Showing papers in "Analytical Sciences in 2011"
TL;DR: The photostable properties of the trypsin-stabilized AuNCs were examined, and their photochemical stability was found to be similar to that of CdSe quantum dots, and therefore the Au NCs can be used as fluorescent sensors for sensitive and selective Hg(2+) detection to a detection limit of 50 ± 10 nM and the quantitative detection in wide and low concentration range of 50-600 nM.
Abstract: We report on trypsin-stabilized fluorescent gold nanoclusters (Au NCs) for the sensitive and selective detection of Hg(2+) ions. The Au NCs have an average size of 1 nm and show a red emission at 645 nm. The photostable properties of the trypsin-stabilized Au NCs were examined, and their photochemical stability was found to be similar to that of CdSe quantum dots. The fluorescence was particularly quenched by Hg(2+), and therefore the Au NCs can be used as fluorescent sensors for sensitive and selective Hg(2+) detection to a detection limit of 50 ± 10 nM and the quantitative detection of Hg(2+) in wide and low concentration range of 50-600 nM.
132 citations
TL;DR: Especially innovative SPME approaches, including multi-well high-throughput sampling, ligand-receptor binding study for pharmacokinetics, direct in vivo sampling, chip-based microfluidic system, and new sampling techniques using intelligent carbon nanotube and temperature-response polymer in pharmaceutical and biomedical analysis are focused items.
Abstract: Sample preparation is important for the isolation and concentration of desired trace components from complex matrices Sample preparation is the most labor-intensive and error-prone process in analytical methodology, and greatly influences the reliable and accurate determination of analytes The integration of sample preparation with various analytical instruments is most conveniently achieved by using microextraction techniques and/or microdevices Solid-phase microextraction (SPME) is both simple and effective, enabling miniaturization, automation and high-throughput performance Moreover, SPME has reduced analysis times, as well as the costs of solvents and disposal This review describes current developments and future trends in novel SPME techniques, including fiber SPME, in-tube SPME and related new microextraction techniques Especially innovative SPME approaches, including multi-well high-throughput sampling, ligand-receptor binding study for pharmacokinetics, direct in vivo sampling, chip-based microfluidic system, and new sampling techniques using intelligent carbon nanotube and temperature-response polymer in pharmaceutical and biomedical analysis are focused items
88 citations
TL;DR: Electrospray ionization (ESI) liquid chromatography-mass spectrometry (LC-MS) is a very powerful tool for the detection, identification and quantification of DSP and other lipophilic toxins.
Abstract: Diarrhetic shellfish poisoning (DSP) is a severe gastrointestinal illness caused by consumption of shellfish contaminated with DSP toxins that are originally produced by toxic dinoflagellates. Based on their structures, DSP toxins were initially classified into three groups, okadaic acid (OA)/dinophysistoxin (DTX) analogues, pectenotoxins (PTXs), and yessotoxins (YTXs). Because PTXs and YTXs have been subsequently shown to have no diarrhetic activities, PTXs and YTXs have recently been eliminated from the definition of DSP toxins. Mouse bioassay (MBA), which is the official testing method of DSP in Japan and many countries, also detects PTXs and YTXs, and thus alternative testing methods detecting only OA/DTX analogues are required in DSP monitoring. Electrospray ionization (ESI) liquid chromatography-mass spectrometry (LC-MS) is a very powerful tool for the detection, identification and quantification of DSP and other lipophilic toxins. In the present review, application of ESI LC-MS techniques to the analysis of each toxin group is described.
83 citations
TL;DR: The technique has been found to be compatible with a wide range of biological fluids and extraction of drugs directly from untreated human plasma and whole blood has been demonstrated and downscaled into the micro-chip format.
Abstract: Electro-assisted extraction of ionic drugs from biological fluids through a supported liquid membrane (SLM) and into an aqueous acceptor solution was recently introduced as a new sample preparation technique termed electromembrane extraction (EME). The applied electrical potential across the SLM has typically been in the range of 1 – 300 V. Successful extractions have been demonstrated even with common batteries (9 V) instead of a power supply. The chemical composition of the SLM has been crucial for the selectivity and for the recoveries of the extraction. Compared to other liquid-phase microextraction techniques (LPME), extraction times have been reduced by a factor of 6 – 17, and successful extractions have been obtained at extraction times of 1 – 5 min, and even down to a few seconds with online microfluidic EME devices. The technique has provided very efficient sample clean-up and has been found well suited for the extraction of sample sizes in the low μL range. Extractions have been performed with both rod-shaped hydrophobic porous fibers and with flat hydrophobic porous sheets as SLM support. The technique has been successfully downscaled into the micro-chip format. The nature of the SLM has been tuned for extraction of drugs with different polarity allowing extractions to be tailored for specific applications depending on the analyte of interest. The technique has been found to be compatible with a wide range of biological fluids and extraction of drugs directly from untreated human plasma and whole blood has been demonstrated. EME selectively extracts the compounds from the complex biological sample matrix as well as allowing concentration of the drugs. With home-built equipment fully acceptable validation results have been obtained.
