Molecular ions include information about end groups, functional groups and molecular weight. A method for the direct detection of these in the high mass range (m/z > 1000) from poly(dimethylsiloxane) (PDMS) on a solid surface was investigated. It was found that a TOF-SIMS analysis of silver-deposited surfaces (silver deposition/TOF-SIMS) is useful for this purpose. Using the silver-deposition/TOF-SIMS method, silver-cationized quasi-molecular ions were clearly detected from PDMS on solid surfaces, and their structure and molecular weight were evaluated. In addition, their images were observed without the interference of deposited silver. By applying to the analysis of paint defects etc., it was confirmed that this technique is useful to analyze actual industrial materials. Silver-cationized ions were detected not only from PDMS, but also from other organic materials, such as lubricant additives and oils on solid surfaces. Therefore, the silver deposition/TOF-SIMS method was proved to be useful for the analysis of ultrathin substances on solid surfaces.
We describe an efficient and simple minisatellite variant repeat mapping by PCR (MVR-PCR) method based on the assignment of the tandem array of 29 bp repeating units into a-type, t-type and 0-type (a rarely appearing unamplified unit), from the first repeat unit position (code position 0) of 293 bp in D1S8 locus. After microchip electrophoresis of PCR product amplified from the target DNA of a human hair root, each rung of the ladder at the position of 293 + 29 n bp (n: code position) was detected and the type of repeating unit was determined, i.e., aa, a0, tt, t0, at and 00. The peak area of the rungs from PCR product decreased with increase in code position. We found for the first time that the logarithmic plots of the peak area against the code position showed a linear relationship, which implied that peak areas decrease exponentially. The present method was successfully applied to identify 37 individuals using only a hair root as a biological specimen. This “exponential law” is expected to be an effective tool in forensic science.
Amperometric glucose sensors were fabricated using glucose oxidase (GOx) entrapped in zirconium hydrogenphosphate (ZrP), and their performance was evaluated. Reportedly, α-ZrP is one of the candidates that are expected to improve the stability of enzymes immobilized on solid surfaces.1,2 We intercalated GOxs into ZrP (GOx/ZrP), cast the GOx/ZrP suspension in polyvinylalcohol on a platinum electrode, and dried it in a vacuum oven. The morphological layered structure was investigated by scanning electron microscopy. The enzymatic activities, which were determined by open-circuit potentiometric technique, reached the highest when GOxs were immobilized in ZrP at ca. pH 5. In vitro tests showed good linear responses in the 0 - 25 mM range and the sensitivity of 0.14 nA mM-1 at 0.4 V vs. Ag/AgCl. The sensors, as made, were stable for more than 3 days within a limited deterioration.
Hexafluorophosphate salts of mononuclear complexes [RuIICl(L)(terpy)]+ (L = dmbpy (1); dpbpy (2), sambpy (3), and dpp (7), and binuclear complexes [RuII2Cl2(dpp)(terpy)2]2+ (8) and [IrIIIRuIICl2(dpp)(terpy)2]3+ (9) were prepared and characterized. Abbreviations of the ligands are bpy = 2,2′-bipyridine, dmbpy = 4,4′-dimetyl-2,2′-bipyridine, dpbpy = 4,4′-diphenyl-2,2′-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, sambpy = 4,4′-bis((S)-(+)-α-1-phenylethylamido)-2,2′-bipyridine, and terpy = 2,2′:6′,2″-terpyridine. The absorption spectra of 8 and 9 are dominated by ligand-centered bands in the UV region and by metal-to-ligand charge-transfer bands in the visible region. The details of their spectroscopic and electrochemical properties were investigated. In both binuclear complexes, it has been found that the HOMO is based on the Ru metal, and LUMO is dpp-based. [IrIIIRuIICl2(dpp)(terpy)2]3+, indicating intense emission at room temperature, and a lifetime of 154 ns. The long lifetime of this bimetallic chromophore makes it a useful component in the design of supramolecular complexes.
Ultrafast double potential step chronoamperometry at an ultramicroelectrode was achieved through decreasing the ohmic drop by positive feedback compensation, and the lower limit of the time window was extended to the submicrosecond level. With the reduction of anthracene in acetonitrile as a test system, the validity of this instrumentation was demonstrated by comparing between experimental and simulated curves. The capability in kinetic studies of the technique was then approved.
