Human Saliva-Based Quantitative Monitoring of Clarithromycin by Flow Injection Chemiluminescence Analysis: A Pharmacokinetic Study

Human saliva quantitative monitoring of clarithromycin (CLA) by chemiluminescence (CL) with flow injection analysis was proposed for the first time, which was based on the quenching effect of CLA on luminol–bovine serum albumin (BSA) CL system with a linear range from 7.5?×?10^?4 to 2.0 ng/ml. This proposed approach, offering a maximum sample throughput of 100 h^?1, was successfully applied to the quantitative monitoring of CLA levels in human saliva during 24 h after a single oral dose of 250 mg intake, with recoveries of 95.2～109.0 % and relative standard deviations lower than 6.5 % (N?=?7). Results showed that CLA reached maximum concentration of 2.28?±?0.02 μg/ml at approximately 3 h, and the total elimination ratio was 99.6 % in 24 h. The pharmacokinetic parameters including absorption rate constant (0.058?±?0.006 h^?1), elimination rate constant (0.149?±?0.009 h^?1) and elimination half-life time (4.66?±?0.08 h) were obtained. A comparison of human saliva and urine monitoring was also given. The mechanism study of BSA–CLA interaction revealed the binding of CLA to BSA is an entropy driven and spontaneous process through hydrophobic interaction, with binding constant K _BSA–CLA of 4.78?×?10⁶ l/mol and the number of binding sites n of 0.82 by flow injection–chemiluminescence model. Molecular docking analysis further showed CLA might be in subdomain IIA of BSA, with K _BSA–CLA of 6.82?×?10⁵ l/mol and ΔG of ?33.28 kJ/mol.     

pH-controlled morphological structure and electrochemical performances of polyaniline/nickel hexacyanoferrate nanogranules during electrochemical deposition

To explore the dependences of morphology and electrochemical performance of polyaniline/nickel hexacyanoferrate (PANI/NiHCF) nanogranules on pH value of the reaction system, electrodeposition of PANI/NiHCF nanogranules was performed across a pH range from 0 to 7 on carbon nanotubes (CNTs)-modified platinum substrate by cyclic voltammetry in a mixture of 0.002 mol L^?1 NiSO₄, 0.25 mol L^?1 Na₂SO₄, 0.002 mol L^?1 K₃Fe(CN)₆, and 0.01 mol L^?1 aniline solutions. The morphology and structure of PANI/NiHCF nanogranules were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The supercapacitive performances of the nanogranules were investigated with cyclic voltammetry (CV), charge/discharge tests, and electrochemical impedance spectroscopy (EIS). The results showed that the nanogranules with different morphology and sizes were obtained with the change of pH values from 0 to 7, which could control the mechanism of homogeneous or heterogeneous nucleation directly. The nanogranules were dispersed in matrix uniformly at pH 0 and pH 1, while the size of which decreased with the increase of pH values. The smooth cross-linking network structure was found from pH 2 to 7. The structure of PANI/NiHCF nanogranules had slightly changed from pH 0 to 7. PANI/NiHCF nanogranules had good electrochemical performance from pH 0 to 7 in a mixture of 0.5 mol L^?1 H₂SO₄ and 0.5 mol L^?1 KNO₃ solutions, and the highest specific capacitance value of 274 F g^?1 was obtained at current densities of 2 mA cm^?2 in neutral medium. PANI/NiHCF nanogranules had high stability in neutral medium after 2,000 cycles by CV.     

Direct electrochemistry and electrochemical biosensing of glucose oxidase based on CdSe@CdS quantum dots and MWNT-modified electrode

The direct electron transfer of glucose oxidase (GOx) was achieved based on the immobilization of CdSe@CdS quantum dots on glassy carbon electrode by multi-wall carbon nanotubes (MWNTs)-chitosan (Chit) film. The immobilized GOx displayed a pair of well-defined and reversible redox peaks with a formal potential (E ^θ’) of ?0.459 V (versus Ag/AgCl) in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k _s) of GOx confined in MWNTs-Chit/CdSe@CdS membrane were evaluated as 1.56 s^?1 according to Laviron's equation. The surface concentration (Γ*) of the electroactive GOx in the MWNTs-Chit film was estimated to be (6.52?±?0.01)?×?10^?11?mol?cm^?2. Meanwhile, the catalytic ability of GOx toward the oxidation of glucose was studied. Its apparent Michaelis–Menten constant for glucose was 0.46?±?0.01 mM, showing a good affinity. The linear range for glucose determination was from 1.6?×?10^?4 to 5.6?×?10^?3?M with a relatively high sensitivity of 31.13?±?0.02 μA?mM^?1?cm^?2 and a detection limit of 2.5?×?10^?5?M (S/N=3).     

