Showing papers in "Analytical Sciences in 2015"

Silicon nanowire biosensor for highly sensitive and multiplexed detection of oral squamous cell carcinoma biomarkers in saliva.

Abstract: Silicon nanowire (SiNW) field-effect transistor (FET) biosensors have already been used as powerful sensors for the direct detection of disease-related biomarkers. However, the multiplexed detection of biomarkers in real samples is still challenging. Interleukin 8 (IL-8) and tumor necrosis factor α (TNF-α) are two typical biomarkers of oral squamous cell carcinoma (OSCC). In this study, we developed a multiplexed detection methodology for IL-8 and TNF-α detection in saliva using SiNW FET biosensors. We fabricated the SiNW FET sensors using a top-down lithography fabrication technique. Subsequently, we achieved the multiplexed detection of two biomarkers in saliva by specific recognition of the two biomarkers with their corresponding antibodies, which were modified on the SiNW. The established method was found to have a limit of detection as low as 10 fg/mL in 1 × PBS as well as 100 fg/mL in artificial saliva. Because of its advantages, including label-free and multiplexed detection, non-invasive analysis, highly sensitive and specific determination, the proposed method is expected to be widely used for the early diagnosis of OSCC.

Direct Lipido-Metabolomics of Single Floating Cells for Analysis of Circulating Tumor Cells by Live Single-cell Mass Spectrometry.

Abstract: Direct trapping of a single floating cell, i.e. a white blood cell from a drop of blood, within a nanospray tip was followed by super-sonication after the addition of ionization solvent. Molecular detection of an increased number of peaks with a higher intensity and a wider m/z range, which extends from metabolites to lipids, was acquired than of that without sonication. This method was applied to a few separated circulating tumor cells (CTC) from a neuroblastoma patient's blood to obtain their lipido-metabolomic molecular profile at the single cell level. In addition to vital molecules such as amino acids, catechol amine metabolites, which are specific to neuroblastoma, and drugs included in the patient's course of therapy were detected. This established "direct single-cell lipido-metabolomic method" seems to be useful for direct and wide range molecular detection not only for many live single-cells, but also for rare cells, such as CTCs, for future molecular diagnosis.

Simultaneous Determination of Trigonelline, Caffeine, Chlorogenic Acid and Their Related Compounds in Instant Coffee Samples by HPLC Using an Acidic Mobile Phase Containing Octanesulfonate

Abstract: In order to analyze trigonelline, caffeine, chlorogenic acid, and their related compounds simultaneously, an HPLC method using an InertSustain C18 column and a mobile phase containing octanesulfonate as an ion-pairing reagent under an acidic condition was developed. The optimum mobile phase conditions were determined to be 0.1% phosphoric acid, 4 mM octanesulfonate, and 15% methanol at 35°C. Using the proposed method, trigonelline, nicotinic acid, caffeine, theophylline, chlorogenic acid, and caffeic acid in ten instant coffee samples were analyzed. These analytes except for theophylline were detected in all samples. An increase in the caffeine content in instant coffee samples tended to decrease in both trigonelline and chlorogenic acid contents, and the trigonelline content was found to be correlated well with the chlorogenic acid content (R(2) = 0.887).

Evaluation of enzymatic activities in living systems with small-molecular fluorescent substrate probes.

Abstract: In this review, we aim to present an overview of how small-molecular fluorescent substrate probes for studying enzymatic functions are developed and how they are used in biological applications, under the following four headings: (1) History of Visual Detection of Enzymatic Activities, (2) Strategies to Design Fluorescent Substrate Probes to Measure Enzymatic Activities, (3) Development of Fluorescent Substrate Probes Suitable for Biological Studies, and (4) Biological Applications of Fluorescent Substrate Probes for Studying Enzymes.

