Chelating fibers prepared with a wet spinning technique using a mixture of a viscose solution and a polymer ligand for the separation of metal ions in an aqueous solution.

Chelating fibers containing polymer ligands such as carboxymethylated polyallylamine, carboxymethylated polyethyleneimine, and a copolymer of diallylamine hydrochloride/maleic acid were prepared with a wet spinning technique using mixtures of a viscose solution and the polymer ligands. The chelating fibers obtained effectively adsorbed various metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), Ti(IV), and Zn(II). The metal ions adsorbed could be readily desorbed using 0.1 or 0.5 mol L(-1) HNO(3). The chelating fiber containing carboxymethylated polyallylamine was available for the separation of some metal ions in synthetic wastewater containing a large amount of Na(2)SO(4). The wet spinning technique using a solution containing a base polymer and a polymer ligand was quite simple and effective and would be applicable for preparing various chelating fibers.

Determination of cadmium in water samples by liquid electrode plasma atomic emission spectrometry after solid phase extraction using a mini cartridge packed with chelate resin immobilizing carboxymethylated pentaethylenehexamine.

Solid phase extraction using a mini cartridge packed with 22 mg of chelate resin immobilizing carboxymethylated pentaethylenehexamine was successfully utilized for separation/preconcentration of cadmium in water samples prior to liquid electrode plasma atomic emission spectrometric (LEP-AES) determination. The combined method with the extraction and LEP-AES was applicable to the determination of cadmium in the certified reference materials (EU-L-1 wastewater and ES-L-1 groundwater); the detection limit was 0.20 microg in 200 mL of sample solution (500-fold preconcentration).

A sensitive and selective method for determination of gold(III) based on electrothermal atomic absorption spectrometry in combination with dispersive liquid-liquid microextraction using dicyclohexylamine.

A combined method with dispersive liquid-liquid microextraction (DLLME) and electrothermal atomic absorption spectrometry (ETAAS) has been developed for determining gold(III). Dicyclohexylamine, a new extractant for gold(III), showed excellent performance in DLLME. Acetone was indispensable to the quantitative extraction of gold(III), contributing to decrease in hydration, decrease in the difference in the dielectric constants between the supernatant phase and the sedimented phase, and dissolution of a part of chloroform as an extraction solvent to the supernatant phase as well as improvement of dipersibility. In DLLME using a mixture of 1.0mL of acetone and 100microL of chloroform containing 50mmolL(-1) of dicyclohexylamine, gold(III) could be extracted selectively and effectively from 8mL of a sample solution in the presence of iron(III), cobalt(II), nickel(II), copper(II), palladium(II), and platinum(IV) at pH 1. The extracted gold(III) was determinable by ETAAS; the detection limit was 0.002microgL(-1) (three times the standard deviation of the blank values, n=8) as a gold(III) concentration in 8mL of sample solution. The proposed method was applicable to the determination of gold in platinum metal and its alloy as well as effluent without any interference by the matrices.

Selective removal of mercury(II) from wastewater using polythioamides.

The potential and feasibility of polythioamides as Hg(II) sorbents were evaluated. Powdered polythioamides quantitatively sorbed Hg(II) from an aqueous solution at pH 1-8. The sorption of Hg(II) on polythioamides obeyed the Langmuir adsorption isotherm; the sorption capacity was 0.70-0.85 g-Hgg(-1). Hg(II) was selectively separated from solutions containing 500 times larger amounts of Mn(II), Fe(III), Cu(II), Zn(II), and Pb(II) at pH 1. The tertiary polythioamide (PTA1) is soluble in chloroform and can be readily coated on a commercially available polymer resin, Amberlite XAD7HP. PTA1-coated resin as well as powdered PTA1 were applicable to the selective removal of Hg(II) from real wastewater.

A solid phase extraction using a chelate resin immobilizing carboxymethylated pentaethylenehexamine for separation and preconcentration of trace elements in water samples.

A chelate resin immobilizing carboxymethylated pentaethylenehexamine (CM-PEHA resin) was prepared, and the potential for the separation and preconcentration of trace elements in water samples was evaluated through the adsorption/elution test for 62 elements. The CM-PEHA resin could quantitatively recover various elements, including Ag, Cd, Co, Cu, Fe, Ni, Pb, Ti, U, and Zn, and rare earth elements over a wide pH range, and also Mn at pH above 5 and V and Mo at pH below 7. This resin could also effectively remove major elements, such as alkali and alkaline earth elements, under acidic and neutral conditions. Solid phase extraction using the CM-PEHA resin was applicable to the determination of 10 trace elements, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn, in certified reference materials (EnviroMAT EU-L-1 wastewater and ES-L-1 ground water) and treated wastewater and all elements except for Mn in surface seawater using inductively coupled plasma atomic emission spectrometry. The detection limits, defined as 3 times the standard deviation for the procedural blank using 500 mL of purified water (50-fold preconcentration, n=8), ranged from 0.003 microg L(-1) (Mn) to 0.28 microg L(-1) (Zn) as the concentration in 500 mL of solution.

