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PubMed2004

Static headspace gas chromatographic method for quantitative determination of residual solvents in pharmaceutical drug substances according to european pharmacopoeia requirements.

A static headspace (HS) gas chromatographic method for quantitative determination of residual solvents in a drug substance has been developed according to European Pharmacopoeia general procedure. A water-dimethylformamide mixture is proposed as sample solvent to obtain good sensitivity and recovery. The standard addition technique with internal standard quantitation was used for ethanol, tetrahydrofuran and toluene determination. Validation was performed within the requirements of ICH validation guidelines Q2A and Q2B. Selectivity was tested for 36 solvents, and system suitability requirements described in the European Pharmacopoeia were checked. Limits of detection and quantitation, precision, linearity, accuracy, intermediate precision and robustness were determined, and excellent results were obtained.

Chromatography, Gas↗
PubMed2005

Specific background electrolytes for nonaqueous capillary electrophoresis.

The use of organic solvents or mixture of solvents in capillary electrophoresis is gaining wider attention. The electroosmotic flow mobility of eight organic solvents (acetonitrile, acetone, dimethylformamide, dimetylsulphoxide, propylene carbonate, methanol, ethanol, n-propanol) and of mixtures of several solvents (methanol-acetonitrile, methanol-propylene carbonate, acetonitrile-propylene carbonate) has been studied. The influence of 1,3-alkylimidazolium salts in different solvents on the separation of different analytes has been investigated. Some of these salts have shown usefulness for matrix-assisted laser desorption ionization matrices and off-line analysis of electrophoresis fractions. It also appears that nonaqueous capillary electrophoresis with 1,3-alkylimidazolium salts as background electrolytes is suitable for separation small inorganic ions.

Electrolytes↗
PubMed2005

Influence of solvent properties on separation and detection performance in non-aqueous capillary electrophoresis-mass spectrometry of basic analytes.

The versatility of non-aqueous capillary electrophoresis (NACE) results mainly from the variety of physico-chemical properties of the different solvents. They provide solubility for a wide range of analytes, enable to control electrophoretic selectivity, but affect in some cases UV absorbance detection. The coupling of NACE to electrospray mass spectrometry (ESI-MS) allows to cope with the high UV cut-off of some CE relevant solvents (e.g., formamides). In this paper the pure organic solvents methanol, acetonitrile, dimethylsulfoxide, formamide, N-methylformamide and N,N-dimethylformamide are evaluated against water for the preparation of ammonium acetate electrolytes to separate the basic model substances 2-aminobenzimidazole, procaine, propranolol and quinine with NACE-MS. MS coupling is assisted with the sheath liquid water-isopropanol (1:4, v/v) with 0.1% formic acid. The goal of the paper is to assess the influence of the solvent on selectivity, separation speed, and peak efficiency for a given set of model compounds on a simple empirical basis. It should give the user an idea how the separation quality is changed when nothing but the running solvent is altered. The obtained efficiency results were discussed with respect to physico-chemical models described in literature (assuming longitudinal diffusion as the only source of band broadening), but no satisfying correlations with solvent properties could be traced. The feasibility of all six organic solvents for MS coupling was demonstrated and the influence of the separation solvent on the MS detection performance was compared. In the seven different solvents, the shortest run time was obtained with acetonitrile, the best peak resolution with the amphiprotic solvents (especially methanol) best peak efficiency with methanol and formamide, and the most sensitive ESI-MS detection with acetonitrile and methanol, but with only slight advantage to water.

Electrophoresis, Capillary↗
PubMed2005

Determination of electroosmotic flow in nonaqueous capillary electrophoresis.

Mobility of the electroosmotic flow (mu(EOF)) in fused-silica capillaries strongly depends on the nature of the background electrolyte. In this study, 27 solvent systems were investigated, namely water, methanol, ethanol, 2-propanol, 1-butanol, acetonitrile (MeCN), formamide, N-methylformamide (NMF), N,N-dimethylformamide and dimethyl sulfoxyde, as well as 8 hydroorganic and 9 organic mixtures. For each system, six mu(EOF) were determined at a different ionic strength in basic conditions, and an absolute electroosmotic flow mobility (mu(EOF,0)) was extrapolated according to the Debye-Huckel Onsager model. The obtained mu(EOF,0) values were correlated with the solvent's relative permittivity (epsilon) and viscosity (eta). A good correlation (r2=0.867) between mu(EOF,0) and the solvent's epsilon/eta ratio was demonstrated, except for two solvents (MeCN and NMF). Furthermore, the donor number (DN) of a solvent took into account the possible zeta potential modification in the electric double layer near the capillary wall. Consequently, the relationship between mu(EOF,0) and epsilon/(eta x DN) was superior, with a r2 of 0.943 for 10 pure solvents.

