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Constant power cold start mode of proton exchange membrane (PEM) fuel cell is essential in practical applications, however, unlike the constant current and voltage cold start modes, the constant power mode was largely ignored in previous fundamental modeling and experimental studies. In this study, a PEM fuel cell stack cold start model for analyzing the constant power cold start process is developed, and the fundamental differences among the various start-up modes are elucidated. In the constant power cold start mode, the start-up process may fail before the ice fully covers the cathode catalyst layers (CLs), because the stack may not be able to supply the required power output, which is different from the constant current and voltage start-up modes. The initial water content and start-up temperature could limit the power output significantly. The constant power can be controlled at higher current (CPHC) or lower current (CPLC). In the CPHC mode, the current density decreases and the stack voltage increases during the cold start process, while it is reversed in the CPLC mode. Generally, the CPLC mode produces less heat during cold start process than the other start-up modes, because the current density is often kept at low level. [ABSTRACT FROM AUTHOR]

Carboxylic group-functionalized single-walled carbon nanotubes (SWNTs) were assembled vertically on the glassy carbon electrode using ethylenediamine as linking agent to fabricate an aligned electrode (SWNTE). Single-stranded DNA (ssDNA) wrapped around the SWNTs to form ssDNA-wrapped SWNTE structures based on the interaction between ssDNA and SWNT. A sensitive differential pulse voltammetric (DPV) response was obtained at the ssDNA-wrapped SWNTE owing to the electrooxidation of guanine bases. Double-stranded DNA (dsDNA) was formed when ssDNA on the ssDNA-wrapped SWNTE was hybridized with complementary ssDNA (cDNA). The dsDNA was removed from the SWNTs by undergoing a process of preconditioning at -0.6 V. Consequentially, the DPV response of guanine bases decreased. The used SWNTE could be renewed easily via ultrasonically rinsing. On the basis of this mechanism, a label-free and readily reusable electrochemical DNA hybridization biosensor was designed by directly monitoring the current change of guanine bases. Under optimum conditions, the plot of the measurement signal of guanine bases versus the cDNA concentrations was a good straight line in the range of 40-110 nM with a detection limit of 20 nM (3s). The biosensor can be switched to detect different target DNAs easily. [ABSTRACT FROM AUTHOR]

Carboxyl group-functionalized single-walled carbon nanotubes (SWNTs) and 2,6-pyridinedicarboxylic acid (PDC) were electropolymerized by cyclic voltammetry on a glassy-carbon electrode (GCE) surface to form composite films (SWNTs/PDC). Zirconia was then electrodeposited on the SWNTs/PDC/GCE from an aqueous electrolyte containing ZrOCl2 and KCl by cycling the potential between −1.1 V and +0.7 V at a scan rate of 20 mV s−1. DNA probes with a phosphate group at the 5′ end were easily immobilized on the zirconia thin films, because of the strong affinity between zirconia and phosphate groups. The sensors were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS was used for label-free detection of the target DNA by measuring the increase of the electron transfer resistance ( R et) of the electrode surface after the hybridization of the probe DNA with the target DNA. The PAT gene fragment and polymerase chain reaction (PCR) amplification of the NOS gene from transgenically modified beans were satisfactorily detected by use of this DNA electrochemical sensor. The dynamic range of detection of the sensor for the PAT gene fragment was from 1.0 × 10−11 to 1.0 × 10−6 mol L−1 and the detection limit was 1.38 × 10−12 mol L−1. [ABSTRACT FROM AUTHOR]