80 citations
TL;DR: The results suggest that the health risk to consumers from beer-based drinks in Japan is relatively low.
Abstract: An analytical method was developed for the identification and quantification of 15 mycotoxins (patulin, nivalenol, deoxynivalenol, aflatoxin B1, B2, G1, G2, M1, T-2 toxin, HT-2 toxin, zearalenone, fumonisin B1, B2, B3, and ochratoxin A) in beer-based drinks (beer, low-malt beer, new genre, and nonalcoholic) by a modified QuEChERS method and an ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS). Mycotoxins were extracted from samples using acetonitrile with sodium chloride, anhydrous magnesium sulfate, and sodium citrate, and were then purified with a solid phase extraction (SPE) cartridge including C18. The UHPLC conditions were also examined to establish its optimal conditions for separation. Fifteen mycotoxins were separated in a total of 6.5 min, and were quantified in the optimal mobile phase conditions. Determinations performed using this method produced high correlation coefficients of 15 mycotoxins (R > 0.99) and recovery rates ranging from 70.3 to 110.7% with good repeatability (relative standard deviation RSD < 14.6%). Further, 24 commercial beer-based drinks in Japan were analyzed using this method, and nivalenol, deoxynivalenol, and fumonisins were detected in several samples, but always under the limit of quantification (< 5 ng/mL). These results suggest that the health risk to consumers from beer-based drinks in Japan is relatively low.
75 citations
TL;DR: This work found that methylene blue caused an efficient quenching of the fluorescence of carbon dots (CDots), and developed a new system for DNA detection based on this phenomenon, which is the first use of CDots forDNA detection.
Abstract: In the present work, we found that methylene blue (MB) caused an efficient quenching of the fluorescence of carbon dots (CDots). However, as ct-DNA was added, the fluorescence of CDots was restored reversibly. Under the experimental conditions, CDots were excellent electron donors. MB adsorbed on the surface of CDots and quenched the fluorescence of CDots through an electron-transfer process; and then the addition of DNA caused a restoration of the CDots fluorescence intensity, since DNA could bind with MB and remove it from the CDots. Based on this phenomenon, we developed a new system for DNA detection. A sensitive detection of ct-DNA with a detection limit of 1.0 × 10(-6) mol L(-1) and a linear detection range from 3.0 × 10(-6) to 8.0 × 10(-5) mol L(-1) with a relative fluorescence intensity of CDots were achieved. To the best of our knowledge, this is the first use of CDots for DNA detection.
71 citations
TL;DR: This electrode showed an efficient catalytic activity for the electro-oxidation of 6-thioguanine (6-TG), which leads to lowering 6-TG overpotential by more than 610 mV.
Abstract: The present work describes the preparation and characterization of a carbon nanotube paste electrode modified with 2,7-bis(ferrocenyl ethyl)fluoren-9-one (2,7-BF). This electrode showed an efficient catalytic activity for the electro-oxidation of 6-thioguanine (6-TG), which leads to lowering 6-TG overpotential by more than 610 mV. Also, the values of catalytic rate constant (k = 2.7 × 103 mol−1 L s−1), and diffusion coefficient (D = 2.7 × 10−5 cm2 s) were calculated. In 0.1 M phosphate buffer solution of pH 7.0, the oxidation current increased linearly with two concentration intervals of 6-TG, one is 0.06 to 10.0 μmol L−1 and the other is 10.0 to 160.0 μmol L−1. The detection limit (3σ) obtained by differential pulse voltammetry (DPV) was 22.0 nmol L−1. DPV was used for simultaneous determination of 6-TG, uric acid (UA) and folic acid (FA) at the modified electrode, and for quantification of 6-TG, UA and FA in some real samples by the standard addition method.
68 citations
TL;DR: The results indicate that the CNPE modified with p-aminophenol as a mediator is efficient in terms of its electrocatalytic activity for the oxidation of L-cysteine, leading to an overpotential reduced by more than 550 mV.
