Chemical deposition and characterization of thin polypyrrole films on glass plates: role of organosilane treatment

 Thin chloride-doped polypyrrole films (PPyCl) were deposited chemically onto untreated and silane-treated planar glass plates from aqueous solutions. The organosilanes used to treat the glass substrates were methyltriethoxysilane (Cl), propyltrimethoxysilane (C3), octyltrimethoxysilane (C8) and aminopropyltriethoxysilane (APS). The decreasing order of hydrophobic character of silane-treated glass slides, as measured by water contact angle measurements, was glass–APS ≅ glass–C8 > glass–C3 > glass–C1 > glass. X-ray photoelectron spectroscopy was used to determine the surface chemical composition of the glass plates before and following coating with the silane coupling agents and/or the PPy thin layer, respectively. The attenuation in intensity of the glass Na_{1 s} peak enabled the average thickness of the various organosilane overlayers to be estimated. Atomic force microscopy showed that the morphology of the organosilane overlayers was islandlike. The domains have a structure which depends upon the nature of the organosilane in question. Scanning electron microscope images showed that the morphology of the PPyCl thin films was homogeneous when coated onto glass–APS and glass–C8, but wrinkled at the surface of glass, glass–C1 and glass–C3 plates. Qualitative peel tests using 3M adhesive tape showed very good adhesion of PPyCl to the glass–APS substrate, whereas adhesion was fairly poor in the case of glass–PPy and PPy–alkylsilane–glass interfaces. The results of this multitechnique study suggest that hydrophobic interactions are important to obtain homogeneous and continuous thin PPy films, but Lewis acid–base interactions are the driving forces for strong and durable PPy–glass adhesion. Received: 3 January 2000/Accepted: 19 May 2000     

Structure and Magnetic Properties of Nickel–Zinc Ferrite Nanoparticles Prepared by Glass Crystallization Method

Summary. The magnetic and microstructure properties of Fe₂O₃–0.4NiO–0.6ZnO–B₂O₃ glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni_0.4Zn_0.6-Fe₂O₄ crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and 3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer. The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with saturation magnetization ranging from 12.25 to 17.82 emu/g.     

Structure and Magnetic Properties of Nickel–Zinc Ferrite Nanoparticles Prepared by Glass Crystallization Method

The magnetic and microstructure properties of Fe₂O₃–0.4NiO–0.6ZnO–B₂O₃ glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni_0.4Zn_0.6-Fe₂O₄ crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and 3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer. The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with saturation magnetization ranging from 12.25 to 17.82 emu/g.     

Quantification of Teicoplanin in Human Plasma by Liquid Chromatography with Ultraviolet Detection

A simple high-performance liquid chromatographic method was developed for determining five major components of teicoplanin, designated A2–1, A2–2, A2–3, A2–4 and A2–5, in human plasma. Using piperacillin sodium as internal standard, teicoplanin in plasma samples was extracted by coextractive cleanup procedure. The extracts were injected into a Nova-Pak C₁₈ column maintained at ambient temperature. The mobile phase consisted of acetonitrile–0.1% trifluoroacetic acid (27:73, pH = 2.2), at a flow rate of 1.0 mL min⁻¹. The analytes were detected at the UV wavelength of 218 nm. The method was found to be linear over the concentration range of 2.5–50 mg L⁻¹ for teicoplanin (r = 0.9993 ± 0.0038), which covered the clinically expected trough plasma levels. The percentage error of the analytical method was below 9%. The intra- and inter-day reproducibility was adequate with coefficients of variation less than 7%. The chromatographic running time was 11 min. Thus, the method can be effectively applied to measure teicoplanin concentrations in clinical samples.     

Prompt gamma-ray neutron activation analysis methodology for determination of boron from trace to major contents

Prompt gamma ray neutron activation analysis methodologies were standardized using a reflected neutron beam and Compton suppressed γ-ray spectrometer to quantify boron from trace to major concentrations. Neutron self-shielding correction factors for higher boron contents (0.2–10 mg) in samples were obtained from the sensitivity of chlorine by irradiating KCl with and without boron. This method was validated by determining boron concentrations in six boron compounds and applied to three borosilicate glass samples with boron contents in the range of 1–10 mg. Low concentrations of boron (10–58 mg kg⁻¹) were also determined in two samples and five reference materials from NIST and IAEA.     

