Flameless atomic absorption spectrometry of antimony

Flameless atomic absorption spectrometry of antimony has been investigated with a carbon rod device. Antimony may be determined in solution at a level of 10^-10 g with a sample volume of 0.5 μl. Optimal conditions and interferences are described. Matrix effects on antimony necessitated a preliminary solvent extraction of the chloride complex from hydrochloric acid solution containing nitrite with methyl isobutyl ketone. The determination of antimony in metallurgical samples was shown to be satisfactory.     

Synthesis of a novel ferrocene derivative having flame-retardant and smoke-suppressant properties

Reaction of ferrocene with chlorendic anhydride (1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid anhydride) under Friedel–Crafts reaction conditions affords a new monosubstituted dervative of ferrocene which has significant flameretardant and smoke-suppressant properties when incorporated into poly(vinyl chloride) (PVC). The monocarboxylic acid from the above reaction undergoes smooth methylation with diazomethane to give the corresponding methyl ester. ¹H and ¹³C NMR spectra of these compounds have been compared with those obtained from similar compounds, namely β-ferrocenoylpropanoic acid and its methyl ester. Distant asymmetric centres in the chlorendic anhydride substituent markedly affect the proton spectra of the ferrocene derivative.     

Microwave spectrum of propionyl chloride

The microwave spectrum of propionyl chloride has been investigated in the region 18.0–40.0 GHz, and transitions due to a cis conformer have been assigned. This form has a heavy atom planar configuration and the methyl group and the carbonyl oxygen atom are cis to each other. Using the substitution structures of propionic acid and acetyl chloride as molecular models for the propionyl chloride molecule, good agreement is found between observed and calculateò effective rotational constants. For the ³⁵Cl species satellite spectra assigned to the first four excited states of the C-C torsional mode have been observed together with the first excited state of the methyl torsional mode. The ground state spectrum has also been assigned for the ³⁷Cl species. Relative intensity measurements yielded the lowest C-C torsional vibration frequency of 86 ± 10 cm^?1. The CH₃ internal rotation frequency was found to be 197 cm^?1. Nuclear quadrupole coupling constants were determined for the ground state of the ³⁵Cl and ³⁷Cl species. From observed A-E splittings of ^bQ-branch transitions of the first excited state of the methyl torsional mode a barrier to internal rotation was estimated to be V₃ = 2480 ± 40 cal mol^?1 (867 ± 14 cm^?1).     

Copolymerization of isobutylene with 1,4-13C-isoprene

Copolymers of isobutylene with 1,4-¹³C-isoprene have been prepared in methyl chloride solvent at ?90 to ?50°C using aluminum chloride and organoaluminum halide initiators. The examination of these copolymers containing 0.5 to 3.0 mol % of the diolefin by ¹³C-NMR has given new information about the mechanism of the copolymerization. It appears that every macromolecule ends in an isoprene derived unit; that chain transfer to monomer by an isoprene-derived propagating carbocation is the dominant chain breaking process. The copolymer triad sequences have been unambiguously assigned and analyzed in both batch and continuous stirred tank reactor copolymers. The relative concentrations of the triads agree with those predicted by published reactivity ratios.     

Sorption of mercury on chemically synthesized polyaniline

Summary Sorption of inorganic mercury (Hg²⁺) and methyl mercury, on chemically synthesized polyaniline, in 0.1-10N HCl solutions has been studied. Hg²⁺ is strongly sorbed at low acidities and the extent of sorption decreases with increase in acidity. The sorption of methyl mercury is very low in the HCl concentration range studied. Sorption of Hg²⁺ on polyaniline in 0.1-10N LiCl and H₂SO₄ solutions has also been studied. The analysis of the data indicates that the sorption of Hg²⁺ depends on the degree of protonation of polyaniline and the nature of mercury(II) chloride complexes in solution. X-ray photoelectron spectroscopy analysis (XPS) of polyaniline sorbed with mercury show that mercury is bound as Hg²⁺. Sorbed mercury is quantitatively eluted from polyaniline with 0.5N HNO₃. Polyaniline can be used for separation and pre-concentration of inorganic mercury from aqueous samples.     

Electron Capture Gas Chromatography of Nitrazepam in Human Plasma as Methyl Derivative

Abstract

A method for quantitative determination of nitrazepam in human plasma in the range 5 - 100 ng/ml is presented.

Nitrazepam is extracted with benzene from plasma samples of 0.5 ml, methylated with methyl iodide and determined gas chromatographically with an electron capture detector of ⁶³Ni-type.

Acid dissociation constants of nitrazepam are determined and the partition properties studied with benzene, methylene chloride and diethyl ether as organic phases.

