Synthesis and characterization of new liquid crystalline materials containing a non-activated arylazoindolinobenzospiropyranyl group as a chiral unit. Part II

Two series of new liquid crystalline compounds containing a non-activated arylazoindolinobenzospiropyran, ABP-SPAB 1a-1e (series 1) and SPAP-ABPC 2a-2e (series 2), have been synthesized. These LC dyes were characterized by a differential scanning calorimetry polarizing optical microscopy, X-ray diffraction and electro-optical measurements. All but one of the series 1 compounds examined exhibit monotropic second and/or third transition liquid crystal phases on cooling from the isotropic liquid. In particular, ABP-SPAB 1b shows a monotropic SmC phase, in addition to a SmA phase. In series 2, most of the compounds exhibit a monotropic nematic phase on cooling. SPAP-ABPC 2c forms an enantiotropic nematic phase and a monotropic SmA phase; 2e shows enantiotropic nematic and SmA phases.     

Simultaneous Determination of Microgram Amounts of Platinum and Palladium in Presence of Base Metals by Isolation on Anion Exchange Resin-Loaded Paper and X-Ray Spectrometry

Abstract

A procedure for simultaneous determination of microgram amounts of platinum and palladium in solutions of base metals is described. The two metals are isolated on an anion exchange resin-loaded paper disk and determined by X-ray spectrometry. The method is applied to the determination of platinum and palladium in nickel matte.     

Liquid Chromatographic Assay for Salicylic Acid in Liquid and Semisolid Formulations

Abstract

A high performance liquid chromatographic assay for quantitating salicylic acid (S) in lotion, collodion, ointment and cream formulations is described. The method involved direct determination of S in the liquid dosage forms after appropriate dilutions with the mobile phase. Prior extraction of S from ointments and creams was carried by chloroform. Metronidazole was used as the internal standard and a μ-Bondapak phenyl column with a mobile phase made of 30%, methanol in 5 mM solution of tetrabutylammonium phosphate (pH 7.5) led to an efficient separation. Retention times of about 3 and 7.5 min were obtained for the internal standard and S respectively. The recovery of S from the dosage forms was tested by adding known amounts of S to each preparation and mixing before determination. The mean percentage recovery was in the range of 98–101.1%. The method was found to be accurate, simple and reproducible.     

Modeling of Dispersed-Emulsion Separation Systems

A dispersed-emulsion separation system is a type or configuration of liquid-membrane separation systems. Such systems are comprised of three liquid phases: two of these liquid phases are miscible with each other but are separated by a third liquid phase (the membrane) which is immiscible with both. The interfaces may be stabilized by a surfactant. Mass is transferred from one of the miscible phases across the liquid membrane to the second miscible phase. These systems were introduced by Li^1,2.     

Colorimetric Determination of Microgram Quantities of Urea

Abstract

A sensitive colorimetric method of determining urea is described. It involves measurement of the absorbance of the red color formed when urea is heated with diacetyl monoxime and thiosemicarbazide under acidic conditions (phosphoric acid-sulfuric acid medium). The method is accurate and precise, and it permits determination of microgram amounts of urea in the presence of ammonium, nitrate, amino acids, amides, and amino sugars.     

Dosage Simultane Des Traces D′eau Et C′oxygexe Dans Les Solvants Crganiqufs

Abstract

The method involves gas-liquid chromatographtc detenninatlons of samples picked up from the liquid phase of an organometalllc solution and from the gas phase above it; the first sample is hydrolyzed before analysis. Comparfng the results before and after introduction of a known amount of a solvent to be analyzed give simultaneous determination of owgen and water present in this solvent of contents less than one part per million.     

Vapor-Liquid Equilibrators To Aid In Making Measurements To Determine Solvent Adducts On Metal Chelates

Abstract

Two vapor-liquid equilibrators to saturate water with organic solvent without forming two liquid phases were developed, thus permitting a more accurate determination of organic adducts to metal chelates. An equation was developed to show that vapor pressure measurements could be used as an alternative method for determining the number of organic adducts on a metal chelate in the aqueous phase.     

Determination of Phosphate in Aqueous Solutions Containing NTA and EDTA

Abstract

A simple and precise colorimetric method of determining phosphate in aqueous solutions containing nitrilotriacetic acid (NTA) or ethylendiaminetetraacetic acid (EDTA) is described. It involves precipitation of the NTA or EDTA by acidification to pH 1.5 and colorimetric determination of the phosphate in the filtrate by a heteropoly blue method. The method is sensitive and accurate, and it permits determination of microgram amounts of phosphate in samples of aqueous solutions containing up to 300 mM of NTA and (or) EDTA.     