Ethylenediamine (En) was introduced onto an electrochemical oxidized glassy carbon electrode using water-soluble 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). DNA was then covalently immobilized onto the En modified GCE with surface-bound primary amino group in the presence of EDC. Cyclic voltammetry and differential pulse voltammetry were used to characterize the DNA modified electrodes using methylene blue (MB) as electro-active indicator. The results showed that ssDNA immobilized using ethylenediamine as connector (ssDNA/En/GCE) could hybridize with target ssDNA more effectively than that immobilized directly on the bare GCE (ssDNA/GCE). The ssDNA/En/GCE was successfully employed for the selective detection of CaMV35S gene (presented in almost all the genetically modified plants) in a fragment of 20-base oligodeoxynucleotides sample. The electro-reduction signal of MB was related to the CaMV35S gene concentration over the range of 5.0x10-9∼1.2x10-7 mol/L. [ABSTRACT FROM AUTHOR]

In pH 3.0 acidic buffer solution, 2-(2-hydroxy-3,6-disulfo-1-naphthyl)-azo-phenylarsenic acid (thorin) can interact with protein to form a supramolecular complex. The interaction of thorin with human serum albumin (HSA) was studied in solution by cyclic voltammetry on mercury electrode. In the presence of HSA, the reductive peak current of thorin at -0.49 V (vs.SCE) was decreased apparently without the changes of peak potentials and no new peaks appeared. The electrochemical parameters of the thorin-HSA interaction solution were calculated and compared with that of thorin solution, the results showed that there were no obvious differences in the two sets of parameters. So the formed biosupramolecular complex was electrochemical inactive and couldn't take place redox reaction on the mercury electrode. The binding reaction resulted in the decrease of the free concentration of thorin in the reaction solution, and the decrease of the reductive peak current of thorin. The binding constant and the binding ratio of thorin-HSA were calculated as 1.15x109 and 2:3, respectively. Based on the decrease of peak current, a sensitive protein assay method was proposed with second order derivative linear sweep voltammetry. The optimal conditions such as the effect of pH, the concentration of thorin, reaction time and temperature, ionic strength et al on the binding reaction had been carefully studied. The interference of coexisting substances was checked. Under the selected conditions, the decrease of the reductive peak current of thorin was in proportion to the concentration of 1.0∼12.0 mg L-1 for HSA, 0.1∼16.0 mg L-1 for bovine serum albumin (BSA), 1.0∼20.0 mg L-1 for oval albumin (OVA) and 0.4∼18.0 mg L-1 for lipase et al. This new electrochemical method was further applied to the determination of human serum samples and the results were in good agreement with the traditional Commassie Brilliant Blue G-250 (CBB G-250) spectrophotometric method. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional numerical model, based on the volume-of-fluid (VOF) method, was developed to investigate the water transport characteristics in the cathode of a proton exchange membrane fuel cell (PEMFC) taking into account the deformation of the gas diffusion layer (GDL). Simulations are carried out with different inlet flow rates, amount of liquid water in the GDL, positions of water droplet in the flow channel, and contact angles of the GDL and flow channel surfaces. Two mechanisms of liquid water droplet leaving the GDL are observed. One is driven by the surface tension when the gas flow rate is low, whereas the other is driven by the gas flow at high gas flow rates. Meanwhile, the deformation of the GDL and other factors highly influence the water droplet dynamics. [ABSTRACT FROM AUTHOR]

A carbon ionic liquid electrode ( CILE) was fabricated by mixing N-butylpyridinium hexafluoro-phosphate ( BPPF 6) with graphite powder and further used for the investigation on the electrochemical behavior of L-tryptophan ( Trp). The fabricated CILE showed good conductivity, inherent electrocatalytic ability and strong promotion to the electron transfer of Trp. On the CILE, an irreversible oxidation peak appeared at 0.948 V (vs. saturated calomel reference electrode). For 5.0 × 10−5 M Trp the oxidation peak current increased about 5 times and the oxidation peak potential decreased on 0.092 V compared to carbon paste electrode. The results indicated that an electrocatalytic reaction occurred on CILE. The conditions for the electrochemical detection were optimized and the electrochemical parameters of Trp on CILE were carefully investigated. Under the selected conditions, the oxidation peak current showed linear relationship with Trp concentration in the range of 8.0 × 10−6 ∼1.0 × 10−3 M for cyclic voltammetry and the detection limit was estimated as 4.8 × 10−6 M (3σ). The interferences of other amino acids or metal ions on the determination were tested and the proposed method was successfully applied to the synthetic sample analysis. [ABSTRACT FROM AUTHOR]