Molecular and Kinetic Characterization of Two Extracellular Xylanases Isolated from Leucoagaricus gongylophorus

In this work, the xylanolytic profile of Leucoagaricus gongylophorus was studied, and two extracellular enzymes with xylanolytic activity (XyLg1 and XyLg2) were isolated, purified, and characterized. XyLg1 has a molecular mass of about 38 kDa and pI greater than 4.8. For beechwood xylan substrate, XyLg1 showed an optimum temperature of 40 °C, optimum pH between 8.5 and 10.5, and Km?=?14.7?±?7.6 mg mL^?1. Kinetic studies of the XyLg1 using polygalacturonic acid as substrate were developed, and the enzyme showed optimum pH 5.5, optimum temperature between 50 and 60 °C, and Km?=?2.2?±?0.5 mg mL^?1. XyLg2 has molecular weight of about 24 kDa and pI less than 4.8, and thus is an acid protein. Parameters such as optimum temperature (70 °C) and pH (4.0), as well as the kinetic parameters (Km?=?7.4?±?2.0 mg mL^?1) using beechwood xylan as substrate, were determined for XyLg2. This enzyme has no activity for polygalacturonic acid as substrate. XyLg1 and XyLg2 are the first native xylanases isolated and characterized from L. gongylophorus fungi and, due to their biochemistry and kinetic features, they have potential to be used in biotechnological processes.     

Pure copper vs. mixed copper and palladium hexacyanoferrates for glucose biosensing applications

A glucose amperometric biosensor was developed. Glucose oxidase enzyme was immobilized by means of a Nafion membrane on glassy carbon modified with an electrochemically deposited mixed Cu and Pd hexacyanoferrate (CuPdHCF). According to the data provided by X-ray atomic spectroscopy measurements, this Cu- and Pd-based hexacyanoferrate is likely to be a mixture of single CuHCF and PdHCF pure phases. The biosensor performances were evaluated by recording the steady-state currents due to submillimolar additions of glucose to a potassium buffer solution (pH 5.5) and exploiting the electrocatalytic reduction of the enzymatically produced hydrogen peroxide. The CuPdHCF-based biosensor exhibited a sensitivity of 8.1?±?0.6 A M^?1 m^?2, a limit of detection of 1.4?×?10^?5 M, and a linear response range extending between 5?×?10^?5 and 4?×?10^?4 M, with a dynamic response range up to 4?×?10^?3 M glucose. Electrode sensitivity and signal stability resulted more satisfactory as compared to those of a CuHCF-based biosensor fabricated according to the same procedure. The selectivity was investigated through an interference study. The response to easily oxidizable species was found to be low enough to allow glucose determination in biological samples.     

HPLC�CDAD Analysis of Hydrochlorothiazide and Irbesartan in Hypertensive Patients on Fixed-Dose Combination Therapy

Hydrochlorothiazide (HCTZ) and the angiotensin II type 1 receptor antagonist (ARB) irbesartan (IRBE) are well-known antihypertensive drugs, frequently administered as a low-dose combination in a single pill. In this work, a simple, sensitive, and selective high-performance liquid chromatographic (HPLC) method with diode-array detection was developed for simultaneous determination of HCTZ and IRBE levels in the plasma of hypertensive patients given a fixed combination of 12.5 mg HCTZ and 300 mg IRBE. Compounds were extracted from acidified plasma samples with 3 mL ethyl acetate, and eluted at 6 and 19 min from a C₄ column by elution with an acetonitrile?Cphosphate buffer (pH 3.6) mobile-phase gradient at a flow rate of 1 mL min^?1. The assay was linear over the ranges 2.5?C500 and 20?C4,000 ng mL^?1 for HCTZ and IRBE, respectively. Overall intra-assay and inter-assay variation were within acceptance limits. Limits of quantification were 2.5 and 20 ng mL^?1 for HCTZ and IRBE, respectively. Plasma samples remained stable for 12 h at room temperature, through three thaw?Cfreeze cycles, and for 2 and 7 months at ?20 °C. In hypertensive patients, residual concentrations were 22.3 ± 6.0 and 241.8 ± 39.0 ng mL^?1 for HCTZ and IRBE, respectively. There was no interference from other co-administered drugs. Despite the different physicochemical properties of HCTZ and IRBE, our method enables accurate measurement of both drugs for assessment of compliance by patients treated by fixed-dose combination therapy with HCTZ?CIRBE.     