Non-linear dielectric spectra of ferroelectric liquid crystals

Abstract

The non-linear dielectric relaxation spectroscopy has been recently developed and applied to soft materials such as polymers. We have applied this new method to the S*_C phases of some ferroelectric liquid crystals. Under a weak AC electric field, the original and third order harmonic frequency components of electric displacement are proportional to the first and third powers of the applied electric field, respectively. The linear spectrum obtained from the original frequency component shows the relaxation of Debye type and the third order non-linear spectrum shows the relaxation with an extended form of Debye type to the non-linear case. The third order non-linear dielectric increment is found to be negative, which implies that the dielectric non-linearity of the liquid crystal in the S*_C phase is due to the saturation of molecular dipole moments induced by the applied electric field. The temperature dependence of the linear and third order non-linear spectra in the S*_C phase are also studied. Both spectra do not change their forms much through the whole temperature range of the S*_C phase. In the vicinity of the S_A–S*_C transition temperature, the critical behaviour is more remarkable in the third order spectrum than in the linear one.     

Liquid–Liquid–Liquid Micro Extraction Combined with CE for the Determination of Rare Earth Elements in Water Samples

A simple method for determination of rare earth elements (REEs) by liquid–liquid–liquid microextraction (LLLME) coupled with capillary electrophoresis and ultraviolet technique was developed. In the LLLME system, 40 mmol L^?1 4-benzoyl-3-methy-1-phenyl-5-pyrazolinone (PMBP) acted as extractant and 4% (v/v) formic acid was used as back-extraction solution. The parameters influencing the LLLME, including the type of the organic solvent, sample pH, formic acid concentration, PMBP concentration, extraction time, volume of organic solvent, stirring rate and phase volume ratio, were investigated. Under the optimized conditions, the detection limits (S/N = 3) of REEs were in the range of 0.19–0.70 ng mL^?1. The developed method was successfully applied to the determination of trace amounts of REEs in water samples.     

Isolation and Identification of Drugs of Forensic Interest by High Performance Reverse Phase Ion Pair Partition Chromatography

Abstract

A method is presented for the isolation and identification of milligram or microgram quantities of drugs of forensic interest. High performance reverse phase ion pair partition chromatography is performed on a 9.4 millimeter internal diameter microparticulate octadecylsilane column employing a water, methanol, acetic acid, alkylsulfonate mobile phase. Subsequent to collection from the liquid chromatograph, a simple extraction is performed followed by Infrared (IR) analysis and/or solid probe Mass Spectrometry (MS). A study is presented using phenylpropanolamine hydrochloride and ephedrine hydrochloride as a test model for the determination of the optimum concentration of counter ion required for a semi-preparative separation. The method is applied to an LSD seizure from a clandestine laboratory, methamphetamine in a street exhibit, and an amobarbital - secobarbital mixture in a multi-barbiturate capsule.     

A rapid routine method for the determination of sub-microgram and microgram amounts of beryllium in filter paper

A rapid routine method for the determination of submicrogram and microgram amounts of beryllium in filter paper smears is presented. Beryllium is determined fluorimetrically with 3,5,7,2',4'- pentahydroxyflavone (Morin). Many interfering elements are removed by adsorption on a strongly basic anion-exchange resin from 9N hydrochloric acid.     

Determination of tin in indium by neutron activation with pre-irradiation separation

A method has been developed for chemical control of a short-lived radiopharmaceutical,⁵²Fe. The optimum conditions have been investigated for the simultaneous determination of microgram amounts of nickel, iron and chromium in an admixture. The method developed is applicable for the determination of 0.01 to 20 μg·ml^?1 of nickel, 0.01 to 50 μg·ml^?1 of iron and 0.05 to 50 μg·ml^?1 of chromium. A study has been made of the mutual interference of these elements at different concentrations, and also of the interference by various other cations and anions. A list has been given of the other elements that can be analysed using the supporting electrolyte. A method of routine analysis is described.     

Vibrational spectra and conformational behavior of dicyclopropylmethane

Raman spectra of the condensed phases of dicyclopropylmethane have been recorded. In addition, i.r. spectra of this compound have been obtained for all three phases. From the appearance of spectral doublets in the liquid phase Raman (and i.r.) spectra, one member of each of which vanishes upon crystallization, it has been concluded that, in the liquid state, DCPM exists as an equilibrium mixture of at least two conformers. Based upon the spectral results for DCPM, and upon the conformational preferences of a number of related molecules, it has been concluded that these two conformers are the C₂ and C_sgauche/gauche rotational isomers, with the C₂ form being the one which remains in the solid phase. From a variable temperature study of liquid phase Raman peaks, it has been determined that the C₂ conformer of DCPM is more stable than the C_s conformer by 0.93 ± 0.10 kcal/mole. In addition, it appears that the C₂ rotamer of DCPM also predominates in the gaseous phase. Tentative assignments of the major spectral bands of DCPM have also been proposed.     