An Electrochemical Biosensor Based on a Myoglobin-specific Binding Peptide for Early Diagnosis of Acute Myocardial Infarction

Abstract: In this study, a simple, highly sensitive electrochemical biosensor for myoglobin was developed using a myoglobin-specific binding peptide as a sensing probe. A peptide (Myo-3R7, CPSTLGASC, 838 Da) identified by phage display and that specifically binds to myoglobin was covalently immobilized on a gold electrode functionalized via a dithiobis(succinimidyl propionate) (DSP) self-assembled monolayer (SAM). The peptide immobilization was confirmed with fluorescence microarray scanning and cyclic voltammetry (CV). The electrochemical performance of the biosensor with respect to myoglobin was characterized by CV and differential pulse voltammetry (DPV) using Fe(CN)6(3-)/Fe(CN)6(4-) as a redox probe. We successfully detected myoglobin in a broad working range of 17.8 to 1780 ng mL(-1) with a correlation coefficient (R(2)) of 0.998. The estimated limit of detection (LOD) was fairly low, 9.8 ng mL(-1) in 30 min. The electrochemical biosensor based on a myoglobin-specific binding peptide offers sensitivity, selectivity, and rapidity, making it an attractive tool for the early detection of cardiac infarction.

A Portable Liquid Chromatograph with a Battery-operated Compact Electroosmotic Pump and a Microfluidic Chip Device with a Reversed Phase Packed Column

Abstract: A compact and lightweight liquid chromatography system is presented with overall dimensions of 26 cm width × 18 cm length × 21 cm height and weight of 2 kg. This system comprises a battery-operated compact electroosmotic pump, a manual injector, a microfluidic chip device containing a packed column and an electrochemical detector, and a USB bus-powered potentiostat. The pumping system was designed for microfluidic-based reversed-phase liquid chromatography in which an electroosmotically generated water stream pushes the mobile phase via a diaphragm for the output. The flow rate ranged from 0 to 10 μL/min and had a high degree of precision. The pumping system operated continuously for over 24 h with dry batteries. The column formed in the microfluidic device was packed with 3-μm ODS particles with a length of 30 mm and a diameter of 0.8 mm. The results presented herein demonstrate the performance of the pumping system and the column using alkylphenols, catecholamine, catechin, and amino acids.

Screen printed paper-based diagnostic devices with polymeric inks.

Abstract: A simple and low-cost fabrication method for paper-based diagnostic devices (PBDDs) is described in this study. Street-available polymer solutions were screen printed onto filter papers to create hydrophobic patterns for fluidic channels. In order to obtain fully functional hydrophobic patterns for fluids, the original polymer solutions were diluted with butyl acetate to yield a suitable viscosity range between 30-200 cP for complete patterning on paper. Typical pH and glucose tests with color indicators were performed on the screen printed PBDDs. Images of the PBDDs were analyzed by computers to obtain calibration curves for pH between 2 and 12 and glucose concentration ranging from 10-1000 mmol dm(-3). Detection of formaldehyde in acetone was also carried out to show the possibility of using this PBBD for analytical detection with organic solvents. An exemplar PBDD with simultaneous pH and glucose detection was also used to demonstrate the feasibility of applying this technique for realistic diagnostic applications.

Fluorescence Probing Live Single-cell Mass Spectrometry for Direct Analysis of Organelle Metabolism

Abstract: Mitochondria in a live HepG2 cell were visualized with a fluorescent probe to specify their location and state in a living cell. Then, mitochondria were selectively captured with a nanospray tip under fluorescence microscope, and thousands of small molecular peaks were revealed and unique steroids specific to mitochondria were also found. This fluorescence imaging combined with live single-cell mass spectrometry opens the door to the analysis of site- and state-specific molecular detection to elucidate precise molecular mechanisms at the single-cell and organelle level.

An Organic Field-effect Transistor with an Extended-gate Electrode Capable of Detecting Human Immunoglobulin A

Abstract: We herein report on the development of an extended-gate type organic field-effect transistor (OFET)-based immunosensor for the detection of human immunoglobulin A (IgA). The titration results of IgA exhibited shifts in the transfer characteristics of the OFET sensor device with increasing IgA concentration. A linear detection range from 0 to 10 μg/mL was realized with a detection limit of 2.1 μg/mL, indicating that the OFET-based immunosensor can be potentially applied to the monitoring of infectious diseases and psychological stress in daily life.

Multi-point scanning two-photon excitation microscopy by utilizing a high-peak-power 1042-nm laser.