Microbial Leaching of Waste Solder for Recovery of Metal

This study proposes an environment-friendly bioleaching process for recovery of metals from solders. Tin-copper (Sn-Cu), tin-copper-silver (Sn-Cu-Ag), and tin-lead (Sn-Pb) solders were used in the current study. The culture supernatant of Aspergillus niger removed metals faster than the culture supernatant of Acidithiobacillus ferrooxidans. Also, the metal removal by A. niger culture supernatant is faster for Sn-Cu-Ag solder as compared to other solder types. The effect of various process parameters such as shaking speed, temperature, volume of culture supernatant, and increased solder weight on bioleaching of metals was studied. About 99 (±1.75)?% metal dissolution was achieved in 60 h, at 200-rpm shaking speed, 30 °C temperature, and by using 100-ml A. niger culture supernatant. An optimum solder weight for bioleaching was found to be 5 g/l. Addition of sodium hydroxide (NaOH) and sodium chloride (NaCl) in the bioleached solution from Sn-Cu-Ag precipitated tin (85?±?0.35 %) and silver (80?±?0.08 %), respectively. Passing of hydrogen sulfide (H₂S) gas at pH 8.1 selectively precipitated lead (57.18?±?0.13 %) from the Sn-Pb bioleached solution. The proposed innovative bioleaching process provides an alternative technology for recycling waste solders to conserve resources and protect environment.     

The influence of pH on the stability constants of lanthanum and europium complexes with humic acids

Complex formation of humic acids (HA)_n with La³⁺ and Eu³⁺ was studied. Commercial (HA)_n was purified and characterized. The stability constants were determined at several pH values and 0.2?M NaClO₄ ionic strength by the Shubert??s method of radiochemical ionic exchange. The slopes of the lines $ \log ((\lambda_{0} /\lambda ) - 1) = \log \beta_{\text{M,j(HA)n}}^{\exp } + {\text{j}} * \log \left[ { ( {\text{HA)}}_{\text{n}} } \right] $ were dependent on the [(HA)_n]. The values of log $ \beta_{\text{M,j(HA)n}}^{\exp } $ for j?=?1 were the following: 6.29?±?0.04 (pH 4.9?±?0.4) and 7.61?±?0.03 (pH 5.9?±?0.1) for lanthanum and 7.31?±?0.01 (pH 5.9?±?0.2) for europium. Log $ \beta_{\text{M,j(HA)n}}^{\exp } $ was determined as well for higher values of the j parameter and these values were: 12.2?±?0.1 (j?=?2, pH 7.7?±?0.2), 15.6?±?0.2 (j?=?3, pH 4.9?±?0.4) and 16.05?±?0.07 (j?=?3, pH 5.9?±?0.1), for lanthanum and 13.18?±?0.03 (j?=?2, pH 5.9?±?0.1) for europium. A discussion is presented about the complex formation regarding pH and [(HA)_n].     

Thermodynamic Model for SnO2(cr) and SnO2(am) Solubility in the Aqueous Na+–H+–OH−–Cl−–H2O System