Electrophoresis, Capillary↗
PubMed2005

Reversed-phase liquid chromatographic characterization and analysis of air particulates humic (-like) substances in presence of pollens.

Newly developed method for characterisation and analysis of humic substances (HS) and humic-like substances (HULIS) in air dust particles was tested for potential interferences caused by abundant co-sampled pollens (common dandelion, common wormwood-absinth, apple tree). RP-HPLC using 10-step gradient of dimethylformamide (DMF) in a buffered aqueous mobile phase and a wide-pore (30 nm) octadecylsilica column has been applied to the analysis of HS and HULIS using tandem of spectrophotometric (DAD) and fluorimetric detection (FLD). Achieved results suggest that the devised method is reliable for characterisation, fractionation and analysis of terrestrial HS, air dust HS and air particulate HULIS in liquid extracts at a trace concentration levels. Fluorimetric detection (ex. 470 nm/em. 530 nm; LOD, 3.1 microg/ml) enables sensitive, highly selective and interference free determination of HS and HULIS regardless the presence of pollen constituents, whereas spectrophotometric detection is susceptible to interferences in UV region above 260 nm. However, even in this case, the interfering substances can be revealed by both different pattern and shape of their peaks, as well as by spectral features different from HS or HULIS. Analytical procedure based on air sampling, extraction and above-mentioned HPLC method enables characterisation and analysis of HS and/or HULIS at relative concentration levels down to 0.1% (m/m) in 10 mg mass scale of sampled air dust and particulate material.

Air Pollutants↗
PubMed2006

Characterization of polydisperse poly(vinyl chloride) by temperature gradient interaction chromatography.

Temperature gradient interaction chromatography (TGIC) was employed to fractionate a commodity polymer, poly(vinyl chloride) (PVC) with wide molecular weight distribution (MWD). The TGIC fractionation was carried out with C18 bonded silica and dimethylformamide (DMF) as the stationary and mobile phase, respectively. TGIC exhibited a high resolution to fractionate the PVC into the fractions with a narrow MWD comparable to the anionically polymerized standards. In combination with light scattering detection, TGIC is able to characterize the polymers with wide MWD and shows a good potential to be further developed as a new preparative fractionation method of synthetic polymers.

Chromatography, Gel↗
PubMed2006

An improved method for isolation and purification of sedimentary porphyrins by high-performance liquid chromatography for compound-specific isotopic analysis.

We describe an improved method for purification of sedimentary vanadyl and nickel porphyrins (i.e., naturally occurring metalloalkylporphyrins). For the purpose of compound-specific isotopic analyses, various sedimentary porphyrins were purified from the complex natural mixtures by the dual-step high-performance liquid chromatography (HPLC) method. The high-sample-capacity reversed-phase HPLCs by adding N,N-dimethylformamide to the mobile phase allow an efficient collection of fractions containing the target compounds even using analytical-scale columns. Furthermore, this method achieved improved chromatographic resolutions but significantly reduced the overall retention time down to 60% compared with the previous work. The target compounds were then isolated with the normal-phase HPLC with the baseline-resolution, which is necessary to avoid chromatographic isotopic fractionation. One of the advantages of this method is that it requires neither derivatization nor demetallation. The purity of these isolated compounds was demonstrated by various HPLC online detection methods utilizing a photodiode-array detector, a mass selective detector. The overall recoveries of Ni porphyrin, VO porphyrin, and porphyrin-free base, respectively, were estimated to be approximately 50-60%, 65%, and 85%.

Chromatography, High Pressure Liquid↗
PubMed2006

Colloidal crystallization of colloidal silica modified with ferrocenyl group-contained polymers in organic solvents.

