Embeddings of SL(2; ?) into the cremona group

Geometric and dynamic properties of embeddings of SL(2; ℤ) into the Cremona group are studied. Infinitely many nonconjugate embeddings that preserve the type (i.e., that send elliptic, parabolic and hyperbolic elements onto elements of the same type) are provided. The existence of infinitely many nonconjugate elliptic, parabolic and hyperbolic embeddings is also shown. In particular, a group G of automorphisms of a smooth surface S obtained by blowing up 10 points of the complex projective plane is given. The group G is isomorphic to SL(2; ℤ), preserves an elliptic curve and all its elements of infinite order are hyperbolic.     

Novel ultrasonic‐assisted deep eutectic solvent‐based dispersive liquid–liquid microextraction for determination of vanadium in food samples by electrothermal atomic absorption spectrometry: A multivariate study

A green, efficient, simple and sensitive pre‐concentration method has been developed for the determination of vanadium(V) in foodstuffs using deep eutectic solvent–ultrasonic‐assisted dispersive liquid–liquid microextraction. In the developed procedure, the extraction of vanadium(V) was achieved using 2‐hydroxy‐3‐methoxybenzaldehyde thiosemicarbazone as a chelating agent, choline chloride–phenol as extracting solvent and tetrahydrofuran as dispersive solvent. Vanadium(V) concentration was measured using electrothermal atomic absorption spectrometry. Various analytical parameters including pH, type and molar ratio of deep eutectic solvent, ultrasonication time and amount of ligand were studied. A multivariate study was carried out for optimization of the variables. The pre‐concentration factor was calculated as 50. Under optimal conditions, limit of detection, limit of quantification and relative standard deviation were calculated as 0.025 μg l^?1, 0.175 μg l^?1 and 3.4%, respectively. The accuracy of the procedure was confirmed using certified reference materials and standard addition method. The obtained results confirm adequate recoveries for vanadium(V) (>96%). This technique was fruitfully applied for determination of vanadium in foodstuffs.     

Liquid chromatography of uranium complexes of tetradentate Schiff bases.

Dioxouranium together with copper(II), nickel(II) and iron(II) were extracted in chloroform as complexes of bis(salicylaldehyde)-dl-stilbenediimine (dl-H2SA2S) or bis(salicylaldehyde)-meso-stilbenediimine (meso-H2SA2S), and separated by liquid chromatography with UV detection. The linear calibration range and detection limits were 40 - 200 ng and 10 ng/injection for each metal ion. The method was applied to the determination of uranium from mineral ore samples at concentrations of 30 - 700 microg/g with coefficients of variation from 3.6 to 5.5%. The relative elution of dioxouranium complexes of different Schiff bases was examined from reversed-phase HPLC; the substitution of methyl and phenyl groups at the bridge position enhanced the column retention of uranyl complexes.     

HPLC determination of copper(II), cobalt(II) and iron(II) in pharmaceutical preparations using 2-acetylpyridine-4-phenyl-3-thiosemicarbazone derivatizing agent

Summary Cu(II) Co(II) and Fe(II) in pharmaceutical preparations were determined using precolumn derivatization and solvent extraction with 2-acetylpyridine-4-phenyl-3-thiosemicarbazone (APPT) as complexing reagent. Liquid chromatography (LC) was carried out on a reversed phase C-18, column. The complexes were eluted isocratically with acetonitrile-water containing sodium acetate and tetrabutyl ammonium bromide as ion-pairing agents. The results obtained were compared with those using atomic absorption.     

GC Determination of Famotidine,Ranitidine, Cimetidine,and Metformin in Pharmaceutical Preparations and Serum Using Methylglyoxal as Derivatizing Reagent

A capillary gas chromatography (GC) procedure has been developed for the determination of four pharmaceutical preparations (famotidine, ranitidine, cimetidine, and metformin) after precolumn derivatization with methylglyoxal (MGo). GC was carried out using an HP-5 column (30 m × 0.32 mm id) at an initial column temperature of 90 °C for 2 min, followed by heating rate of 25 °C min⁻¹ up to 265 °C. Nitrogen flow rate was 2.5 mL min⁻¹ with split ratio 10:1. A linear calibration curve was obtained within 50–1,000 ng mL⁻¹ and the limit of detection (LOD) was within 17–25 ng mL⁻¹. The derivatization, GC elution, and separation were repeatable in terms of retention time and peak height/peak area with relative standard deviation within ±4.6 %. The procedure was applied to the determination of the drugs in pharmaceutical preparations and the sera of volunteers who were given oral doses of the drugs. The results of the analysis agreed with the labeled values of the pharmaceutical preparations and were 147–4,903 ng mL⁻¹ in serum with an RSD within 1.0–4.2 %, after ingestion of a single dose of 40–500 mg of active ingredient in a tablet.

