We proposed to combine an ultra-micro flow analysis instrument using the fused-silica capillary and the CL detector. The CL reaction of luminol and hydrogen peroxide was adopted and the batch-type CL detection cell was used. Luminol and isoluminol-labeled protein as a model were sensitively and reproducibly detected with very small amounts of quantitative reagents. The analyses were repeated at least 100 times without any treatments such as washing capillaries or exchanging the hydrogen peroxide solution. The present system successfully promoted the miniaturization, simplification, and sensitization of the analytical system.
A brief overview of the applications of time-of-flight mass spectrometry (TOF-MS) for analytical purposes is presented. The performance of TOF-MS combined with an inductively coupled plasma (ICP) ion source is discussed in detail. The advantages of TOF-MS detectors over the quadrupole mass filters for multi-elemental analysis of fast transient signals are discussed. The applications of ICP-TOF-MS for the detection of signals from laser ablation, electrothermal vaporization, gas and liquid chromatography, capillary electrophoresis and flow-injection analysis are reviewed.
A new sensor constructed by a platinum electrode coated with a non-plasticized poly(acrylamide) polymer (PAA) film coupled with phthalocyaninato tin(II) ([Sn(II)(pc)]) was developed. The potentiometric response behavior of this PAA- [Sn(II)(pc)] electrode for such anions as CN-, F-, Cl-, and Br- in dimethylacetamide and acetonitrile were investigated. The electrode showed a Nernstian response to CN- and F- and a quite poor response to Cl- and Br-. The mechanism of the peculiar selective response was studied by cyclic voltammetric and spectrophotometric methods. The voltammetric investigation suggested that the charge of the host compound in the sensor membrane had no effect on the potential response of the electrode. It was also found by a spectrophotometric investigation that the complexing of [Sn(II)(pc)] with CN- and F- lead to the selective response of the electrode. The motive force of the complexing was considered to be a ligand exchange of CN- or F- with molecules at the axial site of [Sn(II)(pc)] due to solvent effects to the interest anions.
Poly(vinyl chloride) (PVC) based membranes of zinc-phthalocyanine (ZPC) with hexadecyltrimethylammonium bromide (HTAB) as a cation excluder, and dibutyl phthalate (DBP) and benzyl acetate (BA) as plasticizing solvent mediators were prepared and investigated as a SO42- selective electrode. The best performance was observed with a membrane having a composition of ZPC-PVC-HTAB-BA in a ratio of 5%:32%:3%:60%, which works well over a wide concentration range (1.0 × 10-2 - 1.0 × 10-6 M) with a Nernstian slope of -29.2 mV per decade of activity, between the pH values of 2.0 to 7.0. This sensor shows a very fast response time of 10 s, and can be used over a period of 2 months with good reproducibility. The proposed sensor displays excellent selectivity for SO42- over a large number of common inorganic anions. The sensor has been successfully applied for the direct and indirect determination of sulfate and zinc in zinc sulfate tablets, respectively. It was also used as an indicator electrode in the potentiometric titration of sulfate ions with barium ions.
Chlorophyll (Chl) a′, the C132-epimer of Chl a, is one of the two Chl molecules constituting the primary electron donor (P700) of photosystem (PS) I of a thermophilic cyanobacterium Synechococcus elongatus. To examine whether PS I of other oxygenic photosynthetic organisms in general contain one Chl a′ molecule in P700, the pigment composition of thylakoid membranes and PS I preparations isolated from red algae Porphyridium purpureum and Cyanidium caldarium was examined by reversed-phase HPLC with particular attention to Chl a′ and phylloquinone (PhQ), the secondary electron acceptor of PS I. The two red algae contained one Chl a′ molecule at the core part of PS I. In PS I of C. caldarium, two menaquinone-4 (MQ-4) molecules were detected in place of PhQ used by higher plants and cyanobacteria. The 1:2:1 stoichiometry among Chl a′, PhQ (MQ-4) and P700 in PS I of the red algae indicates that one Chl a′ molecule universally exists in PS I of oxygenic photosynthetic organisms, and two MQ-4 molecules are associated with PS I of C. caldarium.
A simple and rapid high-performance liquid chromatographic method for the separation and determination of process-related impurities of sildenafil was developed. The separation was achieved on a reversed-phase C18 column using acetonitrile-0.05 M potassium dihydrogen orthophosphate (70:30 v/v) as a mobile solvent at a flow rate of 1.0 ml/min and UV detection at 230 nm. The method was used not only for quality assurance, but also for monitoring the chemical reactions during the synthesis of sildenafil. It was found to be specific, precise and reliable for the determination of all process-related impurities of sildenafil in bulk drugs and formulations.
