Flow Injection Analysis of Lactate and Lactate Dehydrogenase Using an Enzyme Membrane in Conjunction with a Modified Electrode

Abstract

A modified electrode for H₂O₂ oxidation, consisting of Pd/Au sputtered on carbon was covered with a lactate oxidase membrane and used in a FIA manifold for selective determination of lactate. The linear range was 0.01-3 mM lactate and up to 200 samples per hour were measured with a relative standard deviation of 1%. Interferences from ascorbic acid and NADH were small because of the low potential of the modified electrode. The lactate oxidase membrane electrode was also used for measurement of lactate dehydrogenase activity using direct injection of the sample into a carrier stream containing pyruvate and NAD⁺.     

Highly Selective Potassium Ion Responsive Liquid-Membrane Electrode

Abstract

The performance of a new liquid-membrane electrode using valinomycin as membrane component is described with respect to selectivity, working range, speed of response and accuracy. The electrode makes possible the measurement of potassium ion activities in the range of 10^?1 M to at least 10^?6 M in unbuffered systems with a selectivity of potassium over sodium ions of more than 4,000. The electrode was used for the direct titration of potassium ions.     

Potassium Dodecatungstocobaltate Trihydrate (K5CoW12O40 · 3H2O) as an Efficient Catalyst for Aminolysis of Epoxides

Abstract

Aminolysis of epoxides using various amines was catalyzed with potassium dodecatungstocobaltate trihydrate in a convenient and efficient method with good selectivities.     

Potentiometric Determination of Potassium in Seawater and Interstitial Water

Abstract

A method is described for the determination of potassium in seawater and marine sediment porewater. After precipitation of the halogen ions with AgNO₃, potassium is precipitated with sodium tetraphenylborate. The excess tetraphenylborate is then determined by AgNO₃ titration, using a silver electrode for end-point detection. Application of this method to seawater samples as small as 1 cm³, gave accuracy and precision of better than 1%.     

Elegant Synthesis of Highly Functionalized 1,2,3-Trisubstituted Cyclopentanes

The conversion of cyclic Baylis–Hillman acetates 1 into the corresponding cyano derivatives 2 was achieved using potassium cyanide in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) in aqueous medium. The obtained Michael acceptors 2 easily add primary amines in absolute ethanol to produce a new family of 1,2,3-trisubstituted cyclpentanes 3 in good yields.     

HPLC Determination of Lactic Acid in Milrinone Injection and Oral Solution Using Ion-Exchange Sample Preparation Methods

Abstract

Lactic acid has been measured in Milrinone Injection and Oral Solution by HPLC using an ion-exclusion polymeric column coupled with a reversed-phase guard column. This dual-column chromato-graphy was preceded by classical ion-exchange sample preparation to eliminate interfering excipient components. The lactic acid lactate content of USP lactic acid was converted to lactic acid in processing. It was also further characterized using a TLC separation.     

Hypervalent Iodine Oxidation of 2-Aryl-1,2,3,4-tetrahydro-4-quinolones: An Easy Access to 2-Aryl-4-quinolones

Oxidation of 2-aryl-1,2,3,4-tetrahydro-4-quinolones (1a-e) using iodobenzene diacetate in methanolic potassium hydroxide leads to dehydrogenation of 1 thereby providing an easy access to 2-aryl-4-quinolones (2a-e).     

Bio-Based Solvent Mediated Synthesis of Dihydropyrimidinthiones Via Biginelli Reaction

Abstract

The three-component Biginelli reaction using aldehyde, thiourea, and 1,3-dicarbonyl compounds was performed smoothly in ethyl lactate (EL) with the catalysis of trimethylsilyl chloride (TMSCl). A class of 3,4-dihydropyrimidinthiones (DHPMs) were synthesized in good to excellent yields via the bio-based solvent mediated catalytic protocol.     

An Efficient Approach to the Synthesis of Ethyl α-Cyanoalkyl β-Substituted Acrylates by the HWE Olefination of Ethyl 2-(Diethoxyphosphoryl) Cyanoalkanoates

Ethyl α-cyanoalkyl β-substituted acrylates 5a–i were prepared in good yields on a synthetic scale by Horner–Wadsworth–Emmons olefination of the corresponding ethyl 2-(diethoxy-phosphoryl) cyanoalkanoates 3a–c using different aldehydes and anhydrous potassium carbonate in dry THF at reflux.     

An Improved Iodine(III) Mediated Method for Thiocyanation of 2-Arylindan-1,3-diones,Phenols, and Anilines

Abstract

An improved method for thiocyanation of 2-arylindan-1,3-diones, phenols, and anilines using a reagent combination of (dichloroiodo)benzene and potassium thiocyanate in dry dichloromethane is described.     

New preorganized calix[4]arenes. Part I. A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27,28-Dodecamethyl-5,11,17,23-tetrahydroxycalix[4] arene

A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27, 28-dodecamethyl-5,11,17, 23-tetrahydroxycalix[4]arene (1) have been prepared by reaction of appropriate oligoethylene glycol ditosylates with (1) in acetonitrile in the presence of potassium carbonate. A potassium template effect is observed during one of the double cyclizations.     

