Determination of lead by hydride generation atomic absorption spectrometry : Part 1. A new medium for generating hydride

A new medium, used to generate lead hydride, was optimized as 0.3% (w/v) oxalic acid-2% (w/v) ammonium cerium (III) nitrate-8% (w/v) potassium tetrahydroborate-1% (w/v) sodium hydroxide solution; 950°C is used for atomization. The characteristic concentration (0.0044 absorbance) obtained under these conditions was 0.04 ng ml^?1. The application of this medium to soil and ferromagano-brass samples is illustrated.     

Determination of phosphorus by electrothermal atomic absorption spectrometry with a phosphorus hollow-cathode lamp as light source

Graphite tubes are pre-heated with a 10% (w/v) zirconium solution, and a 1% (w/v) zirconium solution is injected prior to each phosphorus sample solution. The calibration graph is linear up to ca. 100 ng P, and the detection limit is 5 ng. Phosphorus in water-soluble organic and inorganic compounds can be determined directly by the proposed method, which is also suitable for the determination of phosphorus in NBS standard reference plant materials and in green tea leaves.     

Identification of Coexisting Pentose,Hexose, and Disaccharides with Preliminary Separation through Hydrophilic Interaction on Silica HPTLC Plate Using Aqueous Sodium Deoxycholate-Acetonitrile Mobile Phase System

JPC – Journal of Planar Chromatography – Modern TLC - Aqueous micellar bile salt, sodium deoxycholate (NaDC) solution as additive in acetonitrile (ACN) in the ratio (1:5 v/v) was...     

Total and inorganic mercury determination in fish tissue by flow injection cold vapour atomic fluorescence spectrometry

A simple and reliable method for Hg determination in fish samples has been developed. Lyophilised fish tissue samples were extracted in a 25% (w/v) tetramethylammonium hydroxide (TMAH) solution; the extracts were then analysed by FI-CVAFS. This method can be used to determine total and inorganic Hg, using the same FI manifold. For total Hg determination, a 0.1% (w/v) KMnO₄ solution was added to the FI manifold at the sample zone, followed by the addition of a 0.5% (w/v) SnCl₂ solution, whereas inorganic Hg was determined by adding a 0.1% (w/v) L-cysteine solution followed by a 1.0% (w/v) SnCl₂ solution to the FI system. The organic fraction was determined as the difference between total and inorganic Hg. Sample preparation, reagent consumption and parameters that can influence the FI-CVAFS performance were also evaluated. The limit of detection for this method is 3.7 ng g^?1 for total Hg and 4.3 ng g^?1 for inorganic Hg. The relative standard deviation for a 1.0 µg L^?1 CH₃Hg standard solution (n = 20) was 1.1%, and 1.3% for a 1.0 µg L^–1 Hg²⁺ standard solution (n = 20). Accuracy was assessed by the analysis of Certified Reference Material (dogfish: DORM-2, NRCC). Recoveries of 99.1% for total Hg and 93.9% inorganic Hg were obtained. Mercury losses were not observed when sample solutions were re-analysed after a seven day period of storage at 4°C.     

High-performance liquid chromatographic analysis of the anticancer drug oxantrazole in rat whole blood and tissues.

A reversed-phase high-performance liquid chromatographic (HPLC) assay was developed for the antitumor anthrapyrazole analogue, oxantrazole (OX), in rat whole blood and tissues. Blood samples were mixed with equal volumes of a 25% (w/v) aqueous solution of L-ascorbic acid, whereas tissue samples were homogenized with 1.5-3 volumes of an L-ascorbic acid-methanol-water (1:10:1, w/v/v) mixture to prevent oxidative degradation of OX. Samples were then treated with 60% (v/v) perchloric acid (25-30 microliters/ml of stabilized sample) to precipitate proteins, and centrifuged, with the resultant supernatants analyzed on HPLC utilizing a C8 column. The mobile phase for blood and urine samples consisted of 8% (v/v) glacial acetic acid, 13% (v/v) acetonitrile, 79% (v/v) water, 0.16% (w/v) sodium acetate, and 0.05% (w/v) L-ascorbic acid (final pH 2.7), and was pumped at 1.8 ml/min. Tissue samples were eluted at 2 ml/min with a mobile phase consisting of 8% (v/v) glacial acetic acid, 12% (v/v) acetonitrile, 80% (v/v) water, 0.16% (w/v) sodium acetate, and 0.0;5% (w/v) L-ascorbic acid. OX and internal standard were detected at 514 nm and had retention times of 2.3 and 3.1 min, respectively. The limit of quantitation of OX was 25-50 ng/g. Recovery of OX from biological samples ranged from 50 +/- 0.9% in spleen to 102.8 +/- 1.8% in RG-2 glioma. The analytical method was applied to a pharmacokinetic study in rats.     