The solubility of SnO₂(cassiterite) was studied at 23±2?°C as a function of time (7 to 49 days) and pH (0 to 14.5). Steady state concentrations were reached in <7 days. The data were interpreted using the SIT model. The data show that SnO₂(cassiterite) is the stable phase at pH values of 10 K ⁰ value of ?64.39±0.30 for the reaction (SnO₂(cassiterite) +2H₂O?Sn⁴⁺+4OH^?) and values of 1.86±0.30, ≤?0.62, ?9.20±0.34, and ?20.28±0.34 for the reaction ( $\mathrm{Sn}^{4+} + n\mathrm{H}_{2}\mathrm{O} \rightleftarrows \mathrm{Sn}(\mathrm{OH})_{n}^{4 - n} + n\mathrm{H}^{+}$ ) with values of “n” equal to 1, 4, 5, and 6 respectively. These thermodynamic hydrolysis constants were used to reinterpret the extensive literature data for SnO₂(am) solubility, which provided a log?₁₀ K ⁰ value of ?61.80±0.29 for the reaction (SnO₂(am)+2H₂O?Sn⁴⁺+4OH^?). SnO₂(cassiterite) is unstable under highly alkaline conditions (NaOH concentrations >0.003 mol?dm^?3) and transforms to a double salt of SnO₂ and NaOH. Although additional well-focused studies will be required for confirmation, the experimental data in the highly alkaline region (0.003 to 3.5 mol?dm^?3 NaOH) can be well described with log?₁₀ K ⁰ of ?5.29±0.35 for the reaction Na₂Sn(OH)₆(s)?Na₂Sn(OH)₆(aq).     

Novel potentiometric sensors for pyrilamine maleate

The fabrication and electrochemical response characteristics of four novel potentiometric sensors for determination of pyrilamine maleate (PyraH) were described. The sensors include polymeric membrane electrodes (PME₁, PME₂) and carbon paste electrodes (CPE₁, CPE₂). The fabricated sensors were based on the ion-pair of pyrilamine with sodium tetraphenylborate (NaTPB) and ammonium reineckate (NH₄RN) using dibutyl phthalate (DBP) as plasticizing solvent. The sensors showed linear, stable and near-Nernstian slopes of 56.4 ± 0.4, 54.2 ± 0.2, 58.8 ± 0.3 and 57.9 ± 0.4 mV decade^?1 at 25 ± 0.1 °C and detection limits of 2.0 × 10^?5, 1.8 × 10^?5, 1.0 × 10^?5 and 9.5 × 10^?6 mol L^?1 for PME₁, PME₂, CPE₁ and CPE₂ sensors, respectively. The response time was less than 10 and 8 s for polymeric membrane and carbon paste sensors. The proposed sensors displayed good selectivity for pyrilamine with respect to a number of common inorganic and organic species. The thermal temperature coefficients of the investigated sensors were 0.9508, 0.7012, 0.9450 and 0.6497 mV °C^?1. Modified carbon paste sensors showed lower detection limits, higher thermal stability and faster response time than those of polymeric membrane sensors. The proposed sensors displayed useful analytical characteristics for determination of pyrilamine in pharmaceutical preparation and biological fluids (Human urine and plasma).     

Expression,Purification, and Characterization of NADP+-Dependent Malic Enzyme from the Oleaginous Fungus Mortierella Alpina

Malic enzymes are a class of oxidative decarboxylases that catalyze the oxidative decarboxylation of malate to pyruvate and carbon dioxide, with concomitant reduction of NAD(P)⁺ to NAD(P)H. The NADP⁺-dependent malic enzyme in oleaginous fungi plays a key role in fatty acid biosynthesis. In this study, the malic enzyme-encoding complementary DNA (cDNA) (malE1) from the oleaginous fungus Mortierella alpina was cloned and expressed in Escherichia coli BL21 (DE3). The recombinant protein (MaME) was purified using Ni-NTA affinity chromatography. The purified enzyme used NADP⁺ as the cofactor. The K _m values for l-malate and NADP⁺ were 2.19?±?0.01 and 0.38?±?0.02 mM, respectively, while the V _max values were 147?±?2 and 302?±?14 U/mg, respectively, at the optimal condition of pH 7.5 and 33 °C. MaME is active in the presence of Mn²⁺, Mg²⁺, Co²⁺, Ni²⁺, and low concentrations of Zn²⁺ rather than Ca²⁺, Cu²⁺, or high concentrations of Zn²⁺. Oxaloacetic acid and glyoxylate inhibited the MaME activity by competing with malate, and their K _i values were 0.08 and 0.6 mM, respectively.     