Surface modification of colloidal silica with ferrocenyl-grafted polymer and colloidal crystallization of the particles in organic solvent were studied. Poly(methyl methacrylate-co-vinylferrocene)-grafted silica never formed colloidal crystals in polar solvent, such as acetone, acetonitrile, ethanol and N,N-dimethylformamide (DMF), while poly(methyl methacrylate-co-ferrocenyl acrylate)-grafted silica gave colloidal crystallization in DMF. The particles prepared by grafting of poly(N,N-dimethylacrylamide-co-vinylferrocene), with vinylferrocene (Vfc) mole fraction of 1/13 and 1/23, were observed to give the crystallization in ethanol and DMF over particle volume fraction of 0.058. Further, silica modified with copolymer of Vfc and N-vinyl-2-pyrrolidone, N-vinylcarbazole or N-isopropylacrylamide formed colloidal crystals in ethanol and DMF. Especially, poly(N-isopropylacrylamide-co-Vfc)-grafted silica, which was composed of the highest mole fraction of vinylferrocene, 1/3, afforded colloidal crystallization in ethanol over particle volume fraction of 0.053. Relatively high polar vinylferrocene copolymer grafting of silica resulted in colloidal polymerization in organic solvents.

Amides↗
PubMed2006

Effects of cryopreservation methods on post-thaw motility of spermatozoa from the Japanese pearl oyster, Pinctada fucata martensii.

In order to develop cryopreservation techniques for Japanese pearl oyster spermatozoa, the effects of various cryopreservation conditions on post-thaw motility were examined. Spermatozoa cryopreserved with 10% methanol (MET), dimethylformamide or dimethylacetamide plus 90% diluent comprising 80% seawater and 20% fetal bovine serum (FBS) showed higher percentages of post-thaw motility than those cryopreserved with 10% dimethylsulfoxide or glycerol. When spermatozoa were cryopreserved with various concentrations (0-20%) of MET and 100-80% diluent, 10% MET showed the highest percentages of post-thaw motility. When spermatozoa were cryopreserved with 10% MET and 90% diluent comprising various concentrations (0-100%) of FBS or Ringer solution mixed with seawater, the percentages of post-thaw motility peaked at 20% FBS or Ringer solution, and were significantly higher for 20% FBS than for 20% Ringer solution. The percentages of post-thaw motility increased with increasing dilution ratios from 2.5- to 50-fold. Spermatozoa cooled to -50 degrees C and then immersed in liquid nitrogen (LN) showed higher post-thaw motility than those cooled to -30 degrees C or -40 degrees C. When spermatozoa were cryopreserved to -50 degrees C at various cooling rates by changing the sample height above the LN surface, the post-thaw motilities of spermatozoa cooled at 10 cm (cooling rate: -21.3 degrees C/min) and 12.5 cm (-15.6 degrees C/min) from the LN surface were higher than those at 5, 7.5 or 15 cm. These results indicate that 10% MET plus 90% diluent comprising 80% seawater and 20% FBS is a suitable extender for cryopreservation of Japanese pearl oyster spermatozoa and that samples should be cooled to -50 degrees C at a cooling rate between -15 and -20 degrees C/min for efficient storage.

Animals↗
PubMed2006

Synthesis of compounds with antiproliferative activity as analogues of prenylated natural products existing in Brazilian propolis.

This work describes the syntheses and antitumoral properties of five prenyl compounds from which antiproliferative activities were predicted by using the TOPS-MODE approach, a computational method for drug design. The syntheses of 2-(3-methylbut-2-enyloxy)acetophenone (2), 2-hydroxy-5-(3-methylbut-2-enyl)acetophenone (3), 2-hydroxy-3-(1,1-dimethylallyl)acetophenone (4), and 5-(3-methylbut-2-enyl)-2-(3-methylbut-2-enyloxy)acetophenone (5) were realized by O-prenylation of phenolic compounds with prenyl bromide and by Claisen rearrangement, respectively. Reaction of 2-hydroxy-5-(3-methylbut-2-enyl)acetophenone 3 under Vilsmeier-Haack conditions with phosphoryl chloride and N,N-dimethylformamide yielded 6-(3-methylbut-2-enyl)chromone-3-carbaldehyde (6). The compounds were tested for their cytotoxicity toward a diverse panel of cultured human tumor cell lines. Compound 3 showed significant selective cytotoxic activity (IC(50) < 9 microg/ml).

Acetophenones↗
PubMed2006

Incorporation of camptothecin into N-phthaloyl chitosan-g-mPEG self-assembly micellar system.