     

Liquid chromatographic determination of cis-platin as platinum(II) in pharmaceutical preparation, serum and urine samples of cancer patients

Spectrophotometric and high performance liquid chromatographic (HPLC) methods have been developed for the determination of cis-platin and carboplatin based on the pre-column derivatization of platinum(II) with 2-acetylpyridine-4-phenyl-3-thiosemicarbazone. The complex was extracted in chloroform with molar absorptivity of 2.2 × 10⁴ L mol⁻¹ cm⁻¹ at 380 nm. The complex eluted from a Phenomenex C-18 (150 mm × 4.6 mm i.d.) column with methanol:water:acetonitrile:tetrabutyl ammonium bromide (1 mM) (44:30:25:1, v/v/v/v) with a flow rate of 1 ml/min and UV detection at 260 nm. Ruthenium(IV) and selenium(IV) also separated completely. The linear calibration curve was with 0.5-12.5 μg/ml and detection limit of 10 ng/ml platinum(II).The analysis of cis-platin and carboplatin injections by spectrophotometric and HPLC methods indicated relative standard deviation (R.S.D.) of 0.66-2.1%. The method was used for the determinations of cis-platin in serum and urine of cancer patients after chemotherapy and platinum contents were found 148-444 and 50-90 ng/ml with R.S.D. of 0.3-3.0 and 0.6-2.4% for the serum and urine, respectively. The recovery of platinum(II) from serum was 97% with R.S.D. 2.2%.     

High-performance liquid chromatographic determination of uranium using solvent extraction and bis(salicylaldehyde) tetramethylethylenediimine as complexing reagent

The reagent bis(salicylaldehyde)tetramethylethylenediimine has been used for the determination of dioxouranium(VI), based on complexation in aqueous solution at pH 6, followed by extraction in chloroform and HPLC determination on a Hypersil ODS (3 μm) column. The complex was eluted with the ternary mixture methanol-acetonitrile-water (40:30:30, v/v/v), with UV detection at 260 nm. Oxovanadium(IV), iron(III), copper(II), cobalt(II), nickel(II) and palladium(II) were completely separated and did not interfere in the determination of uranium. The linear calibration range and detection limits have been obtained. The method has been applied to the determination of uranium together with copper, iron and nickel in mineral ore samples.     

PREPARATION AND CHARACTERIZATION OF SCHIFF BASE POLYMERS DERIVED FROM 4,4''''-METHYLENEBIS(CINNAMALDEHYDE)

New Schiff base polymers poly[4,4'-methylenebis(cinnamaldehyde)ethylenediimine] (PMBCen), poly[4,4'-methylenebis(cinnamaldehyde) 1,2-propylenediimine] (PMBCPn), poly[4,4'-methylenebis(cinnamaldehyde) 1,3-propylenediimine] (PMBCPR), poly[4,4'-methylenebis(cinnamaldehyde)l,2-phenylenediimine] (PMBCPh), poly[4,4'-methylene-bis(cinnamaldehyde)meso-stilbenediimine] (PMBCS), poly[4,4'-methylenebis(cinnamaldehyde)urea] (PMBCUR), poly[4,4'-methylenebis(cinnamaldehyde)semicarbazone] (PMBCSc), poly[4,4'-methylenebis(cinnamaldehyde)thiosemicarbazone] (PMBCTSc) and poly[4,4'-methylenebis(cinnamaldehyde)hydrazone] (PMBCH) were formed by polycondensation of 4,4'-methylenebis(cinnamaldehyde) with ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,2-phenylenediamine, meso-stilbenediamine, urea, semicarbazide, thiosemicarbazide and hydrazine, respectively. The dialdehyde and polymers have been characterized through elemental micro-analysis, IR, UV-Vis and 'H-NMR spectroscopic techniques. Thermoanalytical studies and viscous flow of dilute solutions of dialdehyde and its polymers have been examined and compared.