A direct and rapid metabolic analysis of a live single cell was performed by live single-cell video-mass spectrometry. The contents of the cytoplasm and a granule were sucked into a nano-electrospray ionization (nano-ESI) tip, and were directly introduced into a Q-TOF mass spectrometer by nano-spray after the addition of an ionization solvent. The metabolic pathways and the locations of tryptophan and histidine metabolites were traced by this method for a cultured rat basophil leukemia cell line (RBL-2H3). The t-values of detected peaks by a t-test between the different location, e.g. cytoplasm and a granule, revealed the molecular localization of each MS peak. A direct and quick metabolomic analysis of a living cell under simultaneous video-microscopic observations was innovated.
The drift in sensitivity due to carbon deposition on the sampling cone, skimmer cone and ion lenses has been a serious problem in gas chromatography/inductively coupled plasma mass spectrometry (GC/ICP-MS). To overcome this problem, a high-speed switching method between a mixed-gas plasma and a pure-argon plasma (named plasma gas-switching method) using an oxygen permeation tube and a switching valve was developed. This enabled both the cleaning of deposited carbon and an enhancement of the sensitivity; as a consequence, both the repeatability and the sensitivity of polybrominated diphenylether (PBDE) were improved by more than 3 and 4 times, respectively. The drifts of sensitivity over a period of 8 h were less than 5% in most cases. Concerning the analytical performance of thermally labile congeners from octa- to deca-BDE, the detection limits, dynamic ranges of the calibration graphs and unequivalent sensitivities were remarkably improved by using a metal capillary separation column coated with a very thin (0.05 µmm) film of immobilized-polydimethylsiloxane. The detection limits ranged from 0.014 pg (BDE-154) to 0.093 pg (BDE-209), which were equal or superior to the lowest values reported hitherto by GC/MS (high resolution). A remarkable loss of sensitivity for highly-brominated congeners, such as nona- and deca-BDE, was observed in an analysis of PBDE technical mixtures when the solvent was methanol. The loss of sensitivity turned out to be due to an activation of the retention gap used for on-column injection; this problem was solved by changing methanol to isooctane in the sample-preparation step before analysis.
A sample-pretreatment method using a chitosan-based chelating resin, ethylenediamine-N,N,N′-triacetate-type chitosan (EDTriA-type chitosan), was developed for the preconcentration of trace metals in seawater and separation of the seawater matrix prior to their determination by inductively coupled plasma-mass spectrometry (ICP-MS). The resin showed very good adsorption for transition metals and rare-earth elements without any interference from alkali and alkaline-earth metals in an acidic media. In the proposed method, an aliquot of a 50-mL sample at pH 4 was used. Metals adsorbed on the resin were eluted using 10 mL of 1 M nitric and measured by ICP-MS. The method was evaluated by the analysis of NASS-5 seawater reference materials for trace metals. Good agreement was obtained for most metals, which indicates that by the proposed pretreatment using the synthesized resin, seawater samples can be favorably measured by ICP-MS.
The distribution of lead (Pb) accumulated in the pteridophyte Blechnum niponicum, a Pb-hyperaccumulator, was measured using synchrotron-radiation micro X-ray fluorescence (SR-µ-XRF) at BL37XU of SPring-8. From two-dimensional (2D) imagings of Pb at the root, petiole, leaf vein, pinna epidermis and sorus in the Blechnum niponicum, the mechanism for the transportation and accumulation of Pb can be suggested to be as follows: Lead is accumulated in conductive tissues. Most of the Pb solubilized in the rhizosphere is fixed in the conductive tissue, with the remainder being transported with the transpiration stream to the above-ground parts of the plant. Lead transported to the upper parts of the plant ultimately remains at the terminal points of the transpiration stream, including the stomatal apparatus and water pores; it was shown that these sections contain high concentrations of Pb.
The colloid osmotic nature of the cell lysis can be prevented by adding osmotic protectants of appropriate sizes to the outer medium. We introduced inorganic and organic electrolytes as protectants to determine the precise channel sizes of the polyene antibiotics, amphotericin B and nystatin, in addition to the sugars so far widely used for this purpose. Because colloid osmotic cell lysis is evidenced by the loss of membrane permeability barriers for small sizes of ions, such as K+, preceding hemolysis, we firstly simultaneously monitored the time response of the K+ efflux and hemolysis induced by amphotericin B by combining a fiber-optic spectrometer with a K+-selective electrode. Based on this experiment, we evaluated the sizes of channels of the polyene antibiotics formed in the erythrocyte membrane using the radii of hydrated ions calculated from a modified Stokes' law, as well as the radii of sugars. The radii of channels formed by amphotericin B and nystatin were found to be in a very narrow range of 0.36 - 0.37 nm. Similar experiments were performed using calcein-loaded liposomes containing cholesterol or ergosterol, and the radii of channels formed in these liposomal membranes were also found to be the same as when formed in an erythrocyte membrane. The present results demonstrated that introducing the sizes of hydrated ions can afford a more precise channel size than the use of sugars alone.