Synergetic effect of Prussian blue film with gold nanoparticle graphite–wax composite electrode for the enzyme-free ultrasensitive hydrogen peroxide sensor

Enzyme-free amperometric ultrasensitive determination of hydrogen peroxide (H₂O₂) was investigated using a Prussian blue (PB) film-modified gold nanoparticles (AuNPs) graphite–wax composite electrode. A stable PB film was obtained on graphite surface through 2-aminoethanethiol (AET)-capped AuNPs by a simple approach. Field emission scanning electron microscope studies results in formation of PB nanoparticle in the size range of 60–80 nm. Surface modification of PB film on AET–AuNPs–GW composite electrode was confirmed by Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy studies. Highly sensitive determination of H₂O₂ at a peak potential of ?0.10 V (vs. SCE) in 0.1 M KCl PBS, pH?=?7.0) at a scan rate of 20 mVs^?1 with a sensitivity of 23.58 μA/mM was observed with the modified electrode using cyclic voltammetry. The synergetic effect of PB film with AuNPs has resulted in a linear range of 0.05 to 7,800 μM with a detection limit of 0.015 μM for H₂O₂ detection with the present electrode. Chronoamperometric studies recorded for the successive additions of H₂O₂ with the modified electrode showed an excellent linearity (R ²?=?0.9932) in the range of 4.8?×?10^?8 to 7.4?×?10^?8 M with a limit of detection of 1.4?×?10^?8 M. Selective determination of H₂O₂ in presence of various interferents was successfully demonstrated. Human urine samples and stain remover solutions were also investigated for H₂O₂ content.     

LC Analysis of JS38, a Novel Antineoplastic Medicine, in the Plasma, Urine, Bile, Feces, and Other Tissues of Rats

An RP-LC method has been developed for analysis of JS38 in the plasma, urine, bile, feces, and important tissues of rats. Chromatography was performed on a C₁₈ analytical column with 80:20 (%, v/v) acetonitrile–phosphate buffer (0.5% phosphoric acid and 0.3% TEA adjusted to pH 5.0) as mobile phase at a flow-rate of 1.0 mL min^?1. Eluted compounds were detected at 400 nm by ultraviolet diode-array detection (DAD). The method was validated for linearity, accuracy (recovery from biological matrixes such as plasma, urine, bile, feces, and important organs), repeatability (within-day and between-day precision), and stability. The results indicate that the method is suitable for pre-clinical pharmacokinetic study of JS38.     

Host–guest system of 4-nerolidylcatechol in 2-hydroxypropyl-β-cyclodextrin: preparation, characterization and molecular modeling

The interaction of 4-nerolidylcatechol (4-NRC), a potent antioxidant agent, and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated by the solubility method using Fourier transform infrared (FTIR) methods in addition to UV–Vis, ¹H-nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. The inclusion complexes were prepared using grinding, kneading and freeze-drying methods. According to phase solubility studies in water a B_S-type diagram was found, displaying a stoichiometry complexation of 2:1 (drug:host) and stability constant of 6494 ± 837 M^?1. Stoichiometry was established by the UV spectrophotometer using Job’s plot method and, also confirmed by molecular modeling. Data from ¹H-NMR, and FTIR, experiments also provided formation evidence of an inclusion complex between 4-NRC and HP-β-CD. 4-NRC complexation indeed led to higher drug solubility and stability which could probably be useful to improve its biological properties and make it available to oral administration and topical formulations.     

Poly(2-amino-5-(4-pyridinyl)-1, 3, 4-thiadiazole) film modified electrode for the simultaneous determinations of dopamine, uric acid and nitrite

Poly(2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole) (PAPT) modified glassy carbon electrode (GCE) was fabricated and used for the simultaneous determinations of dopamine (DA), uric acid (UA) and nitrite (NO₂ ^?) in 0.1 mol?L^?1 phosphate buffer solution (PBS, pH 5.0) by using cyclic voltammetry and differential pulse voltammetry (DPV) techniques. The results showed that the PAPT modified GCE (PAPT/GCE) not only exhibited electrocatalytic activities towards the oxidation of DA, UA and NO₂ ^? but also could resolve the overlapped voltammetric signals of DA, UA and NO₂ ^? at bare GCE into three strong and well-defined oxidation peaks with enhanced current responses. The peak potential separations are 130 mV for DA–UA and 380 mV for UA–NO₂ ^? using DPV, which are large enough for the simultaneous determinations of DA, UA and NO₂ ^?. Under the optimal conditions, the anodic peak currents were correspondent linearly to the concentrations of DA, UA and NO₂ ^? in the ranges of 0.95–380 μmol?L^?1, 2.0–1,000 μmol?L^?1 and 2.0–1,200 μmol?L^?1 for DA, UA and NO₂ ^?, respectively. The correlation coefficients were 0.9989, 0.9970 and 0.9968, and the detection limits were 0.2, 0.35 and 0.6 μmol?L^?1 for DA, UA and NO₂ ^?, respectively. In 0.1 mol?L^?1 PBS pH 5.0, the PAPT film exhibited good electrochemical activity, showing a surface-controlled electrode process with the apparent heterogeneous electron transfer rate constant (k _s) of 25.9 s^?1 and the charge–transfer coefficient (α) of 0.49, and thus displayed the features of an electrocatalyst. Due to its high sensitivity, good selectivity and stability, the modified electrode had been successfully applied to the determination of analytes in serum and urine samples.     

