data. Alkaline catalysts generated lower levels of long-chain unsaturated FAME than acidic ones. Among these, acetyl chloride and BF(3) were statistically equivalent to each other. The standard method, which involves alkaline treatment of samples before acidic methylation with BF(3), provided equivalent results when compared with acidic methylation with BF(3) alone. Polarity of the reaction medium was found to be of the utmost importance in the process: intermediate values of polarity [e.g., obtained by a 1:1 (v/v) mixture of methanol with diethyl ether or toluene] provided amounts of extracted polyunsaturated fatty acids statistically higher than those obtained via the standard method.
TL;DR: In this paper, solid phase microextraction (SPME) coupled with GC-MS was used to determine trace levels of bisphenol A in water and leached from plastic containers.
TL;DR: The method was applied to several samples of treated and raw wastewater, triclosan was found in all samples, at concentrations from 120 to 14,000 ng/l, and 2,4-dichlorophenol in most of them, at levels up to 2222 ng/L.
TL;DR: In this article, a new method, stir bar sorptive extraction (SBSE) with in situ derivatization and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of chlorophenols, such as 2,4-dichlorophenol (2, 4-DCP), 2, 4,6-trichloropropylopyrin(2,4, 6-TrCP) and pentachlorophenols (PCP), in tap water
TL;DR: A derivatization reagent, 2-hydrazino-1-methylpyridine, was developed for the liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) of oxosteroids but was unsuitable for di-oxosteroids, such as androstenedione and progesterone.
TL;DR: A new approach to the analysis of the lung cancer biomarkers, hexanal and heptanal in human blood that was based on headspace single-drop microextraction with droplet derivatization, followed by gas chromatography-mass spectrometry (GC-MS).
TL;DR: A high-sensitivity analytical method that uses stir bar sorptive extraction (SBSE) with in situ derivatization and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS) for the simultaneous measurement of trace amounts of phenolic xenoestrogens (PXs) in human urine samples was developed.
TL;DR: In this paper, a procedure for simultaneous determination of both natural and synthetic estrogenic steroids (estrone and 17α-ethynylestradiol) in water is described.
TL;DR: In this procedure, estrogens were extracted using the functionalized polar DHPMM polymer with derivatization using N-methyl-N-(trimethylsilyl)trifluoroacetamide followed by gas chromatography-mass spectrometric analysis.
TL;DR: Under optimum CE‐MS conditions it is observed that the MS sensitivity obtained for FITC‐ and DNS‐amino acids is similar (with limit of detection (LOD) in the µM range, corresponding to amounts injected in the fmol range) while chiral resolution is better for F ITC‐aminos acids.
Abstract: In this work, the development of a new chiral capillary electrophoresis-mass spectrometry (CE-MS) method to separate D- and L-amino acids is shown. On-line coupling between CE and MS is established through an electrospray-coaxial sheath flow interface. Enantiomer separation is achieved by using a cheap, nonvolatile, chiral selector as beta-cyclodextrin in the background electrolyte (BGE) together with a physically coated capillary that is aimed to prevent contamination of the electrospray. The capillary coating is simple and easy to obtain as it only requires flushing of the capillary with a polymer aqueous solution for 3 min. Optimization of CE parameters (pH of BGE, type and concentration of chiral selector, and capillary inner diameter) and electrospray-MS parameters (nature and flow rate of the sheath liquid, nebulizer pressure) is carried out. Two different derivatization protocols of amino acids using dansyl chloride (DNS) and fluorescein isothiocyanate (FITC) are compared in terms of MS sensitivity and chiral resolution. Under optimum CE-MS conditions it is observed that the MS sensitivity obtained for FITC- and DNS-amino acids is similar (with limit of detection (LOD) in the microM range, corresponding to amounts injected in the fmol range) while chiral resolution is better for FITC-amino acids. The optimized method is demonstrated to provide the simultaneous analysis of 15 selected amino acids (i.e., FITC-D/L-Asp, -Glu, -Ser, -Asn, -Ala, -Pro, -Arg, and FITC-gamma-aminobutyric acid (GABA) in a single chiral CE-MS run, corresponding to the main amino acids that can be found in orange. Moreover, as a result of the high resolution achieved, it is possible to detect down to 2% of D-Asp in the presence of 98% of L-Asp. The good possibilities of chiral CE-MS in food analysis are corroborated through the detection of the main amino acids in a commercial orange juice (i.e., FITC-L-Asp, -Glu, -Ser, -Asn, -Pro, -Arg, and the nonchiral FITC-GABA) as well as the determination of the fraudulent addition of synthetic amino acids (containing D- and L-forms) to a fresh orange juice.
TL;DR: A liquid chromatographic method with tandem mass spectrometric detection (LC-MS/MS) for the simultaneous analysis of norethindrone, and ethinyl estradiol, was developed and validated over the concentration range of 50-10000pg/ml and 2.5-500PG/ml, and could be used for pharmacokinetic and drug-drug interaction studies in human subjects.
TL;DR: A rapid, selective and sensitive method was developed for the determination of propofol concentration using an off-line dansyl chloride derivatization step to enhance signal intensity and results show that a very important fraction of prop ofol distributes into red blood cells.
TL;DR: In this article, a solid-phase microextraction (SPME) method for the determination of eight phenoxy acid herbicides and dicamba in water samples has been developed, where analytes are concentrated on a SPME fibre, on-fibre silylated using N -methyl- N -( tert -butyldimethylsilyl)-trifluoroacetamide (MTBSTFA), and determined by gas chromatography with mass spectrometry detection (GC-MS).
TL;DR: A new capillary electrophoresis (CE) method with laser-induced fluorescence (LIF) detection was developed for the rapid separation and sensitive detection of glutathione and glutathion disulfide after derivatization by 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol (NBD-Cl) with satisfactory results.
TL;DR: T tert-Butyldimethylsilyl (TBDMS) derivatives proved to be more stable, reproducible and sensitive than corresponding trimethylsilane (T MS) derivatives for the GC-EI-MS analysis of benzodiazepines.
TL;DR: In this paper, a simple, rapid, sensitive, and inexpensive method for determination of the disease biomarkers of acetone, hexanal and heptanal in human blood was developed.
TL;DR: A simple, sensitive, and specific method based on derivatization and subsequent gas chromatography-mass spectrometry (GC-MS) analysis was developed for the identification and quantification of ATCA in synthetic urine and swine plasma, which produced a coefficient of variation of less than 6% for two sets of quality control standards.
TL;DR: The direct and simultaneous chemical derivatization of the two amino functions of the analyte with benzaldehyde enhances the instrumental responses enabling the use of a sensitive and accurate method for the determination of p-phenylenediamine in hair dyes.
TL;DR: Improved selectivity and resolution combined with an automated preparative HPLC or SFC system can lead to the rapid generation of highly purified enantiomers of desirable starting materials, intermediates or final products.
TL;DR: The development of a sensitive assay for the quantitative analysis of carbohydrates from human plasma using LC/MS/MS is described, which is robust, highly sensitive, rapid, and does not require postcolumn addition or derivatization.