A Modified Peng–Robinson Equation of State for Heavy Hydrocarbons

Russian Journal of Physical Chemistry A - A new simple and accurate functional form for an attractive parameter α is introduced for Peng–Robinson equation of state. The modified...     

UPLC–MS–MS Analysis of Quetiapine and Its Two Active Metabolites, 7-Hydroxyquetiapine and 7-Hydroxy-N-dealkylquetiapine, in Rat Plasma and Cerebrospinal Fluid

Quetiapine (QP) is an antipsychotic agent widely used to treat a variety of human psychotic disorders. 7-Hydroxyquetiapine (QPOH) and 7-hydroxy-N-dealkylquetiapine (QPND) are its two active metabolites. A rapid and sensitive ultra-performance liquid chromatographic–tandem mass spectrometric method has been developed for analysis of the three agents in plasma and cerebrospinal fluid (CSF) from rats. The assay was based on liquid–liquid extraction of 100-μL samples. The methods were validated for QP, QPOH, and QPND in both types of sample. Limits of detection (LOD) in plasma were 0.02, 0.01, and 0.02 ng mL^?1 for QP, QPOH, and QPND, respectively; in CSF samples the respective values were 0.02, 0.01, and 0.01 ng mL^?1. The utility of the method was demonstrated by analysis of the pharmacokinetics and CSF distribution properties of QP and its two active metabolites in the plasma and CSF in rats.     

Study on Lead Dioxide Modified Electrode and Its Application in Detection of Phenols

IntroductionOflate,thereisagreatinterestintheimprovementofleaddioxideasananodematerialforelectrosynthesis,ozonegenerationandwastewatertreatmentowingtoitshighelectri calconductivity ,largeoxygenoverpotentialandchemicalin ertness.1 5PbO2 canbeobtainedasanodicdepositsfromsolu tionsofthelow valenceions,basicstudiesontheseelec trodesaremainlyconfinedtothenucleationgrowthprocessofleaddioxidecrystallites ,ormodifiedbyothercationsinordertoimproveitsproperties.6 However,itselectrocatalyticactivi tydepe…     

Synthesis and Characterization of Side Group–Modified Cyclotetraphosphazene Derivatives

Abstract

Two novel cyclotetraphosphazene derivatives were synthesized by the reaction of octachlorocyclotetraphosphazene with the potassium salt of 4-hydroxybenzaldehyde, and subsequent reduction of aldehyde groups to alcohol groups using sodium borohydride. The bromination reaction was carried out using PBr₃ to give N₄P₄(OC₆H₄-p-CH₂Br)₈ (4). This compound was employed in reaction with imidazole or morpholine to produce eight-armed, star-branched title compounds. The target compounds were characterized by ¹H, ³¹P, and ¹³C NMR as well as IR and ESI-MS. The Cu complex of 5a was effective in oxidative cleavage reactions.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT     

Syntheses and Crystal Structures of Two Octamolybdate Compounds Modified by CuⅡ-Imidazole Cations

Two new polyoxomolybdate compounds,namely(CuIIL2)2[CuⅡ(HL)2]2[Mo8O26(HL)2].(H2O)4(1) and [CuⅡ(HL)2]2[β-Mo8O26](HL)2(2)(HL=imidazole),were designed and synthesized under hydrothermal conditions.X-ray diffraction analyses reveal that compound 1 consists of one Mo8O26(HL)24-cluster,two CuL2,two Cu(HL)22+,and four disassociated water molecules;and compound 2 is constructed by one β-Mo8O264-cluster,two Cu(HL)22+,and two uncoordinated imidazole molecules.     

Solubility of Adenine and Kinetin in Water–Ethanol Solutions

We have measured the solubility of adenine and kinetin in water–ethanol solutions. Various models of cosolvency have been taken into account in the analysis of the experimental data. The results are interpreted in terms of hydrophobic interactions.     

Electrocatalytic Oxidation of Hydroquinone at Poly(crystal-violet) Film–Modified Electrode and Its Selective Determination in the Presence of o-Hydroquinone and m-Hydroquinone

Abstract

A stable poly(crystal-violet) (PCV) electroactive film was electrodeposited on a glassy carbon electrode (GCE). The redoxation of hydroquinone showed a pair of well-defined peaks on a PCV electrode with a potential difference of 30 mV, which is 120 mV less than that obtained on the GCE. At optimal conditions, the PCV electrode linearly responded to the hydroquinone in the range of 4 × 10^?6 mol · L^?1 to 3.2 × 10^?3 mol · L^?1 and a detection limit of 8 × 10^?8 mol · L^?1 was obtained. The separations of the oxidation peak potentials between hydroquinone and the coexisting o-hydroquinone and m-hydroquinonewere 100 mV and 430 mV, respectively, which allows their simultaneous determination. The detection of hydroquinone in artificial sewage water was demonstrated with satisfactory results.     