Abstract: Two amino acids, L-cysteine and tryptophan, could be simultaneously determined in an aqueous solution (pH 6.0) using a carbon nanotube paste electrode (CNPE) modified with p-aminophenol as a mediator. The results indicate that the electrode is efficient in terms of its electrocatalytic activity for the oxidation of L-cysteine, leading to an overpotential reduced by more than 550 mV. Using differential pulse voltammetry, we could measure L-cysteine and tryptophan in one mixture independently from each other by a potential difference of about 600 mV. Electrochemical techniques are used to determine the diffusion coefficients, kinetic parameters such as electron transfer coefficient, and the rates of electro-oxidation of L-cysteine at the surface of the p-aminophenol-modified CNPE. The peak current is found to depend linearly on L-cysteine and tryptophan concentrations within the ranges of 0.5 - 100 µmol L(-1) L-cysteine and 10.0 - 300 µmol L(-1) tryptophan. The detection limits for L-cysteine and tryptophan are found to be 0.3 and 5.7 µmol L(-1), respectively. The proposed method is also used for the determination of L-cysteine and tryptophan in urine, river water, blood plasma, and serum samples using standard addition methods.
61 citations
TL;DR: The overall result demonstrates that a glucose sensor with high sensitivity could be readily fabricated by a piezoelectric inkjet printing system.
Abstract: Piezoelectric inkjet printing of polymers and proteins holds great promise for fabrication of miniaturized bioelectronic devices, such as biochips and biosensors. In this study, a bienzymatic glucose biosensor prototype based on poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) (PEDOT-PSS), glucose oxidase (GOD), and horseradish peroxidase (HRP) was fabricated by a piezoelectric inkjet printer. An aqueous bioelectrical ink containing PEDOT-PSS, GOD, and HRP was prepared and printed on an indium-tin-oxide (ITO)-coated poly(ethylene terephthalate) (PET) film. The PEDOT-PSS/GOD/HRP sensor was covered with a cellulose acetate membrane. The use of bienzymatic sensing combined with conducting polymers via piezoelectric inkjet printing showed a synergistic effect resulting in significant amplification of the response signal. The glucose sensor reached steady-state current density within 3 s, indicating a fast response time, and exhibited a linear dose-dependent electrochemical response with high sensitivity. The overall result demonstrates that a glucose sensor with high sensitivity could be readily fabricated by a piezoelectric inkjet printing system.
59 citations
TL;DR: The usefulness and limitations of the Raman markers for protonation/deprotonation, conformation, metal coordination, environmental polarity, hydrogen bonding, hydrophobic interaction, and cation-π interaction of the aromatic side chains are reviewed.
Abstract: UV Raman spectroscopy is a powerful tool for investigating the structures and interactions of the aromatic side chains of Phe, Tyr, Trp, and His in proteins. This is because Raman bands of aromatic ring vibrations are selectively enhanced with UV excitation, and intensities and wavenumbers of Raman bands sensitively reflect structures and interactions. Interpretation of protein Raman spectra is greatly assisted by using empirical correlations between spectra and structure. Many Raman bands of aromatic side chains have been proposed to be useful as markers of structures and interactions on the basis of empirical correlations. This article reviews the usefulness and limitations of the Raman markers for protonation/deprotonation, conformation, metal coordination, environmental polarity, hydrogen bonding, hydrophobic interaction, and cation-π interaction of the aromatic side chains. The utility of Raman markers is demonstrated through an application to the structural analysis of a membrane-bound proton channel protein.
51 citations
TL;DR: A method for the facile fabrication of Ag thin films, simply by soaking glass substrates in ethanolic solutions of AgNO(3) and butylamine, and their application as efficient SERS substrates is introduced.
Abstract: The nature of "hot spots" in surface-enhanced Raman scattering (SERS) and the novel fabrication of Ag thin films for efficient SERS measurements are the main focus of this review. By using 4-aminobenzenthiol or 1,4-phenylenediisocyanide molecules we can characterize the nanogap formed by a metal nanoparticle and a flat metal substrate, or the gap between two spherical metal nanoparticles. These nanogaps are indeed SERS-active sites and the apparent size of "hot spots" is found to be very limited. To use SERS for routine chemical identifications, the substrates should be stable, reproducibly prepared, inexpensive, and easy to make. We introduce a method for the facile fabrication of Ag thin films, simply by soaking glass substrates in ethanolic solutions of AgNO(3) and butylamine, and their application as efficient SERS substrates. Ag-coated glass capillary and Ag deposited magnetic nanoparticles can be used for the microanalysis of bio- and hazardous chemicals.
TL;DR: An ion chromatography dynamic reaction cell inductively coupled plasma mass spectrometric method for the speciation of arsenic and selenium compounds is described and the accuracy of the method has been verified.