Analysis of doxorubicin uptake in single human leukemia K562 cells using capillary electrophoresis coupled with laser-induced fluorescence detection

The doxorubicin (DOX) uptake in single human leukemia K562 cells with changes in both drug dosage and exposure period was studied using capillary electrophoresis (CE) coupled with laser-induced fluorescence (LIF) detection. The cells were treated with DOX at different concentrations (1, 3, 10, 20, 30, and 50 μM) and for different exposure times (1, 3, 5, 24, and 48 h). At least 20 cells were analyzed for each DOX-treated cell population. A marked heterogeneity in DOX uptake among single cells was observed, because the relative standard deviation of the uptake of DOX by single cells ranged from 24.0% to 61.1% within each cell population. The cell-to-cell heterogeneity in DOX uptake first decreased and then became constant with increasing drug concentration, but it did not exhibit regular variation with increasing exposure time. The mean DOX uptake was a linear function of drug concentration (r ≥ 0.9667). In terms of the correlation with exposure time, the mean DOX uptake reached its maximum at 3 h for the cell populations treated with 1–10 μM DOX, while it kept increasing during 48 h exposure of cell populations to 20–50 μM DOX. Because it eliminates DOX fluorescence quenching and sample loss, the CE-LIF method directly detects the true DOX uptake by single cells, and thus presents accurate information on both the cell-to-cell heterogeneity in DOX uptake and the patterns of DOX uptake in K562 cells as functions of drug concentration and exposure time.     

Clonality characterization of natural epitope-specific antibodies against the tumor-related antigen topoisomerase IIa by peptide chip and proteome analysis: a pilot study with colorectal carcinoma patient samples

Patient-specific sequential epitopes were identified by peptide chip analysis using 15mer peptides immobilized on glass slides that covered the topoisomerase IIa protein with a frameshift of five amino acids. Binding specificities of serum antibodies against sequential epitopes were confirmed as being mono-specific by peptide chip re-analysis of epitope-affinity-purified antibody pools. These results demonstrate that serum samples from colon carcinoma patients contain antibodies against sequential epitopes from the topoisomerase IIa antigen. Interactions of patients’ antibodies with sequential epitopes displayed by peptides on glass surfaces may thus mirror disease-specific immune situations. Consequently, these data suggest epitope–antibody reactivities on peptide chips as potential diagnostic readouts of individual immune response characteristics, especially because monospecific antibodies can be interrogated. Subsequently, the clonality of the antibodies present in the mono-specific antibody pools was characterized by 2D gel electrophoresis. This analysis suggested that the affinity-purified antibodies were oligoclonal. Similarly to large-scale screening approaches for specific antigen–antibody interactions in order to improve disease diagnostic, we suggest that “protein-wide” screening for specific epitope–paratope interactions may help to develop novel assays for monitoring of personalized therapies, since individual properties of antigen–antibody interactions remain distinguishable.     

Development and validation of a method for determination of residues of 15 pyrethroids and two metabolites of dithiocarbamates in foods by ultra-performance liquid chromatography-tandem mass spectrometry

This paper reports a novel approach for the detection, confirmation, and quantification of 15 selected pyrethroid pesticides, including pyrethins, and two metabolites of dithiocarbamates in foods by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS). The proposed method makes use of a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure that combines isolation of the pesticides and sample cleanup in a single step. Analysis of pyrethroids and dithiocarbamate metabolites was performed by UPLC–MS–MS operated with electrospray and atmospheric pressure chemical ionization, respectively. Two specific precursor–product ion transitions were acquired per target compound in multiple reaction monitoring (MRM) mode. Such acquisition achieved the minimum number of identification points according to European Commission (EC) document no. SANCO/10684/2009, thus fulfilling the EC point system requirement for identification of contaminants in samples. The method was validated with a variety of food samples. Calibration curves were linear and covered from 1 to 800 μg kg⁻¹ in the sample for all target compounds. Average recoveries, measured at mass fractions of 10 and 100 μg kg⁻¹ for pyrethroids and 5 and 50 μg kg⁻¹ for dithiocarbamate metabolites, were in the range of 70–120% for all target compounds with relative standard deviations below 20%. Method limits of quantification (MLOQ) were 10 μg kg⁻¹ and 5 μg kg⁻¹ for pyrethroids and dithiocarbamate metabolites, respectively. The method has been successfully applied to the analysis of 600 food samples in the course of the first Hong Kong total diet study with pyrethroids and metabolites of dithiocarbamates being the pesticides determined.     

