This review addresses recent developments in electrochemistry and electroanalytical chemistry of carbon nanotubes (CNTs). CNTs have been proved to possess unique electronic, chemical and structural features that make them very attractive for electrochemical studies and electrochemical applications. For example, the structural and electronic properties of the CNTs endow them with distinct electrocatalytic activities and capabilities for facilitating direct electrochemistry of proteins and enzymes from other kinds of carbon materials. These striking electrochemical properties of the CNTs pave the way to CNT-based bioelectrochemistry and to bioelectronic nanodevices, such as electrochemical sensors and biosensors. The electrochemistry and bioelectrochemistry of the CNTs are summarized and discussed, along with some common methods for CNT electrode preparation and some recent advances in the rational functionalization of the CNTs for electroanalytical applications.
Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), some of which are extremely toxic, are present at low concentrations in incinerator flue gases. The on-line real-time measurement of these compounds is necessary, since these concentrations fluctuate drastically with the process conditions used. Supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (SSJ/REMPI/TOF-MS), which provides both high selectivity and sensitivity, appears suitable for application to the on-line real-time monitoring of PCDD/Fs. In this review, the resonant ionization wavelengths of PCDD/Fs and their precursors are given. Moreover, improvements in SSJ/REMPI/TOF-MS that lead to enhanced sensitivity and selectivity are presented. That is, novel ionization sources and advanced ionization schemes are reported for the sensitive measurement of PCDD/Fs and their precursors. Those techniques are advantageous for the trace analysis of these compounds.
The mechanism of volatile hydride generation (HG) and the formation of analyte atoms in the quartz cell atomizer used in the determination of hydride-forming elements (As, Bi, Ge, Pb, Sb, Sn, Te etc.) by atomic absorption spectrometry (AAS), have been critically reviewed. The nascent hydrogen mechanism failed to explain hydride generation under different experimental conditions when tetrahydroborate (THB), amineboreanes (AB) and cyanotrihydroborate (CBH) were used as reductants. Various experimental evidence suggested a non-nascent hydrogen mechanism, in which the transfer of hydrogen directly bonded to boron to an analyte takes place. In electrochemical hydride generation (EcHG), the reduction of the analyte species and subsequent hydrogenation was proposed. The mechanism of analyte atom formation in a quartz tube atomizer has been explained by the following hypotheses: thermal decomposition, oxidation by O2 and collisions by hydrogen free radicals. The free-radical mechanism satisfactorily explains most of the analytical implications. The significant variation in the experimental conditions required to generate different analyte hydrides makes it difficult to arrive at a generalized mechanism of hydride formation.
A combined method of laser ablation (LA) and ICP-MS has gained much attention as a direct analytical method for solid samples. The determination of some elements, however, is seriously disturbed by isobaric interferences, mainly caused by argon and ambient air constituents. The use of low-pressure helium-ICP is a promising solution of the problem. A 1:1 mixture of alumina powder and glycerol was deaerated and irradiated with a pulsed laser beam (150 mJ) for 10 s. The sample aerosol was transported to the ICP with a stream of helium. Indium was used as an internal standard for correcting the ablated sample amount. Calibration curves were prepared from glycerol containing high-purity alumina, trace metals and indium. The detection limits for Cr, Mn, Fe, Co, Ni, and Cu approached the fractional ppm levels. The proposed method was successfully applied to the analysis of different alumina samples (99 - 99.995% purity).
A liquid membrane disk electrode, LMDE, and a liquid membrane ring-liquid membrane disk electrode, LMRE-LMDE, were developed by placing a gelled polyvinyl chloride thin membrane impregnated with 2-nitrophenyl octyl ether, NPOE-LM, on the surface of a glassy carbon, GC, disk or ring electrode. The voltammogram for the ion transfer at the interface between an aqueous solution, W, and NPOE-LM was recorded by setting the developed electrode in W and rotating at a rate, ω, between 0 and 4000 rpm. The sensitivity of the ion-transfer current at the W|NPOE-LM interface, I, was enhanced to be more than 100 times better than that at the W|NPOE (solution) interface when LMDE was rotated at ω higher than 200 rpm. The reversibility of the ion transfer reaction could be evaluated based on the dependence of I on ω of LMDE, and the reaction product at LMDE could be identified at LMRE when the rotating LMRE-LMDE system was adopted.