Inductively coupled plasma atomic emission spectrometric determination of 27 trace elements in table salts after coprecipitation with indium phosphate.

The coprecipitation method using indium phosphate as a new coprecipitant has been developed for the separation of trace elements in table salts prior to their determination using inductively coupled plasma atomic emission spectrometry (ICP-AES). Indium phosphate could quantitatively coprecipitate 27 trace elements, namely, Be, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, in a table salt solution at pH 10. The rapid coprecipitation technique, in which complete recovery of the precipitate was not required in the precipitate-separation process, was completely applicable, and, therefore, the operation for the coprecipitation was quite simple. The coprecipitated elements could be determined accurately and precisely by ICP-AES using indium as an internal standard element after dissolution of the precipitate with 5 mL of 1 mol L(-1) nitric acid. The detection limits (three times the standard deviation of the blank values, n=10) ranged from 0.001 microg (Lu) to 0.11 microg (Zn) in 300 mL of a 10% (w/v) table salt solution. The method proposed here could be applied to the analyses of commercially available table salts.

Use of yttrium phosphate as a coprecipitant for separation/concentration of lanthanoids.

A useful method to separate/concentrate lanthanoids was developed based on a rapid coprecipitation technique using yttrium phosphate. Lanthanoids, which were quantitatively coprecipitated at pH 3 with yttrium phosphate, could be readily determined by inductively coupled plasma atomic emission spectrometry with indium used as an internal standard element. The detection limits ranged from 0.0003 microg (Yb, Lu) to 0.0099 microg (Er) in 100 mL of sample solutions. The proposed method was applicable to the separation/concentration of lanthanoids in NIST SRM 1515 (apple leaves).

Controlled diffusion for laboratory solution preparation.

We report here on a method for preparation of precise laboratory solutions using controlled diffusion for dosing. The desired chemical is delivered into the target solution from a stock solution through a mass-transport-limiting delivery port that blocks convection but allows reproducible diffusive transport. Solution making with this approach involves a single step irrespective of how low the desired concentration is. Diffusional delivery of chemicals involves no appreciable movement of water and, thus, no addition of volume. The approach is therefore particularly suitable for standard addition. Precise solutions of usual laboratory volumes can be made within a short time period with proper design of the delivery port or ports. Comparison with the performance of conventional methods of routine solution preparation shows that better precision can be achieved with less labor using this approach.

Rapid coprecipitation technique using yttrium hydroxide for the preconcentration and separation of trace elements in saline water prior to their ICP-AES determination.

Yttrium hydroxide quantitatively coprecipitated Be(II), Ti(IV), Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) at pH 9.6 - 10.0 for seawater and pH 10.5 - 11.4 for a table-salt solution. The coprecipitated elements could be determined by inductively coupled plasma atomic emission spectrometry; yttrium was used as an internal standard element. The detection limits ranged from 0.001(6) microg (Mn(II)) to 0.22 microg (Zn(II)) in 100 mL of sample solutions. The operation time required to separate 11 elements was approximately 30 min.

Micro-miniature autonomous optical sensor array for monitoring ions and metabolites 2: color responses to pH, K+ and glucose.

In Part 1 of this series (Anal. Sci., 2006, 22, 383), design, fabrication, and optical data acquisition of an array of tiny color changing capsules embedded in a cellulose acetate bar, called the "sliver sensor", have been described. Capsule colors are read by a CCD camera and translated into blue, red and green Kubelka-Munk variables for quantitative analysis. The respective concentrations are determined using prior calibration. The approach may be adapted to different non-biological analytical problems, as well as in vitro and in vivo applications. To demonstrate this adaptability to potential in vivo use as an example, sensitivity for each target ion was tuned to cover the respective interstitial levels by varying the relative amount of ionophore used in the corresponding microscopic beads. After optimizing the ratio of glucose oxidase (GOX)-containing beads relative to the coupled pH sensing beads and their composition, reversible color response to glucose was obtained in the entire clinically relevant glucose concentration range (10 to 600 mg/dL, 0.55 to 33 mM). Decoupling of pH and glucose sensing from possible variations in interstitial sodium level and buffer capacity is currently being optimized for future in vivo use. In vitro and non-biological applications are also being explored.

Micro-miniature autonomous optical sensor array for monitoring ions and metabolites 1: design, fabrication, and data analysis.

A micro-miniature array of sensing capsules for optical monitoring of pH, potassium and glucose is described. Optode technology translates the respective ionic levels into variable colors of ionophore/dye/polymeric liquid micro-beads stuffed into individual capsules. Glucose is monitored indirectly, by coupling through glucose oxidase (GOX) immobilized in cellulose acetate phthalate (CAP) based microscopic beads that are stuffed into another microcapsule together with pH sensitive optical microscopic beads. The electrolyte and glucose sensing capsules are embedded in a transparent cellulose acetate bar 300-500 microm wide and 2-2.5 mm long called the sliver sensor that includes also a white capsule made of micro-beads without dye for optical reference. By adding further capsules custom combinations of analytes can be monitored in biomedical and non-biological contexts. In this work, as an example, design, fabrication and testing of a sliver sensor that could be developed for in vivo use are described.