Abstract: The temporal resolution of a two-photon excitation laser scanning microscopy (TPLSM) system is limited by the excitation laser beam's scanning speed. To improve the temporal resolution, the TPLSM system is equipped with a spinning-disk confocal scanning unit. However, the insufficient energy of a conventional Ti:sapphire laser source restricts the field of view (FOV) for TPLSM images to a narrow region. Therefore, we introduced a high-peak-power Yb-based laser in order to enlarge the FOV. This system provided three-dimensional imaging of a sufficiently deep and wide region of fixed mouse brain slices, clear four-dimensional imaging of actin dynamics in live mammalian cells and microtubule dynamics during mitosis and cytokinesis in live plant cells.

Multiplex MicroRNA Detection on a Power-free Microfluidic Chip with Laminar Flow-assisted Dendritic Amplification.

Abstract: MicroRNA (miRNA) profile-based point-of-care (POC) diagnostic methods have attracted considerable attention. In our laboratory, singleplex miRNA detection on a power-free poly(dimethylsiloxane) (PDMS) microfluidic chip with laminar flow-assisted dendritic amplification (LFDA) has been developed. In this study, to obtain the miRNA profile and to improve the reliability of the diagnosis, multiplex miRNA detection on the same system is demonstrated without compromising any advantages of the singleplex miRNA detection. The limit of detection (LOD) was at the femto- to picomolar level and the assay time was 20 min. The sensitivity, rapidity, and portability of the microfluidic chip are adequate for POC diagnosis.

Developing a new micro cloud point extraction method for simultaneous preconcentration and spectrophotometric determination of uranium and vanadium in brine.

Abstract: A fast, simple, and economical method was developed for simultaneous spectrophotometric determination of uranium(VI) and vanadium(V) in water samples based on micro cloud point extraction (MCPE) at room temperature. This is the first report on the simultaneous extraction and determination of U(VI) and V(V). In this method, Triton X114 was employed as a non-ionic surfactant for the cloud point procedure and 4-(2-pyridylazo) resorcinol (PAR) was used as the chelating agent for both analytes. To reach the cloud point at room temperature, the MCPE procedure was carried out in brine. The factors influencing the extraction efficiency were investigated and optimized. Under the optimized condition, the linear calibration curve was found to be in the concentration range between 100 - 750 and 50 - 600 μg L(-1) for U(VI) and V(V), respectively, with a limit of detection of 17.03 μg L(-1) (U) and 5.51 μg L(-1) (V). Total analysis time including microextraction was less than 5 min.

Colorimetric and Fluorometric Assays for Dopamine with a Wide Concentration Range Based on Fe-MIL-88NH2 Metal-organic Framework

Abstract: Metal-organic framework Fe-MIL-88NH2 as a dual colorimetric and fluorometric sensor has been designed for a wide range of dopamine quantitative detection. It is easy to implement the assay for visual detection of dopamine based on restraining the color change of the 3,3',5,5'-tetramethylbenzidine-H2O2 system that is catalyzed by Fe-MIL-88NH2 with intrinsic peroxidase-like catalytic activity. The linear range is from 50 nM to 30 μM. In addition, the Fe-MIL-88NH2 can exhibit a dramatic decrease of its fluorescent intensity when exposed to dopamine, which may be attributed to the electron transfer from the Fe-MIL-88NH2 to the oxidized dopamine-quinone. The linear response range is from 30 μM to 4 mM. Meanwhile, both colorimetric and fluorometric methods exhibit higher selectivity for DA over a number of possible interfering substances. Furthermore, the proposed method has been successfully applied to detect DA in human serum samples, which suggests its great potential for analytical applications.

Yeast-based Biochemical Oxygen Demand Sensors Using Gold-modified Boron-doped Diamond Electrodes

Abstract: A gold nanoparticle modified boron-doped diamond electrode was developed as a transducer for biochemical oxygen demand (BOD) measurements. Rhodotorula mucilaginosa UICC Y-181 was immobilized in a sodium alginate matrix, and used as a biosensing agent. Cyclic voltammetry was applied to study the oxygen reduction reaction at the electrode, while amperometry was employed to detect oxygen, which was not consumed by the microorganisms. The optimum waiting time of 25 min was observed using 1-mm thickness of yeast film. A comparison against the system with free yeast cells shows less sensitivity of the current responses with a linear dynamic range (R(2) = 0.99) of from 0.10 mM to 0.90 mM glucose (equivalent to 10 - 90 mg/L BOD) with an estimated limit of detection of 1.90 mg/L BOD. However, a better stability of the current responses could be achieved with an RSD of 3.35%. Moreover, less influence from the presence of copper ions was observed. The results indicate that the yeast-immobilized BOD sensors is more suitable to be applied in a real condition.

