Separation and acid equilibria of xylenol orange and semi-xylenol orange

A mixture of Xylenol Orange (XO) and Semi-Xylenol Orange (SXO) was chromatographed on a cellulose column and ion-exchanged with Diaion SK-1 resin. XO and SXO in the acidic forms were titrated with sodium hydroxide to determine the basicities and the acid formation constants. The absorption spectra of XO and SXO were measured over a wide pH range, and were used for the calculation of acid formation constants, molar absorptivities, and the effect of ionic strength on the activity of XO. The purity of a commercial XO was measured by absorption spectroscopy, and it was found that the sample contained 36.3% of XO and 17.2% of SXO. Pure XO and SXO form a 1:2 and a 1:1 complex respectively with Zn(II). On the basis of these data the ionic structure of XO and SXO have been compared with those of Cresol Red and iminodiacetic acid, and discussed.     

ISolement du groupe des terres rares de l'apatite par l'acide di-(2-ethyhexyl)phosphorique (hdehp)

The liquid-liquid extraction of rare-earth elements (REE) by 0.75 M di-(2-ethylhexyl) phosphoric acid (HDEHP) in cyclohexane from perchloric acid (1–12M) has been investigated. At moderate perchloric acid molarities (1–6 M), the distribution coefficient, E, has an inverse third-power dependency upon the acid concentration in the aqueous phase. However, at higher perchloric acid concentrations, the slope of the resulting curve is about +18, which means a change in the extraction mechanism. In 12 M perchloric acid medium, REE are quantitatively and selectively extracted from apatite minerals, in the organic phase. In order to strip out all the lanthanides, back-extractions were carried out with 9 M hydrochloric acid solutions.     

Spectrophotometric Investigation and Determination of Scandium Using Semi-Xylenol Orange

Abstract

The composition, stability constant and molar absorption coefficient of the chelate of scandium ion with Semi-Xylenol Orange (SXO) are determined speotrophotometrically in a medium of chloroacetate buffer. In the scandium-Semi-Xylenol Orange system, Sc(SXO) chelate is formed with a logarithmic stability constant of 19.66 and molar absorptivity of 2.4x10⁴ (530 nm) 1 mole^?1cm^?1.

The precision and accuracy attainable in a direct photometric microtitration of Sc⁺⁺⁺ ion with a 0.001M solution of EDTA using SXO as a metallochromic indicator has been studied. Interferences of different anions and cations on scandium determination are also investigated.

Spectrophotometric determination of scandium(III) using SXO at the optimum conditions has been carried out. Beer's law is obeyed for 0–13.49 μg scandium/25 ml.     

Separation of Xylenol Orange, Semi-Xylenol Orange and o-Cresol Red

Several aqueous organic solvent systems have been investigated for the extractive separation of Xylenol Orange (XO), Semi-Xylenol Orange (SXO) and o-Cresol Red (CR). Four methods of determination of the extracted species were used. The best separation of CR and SXO was obtained with aqueous 1-butanol and of SXO and XO with the 0.5M sulphuric-1-butanol system.     

Extraction of perchloric acid by the nitrobenzene solution ofp-nonylphenylnonaethylene glycol

Extraction of perchloric acid by the nitrobenzene solution of Slovafol 909 (p-nonylphenylnonaethylene glycol, L) has been investigated and the composition of species in the organic phase has been determined. It has been found, that perchloric acid is full dissociated in both phase, and H⁺ ion in the organic phase is partially solvated by one or two molecules ofp-nonylphenylnonaethylene glycol. Extraction and stability constants of HL⁺ and HL ₂ ⁺ species in the organic phase has been evaluated.     

High-performance liquid chromatographic assay for amiloride in plasma and urine

A sensitive and simplified high-performance liquid chromatographic procedure has been developed for quantification of amiloride in rabbit plasma, as well as human plasma and urine. Following protein precipitation with perchloric acid, the supernatant was directly injected into a C18 Nucleosil column. The mobile phase consisted of methanol-water (45:55) containing 0.1 M perchloric acid, and the compound was quantitated using a fluorescence detector at excitation and emission wavelengths of 286 and 418 nm, respectively. The average recovery was 97.6%. The calibration curve was linear over the range 2.0-20.0 ng/ml. The limit of detection was 0.5 ng/ml.     

