Multielement analysis with ICP-AES-possibilities for quality control with CRMs

Summary An analysis using Certified Reference Materials (CRMs) together with routine samples is by far the best approach for quality control in multielement analysis of environmental samples. The selection of the correct CRM is thus the first important step for all reliable analysis. The chosen material should have a similar matrix, similar concentration of the element(s) of interest and a sufficient number of well-certified elements. For the analysis of samples from the Environmental Specimen Bank only a few CRMs could be successfully used. These were analyzed for a considerable period of time, together with the routine samples for quality control. The results of these analyses were compared with the certified values.     

The mixing properties of hexafluorobenzene with carbon tetrachloride and with perfluoromethylcyclohexane

Excess thermodynamic functions (free energies, enthalpies and entropies of mixing) have been obtained from measurements of vapour pressures, together with excess volumes of mixing, for mixtures of hexafluorobenzene with carbon tetrachloride and with perfluoromethyl-cyclohexane (tetradecafluoromethylcyclohexane). Deviations from thermodynamic ideality are large, although the systems are completely miscible. Critical temperatures of the mixtures are also reported. A correlation between the data, anticipated from a simple model for mixtures of asymmetric molecules, does not obtain.     

Hydrodynamic injection with pneumatic valving for microchip electrophoresis with total analyte utilization

A novel hydrodynamic injector that is directly controlled by a pneumatic valve has been developed for reproducible microchip CE separations. The PDMS devices used for the evaluation comprise a separation channel, a side channel for sample introduction, and a pneumatic valve aligned at the intersection of the channels. A low pressure (≤ 3?psi) applied to the sample reservoir is sufficient to drive sample into the separation channel. The rapidly actuated pneumatic valve enables injection of discrete sample plugs as small as ~ 100?pL for CE separation. The injection volume can be easily controlled by adjusting the intersection geometry, the solution back pressure, and the valve actuation time. Sample injection could be reliably operated at different frequencies (< 0.1?Hz to > 2?Hz) with good reproducibility (peak height relative standard deviation ≤ 3.6%) and no sampling biases associated with the conventional electrokinetic injections. The separation channel was dynamically coated with a cationic polymer, and FITC-labeled amino acids were employed to evaluate the CE separation. Highly efficient (≥ 7.0 × 103 theoretical plates for the ~2.4-cm-long channel) and reproducible CE separations were obtained. The demonstrated method has numerous advantages compared with the conventional techniques, including repeatable and unbiased injections, little sample waste, high duty cycle, controllable injected sample volume, and fewer electrodes with no need for voltage switching. The prospects of implementing this injection method for coupling multidimensional separations for multiplexing CE separations and for sample-limited bioanalyses are discussed.     

Reactions of indole derivatives with cardioprotective activity with reactive oxygen species. Comparison with melatonin

We have previously reported on the synthesis of novel indole derivatives containing an amine-triazole moiety (1a-d, 2a-c), and their antioxidant activity on in vitro non-enzymatic rat hepatic microsomal lipid peroxidation. Some of the compounds showed protective activity against oxidative injury of ischemic myocardium. In the present paper we investigated the interactions of these derivatives with reactive oxygen species, in order to find a mechanism of their antioxidant capacity and to identify structural characteristics responsible for these properties. These interactions were compared with melatonin, which is also an indole derivative. The antioxidant profiles of the compounds were established by different in vitro protocols as follows: 1) by the interaction of the compounds with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable free radical, 2) their scavenging effects on superoxide anions using an enzymic system of xanthine-xanthine oxidase, 3) their inhibitory effects on xanthine oxidase and 4) their ability to scavenge hydroxyl radicals by comparison with dimethyl sulfoxide (DMSO) for *OH. All compounds were found to interact with DPPH, most of them to be superoxide anion scavengers and to be strong hydroxyl radical scavengers. Derivatives 1a and 1d substituted on the nitrogen of the indolic nucleus were found to have better antioxidant properties than the reference compounds used and melatonin.     