Abstract  The electrochemical behaviors of metol on an ionic liquid N-butylpyridinium hexafluorophosphate modified carbon paste electrode (IL-CPE) were studied in this paper. The results indicated that a pair of well-defined quasi-reversible redox peaks of metol appeared with the decrease of overpotential and the increase of redox peak current, which was the characteristics of electrocatalytic oxidation. The electrocatalytic mechanism was discussed and the electrochemical parameters were calculated with results of the charge-transfer coefficient (α) as 0.45, the electrode reaction rate constant (k s) as 4.02 × 10−3 s−1, and the diffusion coefficient (D) as 6.35 × 10−5 cm2/s. Under the optimal conditions, the anodic peak current was linear with the metol concentration in the range of 5.0 × 10−6 ∼ 1.0 × 10−3 mol/L (n = 11, γ = 0.994) and the detection limit was estimated as 2.33 × 10−6 mol/L (3σ). The proposed method was successfully applied to determination of metol content in synthetic samples and photographic solutions. [ABSTRACT FROM AUTHOR]

A room-temperature ionic liquid N-butylpyridinium hexafluorophosphate was used as a binder to construct an ionic liquid modified carbon paste electrode, which was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The ionic liquid carbon paste electrode (IL-CPE) showed enhanced electrochemical response and strong analytical activity towards the electrochemical oxidation of dopamine (DA). A pair of well-defined quasireversible redox peaks of DA appeared, with the redox peaks located at 215 mV ( E pa) and 151 mV ( E pc) (vs. the saturated calomel electrode, SCE) in pH 6.0 phosphate buffer solution. The formal potential ( E 0´) was calculated as 183 mV (vs. SCE) and the peak-to-peak separation as 64 mV. The electrochemical behavior of DA on the IL-CPE was carefully investigated. Under the optimal conditions, the anodic peak currents increased linearly with the concentration of DA in the range 1.0 × 10−6–8.0 × 10−4 mol/L and the detection limit was calculated as 7.0 × 10−7 mol/L (3 σ). The interferences of foreign substances were investigated and the proposed method was successfully applied to the determination of DA injection samples. The IL-CPE fabricated was sensitive, selective and showed good ability to distinguish the coexisting ascorbic acid and uric acid. [ABSTRACT FROM AUTHOR]

Room temperature ionic liquid N-butylpyridinium hexafluorophosphate (BPPF6) was used as a binder to construct a new carbon ionic liquid electrode (CILE), which exhibited enhanced electrochemical behavior as compared with the traditional carbon paste electrode with paraffin. By using the CILE as the basal electrode, hemoglobin (Hb) was immobilized on the surface of the CILE with nano-CaCO3and Nafion film step by step. The Hb molecule in the film kept its native structure and showed good electrochemical behavior. In pH 7.0 Britton−Robinson (B−R) buffer solution, a pair of well-defined, quasi-reversible cyclic voltammetric peaks appeared with cathodic and anodic peak potentials located at −0.444 and −0.285 V (vs SCE), respectively, and the formal potential (E°‘) was at −0.365 V, which was the characteristic of Hb Fe(III)/Fe(II) redox couples. The formal potential of Hb shifted linearly to the increase of buffer pH with a slope of −50.6 mV pH-1, indicating that one electron transferred was accompanied with one proton transportation. Ultraviolet−visible (UV−vis) and Fourier transform infrared (FT-IR) spectroscopy studies showed that Hb immobilized in the Nafion/nano-CaCO3film still remained its native arrangement. The Hb modified electrode showed an excellent electrocatalytic behavior to the reduction of H2O2, trichloroacetic acid (TCA), and NaNO2. [ABSTRACT FROM AUTHOR]