The role of 70-80% perchloric acid as oxygen donor and the oxidation potentials made available

A study has been made of the probable oxidation potentials provided by perchloric acid in the concentration range 70-80 %. The effect of acid concentration and temperature on the oxidation of chromium, vanadium, cerium, and manganese has been investigated. Available oxidation potentials appear to be 2.0-2.1 V or higher. The monohydrate of perchloric acid, HClO(4).H(2)O, containing 84.6% of perchloric acid, has been made commercially available and authorized for distribution by common carrier. It can be diluted to give acid concentrations from 73.6% (corresponding to HClO(4).2H(2)O) upwards. Perchloric acid mixed with sulphuric acid is equivalent to high concentrations of perchloric acid and can be used for dissolution of ores and destruction of organic matter.     

Étude d'équilibres en solution à l'aide des échangeurs d'ions: II Détermination des constantes de dissociation des perchlorates alcalins dans les mélanges eau—acide acétique—acide perchlorique

The thermodynamic dissociation constants of lithium, sodium, potassium, rubidium and cesium perchlorates in water—acetic acid—perchloric acid mixtures have been determined by an ion-exchange method. The distribution coefficients of alkaline elements have been measured in water—acetic acid—perchloric acid mixtures containing a variable quantity of water (4–100 % by weight) and a constant amount of perchloric acid. The variation of these distribution coefficients with perchloric acid concentration has been studied in various mixtures containing a constant amount of water (less than 20 % $\text{w}\text{w}$). The results have been used to determine the dissociation constants of alkaline perchlorates and the selectivity coefficients of alkaline ions and hydrogen ion in the aqueous organic mixtures studied.     

石墨炉原子化器中原子化过程的研究(Ⅴ)——高氯酸对锂和锗的干扰

本文详细地研究了HClO₄对Li和Ge的干扰.HClO₄对Li原子吸收信号有明显的抑制作用,干扰的主要原因是气相中形成LiCl。当预加热温度达2000℃时,残留HClO₄干扰可消除。在HClO₄分解之前加入NH₄NO₃,可消除其干扰。HClO₄对Ge有增感作用,并与灰化温度有密切关系。500℃以前HClO₄增感效应随温度升高变化较小,高于500℃增感效应明显增加。     

Extraction chromatography of palladium and platinum complexes with nitroso-R-salt

The retention of palladium and platinum complexes with nitroso-R-salt on silica gel treated with Aliquat 336 has been investigated. The complexation of platinum with nitroso-R-salt (NRS) requires heating of H₂PtCl₆ with an excess of NRS at 100°. The affinity of the complexes for an Aliquat 336 stationary phase increases in the following order: PdCl₄²⁻ ˜ Pt-NRS < PtCl₆²⁻ Pd-NRS. The complexes of palladium and platinum can be separated by column chromatography on silica treated with Aliquat 336 and eluted with 0.25M perchloric acid (Pt) and 1M perchloric acid (Pd).     

Extraction of scandium ions by 1-alkyl-3-methyl-2-pyrazolin-5-ones from perchlorate solutions

The extraction of perchloric acid and the two-phase partition of 1-alkyl-3-methyl-2-pyrazolin-5-ones (AMPs) in the system water-chloroform-perchloric acid are studied. These reagents can extract scandium cations from weak acid solutions in the presence of perchlorate ions. 1-Alkyl-3-methyl-2-pyrazolin-5-ones separate aqueous perchloric acid solutions into a pair of liquid phases. Scandium ions concentrate in the lower phase, which has a small volume.     

Determination of glycyrrhizin in rabbit plasma by high-performance liquid chromatography with photodiode-array ultraviolet detection and its pharmacokinetics application.