Antioxidant activity was analyzed using the liposomal membrane system for lipid peroxidation. Diphenyl-1-pyrenylphosphine incorporated into lipid-bilayer liposomes, which were prepared with unsaturated phospholipids and cholesterol, was converted to the corresponding fluorescent phosphine oxide by the reaction with lipid hydroperoxides. Under the optimal conditions, the liposomes were pretreated with tested compounds. Thereafter, they were reacted with oxidants: 1 - 50 µM peroxynitrite, 1.0 mM hydrogen peroxide or 0.4 mM t-butylhydroperoxide, followed by fluorometric analysis. The antioxidant activity was determined by comparing the obtained fluorescence intensities with controls. The proposed method was successfully applicable to various anesthetics (10 and 100 µM for each) and reference antioxidants: α-tocopherol (1.0 and 2.5 µM), quercetin (1.0 and 5.0 µM) and (-)-epigallocatechin-3-gallate (1.0 and 5.0 µM) with intraand inter-assay C.V.s of 0.2 - 7.0%. In analyses of general and local anesthetics, propofol was the most active, and showed a concentration of 6.8 µM to produce 50% inhibition against the peroxynitrite-induced lipid peroxidation of cell model membranes, supporting its potential benefit in clinical use.
A kind of novel nanocomposites, poly(3-methylthiophene) (P3MT)/gold nanoparticles (AuNPs), were successfully deposited onto the surface of a glassy carbon electrode. A field emission scanning electron microscope (FE-SEM) and electrochemical techniques were used for characterizing this modified electrode. The results showed that the AuNPs were inserted into a P3MT layer uniformly, and formed a porous 3D structure. This modified electrode showed excellent electrocatalytic activity towards the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA); the overlapping anodic peaks of AA, DA and UA were completely divided into three well-defined voltammetric peaks. A further study showed that there existed a linear relationship between the peak current and the concentration of DA in the range of 1.0 × 10-6 to 3.5 × 10-5 mol L-1, and UA in the range of 1.0 × 10-6 to 3.2 × 10-5 mol L-1. The detection limits were 2.4 × 10-7 mol L-1 for DA and 1.7 × 10-7 mol L-1 for UA. This proposed method was applied to the detection of real samples, and the results were satisfactory.
An electroanalytical study for the amperometric determination of ascorbic acid (AA) in a human urine sample at a bare glassy carbon electrode using the CPC (cetylpyridinium chloride) surfactant is described. Under the optimized conditions of Epa, Ipa, CPC concentration and pH, the oxidation peak potential of the AA shifts towards a less positive potential, and the peak current increase in a significant way in the presence of the surfactant. Under the best conditions, the method provided a linear calibration curve to AA in a 0.1 mol L-1 phosphate buffer solution (pH 7.0) in the concentration range from 5.0 × 10-7 up to 4.3 × 10-4 mol L-1, with a detection limit of 2.0 × 10-7 mol L-1 and a high correlation coefficient (r = 0.9996). The recovery test presented values of 98 - 105%, suggesting a great potential of the proposed method for AA determination in complex samples, such as urine.
The redox potentials of cobalt and iron complexes with ten pyridylazo compounds, E0ML2 (ML2+/0; M: CoIII/II, FeIII/II; L-: pyridylazo compounds), have been determined in order to explore the difference in their reversed-phase HPLC behavior. The redox potentials of Co complexes were in the range of -0.62 - 0.03 V, while those of Fe complexes were -0.06 - 0.59 V relative to 0.20 V for ferricinium/ferrocene. The redox potentials of both the Co and Fe complexes were linearly correlated to the basicities of the ligands. The correlation was quantitatively explained by a difference in dependence of the stabilities of MIII and MII complexes on the ligand basicities. The complex of [CoIIIL2]+ or [FeIIL2] with any compound injected in the reversed-phase HPLC system was detected without any change in the composition. When [CoIIL2] was injected, only those complexes having the highest potentials of E0CoL2 ≅ 0.0 V were detected as [CoIIL2], while other complexes having lower potentials gave a peak of [CoIIIL2]+. When [FeIIIL2]+ was injected, only complexes having the lowest potentials of E0FeL2 ≅ 0.0 V were detected as [FeIIIL2]+, while others having higher potentials gave a peak of [FeIIL2].