Phytochemical investigation of the aerial parts of three Baccharis species (Asteraceae family) was performed using HPLC and chemometric methods, with the objective of distinguishing between three morphologically very similar species: Baccharis genistelloides Persoon var. trimera (Less.) DC, B. milleflora (Less.) DC and B. articulata (Lam.) Persoon. With the help of Principal Component Analysis (PCA) and variance weights, it was possible to characterize the chromatographic profiles of the alcoholic extracts of the three species. Application of Soft Independent Modeling of Class Analogy (SIMCA) and K-Nearest Neighbor (KNN) methods on a training set of 74 extracts resulted in models that correctly classified all eight samples in an independent test set.
We developed an FIA system equipped with a chemiluminescence detector using a mixed chemiluminescence reagent of luminol and 1,10-phenanthroline for the detection of metal ions and metal complexes. The carrier, mixed chemiluminescence reagent comprising luminol, 1,10-phenanthroline, and cethyltrimethylammonium bromide, and H2O2 solutions were fed by corresponding pumps at a definite flow rate. Sample solutions dissolving hematin, [Co(NH3)4(H2O)2]2(SO4)3, CuSO4, NiCl2, K3[Fe(CN)6], and K4[Fe(CN)6] were analyzed as models by the means of the present FIA system. Solutions of hematin, [Co(NH3)4(H2O)2]2(SO4)3, CuSO4, and NiCl2 were detected as positive peaks, as usual. The order of the catalytic activity of these samples for the present chemiluminescence reaction using the mixed chemiluminescence reagent was [Co(NH3)4(H2O)2]2(SO4)3 > hematin > CuSO4 > NiCl2. On the other hand, sample solutions of K3[Fe(CN)6] and K4[Fe(CN)6] were detected as negative peaks and were determined over the ranges of 1 × 10-8 - 1 × 10-6 M with a detection limit of 1 × 10-8 M and 2 × 10-8 - 4 × 10-6 M with a detection limit of 2 × 10-8 M, respectively. Their negative peaks were observed reproducibly with a relative standard deviation of 2 - 5%.
A four-channel absorbance detector was developed for simplifying the flow-injection analysis (FIA). This detector used four light-emitting-diodes (LEDs) as light sources; their wavelengths were 470, 495, 590 and 635 nm, respectively. Their amplitudes were modulated electronically with different frequencies. The light emissions from them were merged by plastic-core fiber optics, and were detected by a photo-diode (PD). The mixed signal was then sent to and discriminated by a four-channel lock-in amplifier corresponding to each modulation frequency. Neither a monochromator nor an optical filter was used. This detector was conveniently applied to the determination of iron in river water by FIA using 1,10-phenanthroline. Though a noisy peristaltic pump was used to propel the solutions, practical precision and accuracy were obtained by means of on-line dual-wavelength measurements and off-line moving average calculations.
Two flow methods for the enzymatic determination of pyrophosphate are described that are used to diminish the consumption of reagents. One method is based on the use of an open-close circuit with manual injection using a syringe. The other is a sequential injection method. The analytical features of both methods are: a linear range of 0.4 - 20 mg L-1, an LOD of 0.38 mg L-1, and a CV of 2.0% for the sequential injection method, and a linear range of 0.3 - 15 mg L-1, an LOD of 0.29 mg L-1, and CV of 2.2% for the open-close circuit method. The methods were applied to the determination of pyrophosphate in urine. The pyrophosphate concentration determined in urine samples varied from 1.26 to 6.67 mg L-1.
A simple and fast flow-injection spectrophotometric method has been described for the determination of iron(III). The method is based on the measurement of absorbance intensity of the complex that is formed between iron(III) and N,N-dimethylformamide (DMF) at 310 nm. The carrier stream was just a mixture of water and DMF at ratio 5% (v/v). The method is highly selective; most of the 30 metal ions and anions tested did not effect on the determination of iron(III) even when present up to 1000-fold excess over iron(III). The calibration graph for iron(III) obtained under optimized conditions were linear in the range 5 - 90 ng ml-1 with a detection limit of 0.1 ng ml-1 for a 20 μl injection volume. The reproducibility was satisfactory, with a relative standard deviation of 2.4% (n = 5) in the range of 5 - 90 ng ml-1 of iron(III). The sampling rate was over 60 h-1. The developed method was succesfully applied to the determination of total iron in river water, seawater, hot spring water and iron alloy samples. The accuracy of the method was evaluated using the standard addition method and checked by the certified reference metal alloy samples.