Copolymerizations of 2-hydroxyethylmethacrylate with vinylpyridines and with N-substituted methacrylamides

Studies were made of the copolymerizations of 2-hydroxyethylmethacrylate with 2-, 3- and 4-vinylpyridine. N-(trans-4′-nitro-4-stilbenyl)methacrylamide and N-(trans-4-stilbenyl)methacrylamide. Methods of Fineman-Ross, Joshi-Joshi, Tidwell-Mortimer and Tosi were employed to determine monomer reactivity ratios; the results for 2- and 4-vinylpyridine were compared with those calculated from the Q-e scheme. The monomer reactivity ratios for 2-hydroxyethylmethacrylate with vinylpyridines calculated by different methods showed good agreement. The monomer reactivity is briefly discussed.     

Nanocomposite material with immobilized acid-base dyes conjugated with polysaccharides

Water-soluble acid-base dyes xylenol orange and methyl red are linked by covalent bonds to chitosan macromolecules; neutral dye red is bound to carboxymethyl cellulose to prevent their washing-off from silicate matrix. Dye conjugates were then immobilized by modified sol-gel method using silicate precursor compatible with polysaccharides. Synthesized hybrid nanocomposite materials are optically transparent, which makes it possible to apply them to develop sensors for measuring pH. Spectral characteristics of dyes, their conjugates, and prepared nanocomposites with silicate matrix are studied in detail. It is shown that xylenol orange, which is linked with chitosan by covalent bonds, is the most suitable dye for the development of sensor materials because the conjugation by carboxyl groups, which do not directly bound with chromophore center, does not deteriorate the spectral properties of this dye. In the cases of methyl red and neutral red dyes, undesirable changes in their properties in the course of conjugation are caused by the covalent binding by functional groups, which are auxochromes directly affecting all spectral characteristics of dyes. An increase in the solubility of polysaccharide in water can also positively affect the covalent binding of dyes with chitosan that allows polysaccharide to be used in neutral and alkaline media.     

Retention in liquid chromatography with multicomponent mobile phases: Relationship with binary systems

Summary Using the concept of an effective concentration a method is proposed for predicting retention in liquid chromatography with multicomponent mobile phases based on experiments with corresponding binary ones. The method is verified for normal and reversed-phase systems with ternary mobile phases and agrees closely with experimental data.     

Properties of Low-Density Polyethylene Produced with Organic Peroxides Together with Oxygen

Both organic peroxides and molecular oxygen can be used for the high-pressure polymerization of ethylene. In order to answer the question if the product quality is influenced by the choice of the initiator, polyethylenes were produced in a stirred autoclave under 1700 bar at temperatures of 200–320°C with DTBP, oxygen, and with mixtures of both initiators. The products were compared for density, short- and long-chain branching, the average molar mass, and the molar mass distribution. Except for a slight increase in the number of long-chain branches, and as a consequence of this a slightly broader molar mass distribution, no significant changes of product properties could be noted. There are no objections against the combined use of peroxide and oxygen; for example, when the conversion from oxygen to peroxide takes place.     

Extraction chromatography with macroreticular polymer beads impregnated with monothiodibenzoylmethane solution

Extraction chromatography using macroreticular ethylstyrene-divinylbenzene beads impregnated with monothiodibenzoylmethane (SBB) solution has been investigated. Of the solvents used as the stationary phase, heptan-1-ol showed the highest rate of metal extraction, and loading with 0.5 ml of the solvent per g of resin was found to be the optimum. A column packed with such loaded beads can be used for the separation of nickel(II), iron(III) and cobalt(II).     

Amperometric Cholinesterase Biosensors with Carbon Paste Electrodes Modified with Cobalt Phthalocyanine

Biosensors based on a carbon paste electrode with immobilized cholinesterase and cobalt(II) phthalocyanine as a mediator are studied. Electrochemical characteristics of the biosensors are investigated in relation to the carbon paste composition, the enzyme and mediator immobilization procedures, nature of the protective film and procedure of its application, and also storage conditions of the electrodes. A method is suggested for fabricating a cholinesterase biosensor with cobalt(II) phthalocyanine mediator, providing the maximum electrocatalytic response in electrooxidation of butyrylthiocholine iodide (substrate for cholinesterase).     

Activation processes with memory

We propose a mathematical treatment of the activated processes governed by stochastic Langevin dynamics with a colored random force, corresponding to a noise generated by an Ornstein-Uhlenbeck process. Such non-Markovian dynamics take place in a variety of chemical and biological systems. Using the path integral approach, we constructed the conditional probability for passing between two stationary states in configurational space. Our relations can be used for Monte Carlo sampling of evolution trajectories for systems with many degrees of freedom as well as for determining the reaction coordinate used in transition state theory. On the basis of our relation for a conditional probability, we generalize the method of determining the most probable path to the case of colored random force. Using the simple three-hole potential, we examine numerically the effect of nonzero correlation time (memory) on the evolution of the most probable path for a finite temperature.     