To examine the directivity for improving the silver ion discrimination ability of a Schiff base, three kinds of tridentate ligands were synthesized and compared with the similar quadridentate ligand as the silver ionophore. Among the Schiff base derivatives tested, 3-(2-pyridylethylimino)-2-butanoneoxime, having one oxime and a pyridine substituent, was found to be the best ionophore for a silver-ion electrode. The electrode based on this derivative exhibited good silver-ion selectivity, -log KpotAg+,K+ = 3.8, comparable to that of a quadridentate Schiff base, N,N′-bis(2′-hydroxyimino-1′-phenylpropyleden)-1,3-propanediamine, reported previously, except for a pseudo Nernstian response (35.6 mV decade-1) with a wide silver-ion activity change in the activity change from 5.0 × 10-7 to 7.9 × 10-2 mol dm-3
In the buffer solution of NH3-NH4Cl (pH = 8.5, 0.04 mo1 l-1), iron-Methylthymol Blue (MTB) can produce a sensitive polarographic wave at -1.10 V (vs. SCE) in the NaNO2. The peak current is linear with the concentration of the iron in the range of 3 × 10-8 - 5 × 10-6 mol l-1, and the detection limit is 1 × 10-8 mol l-1. By studying the characteristics of the wave and the electrode reaction mechanism, we can prove that the catalytic wave is an adsorption wave and that the peak current comes from the reduction of Fe(II). The molar ratio of iron to ligand was found to be 1:1. Adsorption particles are neutral molecules, the saturated adsorption quantity of the complex on the mercury electrode is 1.92 × 10-9 mol cm-2, according with the Frumkin isothermal formula. In the experiments, the adsorption coefficient (β) is 4.05 × 105; the adsorption factor (γ) is 0.70; the electron transfer number (n) is 2; the free energy (ΔGo) is 31.99 kJ mol-1; the transfer coefficient of the irreversible adsorption is 0.42 - 0.45; and the reaction velocity constant (Ks) is 1.35 s-1. This method, whose result is satisfying, can be applied to the detection of trace total iron contents in medicinal products.
A new solvent polymeric membrane electrode based on N,N′-bis-(dimethylaminobenzaldehyde)-glycine cobalt(II) [Co(II)-BDMABG] as a neutral carrier is described, which displays a preferential potentiometric response to iodide ion and an anti-Hofmeister selectivity sequence in the following order: I- > ClO4- > Sal- > SCN- > NO2- > Br- > NO3- > Cl- > SO32- > SO42-. The electrode exhibits a near-Nernstian potential linear range of 9.0 × 10-7 - 1.0 × 10-1 M with a detection limit of 6.8 × 10-7 M and a slope of -53.0 mV/decade in pH 2.0 of a phosphate buffer solution at 20°C. The response mechanism is discussed in view of the A.C. impedance technique and the UV spectroscopy technique. The electrode was successfully applied to the determination of iodide in Jialing River and Spring in Jinyun Mountains with satisfactory results.
The performance of silver metal complexes with meso-tetraphenylporphyrin ([H2T(4-CH3)]PP) as ionophores for ion-selective electrodes was studied. The electrode exhibited linear response with Nernstian slope of 59.2 ± 1.0 mV per decade within the concentration range of 1.0 × 10-7 - 1.0 × 10-1 M silver ions. The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot, was 1.0 × 10-7 M. The response time of the electrode was < 10 s over the entire concentration range. The silver-selective electrode exhibited good selectivity for Ag(I) with respect to alkali, alkaline earth and heavy metal ions. The electrodes could be used at least three months without a considerable divergence in their potential. The electrodes are suitable for use in aqueous solutions in a wide pH range of 3.0 - 9.0. They were used as indicator electrodes in titration of Ag(I) with sodium iodide solution and were successfully applied to direct determination of silver in real samples.
A new isoelectric focusing (IEF) system for two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) has been proposed. In this system, a super-soft and tough IEF gel was achieved by casting polyacrylamide gel down to 2.0% T using a loose multifilament string (LMS) of nylon as a gel support. The IEF apparatus for the LMS-gel, fabricated from acrylic boards, had a cooling water chamber, and eliminated the need of electrode solutions by directly connecting the two ends of individual gels to platinum electrodes. The carrier ampholyte-generated pH gradients using the new IEF system was stable over a long duration of time and a wide range of voltages, and the IEF time became shorter using a 2.0% T gel than using a 4.0% T gel. Also, the LMS-gels prepared in different runs exhibited excellent reproducibility. The new IEF system was applied to 2-D PAGE of a chicken skeletal muscle extract, and it was found that the protein loading capacity, protein entry into the LMS-gels, and protein transfer efficiency from the first-dimensional to the second-dimensional gels were significantly improved by using a low-concentration (2.5% T) gel. Also, proteins of high molecular weight of more than 200 kDa were observed in the 2-D maps, and therefore the new IEF system has a very good potential to be applied for fast 2-D PAGE of high molecular-weight proteins.
