POLYMETHYLOCTILSILOXANE ADSORBED ON POROUS SILICA AS A PACKING MATERIAL FOR REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Packing material having 10, 20, 30, 40 and 50% loadings of polymethyloctilsiloxane on porous silica particles have been prepared and tested. Solvent extraction tests, measurements of physical properties and determinations of chromatographic parameters show that an initial loading of 40% gives a packing material with satisfactory chromatographic properties.1761265127

Mobile phase optimization for the separation of some herbicide samples using HPLC

To separate and determine a mixture of herbicides containing bentazon, 2,4-D, cyanazine, simazine, atrazine, fluazifop acid, diuron, linuron, and ametryn, an intense study was made to optimize the chromatographic conditions, emphasizing the composition of the mobile phase. After consideration of both analysis time and resolution, the optimum mobile phase to carry out the separation of mixtures of these herbicides was found to be methanol:water 60:40, v/v, pH = 4.6 (adjusted with phosphoric acid). These conditions may be used to analyze mixtures of the cited herbicides present in water samples.2391353136

Simultaneous determination of clobutinol hydrochloride and doxylamine succinate from syrups by RP HPLC using a new stationary phase containing embedded urea polar groups

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A new, simple, fast, reproducible and sensitive reversed phase HPLC method, using a new stationary phase containing embedded urea polar groups, has been developed and validated for the simultaneous determination of clobutinol hydrochloride (CLO) and doxylamine succinate (DOX) in syrups. The determination was carried out on a C8 urea column (125 mm x 3.9 mm id., 5 mu m particle size) synthetized at the Liquid Chomatography Laboratory (LabCrom) of the Chemistry Institute of Unicamp. The mobile phase consisted of a mixture of acetonitrile:methanol:phosphate buffer (pH 2.5) in the gradient mode. The diode array detector (DAD) was operated at 230 nm for CLO and 262 nm for DOX. The method showed adequate precision, with relative standard deviations (RSD) less than 1%. The presence of the excipients did not interfere in the results of the analysis. Accuracy was determined by adding standards of the drugs to a placebo and good recovery values were obtained. The analytical curves were linear (r(2) 0.9999 for CLO and 0.9998 for DOX) over a wide concentration range (2.4-336 mu g mL(-1) for CLO and 2.3-63 mu g mL(-1) for DOX). The solutions were stable for at least 72 hours at room temperature. The criteria for validation using the ICH guidelines were fulfilled.482315323Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Preparation and characterization of a new microwave immobilized poly(2-phenylpropyl)methylsiloxane stationary phase for reversed phase high-performance liquid chromatography

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)A new reversed phase high-performance liquid chromatography (RP-HPLC) stationary phase was prepared and its chromatographic and physical-chemical properties were evaluated. The new stationary phase was prepared with a silica support and poly(2-phenylpropyl)methylsiloxane (PPPMS), a phenyl type polysiloxane copolymer. Since this is a new copolymer and there is little information in the literature, it was submitted to physical-chemical characterization by infrared spectroscopy and thermogravimetry. The chromatographic phase was prepared through sorption and microwave immobilization of the copolymer onto a silica support. The chromatographic performance was evaluated by employing test procedures suggested by Engelhardt and Jungheim, Tanaka and co-workers, Neue, and Szabo and Csato. These test mixtures provide information about the hydrophobic selectivity, silanophilic activity, ion-exchange capacity, shape selectivity and interaction with polar analytes of the new Si-PPPMS reversed phase. Stability tests were developed using accelerated aging tests under both basic and acidic conditions to provide information about the lifetime of the packed columns. (C) 2013 Elsevier B.V. All rights reserved.1297113122Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