The objective of the presented research was to examine the potential of capillary electrophoresis (CE) for the analysis of structurally different reactive dyestuffs, their activation and posterior hydrolysis, with special focus on optimization of the working conditions. Preliminary, the effect of various additives to the background electrolyte on the resolution improvements versus migration time of Reactive Black 5 as a model dyestuff was investigated. Based on these results, the electropherograms of eight commercially interesting reactive dyestuffs of various chemical structures and their converted forms upon alkaline pH were carried-out. In order to examine the behavior of the reactive dyestuff during the dyeing process, the dye-bath absorbance was monitored throughout the Reactive Black 5 exhaustion, and the conversion of the dye's form was highlighted using the CE technique. The obtained results unequivocally prove that CE could offer a fast and efficient detection method of structurally different reactive dyestuffs, as well as their hydrolysis products in the dye-baths and effluents later on.
An environmentally friendly reversed-phase HPLC method for simultaneous determination of creatinine and uric acid in human urine samples has been developed. Human urine samples were pretreated by dilution, protein precipitation, centrifugation and filtration, followed by HPLC separations using a reversed-phase C18 column with an aqueous mobile phase of phosphate buffer. The retention loss of a C18 column when using the highly aqueous mobile phases was avoided by employing a gradient elution using a small volume (<0.23 mL) of acetonitrile and phosphate buffer at pH 4.75. This developed method provides a simple, rapid separation and sensitive detection for the species of interest in 10 min with UV detection at 205 nm. Quantitation was carried out by relating the peak areas of the identified compounds to that of hypoxanthine as an internal standard. The detection limits for creatinine and uric acid were 0.045 and 0.062 µg mL-1, respectively. The recoveries of the standards added to urine samples were 87.3 - 102.2% for creatinine and 97.3 - 108.6% for uric acid, and the relative standard deviation for both analytes was less than 1.0%. This method has been successfully applied to estimating of creatinine and uric acid in human urine.
The proposed approach relies on successive dilution of a solution containing a sample with standard addition and on titration of the solutions obtained until receiving a signal lower than the signal measured for the sample alone. Equations are derived for subsequent dilution factors for the automatic flow injection system applied. The overall calibration strategy including the possibility of prediction of the number of required standard solutions and of positioning the sample signal within the calibration range is presented. The method has been tested on the spectrophotometric determination of hydrochloric acid at two concentration levels (0.193 and 1.21 mol L-1) with sodium hydroxide as titrant. The results of accuracy better than |3.9|% (RE) and repeatability better than 1.3% (RSD) were obtained. The method has been applied to the determination of total acidity in vinegars and soft drinks. The average time necessary to analyze one sample is about 10 min.
An automated hydrodynamic sequential injection (HSI) system with spectrophotometric detection was developed. Thanks to the hydrodynamic injection principle, simple devices can be used for introducing reproducible microliter volumes of both sample and reagent into the flow channel to form stacked zones in a similar fashion to those in a sequential injection system. The zones were then pushed to the detector and a peak profile was recorded. The determination of nitrite and nitrate in water samples by employing the Griess reaction was chosen as a model. Calibration graphs with linearity in the range of 0.7 - 40 μM were obtained for both nitrite and nitrate. Detection limits were found to be 0.3 μM NO2- and 0.4 μM NO3-, respectively, with a sample throughput of 20 h-1 for consecutive determination of both the species. The developed system was successfully applied to the analysis of water samples, employing simple and cost-effective instrumentation and offering higher degrees of automation and low chemical consumption.
Different natural water samples were investigated to determine the total concentration and the distribution of species for Cu(II), Pb(II), Al(III) and U(VI). The proposed method, named resin titration (RT), was developed in our laboratory to investigate the distribution of species for metal ions in complex matrices. It is a competition method, in which a complexing resin competes with natural ligands present in the sample to combine with the metal ions. In the present paper, river, estuarine and seawater samples, collected during a cruise in Adriatic Sea, were investigated. For each sample, two RTs were performed, using different complexing resins: the iminodiacetic Chelex 100 and the carboxylic Amberlite CG50. In this way, it was possible to detect different class of ligands. Satisfactory results have been obtained and are commented on critically. They were summarized by principal component analysis (PCA) and the correlations with physicochemical parameters allowed one to follow the evolution of the metals along the considered transect. It should be pointed out that, according to our findings, the ligands responsible for metal ions complexation are not the major components of the water system, since they form considerably weaker complexes.