Poly(octadecyl acrylate) with a terminal reactive group was synthesized by radical telomerization in various solvents. The polymers were grafted onto porous silica for use in RP-HPLC, and the molecular recognition ability was investigated along with the selectivity for the structural isomers of polycyclic aromatic hydrocarbons. The mechanism of selectivity was also investigated with differential scanning calorimetry and NMR spectroscopic observations.
An improved high-performance liquid-chromatographic (HPLC) assay for the simultaneous determination of serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) in human urine is reported. Following the automated precolumn derivatization of urinary 5-HT and 5-HIAA with benzylamine, the derivatives are separated by isocratic elution on a reversed-phase C18 semi-microbore column, and are fluorometrically detected at an excitation wavelength of 345 nm and an emission wavelength of 480 nm. The detection limits of 5-HT and 5-HIAA are 7 and 5 nmol/l in urine (0.7 and 0.5 fmol/20-µl injection). The proposed automatic method permits a highly selective and sensitive determination of 5-HT and 5-HIAA in human urine without any sample purification.
A method of two-step gradient capillary electrochromatography (CEC) was developed to measure 12 carbonyls (aldehydes and ketones) in indoor air samples. The carbonyls were derivatized with 2,4-dinitrophenylhydrazine (DNPH) and then separated by a two-step gradient CEC on a C8 column. Effects of various instrumental conditions on the separation, including buffer concentration, organic modifiers, voltage, and cassette temperature, were investigated. The method detection limits for the 12 carbonyls ranged from 0.2 µg to 1.6 µg per sample and the recoveries were generally between 90 and 120%. A subset of 30 indoor air samples containing formaldehyde and acetaldehyde from 75 randomly selected homes in the city of Ottawa, Canada were measured using the CEC method. The concentrations of formaldehyde and acetaldehyde in these indoor air samples ranged from 5.8 µg/m3 to 85 µg/m3, and from 4.4 µg/m3 to 38 µg/m3, respectively. The comparison between CEC and the traditional HPLC method shows a good agreement in measured values.
Trace amounts of Be (0.046 - 2.59 ng) in a dried marine organism sample (10 mg) could be accurately determined by GFAAS after treating with microwave digestion (HNO3/H2O2) at 85°C for 10 min and using acetylacetone as a chelating agent in the presence of an acetate buffer (pH 6.0). The method detection limit (MDL, 3 σ) for Be was found to be 4.6 ng g-1; the calibration graph was linear up to 259 ng g-1. Good recoveries (98.5 - 105.0%) were obtained for eight marine organism samples (including five fish, one lobster, one oyster, and one algae) with a relative standard deviation (RSD, n = 3) < 3.0%. The proposed method could be applied measurements of Be in various marine organisms.
Microcrystalline naphthalene extraction has been used for the preconcentration of p-benzoquinone and tetrachloro-p-benzoquinone (chloranil), after their reaction by aniline, and later simultaneous spectrophotometric analysis by genetic algorithm-partial least squares (GA-PLS) calibration. The chemical variables affecting the analytical performance of the methodology were studied and optimized. Under the optimum conditions i.e., [aniline] = 0.05 M and [naphthalene] = 2.2% (w/v), preconcentration of 25 ml of sample solution permitted the detection of 0.32 and 0.23 µg ml-1 for p-benzoquinone and chloranil, respectively. The predictive abilities of partial least squares regression (PLS) and genetic algorithm-partial least squares regression (GA-PLS) were examined for simultaneous determination of two quinones. The GA-PLS shows superiority over other PLS methods due to the wavelength selection in PLS calibration using a genetic algorithm without loss of prediction capacity, provides useful information about the chemical system.
A simple spectrophotometric method for the determination of propoxur, a widely used insecticide, in various environmental samples and pesticide formulations is described. The method is based on the coupling of the hydrolysis product of propoxur with diazotized 3-aminopyridine in an alkaline medium, to form an azo-dye which has a maximum absorbance at 463 nm. Beer’s law is obeyed over the concentration range of 0.05 to 1.2 µg ml-1 of propoxur. The molar absorptivity and Sandell’s sensitivity are found to be 3.10 × 104 l mol-1 cm-1 and 0.007 µg cm-2, respectively. The important analytical parameters and optimum reaction conditions were evaluated. The method is free from the interference of other commonly used pesticides and inorganic metal ions.