Electrospinning of polystyrene/poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene vinylene) blends

Ultrafine polystyrene (PS)/poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene vinylene) (MEH‐PPV) fibers were successfully prepared by electrospinning of PS/MEH‐PPV solutions in chloroform, 1,2‐dichloroethane, and tetrahydrofuran (THF). Three concentrations of the solutions were prepared: 8.5, 16, and 23.5% (w/v), with the compositional weight ratios between PS and MEH‐PPV being 7.5:1, 15:1, and 22.5:1, respectively. Smooth fibers only observed from 23.5% (w/v) PS/MEH‐PPV solution in chloroform. Improvement in the electrospinnability of 8.5% (w/v) PS/MEH‐PPV solution in chloroform was achieved by addition of an organic salt, pyridinium formate (PF), or by addition of a minor solvent with a high dielectric constant value. The average diameters of the as‐spun PS/MEH‐PPV fibers were between 0.30 and 5.11 μm. Last, photoluminescence of 8.5% (w/v) solutions of PS/MEH‐PPV in a mixed solvent system of chloroform and 1,2‐dichloroethane of various volumetric compositions and the resulting as‐spun fibers was investigated and compared. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1881–1891, 2005     

Determination of arsenic in biological fluids by electrothermal atomic absorption spectrometry

A procedure for the determination of the total content of arsenic in urine, serum and blood by electrothermal atomic absorption spectrometry (ETAAS) is described. Zeeman correction is used to compensate the high background signals. The samples are diluted (1 + 1 for urine and 1 + 3 for both serum and blood samples) in a medium containing 0.1% w/v Triton X-100 before being introduced directly into the furnace. A solution containing 15% w/v hydrogen peroxide, 0.65% w/v nitric acid and 0.5% w/v nickel is also introduced into the atomizer by means of a separate injection. Calibration is carried out against aqueous standards for blood and serum samples and using the standard additions method for urine samples. The detection limit is 20 pg (2 ng ml-1). The reliability of the procedure is checked by analyzing three certified reference materials and by recovery studies.     

Novel Dispersion of MWCNTs in Polystyrene Polymer Induced by the Addition of 3-Hydroxy-2-Napthoic Acid

This article reports an extensive investigation of the unique dispersion behavior of solutions with multi-walled carbon nanotubes (MWCNTs) and 3-hydroxy-2-napthoic acid (β-HNA) in tetrahydrofuran (THF) solvent, which results into a multifold enhancement in the electrical properties of polystyrene (PS). A number of solutions with 0.4% of MWCNTs (w/v) and β-HNA (0–1%, w/v) in THF were prepared separately. MWCNTs precipitated out in THF solvent shortly after the preparation and formed two distinct phase regions (2φ). Gratifyingly, addition of β-HNA solution to the MWCNTs solution offered an unprecedented enhancement in the dispersion of MWCNTs. Such dispersion in solutions with only 0.02% β-HNA (w/v) was found to be stable up to 2 weeks at room temperature. FTIR spectroscopy was incorporated to illustrate the adsorption of β-HNA onto the surface of carbon nanotubes (CNTs). After this successful dispersion, nanocomposites solutions comprising of 0.067% β-HNA (w/v), 6.7% PS (w/v), and varying concentrations of MWCNTs (0–0.33%, w/v) were prepared. A remarkable dispersion behavior of MWCNTs in the presence of polymer was also observed. Finally, thin films made up of consistent polystyrene/β-HNA concentrations and increasing amounts of MWCNTs were prepared by casting technique to investigate the influence of dispersion on the electrical properties of the film. The dispersion significantly affected the DC electrical conductivity and incorporation of 5% MWCNTs elevated the electrical conductivity up to 10 orders of magnitude with respect to neat PS.     