Abstract: An ion chromatography dynamic reaction cell inductively coupled plasma mass spectrometric (IC-DRC-ICP-MS) method for the speciation of arsenic and selenium compounds is described. Chromatographic separation was performed in a gradient elution mode using 0.5 mmol L(-1) ammonium citrate in 1% methanol (pH 4.5) and 15 mmol L(-1) ammonium citrate in 1% methanol (pH 8.0). The potentially interfering (38)Ar(40)Ar(+) and (40)Ar(40)Ar(+) at selenium masses of m/z 78 and 80 were reduced in intensity by approximately 3 orders of magnitude by using 1.0 mL min(-1) CH(4) as a reactive cell gas in the DRC. Arsenic was determined as the adduct ion (75)As(12)CH(2)(+) at m/z 89. The detection limits of the procedure were in the ranges of 0.006-0.009 ng As mL(-1) and 0.009-0.03 ng Se mL(-1), respectively. This method has been applied to determine various arsenic and selenium compounds in cereal samples. The accuracy of the method has been verified by comparing the sum of the concentrations of individual species obtained by the present procedure with the total concentration of elements. The arsenic and selenium compounds were quantitatively extracted with a Protease XIV and α-amylase solution in a microwave field at 70°C during a period of 30 min. The spike recoveries were in the range of 94-105% for all determinations.
TL;DR: The amperometric L-ascorbic acid biosensor fabricated by immobilizing ascorbate oxidase (AO) in poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs) composite films was reported for the first time and exhibits good anti-interferent ability, good reproducibility and remarkable storage stability.
Abstract: An amperometric L-ascorbic acid (AA) biosensor fabricated by immobilizing ascorbate oxidase (AO) in poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs) composite films was reported for the first time. The entrapment of AO in PEDOT/MWCNTs composite films was performed during an electrochemical polymerization process. The influence of various experimental conditions was examined for determining the optimum analytical performance. The response of the biosensor towards AA under the optimized conditions is linear from 0.05 to 20 mM with a detection limit of 15 μM (S/N = 3). The biosensor shows a response time of 20 s and a sensitivity of 23.95 mA M−1 cm−2. The apparent Michaelis–Menten constant (Km) and apparent activation energy (Ea) are 19.5 mM and 21 kJ mol−1, respectively. Moreover, the biosensor exhibits good anti-interferent ability, good reproducibility and remarkable storage stability.
TL;DR: High-throughput cupric ion reducing antioxidants capacity (CUPRAC) methods were developed for assessment of total antioxidant capacity (TAC) in urine and serum, based on reduction of Cu(II)-neocuproine complex to highly colored Cu(I)-neOCuproines complex, measured spectrophotometrically at 450 nm.
Abstract: High-throughput cupric ion reducing antioxidant capacity (CUPRAC) methods were developed for assessment of total antioxidant capacity (TAC) in urine and serum, based on reduction of Cu(II)-neocuproine complex to highly colored Cu(I)-neocuproine complex, measured spectrophotometrically at 450 nm. The reaction time was significantly reduced from 30 to 4 min by application of a calibration compound (uric acid) with kinetic behavior similar to that shown by urine samples. The method was implemented in a microformat (96 well plates) and also in an automatic fashion (flow injection analysis, FIA). A determination throughput value of 288 h−1 (microplate method) or of 15 h−1 (automatic FIA) was attained. Application of both methods to human serum (SRM 909b, level I) and urines (n = 9) provided TAC values in agreement with those of the end-point batch method.
TL;DR: Oligonucleotides with sequences of human telomere DNA or thrombin binding aptamer (TBA) are known to form tetraplex structures upon binding the K(+) ion, which led to the development of potassium-sensing oligonucleotide (PSO) probes, in which two fluorescent dyes were attached to both termini of particular oligon nucleotide.
Abstract: Oligonucleotides with sequences of human telomere DNA or thrombin binding aptamer (TBA) are known to form tetraplex structures upon binding the K(+) ion. Structural changes associated with the formation of tetraplex assemblies led to the development of potassium-sensing oligonucleotide (PSO) probes, in which two fluorescent dyes were attached to both termini of particular oligonucleotide. The combination of dyes included fluorescence resonance energy transfer (FRET) and excimer emission approaches, and the structural changes upon binding K(+) ion could be monitored by a fluorescence technique. These systems showed a very high preference for K(+) over Na(+) ion, which was suitable for fluorescence imaging of the potassium concentration gradient in a living cell. In the case of human telomere DNA, it was also possible to follow the polymorphism of its tetraplex structures.