A novel one-step electrochemical synthesis of the reduced graphene oxide and poly(m-aminobenzenesulfonic acid, ABSA) nanocomposite (PABSA-rGNO) via pulse potentiostatic method (PPM) for direct and freely switchable detection of target genes is presented. Unlike most electrochemical preparation of hybrids based on rGNO and polymer, electrochemical synthesis of PABSA (during the pulse electropolymerization period of PPM) and electrochemical reduction of rGNO (during the resting period of PPM), in this paper, were alternately performed. The total progress synchronously resulted in PABSA-rGNO nanocomposite. This nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The PABSA-rGNO nanocomposite integrated graphene (a single-atom thick, two-dimensional sheet of sp2 bonded conjugated carbon) with PABSA (owning rich-conjugated structures, functional groups, and excellent electrochemical activity), which could serve as an ideal electrode material for biosensing and electrochemical cell, etc. As an example, the immobilization of the specific probe DNA was successfully conducted via the noncovalent method due to the π-π* interaction between conjugated nanocomposite and DNA bases. The hybridization between the probe DNA and target DNA induced the product dsDNA to be released from conjugated nanocomposite, accompanied with the self-signal regeneration of nanocomposite ("signal-on"). The self-signal changes served as a powerful tool for direct and freely switchable detection of different target genes, and the synergistic effect of PABSA-rGNO nanocomposite effectively improved the sensitivity for the target DNA detection. [ABSTRACT FROM AUTHOR]

A voltammetric sensor was fabricated by applying a Nafion and multi-walled carbon nanotubes (MWCNTs) composite film on the surface of a carbon ionic liquid electrode (CILE), which was prepared by mixing 1-butyl-3-methylimidazolium hexafluorophosphate with graphite powder. The electrochemical behavior of adenine on the Nafion-MWCNTs/CILE was investigated in pH 5.5 buffer solution. Adenine showed an irreversible adsorption-controlled oxidation reaction with enhanced electrochemical response, which was due to the presence of high conductive MWCNTs on the CILE surface. The electrochemical parameters of adenine electro-oxidation were determined, and the experimental conditions were optimized. Under the optimal conditions, the oxidation peak current was linear to the adenine concentration over the range of 1.0 × 10−7 to 7.0 × 10−5 mol L−1 with a detection limit of 3.3 × 10−8 mol L−1 (signal/noise = 3). The electrode showed good stability and selectivity, and was further applied to milk powder samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The electrochemical behaviors of the interaction of chromotrope 2R (CH2R) with human serum albumin (HSA) are investigated on the hanging mercury drop electrode with linear sweep voltammetry. In the acidic buffer solution (pH 2.5) CH2R has a well-defined voltammetric reductive wave at −0.34 V (SCE). On the addition of HSA into the CH2R solution, the reductive peak current of CH2R decreases with little movement of the peak potential. The voltammetric study shows that the electrochemical parameters of interaction solution do not change and a new electrochemically non-active complex is formed via interaction of CH2R with HSA, which cannot be reduced on the Hg electrode and results in the decrease of the free concentration of CH2R. The decrease of reductive peak current is proportional to HSA concentration and further used for protein detection. The binding ratio and the binding constant are further calculated with the experimental voltammetric data. [ABSTRACT FROM AUTHOR]

An electrode modified with an ionic liquid was used for the electrochemical determination of 3,4-dihydroxybenzoic acid (DHBA). Cyclic voltammetry indicated a pair of well-defined quasi-reversible redox peaks with a formal peak potential located at 586 mV (vs. the SCE). The voltammetric response to DHBA is largely improved compared to a traditional carbon paste electrode. This is attributed to a larger interface (due to the presence of an ionic liquid) with higher conductivity and inherent catalytic capability. The charge transfer coefficient, the standard rate constant and the apparent diffusion coefficient were calculated. The oxidation peak current was linearly related to the concentration of DHBA in the range 0.8–1.5 mM, and the detection limit was 0.62 µM (at 3σ). The effect of potential interferents was investigated, and the method was successfully applied to the determination of DHBA in different samples. [ABSTRACT FROM AUTHOR]

