Nanogold particles of size 15 nm were used to label goat anti-human ceruloplasmin (GCP) to obtain an immunonanogold probe (AuGCP) for ceruloplasmin (CP). In a pH 7.8 citric acid-Na2HPO4 buffer solution and in the presence of polyethylene glycol (PEG), an immunoreaction between AuGCP and CP took place, and the released nanogold particles aggregated to bigger clusters, which caused the resonance scattering (RS) intensity at 552 nm (I552nm) to be enhanced greatly. The enhanced intensity ΔI was proportional to the CP concentration (CCP) in the range from 0.0030 to 1.26 µg/mL, with a regress equation of ΔI = 101.0CCP + 1.8, a correlation coefficient of 0.9970, and a detection limit of 1.1 ng/mL CP. This simple and sensitive RS immunoassay was applied to the determination of CP in human plasma, with satisfactory results.
We utilized self-assembly of cyanine chromophores to study the conformational changes in various types of nucleic acid scaffolds: single and double stranded DNA, linear or circular DNA and RNA. We identified a chromophore that became highly fluorescent after aggregating upon nucleic acids. Fluorescence from the aggregate was instantaneous after self-assembly. Temporal emission profiles displayed a biphasic trend demonstrating kinetic dependence for assembly and disassembly. Absorption spectra of the aggregate showed a red-shifted “shoulder” peak indicative of J-aggregate. Fluorescence from J-aggregates was also red-shifted. We utilized cyanine self-assembly to quantize various nucleic acids. The limits of detection and quantization for φX174 DNA were 3 and 9 fmol, respectively. We similarly determined the sensitivity for various nucleic acids and established the optimum conditions for self-assembly. Collectively, the effects of methanol, salt, and full width at half maximum for cyanine fluorescence on DNA or carboxymethylamylose scaffolds, all suggested noncovalent, electrostatic, and hydrophobic forces were involved in supramolecular self-assembly. Our results facilitate a better understanding of supramolecular self-assembly.
Copper(II) complexes spread on an aqueous solution surface were studied by a polarized total-reflection X-ray absorption fine structure (TR-XAFS) technique. The polarized TR-XAFS spectra at the Cu-K edge for copper(II) porphyrins and copper(II) chlorophyllin in a monolayer were measured in situ at the air-water interface. The polarization dependences of X-ray absorption near-edge structure (XANES) involving a 1s→4pz transition allowed us to estimate the molecular orientation and the local coordination structure around the copper(II) atom in the polarization plane selectively. The extended X-ray absorption fine structure (EXAFS) region of the polarized TR-XAFS spectra for the metal complexes present at the air-water interface was successfully analyzed for the first time. The relative coordination number for the copper center evaluated from the EXAFS analysis indicated larger values in the vertical polarization than in the horizontal one, in agreement with the standing-up molecular orientation at the air-water interface estimated from the XANES region.
A time-resolved spectrometric measurement was conducted to determine temporal variations in the excitation temperature within a single laser plume caused by a Nd:YAG laser plasma. The two-line method using copper atomic lines was employed to estimate the excitation temperature. Two line pairs of copper lines: Cu I 521.82/Cu I 510.55 and Cu I 515.32/Cu I 510.55, were measured by using an Echelle spectrograph equipped with an ICCD detector having a high-speed gating. The excitation temperature was gradually elevated with the progress of the plasma expansion. This result cannot be explained from a direct excitation model in which excited species are principally produced through collisions with energetic particles, but from an indirect excitation model in which second-kind collisions with argon metastables and subsequent step-wise de-excitations produce the excited species. In the latter case, high-lying states of copper atoms are more populated compared to the population expected from the Boltzmann distribution. Temporal variations in the emission intensities of copper atomic lines requiring large excitation energies were also measured, and their emissions remained even in the expansion stage of the laser-induced plasma. This result also implies the over-population of high-lying copper excited levels.
A first-order derivative spectrophotometric method for the simultaneous determination of three textile dyes, Procion Yellow HE4R, Procion Red HE7B and Remazol Black 5 (RB5), has been developed. The effects of pH, heating and ionic strength of the solution on the absorption spectra of the dyes were investigated. The wavelengths selected for the measures of the derivative signals of HE4R (395 nm), HE7B (604 nm) and RB5 (659 nm) presented these coefficients of linear correlation: 0.9978, 0.9992 and 0.9999, and these detection limits: 0.180, 0.317 and 0.0233 mg L-1, respectively. The reliability and reproducibility of the method were tested and showed recovery values of 95.7 to 109%. The proposed method was applied for the determination of dyes in binary and ternary mixtures of textile effluents and showed an estimate of the loss of dyes for the effluents between 6.67 and 28.9%.