TL;DR: C cultured human osteoblasts over two sorts of nanopatterned surfaces with different pattern densities fabricated by using laser interference lithography and the nanoimprinting technique showed relatively higher adaptation to the topography with guided filopodia protrusion and difficulty in finding suitable paths for migration.
Abstract: Anchorage-dependent cells growing over a substratum require stable adhesion areas on the surface for the next cellular activities. The adhesion is achieved by some contact points called focal adhesions. Because focal adhesions were distributed randomly, a trial to control the positions of focal adhesion with a specific order may cause interesting effects like as cytoskeleton rearrangement, which may induce and transfer new signals to the nucleus. Here, we cultured human osteoblasts over two sorts of nanopatterned surfaces with different pattern densities fabricated by using laser interference lithography and the nanoimprinting technique. Of the two nanopatterns, cells over the nanopattern with low pattern density showed relatively higher adaptation to the topography with guided filopodia protrusion. However, cells over the dense nanopattern showed difficulty in finding suitable paths for migration, as judged from the activities of filopodium formation and the presence of a shovel-like feature at the tip of each filopodium.
TL;DR: The MBZ/TMHPP Cu(II)-modified GE showed good stability and selectivity and it can be used to quantify ACV in pharmaceutical formulations and urine samples.
Abstract: The electrooxidation of acyclovir (ACV) was studied using a gold electrode (GE) modified with a self-assembled monolayer of 2-mercaptobenzothiazol (MBZ) and [5,10,15,20-tetrakis(3-methoxy-4-hydroxyphenyl)porphyrinato]copper(II) (TMHPP Cu(II)) by square wave voltammetry (SWV). The self-assembled films are stable and showed blocking characteristics towards the faradaic processes such as gold surface oxidation and under potential deposition of copper. The optimized conditions obtained for the MBZ/TMHPP Cu(II)-modified GE were 0.1 M phosphate buffer solution (pH 7.0), square wave frequency of 15 Hz and square wave amplitude of 25 mV. Under these optimum conditions, the resultant peak current increases linearly with the concentration of ACV in the range of 1.0 × 10(-3) to 1.0 × 10(-8) M with a detection limit of 1.0 × 10(-8) M. The MBZ/TMHPP Cu(II)-modified GE showed good stability and selectivity and it can be used to quantify ACV in pharmaceutical formulations and urine samples.
TL;DR: Analytical results were found to be in satisfactory agreement with those detected by the enzyme-linked immunosorbent assay (ELISA) method, indicating that this new method was a promising alternative tool for clinical diagnosis.
Abstract: A novel approach to fabricate a label-free amperometric immunosensor for the detection of carcinoembryonic antigen (CEA) was described. Herein, methylene blue (MB), gold nanoparticles (AuNPs) and carcinoembryonic antibody (anti-CEA) were layer-by-layer assembled on the graphene-Nafion nanocomposite film-modified electrode by means of a self-assembling technique and the opposite-charged adsorption. Subsequently, the stepwise self-assembling procedure of the immunosensor was further characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The factors influencing the performance of the resulting immunosensor were studied in detail. The developed procedure showed improved features, including larger amount and higher immunoactivity of the immobilized antibody and repeatable regeneration of the sensor, as well as direct, rapid and simple determination for the antigen without multiple separation and labeling steps. The immunosensor could detect the target protein in a range of 0.5 to 120 ng/mL with a limit of 0.17 ng/mL (at 3σ). Finally, the immunosensing system was evaluated on several clinical samples. Analytical results were found to be in satisfactory agreement with those detected by the enzyme-linked immunosorbent assay (ELISA) method, indicating that this new method was a promising alternative tool for clinical diagnosis.
TL;DR: A rapid, specific, and sensitive method for the simultaneous quantitation of organophosphates (fenitrothion, malathion, and phenthoate (PAP), glufosinate (GLUF), and glyphosate (GLYP) in human serum and urine by GC-MS has been validated and was successfully applied to a clinical GLYP poisoning case.
Abstract: A rapid, specific, and sensitive method for the simultaneous quantitation of organophosphates (fenitrothion (MEP), malathion, and phenthoate (PAP)), glufosinate (GLUF), and glyphosate (GLYP) in human serum and urine by gas chromatography-mass spectrometry (GC-MS) has been validated. All of the targeted compounds together with the internal standard were extracted from the serum and urine using a mix-mode TiO-C(18) monolithic spin column. The recovery of organophosphates from serum and urine ranged from 12.7 to 49.5%. The recovery of GLUF and GLYP from serum and urine ranged from 1.9 to 7.9%. The intra- and inter-accuracy and precision (expressed as relative standard deviation, %RSD) were within 96.7-107.7% and 4.0-13.8%, respectively. The detection and quantitation limits for serum and urine were 0.1 and 0.1 µg/ml, respectively, for organophosphates, 0.1 and 0.5 µg/ml, respectively for GLUF and GLYP. The method had linear calibration curves ranging from 0.1 to 25.0 µg/ml for organophosphates and 0.5-100.0 µg/ml for GLUF, and GLYP. The validated method was successfully applied to a clinical GLYP poisoning case.