Renal function study with 111In-DTPA--in comparison with 99mTc-DTPA

Technetium-99m-diethylene-triamine-penta-acetic acid (DTPA) and 111In-DTPA were injected simultaneously into 21 patients with various levels of renal function. Scintiphoto, camera data renograms and clearance values (plasma sampling) were obtained for each patient. The mixed isotope scintiphoto images were of intermediate quality and the images with 111In-DTPA were apparently inferior to those with 99mTc-DTPA. These equations were obtained: (1) y = 0.30 + 0.91 x (coefficient of correlation r = 0.98) where x is the value at T peak (time of maximum count on renogram) obtained with 99mTc-DTPA and where y is the value at T peak with 111In-DTPA. (2) y = -0.09 + 1.006 x (r = 0.99) where x is the value at T3/4 (time interval between the time of maximum count to the time of 3/4 of maximum count on renogram) and where y is the value at T3/4 obtained with 111In-DTPA. (3) y = -0.01 + 1.007 x (r = 0.98) where the x and y values were for the excretion ratios (counts at 20 min/maximum counts on renogram). (4) y = 0.81 + 0.98 x (r = 0.99) where x and y are the clearance values.     

The Reaction of Japanese Reagent with Aminoacetamide with Alkyl Group

2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide¹,commonly known as Lawesson's reagent (LR,1a),and Japanese Reagent (1b),are not only thiating agent for diverse carbonyl compounds^1-3, but also they undergoes ring-closure reactions with contain substrates containing two functional groups to give phosphorus heterocycles which contain phosphonothioyliene {C₆H₄-P(S)〈} moiety. These heterocyclic compounds are of potential interest as herbicides,insecticides,and fungicides^4,5. Glycinamides are known as biologically active materials, for example, herbicides, plant-growth regulator⁶. In order to look for potent herbicides⁷ and to extent the use of Japanese Reagent to other bifunctional substrates,its reactions with 3-alkyl-glycinamides 2 have been investigated and found to give new phosphorus heterocycles which possess Significant selective herbicidal activity against rape. Here are our results.     

Gold-Catalyzed Annulations of N-Propargyl Ynamides with Anthranils with Two Distinct Chemoselectivities

Gold-catalyzed annulation of N-propargyl ynamides with anthranils can proceed by two distinct mechanisms. In the case of a terminal N-propargyl ynamide, its resulting α-imino gold carbene reacts with a tethered alkyne to generate a vinyl cation to enable hydrolysis, which ultimately yields a pyrrolo[2,3-b]quinoline derivative after treatment with p-toluenesulfonic acid. For an internal alkyne, its α-imino gold carbene reacts with a tethered alkyne via either a vinyl cation or an alkenylgold carbene; both paths ultimately lead to a 4-ketone-2-aminopyrrole derivative. Our mechanistic analysis indicates that water is a better nucleophile than anthranil for terminal ynamides, whereas water and anthranils are equally reactive for internal ynamides.     

Determination of urea with an ammonia gas-sensitive semiconductor device in combination with urease

An ammonia gas-sensitive Ir/Pd MOS capacitor is used for urea determinations with the aid of urease in two different systems. One combination utilizes a reaction column with immobilized urease in a flow-injection system. The lower limit of urea detection for 150-μl samples was 0.2 μM. Urea in whole blood and blood serum was determined after a 500-fold dilution, and 15 samples per hour could be assayed. The relative standard deviation was 4.6% (n=10). Recovery tests were satisfactory. Values obtained for urea in serum correlated well with those from a spectrophotometric method. The other combination is based on a small flow cell with free urease enclosed between a dialysis membrane and a gas-permeable membrane. Urea was determined in the concentration range 0.01–50 mM. The enzyme probe could be used for up to four days without changes of behaviour.     