Diphenyl Diselenide-Loaded Nanocapsules: Preparation and Biological Distribution

Over the past years, organoselenium compounds have been aimed as targets of interest in organic synthesis. Diphenyl diselenide [(PhSe)₂] is an important example of this class showing several pharmacological properties. However, the poor water-solubility and its low oral bioavailability may be considered an obstruction for the clinical utility of this compound. For this reason, the use of nanocapsules is a prominent approach to increase the bioavailability of lipophylic molecules. This study aims to prepare diphenyl diselenide-loaded nanocapsules with two different concentrations, by interfacial deposition of the preformed polymer in order to develop a system to improve its oral bioavailability. The drug-loaded nanocapsules with 1.56 and 5 mg ml^?1 and unloaded nanocapsule suspensions presented macroscopic homogeneous aspect, as well as submicronic sizes, low polydispersity, negative zeta potentials and slightly acid or neutral pH values. The biological tests of selenium distribution in different tissues of mice show a higher bioavailability of the (PhSe)₂ nanocapsules when compared with the free (PhSe)₂, both administered by per oral route at the dose of 50 mg/kg, showing a prominent influence of the nanocarries systems for biological properties of this organochalcogenium compound.     

HPLC Analysis and Pharmacokinetic Study of Paeoniflorin after Intravenous Administration of a New Frozen Dry Powder Formulation in Rats

A simple and specific high performance liquid chromatographic (HPLC) method with UV detection using picroside II as the internal standard was developed and validated to determine the concentration of paeoniflorin in rat plasma and study its pharmacokinetics after an single intravenous administration of 40 mg kg^?1 paeoniflorin to Wistar rats. The analytes of interest were extracted from rat plasma samples by ethyl acetate after acidification with 0.05 mol L^?1 NaH₂PO₄ solution (pH 5.0). Chromatographic separation was achieved on an Agilent XDB C₁₈ column (250 × 4.6 mm I.D., 5 μm) with a Shim-pack GVP-ODS C₁₈ guard column (10 × 4.6 mm I.D., 5 μm) using a mobile phase consisting of acetonitrile–water–acetic acid (18:82:0.4, v/v/v) at a flow rate of 1.0 mL min^?1. The UV detection was performed at a wavelength of 230 nm. The linear calibration curves were obtained in the concentration range of 0.05–200.0 μg mL^?1 in rat plasma with the lower limit of quantification (LLOQ) of 0.05 μg mL^?1. The intra- and inter-day precisions in terms of % relative standard deviation (RSD) were lower than 5.7 and 8.2% in rat plasma, respectively. The accuracy in terms of % relative error (RE) ranged from ?1.9 to 2.6% in rat plasma. The extraction recoveries of paeoniflorin and picroside II were calculated to be 69.7 and 56.9%, respectively. This validated method was successfully applied to the pharmacokinetic study of a new paeoniflorin frozen dry power formulation. After single intravenous administration, the main pharmacokinetic parameters t _1/2, AUC_0-∞, CL_TOT, V _Z, MRT_0-∞ and V _ss were 0.739 ± 0.232 h, 43.75 ± 6.90 μg h mL^?1, 15.50 ± 2.46 L kg^?1 h^?1, 1.003 ± 0.401 L kg^?1, 0.480 ± 0.055 h and 0.444 ± 0.060 L kg^?1, respectively.     