Separation of phenolic acids in soil and plant tissue extracts by co-electroosmotic capillary electrophoresis with direct UV detection

Summary A capillary zone electrophoretic method for the analysis of phenolic acids in soil and plant extracts was developed with direct UV detection using a phosphate electrolyte solution. The electrophoretic separation required the phenolic acids to be charged at a pH above their pKa in order to achieve their migration towards the anode. Electroosmotic flow (EOF) was reversed in direction by adding tetradecyltrimethylammonium bromide (TTAB). Factors affecting the separation selectivity, including the buffer pH and EOF modifiers, were investigated systematically. Eight phenolic acids were separated and detected in 10 min using an electrolyte containing 25 mM phosphate, 0.5 mM TTAB and 15% acetonitrile (v/v) at pH of 7.20. Linear plots for the test phenolic acids were obtained in a concentration range of 0.01–1 mM with detection limits in the range of 1.0–7.0 μM. The recoveries ranged from 92.8 to 102.3% in soil and plant tissues samples spiked at 100 μM and the relative standard deviation based on the peak area were ranged 2.0 to 4.5%. The proposed method was used for the determination of phenolic acids in plant tissue and soil extracts with direct injection.     

Electroless Ni–P coated on graphite as catalyst for the electro-oxidation of dextrose in alkali solution

Graphite particles were coated with Ni–P by electroless deposition using a conventional bath consisting of a nickel salt and hypophosphite. After 15 min of electroless deposition, the graphite particles were covered with 10 wt% nickel and 0.7–1.0 wt% phosphorus as analysed by wet chemical method. Surface morphology was studied by scanning electron microscopy (SEM). Electrochemical characterisation for the catalytic activity was done by cyclic voltammetry. Pure Ni powder and electroless Ni–P coated on graphite were used as catalysts for the electro-oxidation of dextrose (1.8 × 10⁻³ to 4.5 × 10⁻³ M) in 0.1 M KOH solution. Comparative studies revealed that electroless Ni–P coated on graphite particles acted as a better catalyst than pure Ni powder for catalytic reaction.     

Chromatographic separation of uranium(VI) from other elements using L-valine and poly[dibenzo-18-crown-6]

A selective and effective column chromatographic separation method has been developed for uranium(VI) using poly[dibenzo-18-crown-6]. The separation was carried out in L-valine medium. The adsorption of uranium(VI) was quantitative from 1.0 × 10⁻⁴ to 1 × 10⁻¹ M of L-valine. Amongst various eluents 2.0–8.0 M hydrochloric acid, 1.0–4.0 M sulfuric acid, 1.0–5.0 M perchloric acid, 6.0–8.0 M hydrobromic acid and 5.0–6.0 M acetic acid were found to be efficient eluents for uranium(Vl). The capacity of poly[dibenzo-18-crown-6] for uranium(VI) was 0.25 ± 0.01 mmol/g of crown polymer. Uranium(VI) was separated from number of cations and anions in binary mixtures in which most of the cations and anions show a very high tolerance limit. The selective separation of uranium(VI) was carried out from multicomponent mixtures. The method was extended to determination of uranium(VI) in geological samples. The method is simple, rapid and selective with good reproducibility (approximately ∼2%).     

Integrated microfluidic device with an electroplated palladium decoupler for more sensitive amperometric detection of the 8-hydroxy-deoxyguanosine (8-OH-dG) DNA adduct

8-Hydroxy-deoxyguanosine (8-OH-dG) DNA adduct is one of the most frequently used biomarkers reporting on the oxidative stress that leads to DNA damage. More sensitive and reliable microfluidic devices are needed for the detection of these biomarkers of interest. We have developed a capillary electrophoresis (CE)-based microfluidic device with an electroplated palladium decoupler that provides significantly improved detection limit, separation efficiency, and resolving power. The poly(dimethylsiloxane) (PDMS)/glass hybrid device has fully integrated gold microelectrodes covered in situ with palladium nanoparticles using an electroplating technique. The performance and coverage of the electrodes electroplated with palladium particles were evaluated electrochemically and via scanning electron microscope (SEM) imaging, respectively. The performance of the device was tested and evaluated with different buffer systems, pH values, and electric field strengths. The results showed that this device has significantly improved resolving power, even at separation electric field strengths as high as 600 V cm⁻¹. The detection limit for the 8-OH-dG adduct is about 20 attomoles; the concentration limit is on the order of 100 nM (S/N = 3). A linear response is reported for both 8-OH-dG and dG in the range from 100 nM to 150 μM (≈100 pA μM⁻¹) with separation efficiencies of approximately 120,000–170,000 plates m⁻¹.     