TL;DR: The obtained fluorescence images showed that the TRDP in the capillary tube created the inner and outer phases, i.e., the organic solvent-rich major inner and the water-rich minor outer phases in this case, providing the kinetic liquid-liquid interface.
Abstract: When ternary mixed solutions of water-hydrophilic/hydrophobic organic solvents are fed into a microspace under laminar flow conditions, the solvent molecules are radially distributed in the microspace. The specific fluidic behavior of the solvents is termed "tube radial distribution phenomenon" (TRDP). In this study, water-acetonitrile-ethyl acetate mixed solutions (3:8:4 volume ratio) containing fluorescent dyes, perylene (0.1 mM) and Eosin Y (1 mM), were fed into fused-silica capillary tubes (75 µm i.d.) for investigating the TRDP with a fluorescence microscope-CCD camera under various analytical conditions. The pressure at the observation point for the fluorescence on the tube was changed by altering the flow rates, capillary total lengths, and capillary effective lengths. The obtained fluorescence images showed that the TRDP in the capillary tube created the inner and outer phases, i.e., the organic solvent-rich major inner and the water-rich minor outer phases in this case, providing the kinetic liquid-liquid interface. The formation of the inner and outer phases in the capillary tube was observed at flow rates of 0.5-2.0 µL min(-1) under the present analytical conditions. We also discuss the specific formation locations of the major and minor solvents.
TL;DR: An efficient and eco-friendly injection-port tert-butyldimethylsilylated (TBDMS) derivatization and gas chromatography-mass spectrometry (GC/MS) were developed to determine an antibacterial agent, triclosan, and its metabolite: methyltriclosan (MTCS), in wastewater and surface water samples.
Abstract: An efficient and eco-friendly injection-port tert-butyldimethylsilylated (TBDMS) derivatization and gas chromatography-mass spectrometry (GC/MS) were developed to determine an antibacterial agent, triclosan (TCS), and its metabolite: methyltriclosan (MTCS), in wastewater and surface water samples. The effects of several parameters related to the TBDMS-derivatization process (i.e., injection-port temperature, residence time and volume of silylating agent) were investigated. This on-line derivatization-coupled large-volume (10 µL) sample introduction provides sensitive, fast and reproducible results for TCS residue analyses. Each water sample was extracted by reversed-phase C18 solid-phase extraction (SPE) cartridge, and then the recovery efficiency was evaluated using various eluting solutions. Limits of quantitation (LOQs) for MTCS and TCS were 3.0 and 1.0 ng/L in 100 mL of water samples, respectively. Intra- and inter-batch precision with their accuracy were also investigated. The precision for these analytes, as indicated by relative standard deviations (RSDs), proved to be less than 7 and 11%, respectively, for intra- and inter-batch. Accuracy, expressed as the mean recovery, was between 80 and 95%. The method was then applied to environmental water samples, showing the occurrence of TCS in both surface water and municipal wastewater treatment plant (MWTP) influent/effluent samples.
TL;DR: This review summarizes the techniques used for the immobilization of biomolecules by polyelectrolyte complexes; it also discusses related subjects.
Abstract: The immobilization of biomolecules is an important technique for bio-analysis, and can be applied to biosensors with both high selectivity and high sensitivity. Many researchers have developed immobilization techniques to optimize these characteristics. In the last two decades, an immobilization technique that meets the desired requirements was developed by using polyelectrolytes to form complexes, based on the electrostatic binding between polycations and polyanions. This review summarizes the techniques used for the immobilization of biomolecules by polyelectrolyte complexes; it also discusses related subjects.
TL;DR: The results showed that alizarin strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure, and non-radiation energy transfer occurred within the molecules, indicating that hydrophobic and electrostatic interactions are the main binding forces in the aliz Karin-HSA system.