The selectivity of the method with respect to the metabolites has been thoroughly studied.     

Esterification at Room Temperature:A Mixing Affair Only

Carboxylic acids in absolute alcohols, on treatment with thionyl chloride at room temperature give good yields of corresponding esters.

Photochemistry¹ of maleianilic acid and its derivatives has been of interest to us. It was thought that the yield of the photocyclised product is less because of probable decarboxylation which may be resulting during photolysis, and hence the need for esterification. Numerous new methods of esterification have been developed and reviewed by Haslam², but we like to claim our method as the simplest and the easiest method to date. Another report by Huber and Brenner^4,5 has used absolute methanol, thionyl chloride and HCl for preparing methyl esters of two amino acids (Methionine and Leucine) using a methodology which includes an unnecessary use of HCl.     

New procedure of silica gel surface modification preparation of gaseous standard mixtures for calibration purposes

The new type of silica gel surface modification with using the trimethylamine as a reagent is described. The samples of chemically modified silica gel have been used for generation of gaseous standard mixtures (methyl chloride as a measurand) using the technique of thermal decomposition of the surface compound. The main aim of the research was to check the suitability of the new type of silica gel surface modification for obtaining methyl chloride as a measurand of gaseous standard mixture. The gaseous standard mixture obtained with using this technique was used for calibration of a thermal desorber-gas chromatography-flame ionization detector (TD-GC-FID) system. The homogeneity of coverage of silica gel surface with the immobilized compound has been evaluated. The full uncertainty budget of determination of liberated amount of methyl chloride has been calculated. The average amount of methyl chloride liberated from the unit sample of chemically modified silica gel is 3.59 +/- 0.13 mg g(-1). The influence of the modification way on the amount of liberated analyte has also been determined.     

Vertical Distributions of Nonmethane Hydrocarbons Over Western Europe: Seasonal Cycles of Mixing Ratios and Source Strengths

Abstract

Airborne measurements of the vertical and horizontal distributions of nonmethane hydrocarbons and methyl chloride over western Europe are reported. Annual emission cycles have been calculated from the seasonal variations of mixing ratios using a simple one-dimensional two-box model. They indicate natural sources of ethene, propene, i-butane, i-pentane, and methyl chloride. Grab samples were analysed by subambient temperature programmed gas chromatography.     

Analysis of Morpholinium Ionic Liquid Cations by Hydrophilic Interaction Columns Coupled with Indirect UV Detection

A method was developed for the separation and detection of morpholinium ionic liquid cations by hydrophilic interaction column combined with indirect ultraviolet detection using imidazolium ionic liquids as ultraviolet absorbents in high‐performance liquid chromatography. The effects of the ultraviolet absorbents, organic solvents, and the pH value of the aqueous solution in the mobile phase for the determination of morpholinium cations were investigated by using a hydrophilic column with carbamoyl group as the analytical column. The retention and detection behavior of morpholinium cations was discussed. The suitable chromatographic conditions were 0.8 mmol/L 1‐ethyl‐3‐methyl‐imidazolium tetrafluoroborate aqueous solution (pH 3.5 adjusted with acetic acid)/acetonitrile (45/55, v/v) as the mobile phase and a detection wavelength of 210 nm. Under these conditions, the baseline separation of N‐methyl‐N‐ethyl‐morpholinium cation ([MEMo]⁺) and N‐methyl‐N‐propyl‐morpholinium cation ([MPMo]⁺) was successfully achieved in 15 min. The detection limits of [MEMo]⁺ and [MPMo]⁺ were 0.595 and 0.531 mg/L, respectively. Relative standard deviations were less than 0.2%. This method has been successfully applied to the analysis of morpholinium ionic liquid samples synthesized in chemical laboratories, which is simple, reliable, and practical.     

Addition of chlorine,bromine and bromine chloride to some α,β-unsaturated methyl esters

The additions of chlorine, bromine and bromine chloride to trans methyl 2-butenoate 1, trans methyl 2-methyl-2-butenoate 2 and methyl 3-methyl-2-butenoate 3 under ionic conditions were studied. Bromine chloride addition always gave as a major regioisomer the 2-bromo-3--chloro compound,almost quantitatively in the case of 3. The mechanism of bromonium ion ring-opening (S_N1 or S_N2) is discussed with respect to the double bond substitution and regioisomer proportions. The dihalo products were identified by MS, ¹H and ¹³C NMR.     