Indirect fluorescence detection of phenolic compounds by capillary electrophoresis on a glass device

A micromachined capillary electrophoresis system has been fabricated on a glass device for the separation and indirect fluorescence detection of phenols. Using this device two phenols viz., 2,4-dichlorophenol and pentachlorophenol, were separated within 12 s compared to under 19 min on a conventional capillary electrophoresis system using direct ultraviolet detection. The precision of the glass device ranged from 12.7%–16.7% compared to 0.42%–4.9% for the conventional system. Both systems showed good linearity in the concentration range of 0.8– 6.38 mM for the glass device and 5–130 μM for the conventional system. The relationship between temperature and high voltage with baseline drift was also investigated. These results provide a foundation for the development of a miniaturised chemical analysis system for the on-line analysis of phenols in water. Received: 24 January 2000 / Revised: 27 March 2000 / Accepted: 29 March 2000     

Electrochemical behaviour of sertraline at a hanging mercury drop electrode and its determination in pharmaceutical products

The electrochemical behaviour of sertraline at a hanging mercury drop electrode (HMDE) was described. Different voltammetric techniques, such as cyclic, linear sweep, differential pulse and square wave voltammetry, were used. Voltammograms were obtained at different pH values with a Britton-Robinson buffer solution used as supporting electrolyte. The best results were found by square wave voltammetry with electrodeposition at alkaline pH using a borate buffer with a pH = 8.2 for the samples, containing 12% (v/v) methanol. Under optimised conditions, a linear relationship between 2.33 × 10^–7 and 3.15 × 10^–6 M of sertraline with a limit of detection of 1.98 × 10^–7 M was obtained. The electrochemical method developed was applied to the determination of sertraline in pharmaceutical formulations. Recoveries were close to 100%, thus proving efficacy of the proposed method for the quantification of sertraline in commercial samples. Received: 26 September 2000 / Revised: 1 December 2000 / Accepted: 5 December 2000     

History of individuals of the 18th/19th centuries stored in bones,teeth, and hair analyzed by LA–ICP–MS—a step in attempts to confirm the authenticity of Mozart’s skull

A cranium stored in the Stiftung Mozarteum in Salzburg/Austria which is believed to be that of Mozart, and skeletal remains of suspected relatives which have been excavated from the Mozart family grave in the cemetery in Salzburg, have been subjected to scientific investigations to determine whether or not the skull is authentic. A film project by the Austrian television ORF in collaboration with Interspot Film on this issue was broadcast at the beginning of the “Mozart year 2006”. DNA analysis could not clarify relationships among the remains and, therefore, assignment of the samples was not really possible. In our work this skull and excavated skeletal remains have been quantified for Pb, Cr, Hg, As, and Sb content by laser ablation-inductively coupled plasma-mass spectrometry (LA–ICP–MS) to obtain information about the living conditions of these individuals. A small splinter of enamel (less than 1 mm³) from a tooth of the “Mozart cranium” was also available for investigation. Quantification was performed by using spiked hydroxyapatite standards. Single hair samples which are recorded to originate from Mozart have also been investigated by LA–ICP–MS and compared with hair samples of contemporary citizens stored in the Federal Pathologic–Anatomical Museum, Vienna. In general, Pb concentrations up to approximately 16 μg g⁻¹ were found in the bone samples of 18th century individuals (a factor of 7 to 8 higher than in recent samples) reflecting elevated Pb levels in food or beverages. Elevated Pb levels were also found in hair samples. The amount of Sb in the enamel sample of the “Mozart cranium” (approx. 3 μg g⁻¹) was significantly higher than in all the other tooth samples investigated, indicating possible Sb ingestion in early childhood. Elevated concentrations of elements in single hair samples gave additional information about possible exposure of the individuals to heavy metals at a particular point in their life.     

Immobilization of L-glutamate oxidase and peroxidase for glutamate determination in flow injection analysis system

Streptomyces SP.N 14, isolated from soil samples, produced extracellular L-glutamate oxidase (GOD) in liquid culture. After a two-step ammonium sulfate purification and dextran G-150 chromatography, the specific activity was reached at 28.2 U/mg. The partial purified enzyme and horseradish peroxidase (HRP) were covalently coupled to alkylamine controlled pore glass (CPG) by means of glutaraldehyde. About 200–300 U/g of immobilized GOD and 300–400 U/g of immobilized HRP were obtained. The immobilized enzymes were packed into a teflon tube and used in flow injection analysis (FIA) for glutamate in broth. A good linear range was observed for this immobilized enzyme system at 0.1–2.0 mM, and the precision was 2.8% (n = 25). More than 80 samples were measured within an hour. One enzyme column with about 4 U of immobilized GOD and 5 U of immobilized HRP, applied for 50 assays/d, has been used for more than 50 d. The concentration of L-glutamate remaining lower than 2.0 mM, the determination of glutamate in this system was not affected by pH and temperature within the range of 6.0–7.0 and 25–35‡C, respectively. The system was applied to determine L-glutamate in broth samples during L-glutamate fermentation, and good correlation was achieved between results obtained with the system and with the Warburg’s method.     