Electrochemical deposition from a 0.1 M sodium sulphate solution, containing Cu2+ (adjusted to pH 3 with hydrochloric acid) produced a well defined copper nanoparticle deposit on the surface of a boron doped diamond electrode. Changing conditions such as potential (-0.8, -1.0 and -1.2 V), time (5, 2 and 0.5 s) and concentration of Cu2+ (500, 250 and 100 µM) was found to give copper nanoparticles of varying size and particle density. The electrocatalytic properties of the copper surface towards nitrate reduction were explored. An in-situ copper nanoparticle production method was developed for the detection of nitrate; this involves electrodeposition, followed by linear sweep voltammetry for the reduction of nitrate and then application of a stripping potential to renew the electrode surface. The linear sweep was discovered to have homogenised the size of the nanoparticles but their number density was still dependant on the initial conditions of deposition. Some particles were still present at the surface after the stripping potential had been applied but repetitions of the procedure showed these did not have an effect on subsequent deposits. Optimisation of the method lead to applying a deposition potential of -0.8 V, at a BDD electrode for 5 s in a 0.1 M sodium sulphate solution (pH 3) containing 100 µM Cu2+ followed by a linear sweep at 1 V/s; this yielded a limit of detection of 1.5 µM nitrate. The analytical applicability of the technique was evaluated for nitrate detection in a natural mineral water sample and was found to agree well with that stated by the manufacturer.
A surface plasmon resonance (SPR) biosensor for the quantification of a neuropeptide substance P (SP) is described based on an inhibition assay using Au colloid-modified calmodulin (Au-CaM) and a target peptide melittin immobilized on carboxymethylated dextran. The modification of CaM with streptavidin Au colloids was achieved in a sample solution by the amine coupling method. The SPR signal sharply increased, corresponding to the formation of a Ca2+-Au-CaM-melittin complex on the sensor surface, and approached a steady state within 5 min. When SP was added to a sample solution, the SPR signal was decreased, due to the formation of a Ca2+-Au-CaM-SP complex in the sample solution. The modification of CaM with streptavidin Au colloids was effective for enhancing the SPR signal for SP. A decrease in the SPR signal was observed for SP in the concentration range from 0.10 to 5.0 µM, whose lower limit was ten-times superior to that (1.0 µM) with unmodified CaM. The response was highly selective to SP and the selectivity was in the order of SP >> neurokinin A > neurokinin B > neurotransmitters (glycine, GABA, L-glutamate, acetylcholine, norepinephrine, 5HT) ∼ substance P fragment (1 - 7). The potential use of the present sensor for the quantification of SP in mouse brain extracts is demonstrated.
A ferrocenylnaphthalene diimide (FND)-based electrochemical hybridization assay (FND-EHA) was applied to the detection of two mutations in human lipoprotein lipase (LPL) gene, G188E (one base transition) and Arita (one base deletion). A probe oligodeoxyribonucleotide of 13 bases representing the wild type (WT) sequence of LPL was immobilized on a gold electrode, followed by hybridization with a sample PCR product of 350 base pairs under conditions in which both WT and mutated (MT) sequences could form a duplex with the probe. The hybridized electrodes were soaked in an electrolyte containing FND under conditions in which only the mismatched duplex could undergo dissociation. FND was concentrated in proportion to the amount of the duplex remaining on the electrode to give rise to a current signal. Blind tests were run to judge the genotype (WT/WT, WT/MT, or MT/MT) of 10 samples each for the G188E and Arita mutations and then, 8 and 10 of them were judged correctly, respectively.