The capability of N-phthaloylchitosan-grafted poly (ethylene glycol) methyl ether (mPEG)(PLC-g-mPEG) to enhance the aqueous solubility and stability of the lactone form of camptothecin (CPT) was investigated. PLC-g-mPEG formed a core-shell micellar structure after dialysis of the polymer solutions in dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) against water, with a critical micelle concentration (CMC) of 28 microg/ml. CPT was loaded into the inner core of the micelles by dialysis method. The results showed an increase in the CPT-loading amount with an increasing concentration of CPT. The stability of drug-loaded micelles was studied by gel-permeation chromatography (GPC), and their in vitro release behaviors were analyzed. Release of CPT from the micelles was sustained. When compared to the unprotected CPT, CPT-loaded PLC-g-mPEG micelles were able to prevent the hydrolysis of the lactone group of the drug. The kinetics of the CPT hydrolysis in human serum albumin (HSA) and fetal bovine serum (FBS) were pseudo-first order. The hydrolysis rate constants for CPT and CPT-loaded PLC-g-mPEG micelles in phosphate-buffered saline (PBS) pH 7.4, were 7.4 x 10(-3) min(-1) and 9.1 x 10(-3) h(-1), parallel to an increase in half-life of CPT from 94 min to 76.15 h, respectively.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Photoinactivation of Escherichia coli using porphyrin derivatives with different number of cationic charges.

The photodynamic effect of meso-substituted cationic porphyrins, 5-[4-(trimethylammonium)phenyl]-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin iodide 1, 5,10-di(4-methylphenyl)-15,20-di(4-trimethylammoniumphenyl)porphyrin iodide 2 and 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide 3, have been investigated in both homogeneous medium bearing photooxidizable substrates and in vitro on a typical gram-negative bacterium Escherichia coli. Absorption and fluorescence spectroscopic studies were compared in N,N-dimethylformamide. Fluorescence quantum yields (varphiF) of 0.10, 0.06 and 0.08 were calculated for porphyrins 1, 2 and 3, respectively. The singlet molecular oxygen, O2(1Deltag), production was evaluated using 9,10-dimethylanthracene yielding values of 0.66, 0.36 and 0.42 for porphyrins 1, 2 and 3, respectively. Guanosine 5'-monophosphate was used as biological substrate model. Similar decomposition of guanosine 5'-monophosphate was obtained using these cationic porphyrins as sensitizer. In biological medium, photosensitized inactivation of E. coli was analyzed using cells without and with one washing step. E. coli cultures were treated with sensitizer at 37 degrees C for 30 min in dark. In both procedures, a higher photoinactivation of cells (>99.999%) was found for cells treated with 10 microM of tricationic porphyrin 3 and irradiated for 5 min with visible light. Porphyrins 1 and 2 only show an important photodamage when the cells are irradiated without washing step. These results indicated that the tetracationic porphyrin 3 could be a promising sensitizer with potential applications in the photoinactivation of bacterial cells by photodynamic therapy.

Anthracenes↗
PubMed2005

Flow behavior of regenerated wool-keratin proteins in different mediums.

Keratin is abundantly present in nature and the major component of hair, wool, feather, nail and horns. Dissolution of keratin is often required when non-textile applications are demanded. However, the low solubility of keratin in water is the major problem. It becomes unstable and precipitated when stored for a long time. Therefore, it is necessary to find a good solvent that provides high stability and easy processibility. In this research, we used formic acid and dimethylformamide (DMF) to dissolve regenerated keratin protein films. It is shown that formic acid is a good solvent for regenerated keratin proteins for the purpose of storage. Transparent and stable regenerated keratin solution is obtained in formic acid.

Animals↗
PubMed2006

Printed circuit board industry.

The printed circuit board is the platform upon which microelectronic components such as semiconductor chips and capacitors are mounted. It provides the electrical interconnections between components and is found in virtually all electronics products. Once considered low technology, the printed circuit board is evolving into a high-technology product. Printed circuit board manufacturing is highly complicated, requiring large equipment investments and over 50 process steps. Many of the high-speed, miniaturized printed circuit boards are now manufactured in cleanrooms with the same health and safety problems posed by other microelectronics manufacturing. Asia produces three-fourths of the world's printed circuit boards. In Asian countries, glycol ethers are the major solvents used in the printed circuit board industry. Large quantities of hazardous chemicals such as formaldehyde, dimethylformamide, and lead are used by the printed circuit board industry. For decades, chemically intensive and often sloppy manufacturing processes exposed tens of thousands of workers to a large number of chemicals that are now known to be reproductive toxicants and carcinogens. The printed circuit board industry has exposed workers to high doses of toxic metals, solvents, acids, and photolithographic chemicals. Only recently has there been any serious effort to diminish the quantity of lead distributed worldwide by the printed circuit board industry. Billions of electronics products have been discarded in every region of the world. This paper summarizes recent regulatory and enforcement efforts.