Pyronin Y (PY) has a strong resonance fluorescence in sulfuric acid medium. The characteristics of the resonance fluorescence spectra and the factors affecting the spectra were studied. A catalytic resonance fluorometry method for the determination of hydroquinone was proposed based on the catalytic effect of hydroquinone on the oxidation of PY by potassium bromate. The oxidation of PY resulted in the decrease of the resonance fluorescence intensity. The influences of several variables on the sensitivity were studied. At the optimized conditions, the decrease of the resonance fluorescence intensity was in proportion to the concentration of hydroquinone in the range of 4.42 - 1.60 × 103 µg l-1, and the detection limit was 1.46 µg l-1. The proposed method was applied successfully for the determination of trace hydroquinone in environment samples. The relative standard deviation was less than 3.90% and the recoveries were in the range of 95.2 - 104.0%.
Thermal modulation (TM) voltammetry was successfully applied to the determination of phosphate ion in natural water, by using a He-Cd dual laser as a heating source and a graphite-reinforced carbon (GRC) electrode. A heteropoly ion, i.e., 12-molybdophosphate ion ([PMoVI12O40]3-), was formed through a reaction between a phosphate ion and molybdate ions in an acidic solution, and its electroreduction was examined in a flow electrolytic cell by TM voltammetry. Measured TM voltammograms showed two peaks corresponding to two successive two-electron reductions of the 12-molybdophosphate ion, and the peak intensities were proportional to the concentration of the phosphate ion. Because of the strong adsorption of 12-molybdophosphate ion onto the GRC electrode, a detection limit as low as 0.8 nmol dm-3 (S/N = 3) was achieved. The determination of phosphate ion in real samples (river water) was carried out by spectrophotometry (the molybdenum-blue method) and TM voltammetry, and the determination values obtained by both methods were in a good agreement with each other. These results prove the possibility of TM voltammetry as an electroanalytical method.
An easy and fast Fourier transform continuous cyclic voltammetric technique (FFTCV) for monitoring of ultra trace amounts of cyclizine in a flow-injection system has been introduced in this work. The potential waveform, which was applied continuously on an Au disk microelectrode (12.5 µm in radius) consisted of the potential steps for cleaning, accumulation and potential ramp. The proposed detection method has some advantages, the greatest of which are as follows: first, it is no longer necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. The detection limit for cyclizine was 1.8 ng ml-1. The relative standard deviation (RSD) of the proposed technique at 5.0 × 10-7 was 2.0 for 10 runs. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the cyclizine were considered. The proposed method was applied to the determination of cyclizine in a pharmaceutical preparation.
In this research, a new potentiometric enzymatic membrane biosensor for the detection of organophosphorus pesticides (OPs) was constructed. The basic element of this biosensor was a pH electrode modified with an immobilized acetylcholinesterase layer formed by entrapment with methylcellulose, N,N-dimethylformamide, and bovine serum albumin. The response characteristics of the biosensor were measured and discussed. It was shown that there is a good linear relationship between the inhibition rate and the negative logarithm of OPs concentration in the range from 10-7 to 10-5 mol/L, with the detection limits of 10-7 mol/L for the five pesticides. Moreover, the biosensor could resist the disturbances of below 10-6 mol/L of Cu2+ and Pb2+, and below 10-5 mol/L of Cd2+. In addition, the measurement results obtained by the biosensor method were in good agreement with those obtained by the gas chromatography method. This method was successfully applied to detect OPs that remained in the potted lettuce.
Monolithic columns were successfully prepared and used with capillary electrochromatography for the analysis of 3,4-methylenedioxymethamphetamine (MDMA) in ecstasy tablets and its metabolites in urine samples. Cationic and neutral monolith columns provided better efficiencies than anionic monoliths. The neutral butyl methacrylate (BMA) monolith column provided symmetrical peaks with the highest efficiency, high resolution and short analysis times. The developed method using BMA monolithic column provided the detection limits for MDMA and its metabolites at 1 µg mL-1 with excellent intra-day and inter-day precision and linearity from 7.5 to 100 µg mL-1 (R2 ≥ 0.99). MDMA was found as the main component in ecstasy tablets while 4-hydroxy-3-methoxymethamphetamine as the major metabolite in urine samples. High recoveries (97% for MDMA from tablets and 84 - 102% for its metabolites from urine samples) were obtained using simple ultrasonic extraction for ecstasy tablets and liquid.liquid extraction for urine samples.