The direct electrochemistry of herring sperm double-stranded DNA (dsDNA) on an ionic liquid N-butylpyridinium hexafluorophosphate modified carbon paste electrode was investigated. The cyclic voltammogram showed two irreversible oxidation peaks at 0.868 V and 1.188 V ( vs. SCE), which corresponded to the oxidation of guanine and adenine residues, respectively. Compared to the common carbon paste electrode the electrochemical response was greatly improved. The electrochemical behavior of dsDNA on the modified electrode was carefully investigated with the electrochemical parameters were calculated. Under optimal conditions the dsDNA can be directly determined in the concentration range from 50 to 600 μg mL−1 with a detection limit of 17 μg mL−1 (3σ). [ABSTRACT FROM AUTHOR]

An electrochemical DNA detection method was developed for the 35S promoter from Figwort mosaic virus (FMV 35S) gene sequence by using a microplate hybridization assay with PbS nanoparticles as labels. There are four main steps in the procedure including target FMV 35S ssDNA immobilization on the microplate, the hybridization of ssDNA with a PbS NPs-labeled oligonucleotide probe, the dissolution of the PbS anchored on the hybrids by the addition of HNO3 and the detection of released Pb (II) by differential pulse anodic stripping voltammetry. Based on this principle, the voltammetric response of Pb (II) was linearly related to the logarithm of the target FMV 35S concentration in the range from 8.0 × 10−13 to 1.6 × 10−10 mol L−1. The detection limit is 2.5 × 10−13 mol L−1 (3σ). [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) quantum dots modified with ethylenediamine were synthesized under hydrothermal conditions, and labeled onto the probe DNA owing to the electrostatic interaction between the amino group and the negatively charged phosphate skeleton of the DNA molecule. The surface of a chitosan-entrapped carbon paste electrode was modified with gold nanoparticles. The target DNA was immobilized on the gold nanoparticle membrane electrode and hybridized with the probe DNA labeled with CdSe. Then, CdSe was dissolved by the HNO3 solution. The target DNA was detected by differential pulse anodic stripping voltammetry of cadmium. Sequence-specific DNA of the 35S promoter of cauliflower mosaic virus gene was successfully determined with a dynamic detection range from 5.0 × 10−12 to 5.0 × 10−7 mol•L−1, with a detection limit of 6.5 × 10−13 mol•L−1. Complementary DNA could be recognized by this method with good selectivity over non-complementary DNA and 2-base mismatched DNA. [ABSTRACT FROM AUTHOR]

An electrochemical method for the determination of lysozyme (LYS) based on its interaction with alizarin red S (ARS) was established by linear sweep voltammetry in this paper. The electrochemical behaviour of ARS with LYS was investigated on a dropping mercury working electrode in 0.2 mol/L pH 4.8 Britton-Robinson (B-R) buffer solution. ARS showed a sensitive second order derivative linear sweep voltammetric reductive peak at -0.42 V (vs SCE). After the addition of LYS, the reductive peak current of ARS decreased without the shift of the reductive peak potential and no new waves appeared, which was due to the formation of a supramolecular complex of ARS with LYS in the solution. The stoichiometry of the ARS-LYS complex was further calculated by the electrochemical data with the results of the binding ratio as 3 : 1 and the binding constant as 2.82 × 1014. Under the selected conditions, the decrease of the second order derivative linear sweep voltammetric reductive peak current of ARS was in proportion to the LYS concentration in the range from 0.8 to 35.0 mg/L and the detection limit of LYS was calculated as 0.52 mg/L (3s). Different kinds of LYS samples were detected satisfactorily with this method. [ABSTRACT FROM AUTHOR]