Electronics↗
PubMed2005

Synthesis and Characterization of a Novel Gd(III)-Cu(II) Dinuclear Adduct.

Two novel Gd(III)-Cu(II) dinuclear complexes have been prepared by the acid-base reaction between Gd(hfa)(3) and Cu(2,2-oxomac) (1, Cu(2,2-oxomac)Gd(hfa)(3)) and between Gd(hfa)(3) and Cu(3,2-oxomac) (2, Cu(3,2-oxomac)Gd(hfa)(3)). These complexes have been characterized by elemental analysis and infrared spectroscopy. The structure of 1 has been determined by X-ray diffraction. The copper atom is square pyramidal, bound to the four planar nitrogen atoms of the macrocycle and weakly bound to the oxygen atom of a dimethylformamide (dmf) molecule. The gadolinium atom is at the center of a tricapped trigonal prism. The nine-coordinate gadolinium atom is bound to six oxygen atoms of three hfa ligands, the two oxamide oxygen atoms of the copper macrocycle, and one oxygen atom of a second coordinated dmf molecule. Unsymmetric binding of the copper macrocycle to gadolinium leads to a distortion in the bridging atoms not observed in reactions of the copper macrocycles with transition metal hfa's. GRAPHICAL ABSTRACT: The reaction of Cu(2,2-oxomac) with Gd(hfa)(3) yields a Gd(III)-Cu(II) dinuclear complex with an oxamide bridge between copper(II) and gadolinium(III). The gadolinium atom adopts a tricapped trigonal prismatic geometry.

Journal Article↗
PubMed2006

Survismeter--type I and II for surface tension, viscosity measurements of liquids for academic, and research and development studies.

For centuries surface tension (gamma) and viscosity (eta) data have been measured with individual instruments consuming much time and materials. Thus the two different types of survismeters have been designed and made of borosil glass material for surface tension and viscosity data to rationalize frictional and cohesive forces, respectively. Friccohesity (sigma (sm(-1), second per meter)) is derived from Fric of frictional and cohesity of cohesive forces of the liquid respectively, and denoted by rational coefficient a eta/gamma (sigma). The values of the friccohesity are correlated to the dipole moment of liquids and their plot gives a standard calibration curve along with an equation of the curve with definite values of the coefficients, the friccohesity values are put on the calibration curve to retrieve the dipole moment values. Here, the sigma values for each of dimethylformamide, dimethylsulfoxide and acetronitrile solvents along with their 0.05, 0.10 and 0.20 mol kg(-1) aqueous solutions, respectively, were determined at 293.15K and plotted against their dipole moment values for standard calibration curve. The range of the dipole moment values for calibration curve is pre-decided and the sigma values for homogenous solutions of compositions below their saturation point can be measured with +/-1 x 10(-5)sm(-1).

Body Fluids↗
PubMed2004

Evolution of fractal-like surface structures in layers of polyacrylonitrile solutions by interfacial dynamic processes.

Solvent evaporation causes concentration and temperature gradients at the free surface of a coating polymer solution. Thereby surface-tension-driven flows can result in a surface instability with regular structures within the layer. Different types of surface structures can occur at spots with thickness differences. One can find fractal-like structures especially in the edge zone of a layer. The evolution of such fractal-like structures at the surfaces of coating solutions of polyacrylonitrile (PAN) in dimethylformamide (DMF) during layer hardening is examined. Condensation of water on the surface of the fluid layer exerts a strong influence on the formation of these structures. Solutions of PAN in DMF are important for the production of ultrafiltration membranes. Such membranes are produced by precipitation in a water bath after a short open time.

Journal Article↗
PubMed2004

Influence of adsorbing species on properties of equilibrium silver iodide clusters.

Thermodynamically stable AgI clusters were studied in the presence of high- and low-molecular-weight additives: polyethyleneimine (PEI) and dimethylformamide (DMF), respectively. Clusters containing up to 20 silver iodide pairs, roughly twice as many as in the system without PEI or DMF, have been observed. We show that the mechanism stabilizing these clusters is mixed adsorption with iodide ions at the AgI-electrolyte interface. We make it plausible that more strongly adsorbing additives give rise to ultralow interfacial tensions of the AgI-electrolyte interface, with perspectives for "reversible colloids."

Journal Article↗