A sensitive quantification of decabrominated diphenyl ether (deca-BDE) was achieved by optimizing the injection temperature, pressure and column system with gas chromatography mass spectrometry in selected ion monitoring mode. A simple one-step cleanup method with acid silica gel column chromatography showed the optimum efficiency and minimum matrix interference. Ultrasonic-assisted extraction with toluene provided the best performance (111%, 1 h) as compared to Soxhlet extraction (110%, 5 h) and microwave-assisted extraction (63%, 15 min) taking consideration of extraction efficiency and consumed time. The proposed method could meet the requirement for determination of deca-BDE in polymers and has the potential to monitor the content of deca-BDE in electrical and electronic equipment for routine analysis.
So far, there has been no advanced method to assure quality control for herbal drugs (HD) and traditional Chinese medicines (TCM). Because HD and TCM have been becoming more and more important for human health, it is necessary to set up an effective quality control method in terms of overall qualitative and overall quantitative analyses for them. In this study, the HPLC fingerprints (HPLC-FPs) of compound liquoric tablets (CLTs) were established to effectively control their qualities by using the dual qualitative and dual quantitative similarities (DQDQS) method, in which 13 batches of CLTs synthesized the referential FP (RFP) as a norm. Among the 26 batches of CLTs, 11 batches were assessed as completely qualified, the contents of 3 batches were obviously higher while the contents of other 6 batches were lower; the chemical constituents proportion distributed in 1 batch were not qualified and the remaining 5 batches were inferior. HD and TCM can be authentically evaluated by this method.
A rapid method has been developed for monitoring five multiclass pesticides commonly used in citrus fruits. The determination is performed by ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS), after extraction with a mixture of ethyl acetate and sodium sulfate. The method has been validated for orange matrix. Mean recoveries obtained were between 74 - 110% with a repeatability precision of < 7%, intermediate precision of < 10% and reproducibility precision of < 17%. Linearity over the range 0.010 - 0.150 mg/kg was demonstrated (r2 ≥ 0.99) with limits of quantification (LOQs) of ≤0.01 mg/kg. Also, an analytical study focused on the stability of pesticide residues in orange extracts under storage was performed. The method has been applied to the analysis of 365 samples from the agricultural area of the Valencian Community (Spain). Of 103 samples that contained pesticide residues, only abamectin in 2 samples and carbendazim in 5 samples slightly exceeded the European maximum residue limits (MRLs).
Slice-scan method (SS) scans the two-way chromatographic data at each retention time point, and hence obtains the corresponding spectral “slice”s. Then, the spectral slices are transformed into new spectral profiles by spectral transformation, based on which qualitative and quantitative analysis of the overlapping chromatographic peaks could be done. In this work, a new strategy for directly determining the component of interest in the overlapping chromatographic peak is presented, which takes advantage of the selective spectral slices of the determined component and establishes the best calibration curve by applying the new generated spectral profiles after spectral transformation. Meanwhile, the contents of four bioactive lignans, schisandrin, schisantherin, deoxyschizandrin and γ-schizandrin in Schisandra chinensis Baill., a famous herb in China were determined using SS together with the new quantitative strategy, and satisfactory results have been obtained.
A novel chelating polymer including three different functional groups, such as amidoxime (-C(NH2)=NOH), azo (-N=N-) and carboxylic acid (-COOH), was synthesized. The poly(acrylamidoxime-co-(1-(2-pirydylazo)-2-naphtyl-2-methacrylate)-co-methacrylicacid) (APM) polymer, prepared in three steps, was characterized by FT-IR and elemental analyses. The resin was used for solid-phase extractive separation and the preconcentration of trace amounts of uranium(VI). The determination of U(VI) was performed by a spectrophotometric method using Arsenazo III as a complexing agent. The optimum conditions were found for the quantitative recovery of U(VI) (pH 5; eluent, 3 mol L-1 HClO4; sample and eluent flow rates, 1 mL min-1etc.). The capacity of the APM resin for U(VI) was found to be 24.2 mg g-1. A preconcentration factor of 37.5 and the three sigma detection limit of 1.6 µg L-1 (n = 20) were achieved for U(VI) ions. The polymer was used for separating and preconcentrating the uranyl ion existing in seawater samples and a certified reference material (TMDA 70; fortified lake water sample).