One-step Synthesis of Highly Luminescent Nitrogen-doped Carbon Dots for Selective and Sensitive Detection of Mercury(II) Ions and Cellular Imaging

Abstract: In this paper, nitrogen-doped carbon dots (N-CDs) with high quantum yield (QY) of 40.5% were prepared through a facile and straightforward hydrothermal route. The as-prepared N-CDs exhibited excellent photoluminescence properties, good water-solublity and photostability, negligible cytotoxicity and favourable biocompatibility. Such N-CDs were found to serve as an effective fluorescent sensor for selective and sensitive detection of Hg(2+) in a wide linear response concentration range of 0 - 8 μM with a limit of detection (LOD) of 0.087 μM and could be applied to the determination of Hg(2+) in environmental water samples. The corresponding mechanisms were discussed in detail. Moreover, another attractive finding was that the N-CDs showed satisfactory performance in bioimaging before and after the addition of Hg(2+) in human lung cancer PC14 cells. With excellent sensitivity, selectivity and biocompatibility, such cheap carbonmaterials are potentially suitable for monitoring of Hg(2+) in environmental applications and promising for biological applications.

Identification of Ancient Silk Using an Enzyme-linked Immunosorbent Assay and Immuno-fluorescence Microscopy.

Abstract: The identification of ancient silk is of great importance in both archaeology and academia. In the present work, a specific antibody having the characteristics of low cost, easy operation and extensive applicability was developed directly through immunizing rabbits with complete antigen (silk fibroin, SF). Then, antibody-based immunoassays, i.e. enzyme-linked immunosorbent assay (ELISA) and immuno-fluorescence microscopy (IFM), were established and conducted in tandem to identify the corresponding protein in ancient silks. The anti-SF antibody exhibits high sensitivity and specificity for the identification of modern and ancient silks. The detection limit of the ELISA method is about 0.1 ng/mL, and no cross-reactions with other possible interference antigens have been noted. IFM makes it possible to localize target proteins in archaeological samples, and also ensure the reliability of the ELISA results. Based on these advantages, immunological techniques have the potential to become powerful analytical tools at archaeological sites and conservation science laboratories.

Microdevice in Cellular Pathology: Microfluidic Platforms for Fluorescence in situ Hybridization and Analysis of Circulating Tumor Cells

Abstract: Microfluidic devices enable the miniaturization, integration, automation, and parallelization of chemical and biochemical processes. This new technology also provides opportunity for expansion in the field of cellular pathology. Fluorescence in situ hybridization (FISH) is a well-known gene-based method to image genetic abnormalities. Development of a FISH microfluidic platform has offered the possibility of automation with significant time and cost reductions, which overcomes many drawbacks of the current protocols. Microfluidic devices are also powerful tools for single-cell analysis. Capturing the circulating tumor cells (CTCs) from blood samples is one of the most promising approaches to enable the early diagnosis of cancer. The microfluidic devices are also useful to isolate rare CTCs at high efficiency and purity. In this review, I outline recent FISH and CTC analyses using microfluidic devices, and describe their applications for the cellular diagnosis of cancers.