New ranitidine hydrochloride (RaCl)-selective electrodes of the conventional polymer membrane type are described. They are based on incorporation of ranitidine-tetraphenylborate (Ra-TPB) ion-pair or ranitidine-phosphotungstate (Ra-PT) ion-associate in a poly(vinyl chloride) (PVC) membrane plasticized with dioctylphthalate (DOP) or dibutylphthalate (DBP). The electrodes are fully characterized in terms of the membrane composition, solution temperature, and pH. The sensors showed fast and stable responses. Nernstian response was found over the concentration range of 2.0 × 10-5 M to 1.0 × 10-2 M and 1.0 × 10-5 M to 1.0 × 10-2 M in the case of Ra-TPB electrode and over the range of 1.03 × 10-5 M to 1.00 × 10-2 M and 1.0 × 10-5 M to 1.0 × 10-2 M in the case of Ra-PT electrode for batch and FIA systems, respectively. The electrodes exhibit good selectivity for RaCl with respect to a large number of common ions, sugars, amino acids, and components other than ranitidine hydrochloride of the investigated mixed drugs. The electrodes have been applied to the potentiometric determination of RaCl in pure solutions and in pharmaceutical preparations under batch and flow injection conditions with a lower detection limit of 1.26 × 10-5 M and 5.62 × 10-6 M at 25 ± 1°C. An average recovery of 100.91% and 100.42% with a relative standard deviation of 0.72% and 0.53% has been achieved.
In matrix-assisted laser desorption/ionization (MALDI), the true molecular structures of some analytes are not represented by the observed ions due to a redox reaction. In earlier reports, electron transfer from analyte to chemical matrix has been proposed for the oxidation of ferrocene derivatives in MALDI. To address such a redox phenomenon in laser desorption/ionization processes, two ferrocene derivatives, FcCH2CH2Fc and FcCH2NMe2 [Fc:(C5H5)Fe(C5H4)], were analyzed by a matrix-free method, desorption/ionization on porous silicon (DIOS). The oxidized species, Fc+CH2NMe2 and FcCH2CH2Fc+, were detected in the DIOS mass spectra. The results suggested that electron transfer from the analytes to the sample target occurs during the ionization process.
A reflectron time-of-flight mass spectrometer (RTOFMS) with a laser ablation ion source was used to determine the isotopic ratio of 10B/11B present in boric acid solutions, using graphite as the matrix. The atom % 10B values obtained were within ±1% of the actual ones. The determination of the boron isotopic ratio using this method is, in comparison to other methods, faster, less expensive and easier to perform. The results are compared with the values determined using thermal ionization mass spectrometry.
Fatty acids in 42 types of saponified vegetable and animal oils were analyzed by electrospray ionization mass spectrometry (ESI-MS) for the development of their rapid discrimination. The compositions were compared with those analyzed by gas chromatography-mass spectrometry (GC-MS), a more conventional method used in the discrimination of fats and oils. Fatty acids extracted with 2-propanol were detected as deprotonated molecular ions ([M-H]-) in the ESI-MS spectra of the negative-ion mode. The composition obtained by ESI-MS corresponded to the data of the total ion chromatograms by GC-MS. The ESI-MS analysis discriminated the fats and oils within only one minute after starting the measurement. The detection limit for the analysis was approximately 10-10 g as a sample amount analyzed for one minute. This result showed that the ESI-MS analysis discriminated the fats and oils much more rapidly and sensitively than the GC-MS analysis, which requires several tens of minutes and approximately 10-9 g. Accordingly, the ESI-MS analysis was found to be suitable for a screening procedure for the discrimination of fats and oils.
Thirteen polycyclic aromatic hydrocarbons (PAHs) and four nitropolycyclic aromatic hydrocarbons (NPAHs) on the surfaces of airborne particulates, which were collected at an industrial area of a western site of Japan during periods from 1976 to 1998, were retrospectively analyzed. PAHs and NPAHs were extracted from airborne particulates using hexane with ultrasonication, and then analyzed by HPLC systems with fluorescence detection and chemiluminescence detection, respectively. The total concentrations (mean ± SD, n = 34) were 15.54 ± 21.24 ng/m3 for PAHs and 5.85 ± 8.16 pg/m3 for NPAHs. The concentrations of PAHs and NPAHs were found to be highest during the period between 1979 and 1982, and then reduced. The annual concentrations of PAHs and NPAHs were highly correlated with those of air pollutants from motor vehicle origin, such as carbon monoxide, suspended particulates and non-methane hydrocarbons. The results suggested that motor vehicle emissions were one of the predominant sources of atmospheric PAHs and NPAHs.