An improved trilinear decomposition algorithm based on a Lagrange operator (LO) is developed in this paper, which introduces a Lagrange operator and penalty terms in the loss function to improve the performance of the algorithm. Compared to the traditional parallel factor (PARAFAC) algorithm, the algorithm not only may converge much faster, but also overcome the sensibility to estimate the number of components. A set of simulated and measured excitation/emission fluorescence data were treated by both the proposed and traditional PARAFAC algorithm to compare their efficiencies. The analytical results obtained with real chemical system containing aspirin and its metabolic products show that the trilinear decomposition methodology is a promising tool to obtain spectral and composition information from mixtures without chemical separation.
A method was proposed for the simultaneous determination of trace cadmium and mercury by vapor generation nondispersive atomic fluorescence spectrometry using an intermittent flow system. The effects of the parameters on the performance were studied systematically. The parameters such as acid concentration of the reaction medium, flow rate of the carrier gas and shield gas, the observation height and the atomizer temperature, etc. which affected the sensitivity, were optimized. Ascorbic acid, cobalt ion and thiourea were used as enhancement reagents or masking agents to enhance the generation efficiency of the volatile species of Cd and Hg. The mechanisms of their effects on vapor generation were investigated. In the presence of thiourea and ascorbic acid, the influences of some coexisting elements on the determination of cadmium and mercury were investigated. The detection limits (3σ) were 0.010 μg l-1 for Cd and 0.019 μg l-1 for Hg, respectively. The relative standard deviations for Cd and Hg at 1.00 μg l-1 were 2.6% and 0.97% (n = 11), respectively. The proposed method has been satisfactorily applied to the determination of trace cadmium and mercury in Chinese herbal medicine.
An etching technique for the determination of the metallic impurities distribution in silicon wafers has been developed. An area of 10 mmφ and 10 μm depth was etched by 100 μL of an etching solution with a HF and HNO3 mixture. The acid matrix was evaporated on the wafer surface by IR lamp illumination and vacuum exhaust. Metallic impurities remaining on the wafer surface were redissolved into the collection solution, which was measured by electrothermal atomic absorption spectrometry (ET-AAS). The recovery invested by local etching/ET-AAS was within 95-112% for Fe, Cu and Ni. The detection limit (3σ) for Fe, Cu and Ni in silicon was 1×1013 atoms/cm3. To confirm the applicability, local etching was applied to evaluate the effects of metallic impurities in a gettering study and the electronic properties of semiconductor devices. It was found that local etching is a useful sample preparation technique for the analysis of metallic impurities in a specific area on a silicon wafer.
In a weak acid medium, when an isopoly-tungstic acid reacts with berberine to form an ion-association complex, strong resonance Rayleigh scattering (RRS) appears and obvious frequency-doubling scattering (FDS) as well as second-order scattering (SOS) come into being. The scattering peaks are located at 288 and 369 nm for RRS, at 290, 370 and 390 nm for FDS, and at 480, 540 and 740 nm for SOS. Under optimum conditions, all three scattering intensities are directly proportional to the concentration of berberine and can be applied to the determination of berberine. The sensitivity of the RRS method is the highest; the detection limit (3σ) for berberine hydrochloride is 7.6 ng/ml. The method also has good selectivity. It has been applied to the determination of berberine in pharmaceuticals and goldthread extracts with satisfactory results. In the paper, studies of the existing species of isopoly-acid and the component of the ion-association complex are reported and the reasons of enhancement of RRS are discussed.
Cadmium ranging from 1 - 8 ng could be coprecipitated quantitatively with lanthanum phosphate at pH 5 - 6 from up to 200 mL of river water samples spiked with 5 μg of indium as an internal standard. Cadmium and indium coprecipitated were measured by using electrothermal atomic absorption spectrometry. The cadmium content in the original sample solution could be determined by internal standardization with indium. Since complete collection of the precipitate and strict adjustment of the volume of the final solution after coprecipitation are not required in this method, the precipitate could be collected by using decantation and centrifugation, and then dissolved with 1 mL of about 2.4 mol L-1 nitric acid. The proposed method is simple and rapid, and enrichment close to 200-times can be attained; the detection limit (3σ n = 6) was 0.63 ng L-1 in 200 mL of the sample solution.
This article presents a non-invasive, optical technique for measuring particulate flow within microfluidic channels. Confocal fluorescence detection is used to probe single fluorescently labeled microspheres (200-930 nm diameter) passing through a focused laser beam at a variety of flow rates (100-1000 nL/min). Simple statistical methods are subsequently used to investigate the resulting fluorescence bursts and generate single-particle burst width and burst area distributions. Analysis of such distributions demonstrates that the average burst width and burst area decrease as particle size increases. In addition, both burst width and burst area (for a given particle size) are observed to decrease as volumetric flow rate is increased. The dependence of such distributions on particle size is proposed as a potential route to sizing single particles and molecules in microfluidic systems.