Iron powder and tin/tin chloride as new reducing agents of Meerwein arylation reaction with unexpected recycling to anilines

Abstract

Simple and rapid route for Meerwein arylation reaction using iron powder or a mixture of tin/tin chloride has been developed. In the presence of iron powder, different aryl diazonium salts reacted with methyl vinyl ketone, acrylates, and isopropenyl acetate. Production of oximes was detected as the main product with acrylates or in a mixture with β-aryl methyl ketones in the case of methyl vinyl ketone. The in situ produced HNO₂ from an excess of NaNO₂/HCl was trapped by alkyl aryl radical to form oximes in the E configuration form. The presence of tin/tin chloride mixture in the reaction of the aryl diazonium salts with methyl vinyl ketone produced Michael products along with β-aryl methyl ketones. The predicted α-aryl methyl ketones from the reaction of isopropenyl acetate with the diazotized anilines were obtained using iron or tin/tin chloride mixture.     

Characterization of the short-chain branches in poly(vinyl chloride)s by γ irradiation of the reduced polymers

The volatile products from the γ irradiation of samples of poly(vinyl chloride) prepared under different conditions and reduced to the corresponding polyethylenes have been measured quantitatively and compared with those for low- and high-density polyethylenes and copolymers of ethylene with small amounts of α-olefins. The presence of methyl branches is clearly demonstrated and there is also evidence for ethyl and butyl branches, although these had not been considered significant in previous [¹³C] NMR studies. The method is shown to be extremely sensitive to small quantities of residual trialkyl tin hydride reductant occluded in, and possibly also reacted with, the polymer, and to residual chlorine (<0.5%). The yields of alkanes are higher than expected from the branch frequencies determined by i.r. and [¹³C] NMR and results for ethylene-α-olefin copolymers. This difference is apparently due to sensitisation of the radiation degradation by residual chlorine and reductant. Quantitative determinations of branch frequencies by the radiolytic method are unlikely to be obtained until these problems are overcome.     

Room temperature rate constants for the reaction of OH with selected chlorinated and oxygenated hydrocarbons

A study was conducted to measure the hydroxyl radical rate constants using a relative rate procedure in which the photolysis of methyl nitrite was the source of OH. During the course of this study, the OH rate constant was measured for a number of chlorinated solvents for which measurements have not previously been reported or for which there are few reliable measurements. Room temperature OH rate constants are presented for six chlorinated hydrocarbons (allyl chloride, benzyl chloride, chlorobenzene, epichlorohydrin, trichloroethylene, and vinylidene chloride) and four oxygenated hydrocarbons (acrolein, methacrolein, methyl ethyl ketone, and propylene oxide). Also included are OH rate constants for alkanes (ethane, propane, isobutane, and cyclohexane), alkenes (trans?2-butene and isoprene), and aromatic hydrocarbons (benzene, toluene, o^?, m^?, and p-xylene). Rate constants for compounds not previously reported include vinylidene chloride (1.49 ± 0.21 × 10^?11 cm³ molecule^?1 s^?1) and benzyl chloride (2.96 ± 0.15 × 10^?12 cm³ molecule^?1 s^?1). The analysis for chlorinated hydrocarbons included a correction for possible chlorine atom reactions.     

Sensitive detection of dopamine using micelle-enhanced and terbium-sensitized fluorescence

A new terbium sensitized spectrofluorimetric method was developed for the determination of trace amounts of dopamine (DA) using ethylenediaminetetraacetic acid as co-ligand and cetyltrimethylammonium chloride as sensitizer. UV absorption and fluorescent spectra were used to investigate the photophysical properties of the ternary complex. Under the optimum conditions, the enhanced fluorescence intensities of the Tb(III) complexes increased linearly with the concentration of DA over the ranges 8 × 10^–8–5 × 10^–5 M and the limit of detection for DA was found to be 2.4 × 10^–8 M. The proposed method has been applied for the quantitative determination of DA in a pharmaceutical preparation and urine samples. The possible energy transfer mechanisms in the lanthanide complexes were discussed.     

Dehydration of 3- and 4-aryl- substituted 3-hydroxy acids in acetic anhydride in presence of zinc chloride

The reaction of several di- and triaryl-substituted 3-aryl-3-hydroxy acids and a 4-aryl-3-hydroxy acid in acetic anhydride in the presence of anhydrous zinc chloride has been investigated. It has been shown that the reaction discovered with 3-(2′-thienyl)-substituted 3-hydroxy acids, namely, their conversion under the above stated conditions into α, β-unsaturated methyl ketones,^1,2 occurs also with 3-aryl 3-hydroxy acids but to a smaller degree due to the concurrent cyclization reaction which leads to indene-1-ones. It has been established that the unsaturated methyl-ketones obtained, containing three aromatic substituents at the CC bond, exist in s-cis-(CC, CO)-conformation. It has been found that with the 4-aryl-substituted 3-hydroxy acid almost no unsaturated ketone is obtained, whereas instead the main product is a 2,3-disubstituted 1-naphthol which is acetylated under the conditions of the reaction. Its structure has been proved by its UV, IR and NMR spectra and confirmed by the mass spectrum of the compound.     