The H-point standard addition method (HPSAM), based on spectrophotometric measurements for simultaneous determination of beryllium and aluminium, is described. This method is based on the difference between their rates of reactions with Chrome Azurol S (CAS) in cetyltrimethylammonium bromide (CTAB) micellar media. The results showed that beryllium and aluminium could be determined simultaneously in the ranges of 10 - 200 and 10 - 300 ng mL-1, respectively. Under working conditions, the proposed method was successfully applied to the simultaneous determination of beryllium and aluminium in environmental, geochemical and alloy samples.
A novel atomic emission spectrometry comprising laser ablation as a sampling source and hollow cathode plasma for the excitation of ablated sample atoms is proposed. In this arrangement, a conventional Grimm-type discharge lamp is employed, but the polarity of the power supply is reversed so that the cylindrical hollow tube acts as a cathode and the glow discharge plasma is produced within this tube. A laser is irradiated to introduce sample atoms into the discharge plasma. Ablated atoms are excited by collisions with electrons and gas species, and emit characteristic radiation upon de-excitation. The experiments were conducted only in an atmosphere of helium gas so as to avoid a rapid erosion of the cathode hollow tube. Phase-sensitive detection with a lock-in amplifier was utilized to reject the continuous background emission of the plasma gas and emissions of sputtered atoms from the tube material. The unique feature of this technique is that the sampling and excitation processes can be controlled independently. The proposed technique was employed for the determination of Cr, Mn, and Ni in low-alloyed steel samples. The obtained concentrations are in good agreement with the reported values. The relative standard deviation (RSD), a measure of the analytical precision, was estimated to be 2 - 9% for Cr, 3 - 4% for Mn, and 4 - 11% for Ni determination.
An interconnecting technique, the “DMS connection method”, for quartz microchips in a high-pressure system is presented. The connection between quartz microchips is an essential technology for modular microfluidic devices, such as microchip-HPLC. PDMS was applied to the seal material, being spread on the seal side of the chips, and set into the metal housing. The characteristics of the PDMS connection method concerning pressure resistance and the extension of the peak were examined. The experimental results showed a good seal at 5 MPa, which seem to be sufficient for realizing microchip-HPLC utilizing a monolithic silica capillary column as a separation medium. The influence of the extra column effect on chromatographic separation was almost the same as in the case using a commercial union fitting. In addition, the PDMS connection enabled the detachability of chip-based modules with user-friendliness. Our experimental findings suggest that the novel PDMS connection method can possibly be applied as a generic technology in high-pressure µTAS.
A novel polymer modified electrode is discussed in this paper. This resulting electrode can catalyze remarkably toward the electrochemical oxidations of dopamine (DA) and ascorbic acid (AA). Moreover, it can clearly discriminate the electrochemical oxidations of DA from that of AA based on their semi-derivative voltammograms. Hence, a simultaneous determination of DA and AA based on semi-derivative voltammetry at a poly(toluidine blue) modified electrode is suggested. The detection linear range for DA is 0.4 µmol L-1 - 1.5 mmol L-1, and AA 0.2 µmol L-1 - 2.4 mmol L-1, respectively. The resulting modified electrode was tentatively used to determine DA and AA in brain tissue.
We characterized three Japanese firefly species (Luciola lateralis, Luciola cruciata, and Lucidina biplagiata) and three North American firefly species (Lucidota atra, Photuris lucicrescens, and Photuris cinctipennis) based on their surface hydrocarbons. The analysis of firefly extracts by gas chromatography-mass spectrometry (GC-MS) revealed clear differences in the chromatographic profiles and mass spectra. Each firefly could be distinguished by its GC-MS profile. A major difference was observed between Japanese fireflies and North American fireflies. Among the North American fireflies, non-luminous fireflies, Lucidota atra, showed much more complicated GC-MS profile than those of luminous fireflies, Photuris lucicrescens and Photuris cinctipennis.
A separation and preconcentration method has been developed for traces of heavy metals using coagulation of colloidal silica. An appropriate amount of colloidal silica was added to a sample solution, the pH was adjusted to 11 with tetramethylammonium hydroxide solution and calcium chloride solution was then added to coagulate the silica. The coagulated silica and solution were separated by centrifugation, and the silica was then treated with hydrofluoric and perchloric acids. The residue was taken up in dilute nitric acid and subjected to ICP-AES to determine manganese, cobalt, zinc and cadmium. The proposed method was successfully applied to analysis of river-water.