Synthesis and crystal structures of [K(H<Subscript>2</Subscript>O)(Piv)]<Subscript>∞</Subscript> and [K<Subscript>2</Subscript>(Phen)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>(Piv)<Subscript>2</Subscript>]<Subscript>∞</Subscript>

A method for the synthesis of potassium pivalates (trimethylacetates) from potassium tert-butoxide and pivalic acid was proposed. The complexes of the formulas [K(H₂O)(Piv)]_∞(I) and [K₂(Phen)(H₂O)₂(Piv)₂]_∞ (II) (Piv denotes the pivalate anion and Phen denotes 1,10-phenanthroline) were obtained and characterized by elemental analysis and IR and ¹H NMR spectroscopy. The crystal structures of complexes I and II were determined using X-ray diffraction. Crystal structure I has a layered motif with two nonequivalent K atoms (C.N.s 5 + 2 and 6). The coordination of phenanthroline in II gives rise to a ribbon motif, the structure containing three nonequivalent K atoms (C.N.s 6, 6 + 1, and 8).     

四种天然槲皮素-3-糖苷的合成

以芦丁为原料, 经苄基化、酸水解得到关键中间体3′,4′,7-O-三苄基槲皮素(3), 3与相应的1-溴代乙酰糖在四丁基溴化铵催化下在氯仿-0.25 mol•L^－1 K₂CO₃溶液中缩合成相应的糖苷, 脱去保护基得天然槲皮素3-糖苷类化合物 1a～1d. 其结构经IR, ¹H NMR, MS及元素分析确证.     

Synthesis of New β,β′-Diketodithioethers via Swern Oxidation and Study of Their Hydrazone Formation Rate

The synthesis of β,β′-diketodithioethers 4b–j from corresponding β,β′-dihydroxydithioethers 3b–j was carried out by a Swern oxidation using DMSO-oxalyl chloride as oxidizing agent. β,β′-Dihydroxydithioethers 3b–j were prepared by the reaction of two molar equivalents of epoxides 1b–j with dimercaptoethane 2 in the presence of a saturated aqueous solution of potassium carbonate. The reactivity behavior of imine formation of the β,β′-diketodithioethers 4b–j by 2,4-dinitrophenylhydrazine was also investigated, and a mechanism was proposed by using molecular orbital (MO) calculations. To confirm the proposed mechanism, the role of the thia function to activate hydrazone formation by measuring HOMO-LUMO energy levels was also demonstrated.     

二甲基取代五元瓜环与钾离子和钆离子的配位结构

利用X-射线单晶衍射技术表征了2个二甲基取代五元瓜环(DMeQ[5])与金属离子形成的配合物的晶体结构,2个配合物分别为{[K2(H2O)3DMeQ[5]}I2.5H2O(1)和{[Gd(H2O)3][K(H2O)][(NO3)@DMeQ[5]]}(NO3)3.5H2O(2)。与DMeQ[5]和钆离子形成的配合物的结构不同的是,配合物1和2中每个DMeQ[5]端口的所有羰基氧原子都和钾离子或钆离子配位,形成全封闭结构。     

Determination of Silicate By Nonsuppressed Ion Chromatography

Abstract

In previous papers the authors reported that nonsuppressed ion chromatography using potassium hydroxide solution as an eluent was a very sensitive and effective method for the analysis of anions and that this method could be applied to the determination of anions in environmental water samples.

In this paper, this method was applied to the determination of silicate without the interference of fluoride ion when using 0.5mM potassium hydroxide solution, Moreover, this method was compared with silicomolybdate methods and good agreement was obtained between these two methods.

The percent standard deviation was 5.5% when determining lppm of silicate and the calibration curve was linear at concentrations less than 2.5ppm. The detection limit was less than 50ppb.     

Facile Preparation of Benzylic Iodides Under Solvent‐Free Conditions Using Microwave Irradiation

Abstract

Benzylic alcohols are rapidly converted to the corresponding benzylic iodides using combination of p‐toluenesulfonic acid (PTSA) and potassium iodide under solvent‐free microwave irradiation conditions.     

A laser diffraction study of amphiphilic cholesteric liquid crystals prepared from potassium dodecanoyl l-serinate

Abstract

Amphiphilic cholesteric liquid crystal samples have been prepared using potassium dodecanoyl l-serinate (lKDDS). Laser diffraction was used to determine the twist of the helix in these samples. Detergent concentration and the temperature dependence of the twist have been investigated. The results were found to be similar to those using the detergent potassium dodecanoyl l-alaninate (lKDDA). A binary cholesterogen study has been made using both the detergents lKDDS and lKDDA. The twist was not enhanced and the inter-cholesterogen (detergent) interaction was shown not to be present in these micellar mixtures.     

A Solid Potassium Ion Selective Electrode

Abstract

A solid membrane potassium selective electrode has been developed. The following parameters of the potassium ion electrode were investigated; Nernstian response to potassium ion activity, response time to step changes in potassium ion activity, the effect of pH on potassium response, and the electrode response to other cations.     

Sodium tungstate-catalyzed “On-water” synthesis of β-arylvinyl bromides

Abstract

Synthesis of structurally varied β-arylvinyl bromides has been accomplished in an eco-friendly “On-water” condition through bromodecarboxylation reaction of appropriately substituted cinnamic acids with potassium bromide using hydrogen peroxide as oxidant and sodium tungstate as catalyst. Salient mechanistic features have also been highlighted.