Determination of Trace Methyl Tert‐Butyl Ether in Water Samples Using Dispersive Liquid‐Liquid Microextraction Coupled with GC‐FID

A rapid and sensitive analytical method has been developed for trace analysis of methyl tert‐butyl ether (MTBE) in water samples using dispersive liquid‐liquid microextraction and gas chromatography with flame ionization detection. Factors relevant to the microextraction efficiency, such as the kind of extraction solvent, the disperser solvent and their volumes, the effect of salt, sample solution temperature and the extraction time were investigated and optimized. Under the optimal conditions the linear dynamic range of MTBE was from 0.2 to 25.0 μg L^?1 with a correlation coefficient of 0.9981 and a detection limit of 0.1 μg L^?1. The relative standard deviation (RSD%) was less than 5.1% (n = 3) and the recovery values were in the range of 97.8 ± 0.9%. Finally, the proposed method was successfully applied for the analysis of MTBE in aqueous samples.     

Determination of cadmium using radiochemical neutron activation analysis

A method has been developed for the determination of cadmium in samples of food and biological materials using neutron activation analysis with radiochemical separation. The irradiated sample is digested in presence of cadmium carrier, with a nitric-perchloric mixture, evaporated to dryness, dissolved in 6M HCl and placed onto an ion exchange column loaded with Dowex 1-X8 resin in chloride form and conditioned with HCl 6M. The cadmium is retained in the resin. After a washing procedure with several portions of HCl of decreasing concentration, the cadmium is eluted with an ammonia-ammonium chloride buffer. The activity of ^115mIn which is in equilibrium with ¹¹⁵Cd, is measured using a NaI(Tl) well type detector. The method has been evaluated by analyzing certified reference materials with cadmium concentrations covering a range of 0.020 to 200 mg^.kg^-1. The agreement of the results with the certified values is within 95%, which gives an indication of the sensitivity and accuracy of the proposed method.     

Arsenic determination by ICP-QMS with octopole collision/reaction cell. Overcome of matrix effects under vented and pressurized cell conditions

The determination of arsenic by inductively coupled plasma mass spectrometry (ICP-MS) in natural waters with high sodium and chloride content has been investigated. The instrument used is equipped with an octopole collision/reaction cell to overcome spectroscopic interferences. Thus, the optimization of collision/reaction gas flow rates is required when using a pressurized cell. A mixture of 2.9 mL min⁻¹ of H₂ and 0.5 mL min⁻¹ of He has been found to be suitable for the removal of ⁴⁰Ar³⁵Cl⁺ interference.The effect of the introduction of small amounts of alcohol has also been studied in this work under both vented and pressurized cell conditions. It has been observed that the presence of 4% (v/v) of ethanol or methanol results in an increase in arsenic sensitivity. Moreover, under vented cell conditions the addition of alcohol also decreases the formation of polyatomic interference. However, this decrease is not observed under pressurized cell conditions.Different elements have been studied as possible internal standards for arsenic determination in presence of high amounts of sodium. Good results have been obtained for rhodium and yttrium under both vented and pressurized cell conditions. Although the presence of alcohol in the sample matrix also affects their behaviour, rhodium and yttrium are still the most suitable elements to correct for these matrix effects.Different experimental conditions have been compared for arsenic determination in spiked, certified and natural waters with high sodium and chloride content. The best results have been obtained under pressurized cell conditions, in the presence of ethanol and using rhodium as internal standard.     

Simple method of determination of copper,mercury and lead in potable water with preliminary pre-concentration by total reflection X-ray fluorescence spectrometry

Total reflection X-ray fluorescence spectrometry and chemical pre-concentration procedures have been applied for the analysis of trace concentrations of copper, mercury, and lead in drinking water samples. A simple total reflection module has been used in X-ray measurements. The elements under investigation were pre-concentrated by complexation using a mixture of carbamates followed by solvent extraction with methyl isobutyl ketone. The preconcentration procedure was tested with the use of twice-distilled water samples and samples of mineral and tap water spiked with known additions of copper, mercury, and lead. The obtained recovery and precision values are presented. The minimum detection limits for the determination of these elements in mineral and tap water samples were found to be 40 ng l⁻¹, 60 ng l⁻¹, and 60 ng l⁻¹, respectively.