This paper reports on solvent-extraction studies of Ni(II) from sulfate solutions with LIX 84I (2-hydroxy-5-nonylacetophenoneoxime) as the extractant. The extraction of metal depends on the equilibrium pH of the aqueous phase and the extractant concentration. The transfer of metal follows a cation exchange-type mechanism: Ni2+ + 2HA → NiA2 + 2H+. Extraction varies with the nature of the diluents. Temperature has no effect on the extraction of metal. The extraction behavior of associated metals clearly demonstrates the application of LIX 84I as the extractant for the separation of Cu(II), Ni(II) and Zn(II). Based on the results, a flow sheet of the process was developed.
This paper describes the methodological optimization and validation of a simple micellar electrokinetic chromatography for the rapid simultaneous separation of 2-methyl-4-isothiazolin-3-one, methylparaben, ethylparaben, propylparaben, and butylparaben. By using a 30 mM phosphate buffer (pH 7.2) containing 30 mM sodium dodecyl sulfate (SDS), an applied voltage of 10 kV and a separation temperature of 40°C, a quantitative determination was achieved, resulting in an analysis time of approximately 4 min. Only dilution and filtration are needed before analysis. The parameters for validation, such as linear ranges, detection limits, accuracy, and precision, are also reported.
A simple and rapid normal-phase liquid-chromatographic method for the separation and determination of diastereomers of λ-cyhalothrin using a CN column and detection at UV-230 nm has been developed. This method has the advantage of totally resolving each of the diastereomers from impurities, such as meta-phenoxy benzaldehyde, cyhalothric acid and cyhalothric acid chloride, of technical and formulated materials, allowing one to monitor the low-temperature conversion of diastereomers of λ-cyhalothrin for process development.
A new catalytic spectrophotometric method is reported for the simultaneous determination of nitrite and nitrate by flow injection analysis, based on the catalytic effect of nitrite on the redox reaction between pyrogallolsulfonephthalein and potassium bromate in acidic media. Nitrate can also be on-line reduced to nitrite with a modified copper-coated cadmium reduction column. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of pyrogallolsulfonephthalein at 465 nm. Various analytical parameters such as effects of acidity, reagent concentrations, flow rates, sample sizes, lengths of the reaction coil and temperatures were studied and were optimized. Under the optimized conditions, the calibration graph was linear for 2.4 to 160 ng ml-1 of nitrite and 4.0 to 100 ng ml-1 of nitrate. The influences of potential interfering cations and anions for nitrite and nitrate determination were studied. The method is successfully applied for food and water samples. Up to ten samples can be analyzed per hour.
The analytical performance of pyrolytic and non-pyrolytic boron nitride (PBN and NBN) platforms, attached to a commercially available graphite tube furnace, in electrothermal atomic absorption spectrometry (ETAAS) for Cd was studied. Although the tolerable pyrolysis temperature was 300°C with the conventional pyrolytic graphite platform, it increased to 600 and 950°C with the PBN and NBN platforms, respectively. The lifetime of the ceramic platform was 500 firings. The NBN platform provided an enhanced sensitivity with a better reproducibility than others. Using the NBN platform allowed the LOD, based on the variability of the blank (3 σ), to be 0.1 µg l-1 within a seawater matrix (20000 mg NaCl l-1) and a constant sensitivity in the range 0 - 30000 mg NaCl l-1. Good recovery in the range of 90 - 105% was observed for Cd (2.0 µg l-1) spiked into sea, estuarine and river water samples using the recommended procedure. This work proposes that using the NBN platform allows the direct monitoring and control of contaminated water for Cd by ETAAS without any chemical modification.
The reaction of NO2 and NaOH aqueous solution at room temperature was studied for elucidating the behavior of gaseous NO2 in an alkaline solution. Experimental runs related to NO2 absorption have been carried out in various pH solutions. The nitrite and nitrate ions formed in these absorption solutions were quantitatively analyzed. In the case of pH 5 - 12, both of the nitrite and nitrate ions were formed simultaneously. On the other hand, only the nitrite ion was formed when the pH of the absorption solution was higher than 13. In this paper, a new reaction mechanism was proposed to explain the selective formation of nitrite ion in the 10 M alkaline solution. In order to confirm the new reaction mechanism, H218O was used as part of the absorption solution for detecting oxygen gas production. The amounts of reaction products: 18O18O, 18O16O and 16O16O, were quantitatively determined. It was confirmed that the new reaction proceeds mainly in the 10 M alkaline solution.