Abstract: The binding properties on alizarin to human serum albumin (HSA) have been studied for the first time using fluorescence spectroscopy in combination with UV-visible absorbance spectroscopy. The results showed that alizarin strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure, and non-radiation energy transfer occurred within the molecules. The number of binding sites was 1, and the efficiency of Forster energy transfer provided a distance of 1.83 nm between tryptophan and alizarin binding site. ΔH(θ), ΔS(θ) and ΔG(θ) were obtained based on the quenching constants and thermodynamic theory (ΔH(θ) 0 and ΔG(θ) < 0). These results indicated that hydrophobic and electrostatic interactions are the main binding forces in the alizarin-HSA system. In addition, the results obtained from synchronous fluorescence spectra and three-dimensional fluorescence spectra showed that the binding of alizarin with HSA could induce conformational changes in HSA.
TL;DR: It was found that the silver ammonium complex, [Ag(NH(3))(2)](+)(aq), could be reduced in the alkaline medium by GA at room temperature; this reaction formed dispersed AgNPs and the detailed mechanism underlying this special phenomenon was elucidated.
Abstract: A simple, low toxic, sensitive strategy based on the localized surface plasmon resonance light scattering (LSPR-LS) properties of silver nanoparticles (AgNPs) is introduced for the detection of gallic acid (GA). It was found that the silver ammonium complex, [Ag(NH3)2]+(aq), could be reduced in the alkaline medium by GA at room temperature; this reaction formed dispersed AgNPs. Transmission electron microscopy analyses were performed to ascertain the formation of AgNPs. UV-visible spectra revealed the localized surface plasmon resonance (LSPR) absorption at 410 nm corresponding to the LSPR of AgNPs. On these basis, we could quantify the GA concentration in the range of 4 × 10−7 – 5 × 10−6 mol L−1 in the optimized experimental conditions. This method was used for determining the concentration of GA in artificial samples with satisfactory results. The detailed mechanism underlying this special phenomenon was elucidated.
TL;DR: Dedicated synchrotron-based X-ray absorption spectroscopy allows speciation of the large amounts of detrimental sulfur and iron compounds that often are found accumulated within the hull timbers, while high resolutionX-ray imaging shows the distribution within the wood microstructure.
Abstract: Conservation methods applied to historical shipwrecks increasingly rely on combining modern analytical techniques to obtain new insights for specially adapted conservation treatments. Crystalline salts formed on waterlogged wood are identified by powder X-ray diffraction while X-ray fluorescence measurements along wood cores show penetration profiles of contaminating elements. Dedicated synchrotron-based X-ray absorption spectroscopy, especially sulfur and iron K-edge XANES, allows speciation of the large amounts of detrimental sulfur and iron compounds that often are found accumulated within the hull timbers, while high resolution X-ray imaging shows the distribution within the wood microstructure. By fitting spectra of model compounds to high quality sulfur K-edge XANES spectra one can obtain the relative amounts of different types of functional sulfur groups. FT-IR, NMR, ESCA, MALDI-TOF mass spectrometry and size exclusion chromatography are other useful techniques to analyze the status of the wood and of the consolidation agent polyethylene glycol. Examples are given from analyses of famous artifacts.
TL;DR: The obtained results showed that the developed method is a simple, rapid and precise procedure for the simultaneous determination of metformin hydrochloride and glibenclamide in binary mixtures.
Abstract: In this work, a combined discrete and continuous wavelet transform analysis was developed for simultaneous spectrophotometric determinations of metformin hydrochloride and glibenclamide, two antidiabetic drugs, in binary mixtures without any chemical pretreatment. Absorption spectra were subjected to the 4-level db4 discrete wavelet transform (DWT) for signal de-noising. Selected continuous wavelet transform (CWT) families (rbio3.1 with scaling factor, a = 80, and gaus2, a = 60) were applied on these de-noised signals. Finally, a zero-crossing technique was used for the construction of calibration curves for both drugs. The proposed method was validated by analyzing synthetic mixtures of the investigated drugs with various concentrations. The amount of metformin hydrochloride and glibenclamide were determined by using CWT amplitudes in zero-crossing points. The mean recovery values of metformin hydrochloride and glibenclamide were found between 98.6-102.0 and 97.9-102.4% for rbio3 and 98.3-101.2 and 97.1-101.4% for gaus2 families, respectively. The obtained results showed that the developed method is a simple, rapid and precise procedure for the simultaneous determination of metformin hydrochloride and glibenclamide in binary mixtures.
TL;DR: The extraction of cobalt(II) from solutions containing various concentrations of lithium chloride, hydrochloric acid, and mixtures of Lithium chloride plus hydro chlorine is reported using a poly(vinyl chloride) (PVC)-based polymer inclusion membrane (PIM) containing 40% (w/w) Aliquat 336 as a carrier.