Identifying and measuring the ammonia gas that emanates from human skin, which we called skin gas, has been achieved using a modified gas chromatographic system with a nitrogen-selective detector (flame-thermoionic detector: FTD). The skin gas is collected with a home-made sampling probe or bag, which is used to cover the skin surface of a subject's wrist, or a finger, for 5 min. It was proved that ammonia was present in skin gas for healthy persons and patients with hepatic disease. The average amounts of ammonia were 1.7 ± 0.4 and 2.7 ± 0.8 ng/cm2; furthermore, there was a significant difference between them (p < 0.05). In addition, the ammonia levels present in skin gas were correlated with that in blood (r = 0.64, p < 0.05).
A quantitative measurement method with FT-IR was proposed for a thermal degradation analysis of nitrile-butadiene rubber (NBR). An NBR film was prepared as a model sample on a barium fluoride (BaF2) crystal plate, which was subjected to a heat treatment. The absorbances of various functional groups were measured directly by FT-IR after thermal degradation at high temperatures. By measuring the absorbances, it was possible to readily determine quantitatively each of the functional groups after the degradation of NBR. By assuming that the NBR lifetime was the point at which the absorbance of a carbon-carbon double bond reaches 45% of that prior to thermal treatment, a method for predicting the lifetime of NBR heated below 150°C was proposed, by using an Arrhenius plot of the heating time versus heating temperature.
An approach in determining the intrinsic termination efficiency (%T) of transcription termination using green fluorescent protein (GFP) mutants was developed. This approach utilizes a cassette vector in which the tested terminator is introduced between two GFP mutant genes: an ultraviolet-optimized mutant (GFPuv: F99S, M153T, V163A) and a blue-shifted mutant (BFP: F64L, S65T, T145F). The ratio of the fluorescence intensity of BFP to GFPuv after transcription and translation represents the termination efficiency of the terminator. E. coli ribosomal RNA operon T1 terminator, phage lambda terminator site R2, E. coli tryptophane attenuater were introduced into the vector, and their transcriptional efficiencies were estimated as 89, 79, and 24%, respectively, showing good agreement with published data.
This paper reports the experimentally determined and calculated partition coefficients (Kp) in a heterogeneous system consisting of two partially mixing organic solvents for trimethylsilyl derivatives of 119 compounds including phenols, phenolcarboxylic acids, mono- and dicarboxylic acids, and some carbohydrates and polyols. It was demonstrated that a simple model based on the available physico-chemical properties of molecules can be used to accurately predict the hexane-acetonitrile partition coefficients. Phenols, other organic acids, and carbohydrates form complex mixtures in extracts of plant tissues, in various biological fluids, as well as in waste waters. For group identification of these mixture components, it is desirable to use the parameter j which is a combination of Kp and gas chromatographic retention indices: j = kI - log Kp. This approach increases identification reliability in gas chromatographic analysis. The use of the group parameter j in the analysis of nonvolatile organic components of waste waters is reported.
The present paper describes the application of a solid phase extraction system in order to separate traces of calcium from glass and ceramics for its spectrophotometric determination. The method is based on the extraction of calcium from sodium hydroxide solution by tri-n-butyl phosphate (TBP) loaded polyurethane foam (PUF), followed by its elution in hydrochloric acid. The spectrophotometric measurement of the absorbance of calcium complex with calconcarboxylic acid (2-hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid) takes place at pH 12. The following parameters were studied: effects of sodium hydroxide concentration and temperature on the extraction of calcium, time of equilibration for quantitative calcium extraction, effect of TBP concentration, effect of hydrochloric acid concentration for quantitative elution of calcium from PUF, effect of pH and concentration of calconcarboxylic acid for quantitative formation of the complex with calcium, effect of acetone on the stability of calcium-calconcarboxylic acid complex and influence of diverse ions on calcium sorption by TBP-loaded PUF. The results show that calcium traces can be separated onto TBP-loaded PUF from 0.25 mol l-1 NaOH at 30 ± 5°C within 30 min. PUF was loaded with TBP in CCl4 (40% v/v). Elution of calcium was done in 1.0 mol l-1 HCl. The calcium formed a complex with calconcarboxylic acid at pH 12 and absorbance was measured at 560 nm in acetone-water medium. Molar absorptivity was found to be 1.082 × 104 l mol-1 cm-1. The method obeys Beer's law from 0.10 to 5.0 µg ml-1 Ca. The validity of the method was established by its successful application in NIST standard reference materials. The method proposed was applied to determine calcium in glass and ceramic materials. The results of the proposed method are comparable with the results of ICP-AES analysis and they are found to be in good agreement.