Inorganic approaches for radiolabelling biomolecules with fluorine-18 for imaging with positron emission tomography

Conventional methods for radiolabelling biomolecules such as proteins and peptides with fluorine-18 for PET imaging rely on carbon-fluorine bond formation and are complex and inefficient. Several non-carbon elements form strong bonds (i.e. with high bond enthalpy) with fluorine, but with lower activation energy for their formation compared to carbon-fluorine bonds, whilst preserving a relatively high kinetic stability. In particular, by incorporating boron-, aluminium- and silicon-containing prosthetic groups into biomolecules, promising results have recently been achieved in the radiolabelling with F-18-fluoride under mild aqueous conditions, affording a level of convenience, efficiency and specific activity potentially superior to those offered by conventional C-F bond formation methods. The promise already shown by these early studies heralds a new branch of bioconjugate radiochemistry involving a wider range of "fluoridephilic" elements for synthesis of PET molecular imaging agents.     

An adaptive breath sampler for use with human subjects with an impaired respiratory function

An adaptive sampler for collecting 2.5 dm(3) samples of exhaled air from human subjects with an impaired respiratory function is described. Pressure in the upper respiratory tract is continuously monitored and the data used to control an automated system to collect select portions of the expired breathing cycle onto a mixed bed Tenax(trade mark) and Carbotrap(trade mark) adsorbent trap for analysis by GC-MS. The sampling approach is intended for use in metabolomic profiling of volatiles in human breath at concentrations greater than microg m(-3). The importance of experimental reproducibility in metabolomic data is emphasised and consequently a high purity air supply is used to maintain a stable exogenous volatile organic compound profile at concentrations in the range 5 to 30 microg m(-3). The results of a 90 day stability study showed that exogenous VOCs were maintained at significantly lower levels (40 times lower for isopropyl alcohol) and with significantly higher reproducibility (80 times lower standard deviation for isopropyl alcohol) than would have been be the case if ambient air had been used. The sampling system was evaluated with healthy controls alongside subjects with chronic obstructive pulmonary disease. Subjects were able to breathe normally with control subjects observed to breathe at a rate of 9 to 17 breaths per minute, compared to 16 to 30 breaths per minute for subjects with COPD. This study presents, for the first time, observations and estimates of intra-subject breath sample reproducibility from human subjects. These reproducibility studies indicated that VOCs in exhaled breath exhibit a variety of dynamic behaviours, with some species recovered with a RSD <30%, while other species were observed to have significantly more variable concentrations, 30 to 130% RSD. The approach was also demonstrated to reliably differentiate the differences in the VOC profiles between alveolar and dead space air.     

Separation of platinum and palladium with silicone-rubber foam treated with dimethylglyoxime

Open-pore silicone-rubber foam is shown to be a good inert solid support for column separations. Foams treated with dimethylglyoxime were studied for their adsorption of platinum and palladium from solution. The separation of platinum and palladium was achieved in solutions containing as little as 1.0 ppm.     

Long chain cellulose esters with very low DS obtained with non-acidic catalysts

Long-chain cellulose esters with very low degree of substitution (DS<0.3), useful for specialty applications, were obtained by reaction with fatty acids (FAs) without solvent for cellulose. Non-acidic catalysts such as FA salts were used to limit the cellulose degradation when subjected to reaction at high temperatures. The surfactant character of this type of molecules was employed to create an emulsion with FA and water to favor the contact of hydrophobic FA and hydrophilic cellulose. Response surface methodology was used as a statistical optimization method to find the best proportions of octanoic acid, potassium laurate and water. A highly hydrophobic product with retention of fibrous structure was thus obtained. The reactions with higher saturated FAs (C₁₀–C₁₈) yielded lower DS values but still comparable hydrophobicity.     

Particle arrays with patterned pores by nanomachining with colloidal masks

In summary, we have developed a new strategy for the fabrication of arrayed colloidal particles well-ordered nanometric holes of three or four fold symmetry by anisotropic reactive ion (plasma) etching of self-organized layers of colloidal spheres. We demonstrated that a mesoporous silica matrix with regular open windows could be used as a lithographic mask and the resulting arrangement of pores on a particle was dependent on the orientation of the colloidal particle stacking. A variety of organic and inorganic materials such as metals for metal-polymer composites, DNA and proteins, semiconducting and ceramic materials, and other polymers and small chemicals can be incorporated via chemical and physical attachment. Particles with patterned pores and composite particles by our nanomachining process can be used as novel functional materials in the field of electronics, photonics, and biotech areas.