Abstract  A novel biocompatible composite film containing sodium alginate (SA), room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), SiO2 nanoparticle, and hemoglobin (Hb) was fabricated and covered on the surface of a traditional carbon paste elecrode (CPE). The immobilized Hb on the electrode surface showed good direct electrochemical behaviors, and a pair of quasi-reversible redox peaks of Hb was obtained, which indicated that the direct electron transfer of Hb with the electrode surface had been achieved. The SA/nano-SiO2/BMIMPF6/Hb/CPE showed dramatically electrocatalytic activity to the reduction of trichloroacetic acid, hydrogen peroxide (H2O2), and oxygen (O2). The kinetic parameters for the electrocatalytic reactions were evaluated. The composite film showed the potential to the biosensor and biocatalysis. [ABSTRACT FROM AUTHOR]

Abstract: Well-dispersed Ag2S nanocrystals with size of about 20~30 nm were prepared in distilled water at room temperature with the assistance of imidazoline surfactant quaternary ammonium salt of 2-undecyl-1-dithioureido-ethyl-imidazoline (SUDEI) prepared in-house. The products were characterized by TEM, XRD, and FT-IR, respectively. The influence of SUDEI concentration on the dispersion of Ag2S products was briefly discussed. Furthermore, the obtained Ag2S nanocrystals product was applied into DNA hybridization analysis, and the results indicated that the detection limit of target ssDNA was up to pmol/L, showing that the DNA probe labeled with Ag2S nanoparticles is of promising application value in electrochemical DNA detection analysis and biosensors. [Copyright &y& Elsevier]

A mercaptoacetic acid (MAA)-modified cadmium sulfide (CdS) nanoparticle was synthesized in aqueous solution and used as an oligonucleotide label for the electrochemical detection of nopaline synthase (NOS) terminator gene sequence. The carboxyl groups on the surface of the CdS nanoparticle can be easily covalently linked with NH2-modified NOS oligonucleotide probe sequences. The target ssDNA sequence was fixed onto the electrode surface by covalently linking to a mercaptoethanol self-assembled gold electrode, and the DNA hybridization of target ssDNA with probe ssDNA was accomplished on the electrode surface. The CdS nanoparticles anchored on the hybrids were dissolved in the solution by the oxidation with HNO3 and further detected by a sensitive differential pulse anodic stripping voltammetric method. The detection results can be used for monitoring the hybridization, and the NOS target sequence was satisfactorily detected in the approximate range from 8.0 × 10−12 to 4.0 × 10−9 mol L−1 with a detection limit of 2.75 × 10−12 mol L−1 (3 σ). The established method extended the nanoparticle-labeled electrochemical DNA analysis to genetically modified organisms (GMOs) specific sequence samples with higher sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

The interaction of acridine orange (AO) with double-stranded (ds) DNA in aqueous solution was investigated by linear sweep polarography (LSP) on a dropping mercury working electrode (DME). In pH 2.5 Britton-Robinson (B-R) buffer solution, AO had a sensitive linear sweep polarographic reductive peak at -0.89 V (vs. SCE), which could be greatly inhibited by the addition of dsDNA, with a positive shift of the peak potential. Based on the decrease of the reductive peak current, a new quantitative electrochemical determination method for dsDNA was developed with a linear range of 2.0-20.0 mg l-1 and the linear regression equation: ΔIp" (nA) = 111.90 C (mg l-1)+125.32 (n = 9, γ = 0.997). The influences of commonly co-existing substances, such as metal ions, amino acid, etc., on the determination were also investigated. The method is sensitive, rapid and simple with good selectivity. The new proposed method was further applied to the detection of RNA and three synthetic samples containing dsDNA with satisfactory results. The binding number and the equilibrium constant between dsDNA and AO were calculated by an electrochemical method. [ABSTRACT FROM AUTHOR]