The chromatographic behavior of coated stationary phases with different silicas

Different silicas coated with poly(methyloctylsiloxane) are compared in terms of the effect of particle shape, particle diameter, mean pore diameter and specific surface area. For irregular particles, the carbon contents (% C) coated are essentially identical even though there are considerable variations in surface area for the different silica supports. Sample retentions (k) increase with increasing surface area while efficiences (N/m, naphthalene) increase as the particle diameter decreases. Excellent peak symmetries (As) are obtained with most packings. Spherical particles, with significantly lower surface areas, have lower carbon loadings and higher surface coverage but produce columns with significantly higher efficiences than the irregular particles having similar particle diameter.21564565

Determination of some organic contaminants in water samples by solid-phase extraction and liquid chromatography tandem mass spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Independent methods for determination of organic contaminants such as pharmaceuticals and pesticides in drinking water samples, using SPE as the extraction technique and LC-MS/MS in the MRM mode with electrospray ionization, were developed and validated. Different SPE sorbents were evaluated, including lab-made fluorinated and phenyl and commercial Oasis HLB and C18, with the commercial phases being more suitable for the target compounds. Recoveries in the range of 70-120% were obtained for all target compounds, with the exception for paracetamol (acetaminophen), and precision values (inter-day and intra-day), expressed in terms of relative standard deviations (RSD), lower than 20% were obtained for all target compounds. Quantification limits were in the range of 0.006-0.208 mu g L-1 and the methods developed were successfully applied for the analysis of drinking water samples, detecting some pharmaceuticals and pesticides, but at concentration levels lower than the MRL. (C) 2012 Elsevier B.V. All rights reserved.1003844Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Preparation and Characterization of a Microwave-Immobilized Fluorinated Stationary Phase for RP-LC

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A fluorinated stationary phase was prepared through the immobilization of poly(methyl-3,3,3-trifluoropropylsiloxane) onto 5 mu m Kromasil silica by microwave irradiation. The best conditions of immobilization time and temperature were determined by central composite design and response surface methodology. Physical-chemical characterizations (IR, (29)Si NMR and elemental analysis) confirmed that the polymer was attached onto the chromatographic support by different mechanisms that resulted in a percent carbon loading of 10%. Some pharmaceuticals were completely separated with the fluorinated stationary phase using a simple mobile phase while the same separation was not possible with a C18 stationary phase.7241858617626Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Preparation of a C-18 stationary phase immobilized by gamma radiation for use in high performance liquid chromatography

A liquid stationary phase, poly(methyloctadecylsiloxane), was immobilized on a silica support, in the proportion 50:50 m/m, by gamma radiation doses of 20 to 90 kGy, with the purpose of obtaining a highly stable chromatographic stationary phase. This stationary phase exhibited higher efficiency and shorter analysis times than similar columns prepared with commercial C-18 packings.21162447245

Methods of extraction and/or concentration of compounds found in biological fluids for subsequent chromatographic determination.

When organic compounds present in biological fluids are analysed by chromatographic methods, it is generally necessary to carry out a prior sample preparation due the high complexity of this type of sample, especially when the compounds to be determinated are found in very low concentrations. This article describes;some of the principal methods for sample preparation in analyses of substances present in biological fluids. The methods include liquid-liquid extraction, solid phase extraction, supercritical fluid extraction and extraction using solid and liquid membranes. The advantages and disadvantages of these methods are discussed.241687

The key role of copper complexes adsorbed on a chemically endcapped diamine bonded phase for HPLC

Chromatographic silica (10 mum) was chemically modified with the organosilane [3-(2-aminoethyl)aminopropyl]trimethoxysilane (AEAPTS) and further endcapped with trimethylchlorosilane (TMCS). Copper ions were complexed onto the modified silica surface through pendant amine groups. The purpose of the immobilized copper complexes is to provide new sites in the stationary phase that can interact strongly with basic organic compounds. A conventional test mixture composed of dipolar compounds such as benzene, toluene, naphthalene, anthracene, pyrene, and nitrobenzene was used to evaluate these new columns. A second mixture, composed of aromatic amines, N,N-diethylaniline, and aniline, was chosen to evaluate the effects caused by complexation of copper ions on the modified silica.24319720