Rapid and sensitive high-performance liquid-chromatographic methods were developed for the determination of cyadox, an antimicrobial growth-promoter, and its main metabolites (1,4-bisdesoxycyadox, quinoxaline-2-carboxylic acid) in goat muscle, liver, kidney and fat. Cyadox (CYX) and 1,4-bisdesoxycyadox (BDCYX) in fat were extracted with acetonitrile, and in other tissues with ethyl acetate. Quinoxaline-2-carboxylic acid (QCA) was isolated from tissue hydrolysates by solvent extraction, cleaned up with ion-exchange chromatography, followed by a final liquid-liquid extraction step. UV detections of CYX, BDCYX and QCA were performed at 305, 280 and 320 nm, respectively. The average recoveries of CYX, BDCYX and QCA in spiked tissues at levels of 25, 50, 100 µg/kg were 65 - 92%. The inter-day relative standard deviation for three compounds in different tissues was 5 - 16%. The quantitation limit was 25 µg/kg, and the detection limit was 15 µg/kg for three compounds in various tissues. Incurred goat tissues were analyzed to demonstrate the validity of the described methodologies. The present methods were highly selective and could be used in the metabolism and residue studies of cyadox.
Pumpkins were treated by spraying the leaves in the flowering period with a water solution containing 1.5 mg Se per liter in the form of Na2SeO4. The average total selenium content of seeds was found to be 0.19 µg g-1 in nontreated pumpkins and 1.1 µg g-1 in exposed ones. For speciation analysis, enzymatic hydrolysis with different amounts of Protease XIV was carried out. Under optimal conditions of enzymatic hydrolysis, 90% of the total selenium was found in soluble forms. Separation of species was performed using HPLC on anion and cation exchange columns and for detection UV-HG-AFS was applied. In enzymatic hydrolysis extracts, the main fraction of selenium was bound as selenomethionine (SeMet), representing on average of 81 ± 8% of the total Se content in the sample.
Water soluble organic compounds (WSOC) in airborne particulate matter (PM) have received considerable attention in recent years due to their abundance and their importance in atmospheric processes. The analysis of WSOC is necessary for quantifying the relative contribution of individual organic compounds to the total WSOC mass. In the present work, we evaluated the performance of a microwave-assisted extraction (MAE) method for the determination of WSOC in PM and compared the data with those of a conventional ultrasonic extraction (USE). The experimental results showed that the MAE method requires a shorter extraction time (5 min) compared to USE. The isolated water-soluble organic fraction of PM was subsequently analyzed using ion chromatography (IC) for low molecular weight organic acids. The rapid MAE method was used in conjunction with IC for the analysis of organic acids in PM samples, collected from different sources.
The aim of this work was to develop a simple, automatic system for the evaluation of cationic surfactants by combining sequential injection analysis and the sensitized effect of cationic surfactants on the reaction between metal ions and chelating dyes. This reaction is based on the increase in absorbance of the complex formed among molybdenum, bromopyrogallol red and increasing concentrations of cationic surfactants. Under optimum conditions, two calibration plots were obtained for a concentration range between 2.50 × 10-7 mol dm-3 (detection limit) and 5.00 × 10-4 mol dm-3 of cetylpyridinium chloride, used as standard. Solubilization of water insoluble complexes formed for concentrations of cationic surfactants greater than 1.00 × 10-4 mol dm-3 were successfully achieved with Triton X-405. RSD values lower than 5.0% were obtained in all cases. The quality of the results obtained for 18 water samples were evaluated by comparison with conventional methods, with no statistically significant differences for a 95% confidence level.
The first flow-injection method has been developed, optimized and validated for the determination of venlafaxine, an antidepressant drug. The method is based on a direct measurement of the absorbance of the analyte in an acidic medium, at 274 nm. Flow-injection parameters, such as sample injection volume and flow rate, were studied and optimized. The proposed method was validated in terms of linearity, repeatability, detection limit, accuracy and selectivity. Linearity was obeyed in the range 30 - 150 mg L-1 of venlafaxine, while the detection limit (1.5 mg L-1) and repeatability (sr < 1.0%, n = 12) were satisfactory. The sampling rate was 30 h-1. The results of dissolution studies of venlafaxine tablets obtained by the proposed method were in good agreement with those by high-performance liquid chromatography.