Abstract: A room temperature ionic liquid (RTIL) modified carbon paste electrode was constructed based on the substitute of paraffin with 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF6) as binder for carbon paste. Direct electrochemistry and electrocatalytic behaviors of hemoglobin (Hb) entrapped in the sodium alginate (SA) hydrogel film on the surface of this carbon ionic liquid electrode (CILE) were investigated. The presence of IL in the CILE increased the electron transfer rate and provided a biocompatible interface. Hb remained its bioactivity on the surface of CILE and the SA/Hb modified electrode showed a pair of well-defined, quasi-reversible cyclic voltammetric peaks with the apparent standard potential (E 0′) at about −0.344V (vs. SCE) in pH 7.0 Britton–Robinson (B–R) buffer solution, which was attributed to the Hb Fe(III)/Fe(II) redox couple. UV–Vis absorption spectra indicated that heme microenvironment of Hb in SA film was similar to its native status. Hb showed a thin-layer electrochemical behavior in the SA film with the direct electron transfer achieved on CILE without the help of electron mediator. Electrochemical investigation indicated that Hb took place one proton with one electron electrode process and the average surface coverage of Hb in the SA film was 3.2×10−10 mol/cm2. The immobilized Hb showed excellent electrocatalytic responses to the reduction of H2O2 and nitrite. [Copyright &y& Elsevier]

The interactions of heparin with crystal violet were studied by absorption spectrophotometry and voltammetry in pH 3.0 Britton-Robinson (B-R) buffer solution. Heparin, which is negatively charged, can easily bind to the positively charged crystal violet to form a supramolecular ion-association complex. Owing to the formation of the new complex, the maximum absorption wavelength of crystal violet at 592 nm decreased and two new absorption peaks appeared at 510 nm and 363 nm after the addition of heparin. The oxidation peak current of crystal violet on glassy carbon electrode (GCE) at +0.84 V (vs. SCE) also changed correspondingly without change of the peak potential, which also indicated that the binding reaction had taken place. Under the selected conditions a new spectrophotometric analytical method was established for heparin with the linear range between 0.10–4.0 mg L–1 with a linear regression equation as ΔA = –0.002 + 0.227C (mg L–1), (n = 8, γ = 0.997). The relative standard deviation for eleven parallel determinations of 0.40 mg L–1 heparin was 1.69% and the detection limit (3σ) was 0.09 mg L–1. This new method was further applied to the determination of heparin sodium injection samples with satisfactory results. [ABSTRACT FROM AUTHOR]

In the title compound, C23H29N3O10S, the hexa­pyran­osyl ring adopts a chair conformation with all the substituents in equatorial positions. The mol­ecules are linked by C—H⋯S interactions into ribbons parallel to the a axis and two additional intermolecular C—H⋯O interactions provide further stability in a three-dimensional network. [ABSTRACT FROM AUTHOR]

In the title compound, C19H23N3O7S, the hexo­pyran­osyl ring adopts a chair conformation. All the substituents are in equatorial positions. The mol­ecules are linked by C—H⋯S interactions into ribbons, which are connected into a two-dimensional framework via intermolecular C—H⋯O short contacts. [ABSTRACT FROM AUTHOR]

High-speed photography and 3D phase Doppler methods are used to obtain the swirl jet images, 3D velocities and size distribution of different droplets (including deionized water and two kinds of power-law fluid). For the power-law fluids, a short circular jet is formed after the nozzle exit at low pressure. Along the X direction, the distributions of axial velocity w and Sauter mean diameter (SMD) are symmetrical and increase from the center to both sides. The effect of injection pressure on the radial velocity u is not obvious. Along the Z axis, the absolute value of 3D velocities decreases to some extent with droplets moving downstream. The SMD decreases apparently with the increment of the distance along the Z axis at 1.0 MPa. [ABSTRACT FROM AUTHOR]

In the title compound, [Co(C2H3O2)2(C16H32N4)]I3, (I), the Co atom is six-coordinated by four N atoms from the tetradentate cyclo­tetradeca­diene ligand and two O atoms from two acetate ligands. The CoN4O2 coordination is octahedral. There are two independent centrosymmetric cations, and the anion lies in a general position. [ABSTRACT FROM AUTHOR]