Multivariate Methods to Evaluate the Role of Mixed Supports in Reversed-Phase Thin-Layer Chromatography

Abstract

Hydrophobic properties of 17 aniline and phenol derivatives were characterized by reversed-phase thin-layer chromatographic and high performance liquid chromatographic retention data.

In order to elucidate the role of thin-layer chromatographic supports in the hydrophobicity determination paraffin coated silica, aluminium oxide, cellulose, diatomaceous earth and their mixtures were used. Water, water-methanol 7:3 and 1 M NaCl served as mobile phases. The retention data were analyzed by spectral mapping technique.

The potency values differed from support to support proving that the composition of support has a deciding role in the hydrophobicity determination of aniline and phenol derivatives. The eluents did not influence considerably the potency order of supports.     

Phyllohydroquinone (Vitamin K1 H2) and Phylloquinone (Vitamin K1): Purification and Spectral Analysis

Abstract

Simple procedures for the preparation of pure phyllohydroquinone and phylloquinone are described. Phylloquinone is reduced by sodium dithionite and the reduced vitamin is purified by reverse phase high performance liquid chromatography. The essential spectral properties of the pure vitamins in ethanol and methanol are cited. The data provide a convenient spectral method for the accurate determination of the absolute concentrations of the oxidized and reduced vitamins and the rates of oxidation of the reduced vitamin. Pure, dry phyllohydroquinone may be safely stored at -70[ddot]C under nitrogen for a period of months. The stability of Phyllohydroquinone in methanol at 25.0 ± 0.1[ddot]C is also reported.     

Spectrophotometric Method for the Rapid Determination of Microgram Amounts of Ethionamide

Abstract

Spectrophotometric Method for the Rapid Determination of Microgram Amounts of Ethionamide

A simple and sensitive method for the determination of microgram amounts of ethionamide is described. Ethionamide is converted to corresponding 2-ethyl-γ-pyridyl thiohydroxamic acid which gives a purple violet colour (Λmax 510 nm) with ferric chloride in acidic medium. This forms the basis for the quantitative determination of ethionamide in its pure form and in tablet form. The influence of substrates, commonly employed as excipients, is studied. An attempt has been made to determine ethionamide in the presence of other antitubercular drugs.     

Critical Point and Metal-Nonmetal Transition in Expanded Liquid Metals

Abstract

For most metals the two phases of the liquid-gas transition are metallic in a region around the critical point. A method for determining the critical data of expanded liquid metals under such conditions has been published recently. Mercury, however, is a well-known exception with the metal-nonmetal transition inside the liquid phase. Mercury is no longer a metal at the critical point. the metal-nonmetal transtion of the metallic elements has been considered in view of this problem. It is shown that a group of metals (Mg; Zn, Cd; As, Sb; Se, Te), including semi-metals as well, should also have the metal-nonmetal transition completely inside the liquid phase. Thus, the above mentioned method is not applicable in this group. A comparison of the measured electrical conductivity of Al, W, Zn, and Hg with a theoretical approach supports this conclusion.     

Determination of Ethosuximide,Phenobarbital, Carbamazepine,Carbamazepine Epoxide and Phenytoin in Serum by high performance liquid chromatography using Radially compressed Columns and an Aqueous methanolic mobile phase

Abstract

A liquid chromatographic method for the determination of antiepileptic drugs in serum is described. The drugs were adsorbed on activated charcoal from which they were recovered by extraction with methylene chloride. The organic extracts were evaporated to dryness and the residues were dissolved in small volumes of the mobile phase. The extracts were clean. Only trace amounts of endogenic compounds were detected. The chromatographic separation was performed with a radially compressed column (C18) that was used daily for several months.     

On the Determination of the Hold-Up Time in Reversed Phase Liquid Chromatography

Abstract

The determination of the hold-up time in reversed phase liquid chromatography has been studied extensively for the mobile phase system methanol-water. Hold-up times obtained by static methods, linearization of homologous series and so-called “unretained compounds” are discussed and mutually compared. Several n-alkyldimethylsilyl bonded phases have been used for this investigation.

A rough estimate of the hold-up time can be obtained by using components of the mobile phase or highly concentrated salt solutions, but only for mobile phase compositions around 60% (v/v) methanol. Hold-up times accurate to 1% can be obtained over the complete range of mobile phase compositions from the linearization of net retention times of homologous series.