LC Determination and Bioequivalence Study of Pantoprazole in Human Plasma

A selective and sensitive liquid chromatography (LC) method with rapid sample processing was developed for determination of pantoprazole in human plasma using omeprazole as internal standard (IS). The plasma sample (100 μL) was deproteined by precipitation with methanol. The supernatant was directly determined by LC using a Diamonsil C₁₈ ODS column and solution of 10 mM Na₂HPO₄ buffer (containing 0.01% H₃PO₄) and acetonitrile (68:32, v/v, pH = 6.8) as mobile phase with UV detector set at 288 nm. The retention time of IS and pantoprazole were 4.9 ± 0.2 and 5.6 ± 0.2 min, respectively. The method was validated with a linear range of 0.03–5.0 μg mL^?1 and the lowest limit of quantification was 0.03 μg mL^?1 for pantoprazole (r = 0.9999). The coefficient of variation for intra-day and inter-day accuracy and precision was less than 9.5%. The mean extraction recovery was 84.1%. Quality control samples were stable when kept at autosampler temperature for 24 h, at ?20 °C for 42 days and after three freeze-thaw cycles. The assay was successfully applied to a randomized, two-period cross-over bioequivalence study in 20 healthy Chinese volunteers following a single oral dose of 40 mg pantoprazole. Various pharmacokinetic parameters including AUC _0～t , AUC _0～∞, C _max, T _max and t _1/2 were determined from plasma concentration of both formulations. The results indicated that the analytical method was a specific, precise, sensitive and rapid procedure for determination of plasma pantoprazole concentration and therefore, a suitable and valuable tool in the investigation of the clinical pharmacokinetics and bioequivalence.     

Electrochemical properties of LaY2Ni9 hydrogen storage alloy,used as an anode in nickel-metal hydride batteries

The electrochemical properties of LaY₂Ni₉ alloy used as an anode in nickel-metal hydride batteries were investigated at ambient and at different temperatures. Several techniques, such as the galvanostatic charging and discharging, the constant potential discharge, and the potentiodynamic polarization, were applied to characterize these electrochemical properties. The discharge capacity of the LaY₂Ni₉ alloy increases to reach 258 mAh g^?1 after 5 cycles and decreases to 140 mAh g^?1 after 100 cycles then stabilizes around this same value indicating good cycling held. The hydrogen diffusion coefficient D _H in the bulky alloy is estimated to be (1.02?±?0.11)?×?10^?11 cm² s^?1 correlated with the good stability of electrochemical capacity after 100 cycles. The evolution of the ratio \( \frac{D_{\mathrm{H}}}{a^2} \) and the corrosion current density and potential are correlated with the evolution of the electrochemical capacity during the activation and for a long cycling. The enthalpy, the entropy, and the apparent activation energy of the LaY₂Ni₉ hydride formation are evaluated. The calculated results show that the enthalpy change, the entropy change, and the activation energy are (?42.64?±?1.08), (56.85?±?2.11), and (14.84?±?0.35)?kJ mol^?1, respectively.     

Selective phosphate sensing using copper monoamino-phthalocyanine functionalized acrylate polymer-based solid-state electrode for FIA of environmental waters

A novel solid-state selective sensor for mono-hydrogen phosphate (HPO₄)^?2 based on copper monoamino phthalocyanine (CuMAPc) ionophore covalently attached to poly (n-butyl acrylate) (PnBA) has been developed and potentiometrically evaluated. The all solid-state sensor was constructed by the application of a thin film of a polymer cocktail containing a CuMAPc–PBDA ionophore and benzyl-dimethylhexadecyl ammonium chloride (BDMHAC) as a lipophilic cationic additive onto a gold electrode pre-coated with the conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) as an ion and electron transducer. The sensor with 14.31 % of CuMAPc-PnBA (ionophore II) exhibited a good selectivity for (HPO₄)^?2. The thus constructed sensor discriminated many anions, including F^?, Cl^?, Br^?, I^–, CH₃COO^?, NO₃ ^?, ClO₄ ^?, and SO₄ ^2?. The potentiometric response of the phosphate selective electrode was found to be independent of the pH of sample solution in the range 6–9. The sensor showed a Nernstian slope of ?29.8 ± 0.3 mV conc.^?1 decade^?1 with linear range of 4.0 × 10^?9–1.0 × 10^?2 mol L^?1 and detection limit of 1.0 × 10^?9 mol L^?1 at pH 8.0. The proposed phosphate sensor has been utilized as a detector for the flow injection potentiometric determination of phosphate in different water samples at the nanomolar concentration range.