Saw palmetto extract (SPE) has been widely used for the treatment of lower urinary-tract symptoms secondary to benign prostatic hyperplasia. The mechanisms of pharmacological effects of SPE include the inhibition of 5α-reductase, anti-androgenic effects, anti-proliferative effects, and anti-inflammatory effects. Previously, we showed that SPE bound actively to α1-adrenergic, muscarinic and 1,4-dihydropyridine calcium channel (1,4-DHP) receptors in the prostate and bladder of rats, whereas its active constituents have not been fully clarified. The present investigation is aimed to identify the main active components contained in hexane and diethyl ether extracts of SPE with the use of column chromatography and preparative HPLC. Based on the binding activity with α1-adrenergic, muscarinic, and 1,4-DHP receptors, both isolated oleic and lauric acids were deduced to be active components. Authentic samples of oleic and lauric acids also exhibited similar binding activities to these receptors as the fatty acids isolated from SPE, consistent with our findings. In addition, oleic and lauric acids inhibited 5α-reductase, possibly leading to therapeutic effects against benign prostatic hyperplasia and related lower urinary-tract symptoms.
α-Glucosidase (AGH) from the small intestine of rat was immobilized onto a glutaradehyde (GA) activated NH2-96 well microplate to establish a convenient and rapid AGH inhibition assay system. After AGH immobilization, remaining GA groups were blocked by β-alanine to induce a negative charge on the surface of the well. The AGH-plate showed an enzyme activity of 444 nU/well under an assayed condition at 37°C for 2 h using 0.3 mM 4-methylumbelliferyl-α-D-glucopyranoside as a fluorogenic substrate. Inhibitory powers of voglibose and acarbose as therapeutic AGH inhibitors were successfully evaluated to have IC50 values of 13 and 114 nM, respectively.
Cohesive energy densities (Cw,MLA/J cm-3) for ion-pair complexes (MLA: M+ = Li+ to Cs+; w: water) with six crown ethers (L), such as 18-crown-6 ether (18C6), benzo-18C6, and dibenzo-24-crown-8 one, and A- = picrate were calculated at 298 K by a procedure that uses either (i) an equation rearranged from that underlying log KD,MLA-vs.-log KD,L plots or (ii) intercepts of their plots and from both procedures. Here, KD,MLA and KD,L denote the distribution constants of MLA and L from w into a diluent, respectively. As additional MLA, Na(18C6)(2,4-dinitrophenolate) and Na(18C6)(2,6-dinitrophenolate) were employed for the present Cw,MLA calculation. The Cw,MLA values calculated from the two procedures agreed well, and they were proportional to the log(KD,MLA)-1 values. From the log KD,MLA values for dinitrophenolates and previously-reported values for Na(18C6)A, the hydrophobic property of some pairing anions, A-, was ordered as F3CCO2- < ReO4- < MnO4- < 2,4-dinitrophenolate < 2,6-dinitrophenolate < picrate, and then discussed based on a relation with the log Kex values, where Kex shows the extraction constant (mol-2 dm6 unit) for Na(18C6)A into 1,2-dichloroethane.
The unique potentiometric response of mercury sensors was investigated in aqueous Cl--rich media, which are often encountered in natural, especially biological samples. The conventional neutral-carrier-based Hg(II)-ISEs are not practically useful because the Cl- concentrations in natural aqueous samples are normally too high for mercury to be present in the form of Hg2+. Negative potentiometric slopes, which are the opposite behavior of the previously reported Hg(II)-ISEs, were experimentally confirmed and quantitatively reasoned based on the aqueous solution equilibrium of Hg2+.
A simple and rapid quantification method was developed for determining both talniflumate and niflumic acid in human plasma. After simple protein precipitation with acetonitrile, the analytes were chromatographed on a reversed-phase C18 column and detected by LC/MS/MS with electrospray ionization. The assay accuracy and precision were within the FDA guidance for the analytical method validation. This method was used to measure the plasma concentrations of both compounds from healthy subjects after a single oral dose of talniflumate, 740 mg.
A possible replacement of previously recommended Spheron-Thiol resin gel for measuring mercury by diffusive gradients in a thin film (DGT) was studied. Duolite GT73 resin and newly prepared 6-mercaptopurine modified Iontosorb AV as binding phases were tested. The preparation procedure of resin-embedded gels was optimized and DGT with new resin gels verified. The verified DGT containing new resin gels was used for in situ mercury measurement in Svitava River.