Hydrodynamic electrochemistry in 20 microL drops in the rotating sample system.

The Rotating Sample System (RSS) has been conceived in the authors' laboratory as a convection platform for microliter-sized solution volumes. Convection is achieved by rotating a small drop of sample on a stationary substrate by humidified gas jets directed tangentially at the drop base with the working electrode and a liquid junction embedded in it. Simplicity and portability of the device, and substrates complete with microfabricated electrode and junction made potentially disposable, are further competitive advantages with respect to competing, conventional analytical systems. In this work the RSS' performance with variation of system parameters such as the position and size of gas jets used for sample rotation, and position of the working electrode in the substrate are studied. Trace levels of Pb could be detected with this system and is reported here.

Optical detection in microscopic domains. 3. Confocal analysis of fluorescent amphiphilic molecules.

This series of papers demonstrates the feasibility of novel optical methodologies for microchemistry and analysis in aqueous samples of nano-, pico-, and femtoliter in volume. Not a conventional glass cuvette, but water-immiscible organic liquid, is used as the container for microscopic sample droplets in this approach. In part 1, absorption spectra of excellent quality were obtained and used for analysis from samples as small as a few tens of a micrometer in diameter. In part 2, an inert fluorescence marker as an internal standard was employed for indirectly detecting absorbing but nonfluorescent reagents in microsamples, employing inner filter effects. In this part 3, a third modality, confocal fluorescence microscopy, is added to the techniques being examined. A clearly visible emission ring emanating from an amphiphilic molecule, doxorubicin, at the sample boundary is demonstrated for the first time in "optically sliced" microdroplets. Relative intensity of this ring with respect to sample bulk can be used to study adsorption phenomena at liquid-liquid interfaces with proper calibrations for bulk and boundary. Quantitative separation of these two domains, a precondition to such calibrations, is also discussed.

Hydrodynamic micromanipulation of individual cells onto patterned attachment sites on biomicroelectromechanical system chips.

We report on a simple methodology to move selected single live cells to a desired location on a flat substrate, such as a patterned biomicroelectromechanical system chip. A macroscopic syringe-and-tube-based hydrodynamic manipulation system is used to achieve controlled cell navigation onto hydrophilic sites for cell attachment. Centimeter-per-second flow velocities generated by the system get downgraded to micrometers-per-second flow at the height of settled cells as a result of viscous flow in the medium. By pushing/pulling two syringes that produce two orthogonal flows, fine manipulation in any horizontal direction is feasible. After attachment of the desired cell(s) onto the selected hydrophilic site, all other unwanted cells are washed away from the surrounding hydrophobic surface with faster flow. This simple methodology is applicable for rapid cell pattern formation with high precision.

A microscopic, continuous, optical monitor for interstitial electrolytes and glucose.

Ions, such as hydrogen (pH), sodium, or potassium, as well as metabolites, such as glucose or lactate, diffuse easily between blood in the capillaries and the interstitial fluid (ISF) residing between cells, and tissues. This work represents a synthesis of several unique concepts to achieve accurate, continuous, in vivo monitoring of critical ions and glucose in the ISF under the human skin. Ionic levels are monitored using optode technology that translates the respective concentrations into variable colors of ionophore/dye/polymeric liquid membranes. Glucose is monitored indirectly, by coupling through immobilized glucose oxidase with pH, that is then detected using a similar color scheme. The monitor consists of a tiny plastic bar ("sliver sensor"), 100-300 microns wide and 1-15 mm long, placed just under the skin, with optical spots or stripes for each analyte as well as blanks for calibration. The colors are read and translated into concentration values by a watchlike device placed above the skin. Direct optical coupling between the in vivo sensing bar and the ex vivo detector device requires negligible power, and eliminates the need for wires or optical fibers crossing the skin. The microminiature sliver penetrates the skin easily and painlessly, so that the user could insert it him- or herself. No risk of track infection exists. We are reporting here on the first successful in vitro tests of this approach.

Voltammetric detection of inorganic phosphate using ion-channel sensing with self-assembled monolayers of a hydrogen bond-forming receptor.

A voltammetric ion-channel sensing for phosphate based on gold electrodes modified with the self-assembled monolayers of a bis-thiourea receptor was developed to detect phosphate. The working principle of this voltammetric sensor conceptually mimics that of ligand gated ion-channel proteins, as to chemically stimulated changes in membrane permeability. The response to analytes is based on the change in electron transfer rate constant of the redox reaction of [Fe(CN)(6)](4-/3-) marker, before and after binding of phosphate to the receptor on the electrode surface; where the electrostatic repulsion between a phosphate-receptor complex and the marker induced the decrease in the rate constant. In a solution of pH 7.0, a high selectivity was observed for phosphate and the sensor was virtually insensitive at all to many of other anions, such as SO(4)(2-), AcO(-), NO(3)(-), and Cl(-). The sensor response was obtained with phosphate concentrations above 5.0 x 10(-4) M using cyclic voltammetry and differential pulse voltammetry.