An Extended-gate Type Organic FET Based Biosensor for Detecting Biogenic Amines in Aqueous Solution

Abstract: This study is the first to report on the detection of biogenic amines in an aqueous solution using an organic field-effect transistor (OFET) device with an extended gate electrode modified with a layer of diamine oxidase and a horseradish peroxidase osmium-redox polymer The limit of detection (LOD) for histamine was estimated to be 12 μM These results reveal that extended-gate type OFET devices are highly suitable enzyme-based biosensors for the detection of biogenic amine levels

Kinetic Study of Interaction between Solute Molecule and Surfactant Micelle

Abstract: We developed moment analysis of affinity kinetics by chromatographic capillary electrophoresis (MKCCE) method for the kinetic study of intermolecular interactions. Association and dissociation rate constants of the interaction in a micellar electrokinetic chromatography (MEKC) system between thymol and sodium dodecylsulfate micelle were determined by the MKCCE method. It is a method based on the moment theory for the kinetic study of intermolecular interactions under the conditions that neither immobilization nor chemical modification of molecules is required. In CCE mode, experimental conditions are controlled so that the migration of solute-micelle complex is stopped and only solute molecules migrate in a capillary. Mass transfer behavior of solute molecules in the CCE system is analogous to that in a chromatographic system. However, because it was difficult in practice to really perform CE experiments under the CCE conditions, CE data were measured with changing experimental conditions, i.e., applied pressure, under the conditions that the migration velocity of solute-micelle complex was around zero. The rate constants could be analytically determined from the CE data. In the MKCCE method, it is not necessary to fit elution curves numerically calculated to those experimentally measured for the determination of the rate constants. Regarding the interaction between thymol and SDS micelles, association equilibrium constant and association and dissociation rate constants were determined as 6.35 × 10(3) dm(3) mol(-1), 5.6 × 10(4) dm(3) mol(-1) s(-1), and 8.7 s(-1), respectively. It was demonstrated that the MKCCE method was effective for the kinetic study of intermolecular interactions.

Development and Validation of a New HPLC Method for the Simultaneous Determination of Paracetamol, Ascorbic Acid, and Pseudoephedrine HCl in their Co-formulated Tablets. Application to in vitro Dissolution Testing.

Abstract: The first HPLC method was developed for the simultaneous determination of paracetamol (PC), ascorbic acid (AA), and pseudoephedrine HCl (PE) in their co-formulated tablets. Separation was achieved on a C18 column in 5 min using a mobile phase composed of methanol-0.05 M phosphate buffer (35:65, v/v) at pH 2.5 with UV detection at 220 nm. Linear calibration curves were constructed over concentration ranges of 1.0 - 50.0, 3.0 - 60.0 and 3.0 - 80.0 μg mL(-1) for PC, AA, and PE, respectively. The method was validated and applied for the simultaneous determination of these drugs in their tablets with average % recoveries of 101.17 ± 0.67, 98.34 ± 0.77, and 98.95 ± 1.11%, for PC, AA, and PE, respectively. The proposed method was also used to construct in vitro dissolution profiles of the co-formulated tablets containing the three drugs.

Sensing of intracellular environments by fluorescence lifetime imaging of exogenous fluorophores.

Abstract: Fluorescence lifetime imaging (FLIM) has been recognized as a powerful microscopy technique to examine environments in living systems. The fluorescence lifetime does not depend on the photobleaching and optical conditions, which allows us to obtain quantitative information on intracellular environments by analyzing the fluorescence lifetime. A variety of exogenous fluorophores have been applied in FLIM measurements to examine cellular processes. Information on the correlation between the fluorescence lifetime and the physiological parameters is essential to elucidate the cellular environments from the fluorescence lifetime measurements of exogenous fluorophores. In this review, exogenous fluorophores used for lifetime-based sensing are summarized, with the expectation that it becomes a basis for selecting the fluorophore used to investigate the intracellular environment with FLIM. Experimental results of the intracellular sensing of pH, metal ions, oxygen, viscosity, and other physiological parameters on the basis of the FLIM measurements are described along with a brief explanation of the mechanism of the change in the fluorescence lifetime.

Complementary Use of LC-ICP-MS and LC-ESI-Q-TOF-MS for Selenium Speciation.

Abstract: We demonstrated the complementary use of inductively coupled plasma-mass spectrometry (ICP-MS) and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS) for the analysis of Se-containing compounds, such as selenate, selenomethionine (SeMet), and trimethylselenonium ion (TMSe), found in biological samples. The sensitivity of ESI-Q-TOF-MS for Se-containing compounds was strongly dependent on the chemical species. ICP-MS exhibited higher sensitivity than ESI-Q-TOF-MS, and had no species dependency. On the other hand, ESI-Q-TOF-MS enabled easy and robust identification of Se-containing compounds.