A Modified Phase-Fitted Runge–Kutta Method for the Numerical Solution of the Schrödinger Equation

A modified phase-fitted Runge–Kutta method (i.e., a method with phase-lag of order infinity) for the numerical solution of periodic initial-value problems is constructed in this paper. This new modified method is based on the Runge–Kutta fifth algebraic order method of Dormand and Prince [33]. The numerical results indicate that this new method is more efficient for the numerical solution of periodic initial-value problems than the well known Runge–Kutta method of Dormand and Prince [33] with algebraic order five.     

Electrochemical Behavior of Mitoxantrone and Its Determination at a Pt／C Implanted Modified Microelectrode

In a 0.02 mol/L Na2HPO4-KH2PO4(PBS) buffer solution(pH=6.82), the electrochemical behavior of mitoxantrone was studied by linear-sweep voltammetry and cyclic voltammetry at a Pt/C ion implantation modified microelectrode. A sensitive reduction peak was observed. The peak potential was -0.72 V(vs.SCE), the peak current was proportional to the concentration of mitoxantrone within the ranges of 7.0×10-8-9.0×10-7 mol/L and 1.0×10-6-2.4×10-5 mol/L, with a detection limit of 4.0×10-8 mol/L. The linear correlation coefficients were 0.9994 and 0.9992, respectively. This method has been applied to the direct determination of mitoxantrone in simulated urine. The recoveries were in the range from 96.2% to 105.9%. The reduction process was a quasi-reversible one with adsorptive characteristics at the Pt/C microelectrode. The electrode reaction rate constant ks and the electron transfer coefficient α of the system were determined to be 4.5 and 0.65 s-1, respectively. The experiments showed that Pt element had surely been implanted into the surface of the carbon fiber, and the atomic Pt improved the electrocatalytic activity. The Pt/C microelectrode had a good stability and reproducibility.     

Preparation of β-Cyclodextrin Modified FusedSilica Capillary and Its Application inCapillary Electrophoresis Enantiom eric Separation

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｙｎｔｈｅｓｉｓｏｆｃｈｉｒａｌｃｏｍｐｏｕｎｄｓａｎｄｒｅｃｏｇｎｉｔｉｏｎｏｆｍｏｌｅｃｕｌａｒｃｈｉｒａｌｉｔｙａｒｅｏｆｉｍｐｏｒｔａｎｔｓｉｇｎｉｆｉｃａｎｃｅｉｎｖａｒｉｏｕｓｆｉｅｌｄｓ，ｅｓｐｅｃｉａｌｌｙｉｎｔｈｅｐｈａｒｍａｃｅｕｔｉｃａｌｉｎｄｕｓｔｒｙ．Ｓｏｍｅｍｅｔｈｏｄｓｓｕｃｈａｓｃｈｒｏｍａｔｏｇｒａｐｈｙ［１］ｈａｖｅｂｅｅｎａｐｐｌｉｅｄｔｏｔｈｅｒｅｃｏｇｎｉｔｉｏｎｏｆｃｈｉｒａｌｃｏｍｐｏｕｎｄｓｏｒｔｈｅｓｅｐａｒａｔｉ…     

Electrochemical Behavior and Its Electrocatalytic Activity of A P—Mo Heteropolyanion Modified ITO Electrode

ITO is a versatile material in the electronic industry because of its special transparent and conductive properties. However, there are a few reports regarding the adsorption of organic or organometallic compounds on the ITO surface1-4. The heteropolyanions are interested in the field of material science, catalytics, biology, and medicine owing to their chemical, structural, and electronic versatility5-7. One of the most important properties of polyoxometalate anions is their ability to a…     

Design, Synthesis and Characterization of a Novel Schiff Base Bis(iminoantipyrine) and Its Modified Electrode

ThedevelopmentandaPplicationofchemicallymodifiedelectrodescontinuetobeareasofvigorousresearchactivityl-2.Recently,complexatioswithorganicreagentsasmodifiersincarbonpasteelectrodeshavebeenemployedforanalyticaldeterminations3.Schiffbaseligands,however,havebeenscarcelyreportedasmodifierstodeterminemetalions'.Theprincipalcharacteristicrequiredforthesuccessfulconstr[lctionofamodifiedcarbonpasteelectrodeisthatthesolubilityofthemodifiermustbesoslightinthesolventsemployedthatitremainstablyincorporated…     