Separation of double-stranded DNA fragments by capillary electrophoresis in interpenetrating networks of polyacrylamide and polyvinylpyrrolidone

Mixtures of two polymers with totally different chemical structures, polyacrylamide and polyvinylpyrrolidone (PVP) have been successfully used for double-stranded DNA separation. By polymerization of acrylamide in a matrix of PVP solution, the incompatibility of these two polymers was suppressed. Laser light scattering (LLS) studies showed that highly entangled interpenetrating networks were formed in the solution. Further systematic investigation showed that double-stranded DNA separation was very good in these interpenetrating networks. With a concentration combination of as low as 2% w/v PVP (weight-average molecular mass Mr = 1 x 10(6) g/mol) + 1% w/v polyacrylamide (Mr = 4 x 10(5) g/mol), the 22 fragments in pBR322/HaeIII DNA, including the doublet of 123/124 bp, have been successfully separated within 6.5 min. Under the same separation conditions, similar resolution could only be achieved by using polyacrylamide (Mr = 4 x 10(5) g/mol) with concentrations higher than 6% w/v and could not be achieved by using only PVP (Mr = 1 x 10(6) g/mol) with a concentration as high as 15% w/v. It is noted that the interpenetrating network formed by 2% PVP and 1% polyacrylamide has a very low viscosity and can dynamically coat the inner wall of a fused-silica capillary. The separation reached an efficiency of more than 10(7) theoretical plate numbers/m and a reproducibility of less than 1% relative standard deviation of migration time in a total of seven runs. The interpenetrating network could stabilize polymer chain entanglements. Consequently, the separation speed was increased while retaining resolution.     

Enhanced microdialysis recovery of some tricyclic antidepressants and structurally related drugs by cyclodextrin-mediated transport

The enhanced microdialysis relative recovery (RR) of some hydrophobic tricyclic drugs (imipramine, desipramine, amitriptyline, carbamazepine and promethazine) is discussed. Enhanced RR was achieved by including a binding agent [beta-cyclodextrin (beta-CD) or 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD)] in the microdialysis perfusion fluid to form inclusion complexes with the drugs, which increases the analyte flux through the membrane material. The maximum effect of the RR increase for all the drugs studied was observed using a commercially available polycarbonate-polyether (PC) membrane. With a 4 mm PC membrane and 4.41 mmol l-1 (0.5% w/v) beta-CD included in the microdialysis perfusion fluid (0.9% saline, pH 7.4) at a flow rate of 0.5 microliter min-1, RR enhancements over controls were as follows: carbamazepine 136, imipramine 268, desipramine 298, amitriptyline 634, and promethazine 987%. Increasing beta-CD [up to 17.63 mmol l-1 (2% w/v)] or HP-beta-CD [up to 32.5 mmol l-1 (5% w/v)] concentration in the microdialysis perfusion fluid enhanced carbamazepine RR three (beta-CD) to four (HP-beta-CD) times compared to controls through PC microdialysis membranes. The PC membrane gave enhanced RR values that were twice those for cuprophan or AN-69 membranes. Enhanced RR with cyclodextrins was successfully applied to sampling from a protein solution containing desipramine in a 4% w/v bovine serum albumin solution. These results suggest that addition of cyclodextrins to microdialysis perfusion fluids may be used to increase microdialysis RR during blood sampling.     

Migratory Shift in Oxidative Cyclodehydrogenation Reaction of Tetraphenylethylenes Containing Electron‐Rich THDTAP Moiety

Four tetraphenylethylenes ( 2 a – d ) containing an electron‐rich 2,3,4,6‐tetrahydro‐1,6‐dithia‐3a‐azaphenalene (THDTAP) moiety have been synthesized. The 2 a – d show aggregation‐induced emission (AIE) with yellowish green photoluminescence (PL) in THF‐H₂O (v/v, 1:9) solution and in the solid state. Compounds 2 a – d undergo 1,2‐migratory shift in oxidative cyclodehydrogenation reactions to afford the unexpected products 3 a – d which display green PL in CH₂Cl₂ solution and are non‐emissive in the solid state. The PL intensities of 3 a – d are clearly enhanced in the presence of meta‐chloroperoxybenzoic acid (mCPBA) owing to the oxidation of the S‐atoms on the THDTAP moiety. In contrast, the PL of 2 a – d in THF‐H₂O (v/v, 1:9) solution is quenched by adding mCPBA, ascribable to the oxidation of the C=C bond on the ethylene moiety. It is found that the absorption of 3 a – d is distinctly red‐shifted from the UV/Vis region to the NIR region upon acidification, arising from the protonation of the N‐atom on the THDTAP moiety. Furthermore, 3 a – d display nonlinear optical response (NLO) and optical limiting (OL) behaviour which is superior to that of the well‐known OL material C₆₀.     