Coprecipitation with terbium hydroxide quantitatively recovered trace amounts of chromium(III), copper(II) and lead(II) at pH 8.4 - 10.8, 8.0 - 11.5 and 8.7 - 11.5, respectively. The precipitate was dissolved in 0.85 mol dm-3 nitric acid, and the analytes were determined by graphite-furnace atomic absorption spectrometry (GF-AAS). The presence of terbium (up to 7 g dm-3) did not interfere with the determination. The detection limits were 0.3 µg dm-3 for chromium, 0.4 µg dm-3 for copper and 0.5 µg dm-3 for lead, when the analytes in 200 cm3 of the sample solution were concentrated into 10 cm3. The ions added to river or seawater were quantitatively recovered. Chromium and copper in a contaminated river water were successfully determined.
A three-way resolution method based on PARAFAC model was applied for the UV-Vis spectra to study the simultaneous degradation of anthocyanins extracted from fresh calyces of flowers of the Hibiscus sabdariffa. This methodology was used to resolve a chemical system, for which there was no a priori information about the composition or the pure spectra, a so-called black system. In the pH range from 1 to 13, seven species were identified: flavylium cation, carbinol, quinoidal base, E- and Z-chalcones and E- and Z-ionized chalcones. The concentration changes were determined as functions of pH at different wavelengths. The pK values for the acidity constants as well as tautomeric constant were estimated as 2.70, 3.54 and 0.14, respectively. The spectral profiles recovered by the chemometric methods are in excellent agreement with bands of experimental spectra reported in the literature for the species measured at specific pH values.
The influence of a phospholipid, dipalmitoyl phosphatidylcholine, layer at a nitrobenzene|water interface on the transfer of tetraethylammonium ion and a polyammonium anti-fungus agent, poly[(dimethylimino)(2-oxo-1,2-ethanediyl)imino-1,6-hexanediylimino(1-oxo-1,2-ethanediyl)(dimethylimino)-1,6-hexanediyl] ion, across the interface was studied by normal pulse voltammetry. When the phospholipid was adsorbed to form a monolayer at the nitrobenzene|water interface by its addition to the organic phase, the half-wave potential in the current vs. potential curves for the transfer of tetraethylammonium ion did not change, but the limiting current was significantly decreased at certain sampling times, indicating a retarding effect of the layer on the ion-transfer. On the other hand, in the current vs. potential curves for the transfer of the polyammonium ion, no significant change in either the half-wave potential or the limiting current was observed upon adding the phospholipid, indicating that the polyammonium ion can easily permeate through the phospholipid layer. The results suggest a new application of the voltammetric technique to the study of cell membrane permeability to polyionic bioactive compounds.
An iodide-miconazole ion-paired complex was used as a suitable ion-exchanger for the preparation of a plasticized-PVC membrane electrode. Among different solvent mediators tested, dioctylsebacate exhibited the proper response characteristics, including Nernstian slope of the calibration curve, fast response time and good reproducibility of the emf values. The electrode exhibits a Nernstian slope of -59.8 ± 0.5 mV decade-1 for I- ion over a concentration range of 1.0 × 10-5 - 1.0 × 10-2 M with a limit of detection of 7.0 × 10-6 M. The electrode displays a good selectivity for I- with respect to a number of inorganic and organic species. It can be used over a pH range of 2.5 - 8.5. The membrane sensor was successfully applied to the determination of iodide in water samples and blood serum, as well as in pharmaceutical products such as iodoquinol and thyroxin.
For the diagnosis of unexplained male infertility a multiplex PCR for 6 markers, which are well-known as candidate genes for studying male infertility and located on the human Y-chromosome, has been designed. The multiplex PCR products have been separated on a 12 channel microchip electrophoresis system, which can analyze different samples simultaneously. By combining the technologies of multiplex PCR with multichannel microchip electrophoresis, the number of the DNA markers that can be screened simultaneously is increased to be 72 marker (12 × 6) in a single run while the electrophoresis analysis time is reduced to be only 180 s.