Temperature-responsive Solid-phase Extraction Column for Biological Sample Pretreatment.

Abstract: We have developed a novel solid-phase extraction (SPE) system utilizing a temperature-responsive polymer hydrogel-modified stationary phase. Aminopropyl silica beads (average diameter, 40 - 64 μm) were coated with poly(N-isopropylacrylamide) (PNIPAAm)-based thermo-responsive hydrogels. Butyl methacrylate (BMA) and N,N-dimethylaminopropyl acrylamide (DMAPAAm) were used as the hydrophobic and cationic monomers, respectively, and copolymerized with NIPAAm. To evaluate the use of this SPE cartridge for the analysis of drugs and proteins in biological fluids, we studied the separation of phenytoin and theophylline from human serum albumin (HSA) as a model system. The retention of the analytes in an exclusively aqueous eluent could be modulated by changing the temperature and salt content. These results indicated that this temperature-responsive SPE system can be applied to the pretreatment of biological samples for the measurement of serum drug levels.

A Simplified and Turn-on Fluorescence Chemosensor Based on Coumarin Derivative for Detection of Aluminium(III) Ion in Pure Aqueous Solution.

Abstract: A novel chemosensor L based on coumarin Schiff-base was synthesized and investigated. Sensor L showed remarkable selectivity for Al(3+) in Tris-HCl aqueous buffer solution (pH 7.2), and the selectivity was not affected by the presence of a large excess of other competitive ions. The sensor responded rapidly to Al(3+) in aqueous solutions with a 2:1 stoichiometry. Meanwhile, it indicated significant improvement of quantum efficiency and ideal fluorescent lifetime.

Simulation Analysis of Positional Relationship between Embryoid Bodies and Sensors on an LSI-based Amperometric Device for Electrochemical Imaging of Alkaline Phosphatase Activity

Abstract: In the present study, we monitored the alkaline phosphatase (ALP) activity of embryoid bodies (EBs) of mouse embryonic stem (ES) cells using a large-scale integration (LSI)-based amperometric device with 400 sensors and a pitch of 250 μm. In addition, a simulation analysis was performed to reveal the positional relationship between the EBs and the sensor electrodes toward more precise measurements. The study shows that simulation analysis can be applied for precise electrochemical imaging of three-dimensionally cultured cells by normalization of the current signals.

Electrochemical Molecular Imprinted Sensors Based on Electrospun Nanofiber and Determination of Ascorbic Acid.

Abstract: In this study, electrochemical molecularly imprinted sensors were fabricated and used for the determination of ascorbic acid (AA) Nanofiber membranes of cellulose acetate (CA)/multi-walled carbon nanotubes (MWCNTs)/polyvinylpyrrolidone (PVP) (CA/MWCNTs/PVP) were prepared by electrospinning technique After being transferred to a glass carbon electrode (GC), the nanofiber interface was further polymerized with pyrrole through electrochemical cyclic voltammetry (CV) technique Meanwhile, target molecules (such as AA) were embedded into the polypyrrole through the hydrogen bond The effects of monomer concentration (pyrrole), the number of scan cycles and scan rates of polymerization were optimized Differential pulse voltammetry (DPV) tests indicated that the oxidation current of AA (the selected target) were higher than that of the structural analogues, which illustrated the selective recognition of AA by molecularly imprinted sensors Simultaneously, the molecularly imprinted sensors had larger oxidation current of AA than non-imprinted sensors in the processes of rebinding The electrochemical measurements showed that the molecularly imprinted sensors demonstrated good identification behavior for the detection of AA with a linear range of 100 - 1000 μM, a low detection limit down to 3 μM (S/N = 3), and a recovery rate range from 940 to 1088% Therefore, the electrochemical molecularly imprinted sensors can be used for the recognition and detection of AA without any time-consuming elution The method presented here demonstrates the great potential for electrospun nanofibers and MWCNTs to construct electrochemical sensors

Reversed Phase Column HPLC-ICP-MS Conditions for Arsenic Speciation Analysis of Rice Flour