Anisotropic solutions of methylol cellulose

Methylol cellulose solutions in dimethylsulfoxide exhibit a viscosity maximum at 18% w/v followed by a minimum at 20%, as is characteristic of lyotropic liquid crystals. The biphasic solutions exhibit areas of clear and cloudy appearance. The latter are birefringent. The highly anisotropic solutions are uniformly briefringent and in the 25–33% w/v concentration region they are brightly colored. The optical rotations of the mesomorphic phases are high, indicating a cholesteric structure. The sign of the optical rotation depends on the solution concentration and at high concentrations (25+% w/v) varies with the area of the solution viewed.     

以聚乙烯醇为载体制备微囊化脲酶基因工程菌的研究

研究了以聚乙烯醇为载体制备微囊化脲酶基因工程菌的方法。结果表明：微囊制备的适宜条件是聚乙烯醇(平均聚合度为2450)浓度为6％(w／v)，海藻酸钠添加量为0．1％，气流量为3L／min，射流量为1ml／10min，包菌量为8％(w／v)，反应时间24h，交联剂为含2％CaCl2的饱和硼酸溶液，并用Na2CO3调节pH值到6．5，在该条件下制备出的微囊细胞平均粒径为18-20mesh，机械强度远远高于对照组APA微囊，其细胞酶活性较未包埋的游离细胞略有下降。     

Poly(N-isopropylacrylamide)-g-poly(ethyleneoxide) for high resolution and high speed separation of DNA by capillary electrophoresis.

A new separation medium, poly(N-isopropylacrylamide)-g-poly(ethyleneoxide) (PNI-PAM-g-PEO) solution, used for double-stranded (ds) DNA separation by capillary electrophoresis (CE) is presented. This type of grafted copolymer has a good self-coating ability for quartz capillary tubing and a slightly temperature-dependent viscosity-adjustable property, making it easier to use. One bp resolution was achieved within 12.5 min by using 8% w/v PNIPAM-gPEO in 1 x TBE (Tris-borate-ethylenediaminetetraaceticacid) buffer with an effective column length of 10 cm and an applied electric field strength of 200 V/cm. The PNIPAM-g-PEO solutions had a high sieving ability for relatively small sized DNAs with the relative standard derivation for the first 10 runs being less than 0.9% by using the same polymer solution. With 8% w/v PNIPAM-g-PEO solution in a 1.5 cm column and 2400 V as the running voltage, phiX174/HaeIII digest could be clearly separated within 24 s.     

PEC films prepared from Chitosan-Alginate coacervates

Chitosan-alginate polyelectrolyte complex (PEC) have been prepared in situ in beads and microspheres. This study examines the preparation of suitable chitosan-alginate coacervates for casting into homogeneous PEC films for potential applications in packaging, controlled release systems and wound dressings. Coacervation between chitosan and alginate was rapid, but the rate may be controlled with the addition of water miscible organic solvents. Compared with ethanol and PEG200, acetone was the more promising solvent moderator. Suspensions of fine, uniformly dispersed coacervates were produced by a dropwise addition of 0.25% w/v chitosan solution (solvent: 1: 1 v/v of 2% acetic acid and acetone) into 0.25% w/v sodium alginate solution in water under rapid agitation. The PEC films were transparent and flexible. They exhibited high permeability to water vapor, but resisted complete dissolution in 0.1 M HCI, distilled water and pH 7.4 phosphate buffer solution. Microscopic heterogeneity in the films could be reduced by immersion in aqueous media, but this was accompanied by modifications in the thickness, permeability and mechanical property of the films.     