For the determination of khellin in urine and serum, fluorometry using HPLC-postcolumn photoirradiation has been developed. Khellin and visnagin of similar structure were separated on a column of Capcell Pak C8. The mobile phase consisted of 40%(v/v) ethanol containing 75 mmol l-1 H2O2. The postcolumn reagent, 70 mmol l-1 KH2PO4-NaOH buffer (pH 12.7) containing 50%(v/v) ethanol, were mixed with the mobile phase, which was irradiated with ultraviolet light to induce fluorescence. The fluorescence was monitored with excitation at 378 nm and emission at 480 nm. The calibration graph for khellin was linear over the range of 65-2620 ng ml-1 using an injection volume of 20 μl. The pretreatment of the urine or serum samples consisted of diluting steps or deproteinizing steps using perchloric acid, respectively.
Gold adsorption by persimmon tannin (PT) gel from a solution containing hydrogen tetrachloroaurate(III) was examined. A flow-rate examination in a column system indicated the reduction of Au(III) ion to Au(0). XRD patterns clarified the existence of Au(0) on the gel which adsorbed gold. The gel could also adsorb colloidal Au(0) prepared independently. A model consisting of ligand exchange, Au(III) reduction to Au(0), and resulting Au(0) adsorption by PT gel was presented for the gold adsorption mechanism.
A 1H-NMR procedure based on an analysis of its data by a multivariate calibration method was conducted for the simultaneous determination of theophylline and caffeine in synthetic and real samples. Partial least squares regression (PLS) was chosen as the calibration method. The methyl signals of theophilline at 3.36 and 3.54 ppm that overlapped with those of caffeine were significant characteristics which were employed in this study for their analyses. The proposed method was successfully applied to recovery studies of theophylline and caffeine from real tablet samples.
In an ESR spin-trapping measurement of hydroxyl radicals formed in a Fenton reaction, the trapping efficiency with DMPO increased by about 300 times in a sodium trifluoroacetate solution, whereas it was little changed in a phosphate buffer.
Crystal structure of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenolatochloropalladium(II) (PdLCl) has been determined by X-ray diffraction. A crystal of PdLCl was constructed by two structural isomers of PdLCl molecules, which were particularly different in the positions of the carbon atoms at the diethylamino group, having cis-like or trans-like conformation for the carbon atoms. The molecules of PdLCl in the crystal were warped by a steric hindrance of the diethylamino group.
C15H16N2S is monoclinic [orthorhombic], P21/c [Pbcn]. Unit-cell dimensions at 293 K are a = 9.506(1), b = 7.629(1), c = 20.077(1)Å, β = 99.93(1)°, V = 1434.2(2)Å3, Dx = 1.187 g/cm3, and Z = 4 [a = 11.806(2), b = 13.954(2), c = 8.466(1)Å, V = 1394.7(3)Å3, Dx = 1.221 g/cm3, and Z = 8]. The R value is 0.049 [0.045] for 1620  observed reflections. The dihedral angle between the tolyl rings is 53.6(1)° [47.9(1)°]. The crystal structures are stabilized by N-H···S hydrogen bonds and van der Waals forces.
The structure of the title complex consists of a [p-C6H4(CH2ImMe)2]2+ and [PtCl6]2-pair. The platinum atom is hexacoordinated by six chloride ions in octahedral coordination geometry. The average Pt-Cl bond distance is 2.3199Å. The imidazolium cation and hexachloroplatinate anion are linked via hydrogen bonds, and the crystal packing is governed by the CH···Cl interactions.
The title compound crystallizes in monoclinic space group P21/c. There are two molecules in the asymmetric unit. While one of these molecules is in a general position, the other is in disordered position. The angle between the directions of the molecules in the asymmetric unit is 87.5(1)°.
In the title compound, C23H32N4Se, was synthesized and its crystal structure was determined by single crystal X-ray diffraction. The compound crystallizes in orthorhombic system, space group Pbca, a = 10.9960(10)Å, b = 14.9460(9)Å, c = 27.565(5)Å and Z = 2. According to X-ray crystallographic studies, the diazepine ring is observed to be in a disordered state. The site-occupancy of the major compenent refined to 0.53(1). The C=Se bond length of 1.862(4)Å is a double bond character. The dihedral angle between the two phenyl rings is 37.7(2)°.