Abstract: New measurement conditions for arsenic speciation analysis of rice flour were developed using HPLC-ICP-MS equipped with a reversed phase ODS column. Eight arsenic species, namely, arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), trimethylarsine oxide (TMAO), tetramethylarsonium (TeMA), arsenobetaine (AsB) and arsenocholine (AsC), were separated and determined under the proposed conditions. In particular, As(III) and MMAA and DMAA and AsB were completely separated using a newly proposed eluent containing ammonium dihydrogen phosphate. Importantly, the sensitivity changes, in particular those of As(V) and As(III) caused by coexisting elements and by complex matrix composition, which had been problematical in previously reported methods, were eliminated. The new eluent can be applied to C8, C18 and C30 ODS columns with the same effectiveness and with excellent repeatability. The proposed analytical method was successfully applied to extracts of rice flour certified reference materials.

Fundamental study on the development of fiber optic sensor for real-time sensing of CaCO3 scale formation in geothermal water.

Abstract: This study proposes an optical fiber sensor for calcium carbonate (CaCO3) scale formation in water. The sensor is easily fabricated by removing the cladding of a multimode fiber to expose the core towards the surrounding medium in order to detect refractive index change. A variation of the transmittance response from the high refractive index of CaCO3 which precipitated on the fiber core surface was observed. The proposed setup can be used to analyze the transmittance response over wide range of wavelength using white light as a source and also a spectroscopy detector. The curve of the transmittance percentage over time showed that a fiber core with 200 μm has higher sensitivity as compared to a fiber core with 400 μm. The findings from this study showed that the sensor detection region at near infrared (NIR) wavelengths showed better sensitivity than visible light (VIS) wavelengths. Field tests were conducted using natural geothermal water at Matsushiro, Japan in order to verify the performance of the proposed sensor. The optical response was successfully evaluated and the analytical results confirmed the capability of monitoring scale formation in a geothermal water environment.

On-chip FRET Graphene Oxide Aptasensor: Quantitative Evaluation of Enhanced Sensitivity by Aptamer with a Double-stranded DNA Spacer.

Abstract: We propose a molecular design for a biomolecular probe to realize an on-chip graphene oxide (GO) aptasensor with enhanced sensitivity. Here, GO works as an excellent acceptor for fluorescence resonance energy transfer. We inserted a rigid double-stranded DNA as a spacer between the GO surface and the aptamer sequence to extend the distance between a fluorescence dye and the GO surface during molecular recognition. We examined the dependence of the sensitivity on the length of the spacer quantitatively by using a 2×2 linear-array aptasensor. We used the modified aptamer with 10 and 30 base pair (bp) double-stranded DNA spacers. The signal with a 30bp-spacer was about twice as strong that with a 10bp-spacer as regards both thrombin and prostate specific antigen detections. The improvement in the sensitivity was supported by a model calculation that estimated the effect of spacer length on fluorescence recovery efficiency.

Automatic On-line Solid-phase Extraction-Electrothermal Atomic Absorption Spectrometry Exploiting Sequential Injection Analysis for Trace Vanadium, Cadmium and Lead Determination in Human Urine Samples.

Abstract: A fully automated sequential injection column preconcentration method for the on-line determination of trace vanadium, cadmium and lead in urine samples was successfully developed, utilizing electrothermal atomic absorption spectrometry (ETAAS). Polyamino-polycarboxylic acid chelating resin (Nobias chelate PA-1) packed into a handmade minicolumn was used as a sorbent material. Effective on-line retention of chelate complexes of analytes was achieved at pH 6.0, while the highest elution effectiveness was observed with 1.0 mol L(-1) HNO3 in the reverse phase. Several analytical parameters, like the sample acidity, concentration and volume of the eluent as well as the loading/elution flow rates, have been studied, regarding the efficiency of the method, providing appropriate conditions for the analysis of real samples. For a 4.5 mL sample volume, the sampling frequency was 27 h(-1). The detection limits were found to be 3.0, 0.06 and 2.0 ng L(-1) for V(V), Cd(II) and Pb(II), respectively, with the relative standard deviations ranging between 1.9 - 3.7%. The accuracy of the proposed method was evaluated by analyzing a certified reference material (Seronorm(TM) trace elements urine) and spiked urine samples.