A simple and sensitive high-performance liquid chromatographic method for the determination of glycyrrhizin in rabbit plasma has been developed. Up to 0.1 ml of plasma containing glycyrrhizin was deproteinized by acetonitrile, which contained an internal standard (indomethacin). The supernatant was injected onto a LiChrospher RP-18 column using a methanol-water-ammonia solution (80:20:0.1, v/v, pH 3.0-3.2, adjusted with perchloric acid) as the mobile phase and ultraviolet detection at 254 nm, followed by ultraviolet spectrum identification (between 200 and 380 nm) with a photodiode-array detector. The method is rapid, easily reproduced, selective and sensitive. It was applied to pharmacokinetic studies of glycyrrhizin in rabbit, after a 2 mg/kg intravenous administration. A biphasic phenomenon with a rapid distribution followed by a slower elimination phase was observed from the plasma concentration-time curve. Compartmental analysis yielded a two-compartment model.     

Monitoring propofol serum levels by rapid and sensitive reversed-phase high-performance liquid chromatography during prolonged sedation in ICU patients.

A quick and sensitive reversed-phase high-performance liquid chromatography (HPLC) method has been developed in order to determine the concentration of Propofol (2,6 diisopropylphenol) in human serum. Propofol can be isolated from serum by adding 0.5 mL precipitating solution. This consists of an acetonitrile and perchloric acid (67:33, v/v) mixture, which also contains dibutylphthalate (2 mg/100 mL) as internal standard. The sample is then mixed for 1 min on a vortex-mixer. The endogenous serum substances precipitated by acetonitrile and perchloric acid are further separated by centrifugation. The supernatant is directly injected into the HPLC system. A 250- x 4.6-mm column, packed with 10-microns Spherisorb reversed-phase octadecylsilane particles (C18), is used for chromatographic separation. The mobile phase consists of an acetonitrile-water mixture (67:33 ratio) with 0.4 mL acetic acid (pH 4). Propofol is monitored by a UV-visible detector at 270 nm and 0.1-0.002 absorbance units full scale (AUFS). The detection limit of Propofol (in human serum) is 0.1 mg/L for a 20-microL injection volume. The time of the assay is less than 20 min, including sample preparation.     

Indirect conductimetric detection of amino acids after liquid chromatographic separation

A liquid chromatographic method using indirect conductimetric detection is proposed for the determination of low levels of organic compounds, which does not require any special functional characteristics of the analyte. The signal detected is proportional to the molar concentration of the analyte and independent of its nature. The detector response is linearly dependent on analyte concentrations over at least three orders of magnitude. The basis of the detection is to create a conducting background, which will decrease on elution of the organic compounds. The theory of the method is discussed, with special reference to the quantitative displacement of the conducting species of the mobile phase from the column by the analyte on sample injection. The proposed method has been applied to study the chromatographic behaviour of twenty-one amino acids, where a 5 -μm Econosil CN column was used as the stationary phase with a mixture of water-acetonitrile-tetrahydrofuran (70:20:3) containing 1 mM perchloric acid or trichloroacetic acid as the mobile phase. The proposed method allows as little as 10 ng of each amino acid to be determined.     

Graft Copolymerization of Methyl Methacrylate onto Nylon 6 Using Thallium(III) Ions as Initiator

Abstract

Graft copolymerization of methyl methacrylate onto nylon 6 was investigated in aqueous perchloric acid medium using thallium(III) ions as initiator. The rate of grafting was evaluated by varying the concentrations of monomer, initiator, acid, and temperature. The rate of grafting was found to increase with an increase of both monomer and initiator concentrations. The graft yield was found to increase with an increase in the acid concentration up to 0.49 mL^?1, and beyond this concentration of perchloric acid the graft yield was found to decrease. It also increased with an increase of temperature. From the Arrhenius plot the overall activation energy was found to be 3.9 kcal/mol. The effects of inhibitors, various solvents, inorganic salts, and swelling agents on graft yield were studied. A suitable kinetic scheme has been proposed and a rate equation has been derived.     