The uptakes of cycloalkanes (C5 - C8) and bicyclic aromatic compounds (naphthalene, biphenyl, and azulene) by both strong acid cation (Dowex 50W-X4 and X8) and strong base anion (Dowex 1-X4 and X8) exchange resins have been studied in aqueous solutions at 25°C; their distribution constants (K) have been determined. The relationship between the octanol-water partition coefficient and the resin affinity for solutes has been analyzed. The K values of three aromatic compounds were found to be much higher than expected from the octanol-water partition coefficients. This is probably due to the π interaction of aromatic rings with the resin matrix. Microscopic observations revealed that azulene molecules are uniformly distributed inside a resin particle.
A normal-phase high-performance liquid chromatography (NP-HPLC) method for the determination of tocopherols and tocotrienols in hazelnuts is reported. Three extraction procedures (with and without saponification) were assayed; the best results were obtained with a simple solid-liquid extraction procedure. Chromatographic separation was achieved using an Inertsil 5 SI column using isocratic elution with hexane/1,4-dioxane (95.5:4.5, v/v) at a flow rate of 0.7 mL/min. The effluent was monitored by a series arrangement of a diode-array followed by a fluorescence detector. All compounds were separated in a short period of time (17 min). The method proved to be rapid, sensitive, reproducible and accurate, allowing the simultaneous determination of all vitamin E homologues.
A highly spectrophotometric method for the determination of aluminum was developed. This method used the color reaction between m-carboxyphenylfluorone (MCPF) as a novel chemical probe and aluminum in the presence of a surfactant, poly(N-vinylpyrrolidone) (PVP, K-90) (0.03 - 1.40 µg of aluminum in a final volume of 10 ml at 561 nm). The proposed method showed excellent sensitivity (molar absorptibity of 1.70 × 105 l mol-1 cm-1) and reproducibility (within-day precision: RSD = 0.35% n = 6, between-day precision: RSD = 0.44% n = 6). Linearity was achieved over the range 3 - 140 µg L-1 with a correlation coefficient of 0.9999, and the effects of foreign substances were low.
Phytoremediation is an innovative technology that utilizes the natural properties of plants to remediate hazardous waste sites. For more cost-effective phytoremediation, it is important to utilize a hyperaccumulating plant after phytoremediation, i.e. the recovery of valuable metals and the production of useful materials. In this work, the determination of metals in plant component polymers in a fern, Athyrium yokoscense, as a hyper-accumulating plant was established using steam explosion, Wayman's extraction method, and ICP emission spectrometry. After A. yokoscense plants were treated by steam explosion, the steam-exploded A. yokoscense were separated into four plant component polymers, i.e. water-soluble material fraction, holocellulose fraction, methanol-soluble lignin fraction, and residual lignin fraction. The concentrations of Cu, Pb, Fe, and Zn in these plant component polymers and the dry weights of plant component polymers were measured. These analytical process determining metals in the plants will contribute to not only the evaluation and the efforts of phytoremediation using a hyperaccumulating plant, but also to the development of more effective phytoremediation.
Aliphatic amines, such as n-hexylamine (primary), di-n-hexylamine (secondary) and tri-n-hexylamine (tertiary amine), react with tetrabromophenolphthalein ethyl ester molecules (TBPEH) to form reddish or red-violet charge-transfer complexes (CT complexes) in 1,2-dichloroethane (DCE). The absorption maxima of the CT complexes with all primary amines occur at around 560 nm, with secondary amines at 570 nm and, with tertiary amines at 580 nm. The CT complex formation constants with TBPEH in DCE increase in the order of the primary, secondary and tertiary amines, but their constants decrease quantitatively with an increase in temperature. This phenomenon (thermochromism) could be applied to the simultaneous spectrophotometric determination of primary amine and secondary amine, or secondary amine and tertiary amine in a mixed solution utilizing the difference of absorbance with temperature changes.
Modifications of the Zwikker- and Parri color detection tests were examined and compared according to their ability to distinguish between nine different barbituric acids and hydantoins. These tests comprised the formation of complexes with cobalt(II) and copper(II) salts and organic amines. Using the color palette introduced herein, the evaluation of the tests could be reduced to a simple yes/no decision on the basis of only seven defined colors. Suitable components for the color tests could be selected from the thirty six modifications.