Photocatalytic degradation of Orange II by titania addition to sol–gel glasses

Glasses on SiO₂–CaO–ZnO–B₂O₃–K₂O–Al₂O₃ oxide system modified by addition of titania (0, 3, 5, 12, and 20% w) have been prepared by sol–gel method. The obtained gels were aged, dried and fired at 600 °C/1 h in order to stabilise the glass. The resulting fired powders were characterised by UV–Vis–NIR spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Their photocatalytic capacity on the degradation of Orange II dye has been studied. The XRD and TEM studies indicate that system becomes amorphous with a nanostructured microstructure. From UV–Vis–NIR results the band gap calculated is around 3.5 eV for all modified glasses. Photoactivity of powders depends on amount of titania in glass composition and the specific surface area of prepared samples. The sample with highest surface area and lowest addition of titania (3% w sample) shows similar activity than commercial anatase used as reference.     

Determination of sulfonylurea herbicides in soil extracts by solid-phase extraction and capillary zone electrophoresis

Summary Sulfonylurea herbicides in soil extracts were concentrated using off-line solid-phase extraction (SPE), and determined by capillary zone electrophoresis (CZE) and UV detection. The method involves extraction of soils with 0.1 M NaHCO₃ solution and subsequent preconcentration by using C₁₈ cartridges prior to separation of the pesticide using CZE. The results show that a C₁₈ cartridge is suitable for the purification of sulfonylurea herbicides in soil extracts with the recoveries ranging from 65–103%. The separation conditions affecting the resolution and detection sensitivity was systematically investigated. The sulfonylureas were resolved well using 30 mM sodium acetate (NaAc)/acetic acid (HAc)+10% acetonitrile (ACN) buffer at pH 4.80. The calibration plots for the test solutes in the concentration of 0.2–50 mg L⁻¹ were linear with detection limits in the range of 0.05–0.10 mgL⁻¹. The proposed method has been successfully demonstrated for the determination of sulfonylurea herbicides in soil samples.     

Determination of Urinary Glucose by a Flow Injection Analysis Amperometric Biosensor and Ion-Exchange Chromatography

A practical biosensor system has been developed for the determination of urinary glucose using a flow-injection analysis (FIA) amperometric detector and ion-exchange chromatography. Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an immobilized enzyme column. On the basis of its negative charge at pH 5.5, endogenous urate in urine samples was effectively retained by an upstream anion-exchange resin column. The biosensor system possessed a sensitivity of 160 ±2.4 RU μM^-1 (RU or relative unit is defined as 2.86 μV at the detection output) for glucose with a minimum detection level of 10 μM. When applied for the determination of urinary glucose, the result obtained compared very well with that of the widely accepted hexokinase assay. The immobilized glucose oxidase could be reused for more than 1000 repeated analyses without losing its original activity. The reuse of the acetate anion-exchange column before replacement would be about 25–30 analyses. Acetaminophen and ascorbic acid were also effectively adsorbed by the acetate anion exchanger. The introduction of this type of anion exchanger thus greatly improved the selectivity of the FIA biosensor system and fostered its applicability for the determination of glucose in urine samples.     

Validated method for the determination of the novel organo-ruthenium anticancer drug NAMI-A in human biological fluids by Zeeman atomic absorption spectrometry

NAMI-A is a novel ruthenium-containing experimental anticancer agent. We have developed and validated a rapid and sensitive analytical method to determine NAMI-A in human plasma, plasma ultrafiltrate and urine using atomic absorption spectrometry with Zeeman correction. The sample pretreatment procedure is straightforward, involving only dilution with an appropriate hydrochloric acid buffer-solution. Because the response signal of the spectrometer depended on the composition of the sample matrix, in particular on the amount of human plasma in the sample, all unknown samples were diluted to match the matrix composition in which the standard line was prepared (plasma-buffer 1 : 10 v/v). This procedure enabled the measurement of samples of different biological matrices in a single run. The validated range of determination was 1.1–220 μM NAMI-A for plasma and urine, and 0.22–44 μM for plasma ultrafiltrate. The lower limit of detection was 0.85 μM in plasma and urine and 0.17 μM in plasma ultrafiltrate. The lower limit of quantitation was 1.1 and 0.22 μM, respectively. The performance of the method, in terms of precision and accuracy, was according to the generally accepted criteria for validation of analytical methodologies. The applicability of the method was demonstrated in a patient who was treated in a pharmacokinetic phase I trial with intravenous NAMI-A. Received: 1 September 2000 / Revised: 1 November 2000 / Accepted: 12 November 2000