Effect of sodium metasilicate on natural flotability of coal

The effect of the quantity of sodium metasilicate and conditioning time in one set of experiments, and the effect of the solution concentration of sodium metasilicate, added at the same dosage and conditioning time to coal slurry, on flotability of a typical Indian coal in another set of experiments are studied. Two sets of 3² full factorial experiments are carried out to assess the effects of the aforementioned variables. The generated data are analyzed quantitatively and explained qualitatively. At 0.1% (w/v) solution concentration of solution added (0.02 g/kg) and 8 min conditioning time, sodium metasilicate acted as activator for kaolinite, whereas at 1.0% (w/v) solution concentration (0.2 g/kg), it acted as dispersant. The best observed condition of depressant is obtained at an added concentration of 10.0% (w/v, 0.2 g/kg) and 8 min conditioning time. The desired effect of the sodium metasilicate can be achieved by controlling its quantity, solution concentration added, and conditioning time.     

Rapid determination of lead and cadmium in biological fluids by electrothermal atomic absorption spectrometry using Zeeman correction

Procedures for the electrothermal atomic absorption spectrometric determination of lead and cadmium in urine, serum and blood are developed. For serum and blood, the samples are diluted by incorporating 0.015% (w/v) Triton X-100 and 0.1% (w/v) ammonium dihydrogenphosphate to the solutions, which are then introduced directly into the furnace. A solution containing 15% (w/v) hydrogen peroxide and 0.65% (w/v) nitric acid is also introduced into the atomizer by means of a separate injection. Zeeman-based correction is recommended. Both conventional and fast-heating programs are discussed. Calibration is carried out using the standard additions method. The reliability of the procedures is checked by analyzing three certified reference materials and by recovery studies.     

Formation of concentration gradient and its application to DNA capillary electrophoresis

A new method to introduce the concentration gradient into the capillary has been developed and its application to DNA capillary electrophoresis is presented. The concentration gradient produced by mixing 5% w/v polyacrylamide-co-poly(N-dimethylacrylamide) (PAM-co-PDMA) solution and 1 x Tris/N-tris(hydroxymethyl)methyl-3-amino-propanesulfonic acid/EDTA (TT) + 5 M urea buffer was successfully achieved by using two programmable syringe pumps with strict control of dead volume, flow rate, and pressure balance. This method has the advantages of high stability, reproducibility, and versatility. The column with concentration gradient greatly improved the resolution, especially for the large DNA fragments, due to a decrease in band width broadening with time. A column containing 2-4% w/v gradient in four steps had a longer read length, shorter separation time and better resolution (after 380 base) than that of 4% w/v single concentration polymer solution. The number of steps in the gradient had almost no effect on the performance. The change in the average concentration by relocating the position of the same step gradient, i.e., a combination of different low concentration to high concentration polymer solution ratios, resulted in a different migration time, read length and resolution.     

Selective deacetylation using iodine-methanol reagent in fully acetylated nucleosides

Selective deprotection of primary acetyl ester in nucleosides and carbohydrates using 1% iodine-methanol solution (w/v) was described and the mechanism was also discussed.     

Extraction and determination of pyridinium ionic liquid cations in environmental water samples by using strong cation exchange solid phase extraction and ion chromatography

This paper presents a novel analytical method for the determination of pyridinium ionic liquid cations in environmental water samples by ion chromatography coupled with solid phase extraction. The water samples were purified and enriched by a sulphonic acid extraction column, and then the impurities were washed with 10 mL water – 20% (v/v) acetonitrile solution and the analytes eluted with 0.5 mol L^?1 phosphoric acid – sodium dihydrogen phosphate buffer solution – 55% methanol. The eluted analytes were determined by ion chromatography with 3.0 mmol L^?1 methane sulphonic acid – 8% acetonitrile as the mobile phase and direct conductivity detection. Three pyridinium cations were completely separated in 20 min and the retention mechanism basically conforms to the ion exchange mode. The newly developed method has been successfully applied to the analysis of pyridinium cations in spiked environmental water samples, which provided satisfactory recoveries in the range of 98.8% to 100.0% with the relative standard deviations less than 2.8%. The concentration of 0.004 to 0.01 mg L^?1 in water samples can be preconcentrated by this method. The method is accurate, reliable, simple and practical. This research provides a new reference for detecting ionic liquid cations in environmental water samples and studying the environmental risk assessment of ionic liquids.