Removal of Fulvic Acids from Aqueous Solutions via Surfactant Modified Zeolite

IntroductionNatural organic matter(NOM)is composed of acomplex mixture of organic compounds derived fromliv-ing and dead plants,animals and microorganisms,waste products of animals and microorganisms,andfrom the degradation of the above materials[1].Fulvi…     

Dielectric Relaxation in Glycine–Water and Glycine–Ethanol–Water Solutions Using Time Domain Reflectometry

Dielectric relaxation measurements on water–ethanol–glycine ternary system were carried out using time domain reflectometry (TDR) at 25, 30, 35, and 40°C in the frequency range from 10 MHz to 10 GHz. Glycine–ethanol–water solutions are prepared with different concentrations of ethanol (0, 5, 10, 15, 20, and 30%) and also for different glycine molar concentrations (0, 0.2, 0.4, 0.6, 0.8, and 1 M). The dielectric relaxation parameters are measured for aqueous glycine solutions also to compare the results with those for the glycine–ethanol–water ternary system. For all the mixtures considered, only one relaxation peak was observed in this frequency range. All the mixtures display a Cole–Davidson dispersion. The relaxation peaks shift to lower frequency with an increase in glycine concentration and also with ethanol concentration. The logarithm of the relaxation time log() shows a nonlinear relation with glycine concentration which implies a change of relaxation mechanism with glycine concentration. The dielectric strength for these mixtures shows a nearly linear relation with glycine molar concentration.     

The Electrochemical Behavior of Acetaminophen on Multi‐Walled Carbon Nanotubes Modified Electrode and Its Analytical Application

Abstract

A multi‐walled carbon nanotubes modified glassy carbon electrode (MWNTs/GCE) was fabricated, and the electrochemical behaviors of acetaminophen (ACOP) were investigated on the MWNTs/GCE. The results showed that MWNTs exhibited excellent electrocatalytic effects on the reaction of ACOP by accelerating the electron transfer rate. Cyclic voltammetry (CV) was used to explore the electrochemical redox mechanism of ACOP on the MWNTs/GCE and differential pulse voltammetry (DPV) was taken to determine ACOP in samples, respectively. The results showed that the oxidative peak currents were linear with the concentration of ACOP in the range of 4.0×10^?7–1.5×10^?4 mol l^?1 with the detection limit 1.2×10^?7 mol l^?1. The MWNTs/GCE showed satisfactory stability, selectivity, and it can be used to quantify ACOP in effervescent dosage real samples.     

Determination of Nitroglycerin and Its Degradation Products by Solid-Phase Extraction and LC–UV

The usual analytical method EPA 8330B cannot properly separate the four degradation products of nitroglycerin (mononitroglycerin, 2-mononitroglycerin, 1,2-dinitroglycerin and 1,3-dinitroglycerin). An analytical method for the determination of the degradation products of nitroglycerin in water using LC–MeOH was developed at 205 nm. The most suitable solid phase extraction cartridge was selected in order to reach the required detection level of these products in water. The combination of the extraction and LC analysis is sensitive and allows detection of nitroglycerin and its products at μg L^?1 level. The technique is straightforward and can help to understand the environmental fate of nitroglycerin.     

Electrochemical Behavior of Hydroquinone at Poly (Acridine Orange)–Modified Electrode and Its Separate Detection in the Presence of o‐Hydroquinone and m‐Hydroquinone

Abstract

Poly (acridine orange) (PAO) film–modified electrode was prepared by the electrooxidation of Acridine orange on a glassy carbon electrode (GCE) for the detection of hydroquinone in the presence of o‐hydroquinone and m‐hydroquinone. The electrochemical behavior of hydroquinone on the modified electrode was investigated with respect to different solution acidity, scan rate, and accumulation time. A pair of sharp and well‐defined peaks was obtained at 0.45 and 0.42 V [vs. a saturated calomel electrode (SCE)] at the PAO film–modified electrode. The potential difference between this pair of cathodic and anodic peaks was decreased to only 30 mV as compared to the 241 mV that was obtained on the bare glassy carbon electrode (GCE). As to o‐hydroquinone and m‐hydroquinone, their corresponding oxidation peaks appeared at 0.55 V and 0.89 V (vs. SCE), respectively. The oxidation potential differences between these three isomers enabled the separate detection of hydroquinone. Under the optimum experimental situation, the oxidation peak current of hydroquinone was proportional to the concentration at the range of 6.8×10^?7–9.6×10^?5 M. The detection limit was been estimated as 3×10^?7 M with 130 s accumulation. This method was applied to the hydroquinone detection in tap water samples.