Abstract: The extraction of cobalt(II) from solutions containing various concentrations of lithium chloride, hydrochloric acid, and mixtures of lithium chloride plus hydrochloric acid is reported using a poly(vinyl chloride) (PVC)-based polymer inclusion membrane (PIM) containing 40% (w/w) Aliquat 336 as a carrier. The extraction from lithium chloride solutions and mixtures with hydrochloric acid is shown to be more effective than extraction from hydrochloric acid solutions alone. The solution concentrations giving the highest amounts of extraction are 7 mol L(-1) for lithium chloride and 8 mol L(-1) lithium chloride plus 1 mol L(-1) hydrochloric acid for mixed solutions. Cobalt(II) is easily stripped from the membrane using deionized water. The cobalt(II) species extracted into the membrane are CoCl(4)(2-) for lithium chloride solutions and HCoCl(4)(-) for mixed solutions; these form ion-pairs with Aliquat 336. It is also shown that both lithium chloride and hydrochloric acid are extracted by the PIM and suppress the extraction of cobalt(II) by forming ion-pairs in the membrane (i.e. R(3)MeN(+)·HCl(2)(-) for hydrochloric acid and R(3)MeN(+)·LiCl(2)(-) for lithium chloride).
TL;DR: The ability of THz waves to pass through the paper made it possible to perform a quantitative analysis using the same standard spectra as those used for an unwrapped sample, and the accuracy of a direct quantitative analysis of a packaged sample was almost the same as that of an unwRApped sample.
Abstract: We successfully analyzed the concentrations of five amino acids in commercially available dietary amino acid supplements by using terahertz time-domain spectroscopy (THz-TDS) with an error of ± 12% for the best reproduced components. We also succeeded in analyzing tablets of the supplements wrapped in paper, and thus showed the merit of using THz waves for the nondestructive quantitative analysis of packaged samples by employing the fact that THz waves are capable of passing through several types of packaging material. The ability of THz waves to pass through the paper made it possible to perform a quantitative analysis using the same standard spectra as those used for an unwrapped sample, and the accuracy of a direct quantitative analysis of a packaged sample was almost the same as that of an unwrapped sample.
TL;DR: In this first application of the RP-DLLME method to non-polar samples, the phenolic compounds were directly extracted into an aqueous micro-drop, which could be injected into a chromatography column without any further pretreatment.
Abstract: A reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) method coupled to HPLC was developed for the extraction of hydroxytyrosol (HTy) and tyrosol (Ty) from virgin olive oil. In this first application of the RP-DLLME method to non-polar samples, the phenolic compounds were directly extracted into an aqueous micro-drop, which could be injected into a chromatography column without any further pretreatment. A glass test tube with lengthened conical bottom was fitted inside a centrifuge tube in this work for more efficient withdrawal of the sedimented phase with a microsyringe. The volumes of water and ethyl acetate, the pH of water and the centrifuge time as four effective parameters on the extraction were optimized by a central composite design (response surface) method. Five replicated analyses under the optimized conditions (i.e., 0.2 mL ethyl acetate as disperser and 100 µL water at pH 11 as the extraction solvent) resulted in recoveries of 104.3 and 97.6%, and relative standard deviations of 5.75 and 4.57 for HTy and Ty, respectively. The detection limit of the method (3σ) was 0.043 mg L(-1) for HTy and 0.032 mg L(-1) for Ty. The method was successfully applied to the determination of HTy and Ty in five olive oil samples.
TL;DR: A rapid, simple and efficient colorimetric assay was established for the detection of ricin based on the Gal-SiMNPs, and the limits of detection (LODs) of 2 and 4 ng/mL for ricin in physiological buffer and serum were obtained.
Abstract: To generate a new specific recognition module for the enrichment and detection of ricin, galactose-functionalized silanized magnetic iron-oxide nanoparticles (Gal-SiMNPs) were assembled by amino-silanized MNPs (amino-SiMNPs) and a galactose linker. Amino-SiMNPs were produced by a coprecipitation method, and were coated with double layers of silica and aminosilane by hydrolysis of tetraethoxysilane and 3-aminopropyltriethoxysilane, respectively. A galactose with an amido-acid linker was synthesized by four steps of chemical modification from O-acetyl protected galactose. The diameters of Gal-SiMNPs were characterized as being 60 ± 20 nm. The average amount of galactose-loading and ricin-binding on Gal-SiMNPs was 30 ± 2 µg galactose and 29 ± 2 µg ricin toxin on the surface of 1 mg of Gal-SiMNPs, respectively. Furthermore, a rapid, simple and efficient colorimetric assay was established for the detection of ricin based on the Gal-SiMNPs, and the limits of detection (LODs) of 2 and 4 ng/mL for ricin in physiological buffer and serum were obtained, respectively.