反相键合相高效液相色谱法分离测定萘普生

 建立了分离测定萘普生和溴代萘普生的反相键合相高效液相色谱法。采用ＯＤＳ柱，以添加５０ｍｍｏｌ／Ｌ乳酸并用高氯酸调节ｐＨ为２．５的８０％甲醇－水溶液作为流动相，以苯甲酸为内标物，测定了不对称合成工艺产物中萘普生和溴代萘普生的含量。方法的准确度分别为９９．８３％～１０２．０７％（萘普生）和９９．０％～１００．８３％（溴代萘普生），相对标准偏差分别小于２．５８％（萘普生）和３．６４％（溴代萘普生）。方法可用于工艺条件的选择和质量检测。     

Spectrophotometric determination of small amounts of Xylenol Orange, Semi-Xylenol Orange and o-Cresol Red

An extraction method based on the butanol—water system is used in an improved spectrophotometric determination of Xylenol Orange (XO), Semi-Xylenol Orange (SXO) and Cresol Red (CR) in mixtures. Small amounts of SXO in the presence of much greater amounts of XO, and small amounts of XO in the presence of large amounts of SXO can be determined with good accuracy after extractive separation of the compound to be determined, from the bulk of the other components of the mixture.     

Extraction of Hg/II/ with dibutylester of N-/4-antipyryl/-amidophosphoric acid from iodide solutions

A new extraction reagent-dibutylester of N-/4-antipyryl/-amidophosphoric acid/DBAAP/—has been developed and used for the extraction of divalent mercury into chloroform from mixture of sodium iodide and perchloric acid. It was found that the composition of the species extracted into the organic phase depends on the acidity of the aqueous phase. The solvate HgI₂. DBAAP is extracted at low HClO₄ concentrations, an ion-pair, /DBAAPH/⁺.HgI ₃ ^– , is formed and extracted at high concentrations of perchloric acid.     

Purity determination of yunaconitine reference standard using HPLC with experimental design and response surface optimization

Experimental design and response surface methodology have been used for the development of the stability‐indicating HPLC method for the purity determination of yunaconitine reference standard. Significant factors including the contents of ACN, perchloric acid, triethylamine (TEA), and column temperature were optimized using a Box–Behnken design. A mixture of crude yunaconitine extract and degradation solutions of yunaconitine under stress conditions was chromatogramed. The normalized peak area of total impurities, the retention time of yunaconitine, and the resolutions between yunaconitine and its adjacent peaks were selected as optimization criteria. Derringer desirability function of the multicriteria and the tested factors were used to establish 3‐D response surfaces. The optimal condition was achieved with a mobile phase of ACN/water (30:70, containing 0.125% perchloric acid and 1.0% TEA) at a column temperature of 37.5°C. The method was validated and shown comparable to that of phase solubility analysis. As a result, the newly developed method can be used to determine the chromatographic purity and stability of the yunaconitine reference standard.     

Analyte zone sharpening in pressurized capillary electrochromatography based on electrophoretic migration under a heterogeneous field

Significant peak width reductions, or peak height enhancements, of angiotensins were observed when a high voltage was applied to hydrophilic interaction pressurized capillary electrochromatography using gradient elution with mobile phases containing perchloric acid. The investigation using a contactless conductivity detector revealed that perchloric acid was adsorbed on the surface of the stationary phase, when the acetonitrile content in the mobile phase was high, and released from the stationary phase by increasing the water content during a gradient procedure. The released perchloric acid formed a highly concentrated zone moving from the column inlet to the outlet. The electrochromatographic behavior of the analytes, primarily electrophoretic migration, was changed in this zone. As a consequence of the significant variation in migration velocity of the analytes, the sample band width was reduced similar fashion to on‐capillary concentration in capillary electrophoresis. Using this result, the reduction of band width and enhancement in separation efficiency was demonstrated in reversed‐phase pressurized electrochromatography, in which the conductivity of the mobile phase was significantly altered using a step gradient. The resolution between benzoic acid and 1‐naphthalene sulfonic acid was successfully improved from 2.7 to 4.3 by using the band width reduction method based on field‐amplified stacking.