Polycyclic aromatic hydrocarbons (PAHs) represent health and environmental concerns. The present study was designed to develop a highly sensitive and reliable immunochemically-based non-instrumental field assay to monitor the presence of benzo[a]pyrene (BAP) in aqueous samples at the ppt-level using visible test evaluation. The corresponding gel-based immunoassay was set up to combine preconcentration and detection of the target analyte using anti-PAH antibodies and horseradish-BAP tracer conjugate in one single cartridge. Water sample preparation, such as extraction, centrifugation, or filtering was found to be unnecessary. No interference by higher water-soluble PAHs at 4000-fold excess compared to BAP was observed. The assay was configured as a qualitative test (positive/negative) at the cut-off level of 5 ng L-1, however, this level can be adapted to the required analyte concentration by rather simple adjustment of the anti-PAH antibody concentration of the test zone. Test validation was performed with real samples such as surface water, melted snow, and tap water using high performance liquid chromatography with fluorescent detection (HPLC-FLD) with solid phase extraction for validation.
The detection of an antibody against nucleoprotein (NP) of the avian influenza virus (AIV) was attempted by an electrochemical immunoassay by combining a secondary antibody-alkaline phosphatase conjugate and 4-aminophenylphosphate. Released 4-aminophenol was quantitated electrochemically, and the current derived from oxidation of the hydrolysis product increased linearly over a wide primary antibody concentration range (10 - 1000 ng/ml). The detection limit of this electrochemical immunoassay for the antibody against the NP of AIV was found to be 10 ng/ml.
As a tool for micrometer-level size determination, fluorescence correlation spectroscopy (FCS), performed based on our previous report, was compared to flow cytometry (FCM). For this purpose, standard fluorescent beads were subjected to both methods. And hence, it was found that our FCS is a useful method with satisfactory precision for size determinations of individual particles at micrometer size levels, while providing the average size for a mixture of two kinds of particles with different sizes.
A simple and highly sensitive HPLC for the determination of N-ethylglycine in urine was developed. The labeling reaction of N-ethylglycine with 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride was carried out at 70°C for 15 min at pH 9.0. The fluorescent derivative was separated on a reversed-phase column and detected at excitation and emission wavelengths of 320 and 400 nm, respectively. The detection limit of N-ethylglycine was 15 fmol (S/N = 3). The recovery of N-ethylglycine added to urine was 101.9%. The concentration of N-ethylglycine in urine of cancer patients with metastatic bone disease was 11.3 ± 22.0 nmol/mg creatinine, and that of normal subject was 0.4 ± 0.4 nmol/mg creatinine.
Uniformity recognition sites for water-soluble ionic compounds were constructed onto the pores of porous polymer particles. This concept is based on a modified interval immobilization technique, which was used for the selective recognition of paralytic shellfish poison, saxitoxins (STXs). The results of batch adsorption and solid-phase extraction for one of the STX analogues, a prepared polymer that had special sites for the recognition of STXs, showed that the analogue could selectively recognize and concentrate STXs. Selective recognition was facilitated by interval-immobilized functional groups.
Solid-phase extraction (SPE) of gallium(III) with hydrophobic 8-quinolinol derivatives (HQs)-impregnated resin from aqueous acidic and alkaline solutions has been investigated. The HQs used were 7-(4-ethyl-1-methyloctyl)-8-quinolinol (HEMOQ), 5-octyloxymethyl-8-quinolinol (HO8Q), 2-methyl-5-octyloxymethyl-8-quinolinol (HMO8Q), 5-dioctylaminomethyl-8-quinolinol (HN8Q), 7-bromo-5-octyloxymethyl-8-quinolinol (HBrO8Q), and 5-(2-ethylhexyloxymethyl)-8-quinolinol (HOEHQ). Various factors affecting the SPE, such as the substituents of the HQs, HCl and NaOH concentrations in the aqueous phase, the HQ concentration in the resin, and the equilibration time were clarified. The extractability for gallium(III) from the aqueous solution became higher in the following order: HBrO8Q < HEMOQ < HO8Q < HN8Q < HMO8Q at 3 mol l-1 HCl; HMO8Q < HO8Q < HOEHQ < HEMOQ < HN8Q < HBrO8Q at pH 0.4; HMO8Q < HO8Q ≈ HOEHQ < HN8Q < HEMOQ at 3 mol l-1 NaOH.
A useful method to separate/concentrate lanthanoids was developed based on a rapid coprecipitation technique using yttrium phosphate. Lanthanoids, which were quantitatively coprecipitated at pH 3 with yttrium phosphate, could be readily determined by inductively coupled plasma atomic emission spectrometry with indium used as an internal standard element. The detection limits ranged from 0.0003 μg (Yb, Lu) to 0.0099 μg (Er) in 100 mL of sample solutions. The proposed method was applicable to the separation/concentration of lanthanoids in NIST SRM 1515 (apple leaves).