Atomic-absorption spectrophotometric determination of volatile organolead compounds in the atmosphere

Summary The determination of the total concentration of tetraalkyllead compounds in the air is based on the cryogenic condensation in a cooled trap at –130° C, thermal desorption at 60° C into impingers containing nitric acid and hydrogen peroxide and a determination with graphite furnace atomic-absorption. The method is highly specific and suffers no interferences from lead in the particulate phase. The detection limit is 42 ng Pb/m³ for air samples of ca. 3601.This work was carried out within the framework of the National Research and Development Program on Environment of the Interministrial Commission for Science Policy, Belgium.     

Iodimetric determination of 2-mercaptopyrimidines

A new method for the determination of 2-mercaptopyrimidines, using their reaction with iodine in neutral and alkaline medium, is presented. The determinability range in the volumetric titration, in phosphate buffer with starch as an indicator, was found to be equal to 40-1000 mumol for 2-mercaptopyrimidine (I) and 100-2000 mumol for 2-mercapto-4-methylpyrimidine (II), and 200-2000 mumol for 4,6-dimethyl-2-mercaptopyrimidine (III). In the volumetric titration in alkaline medium, with the potentiometric end-point detection, the determinability range is 50-250 mumol for 2-mercapto-4-methylpyrimidine (II), 50-500 mumol for 4,6-dimethyl-2-mercaptopyrimidine (III), 20-250 mumol for 4,5-diamino-2,6-dimercaptopyrimidine (IV), and 20-1000 mumol for 2-thioorotic acid (V). In the coulometric titration, using the biamperometric end-point detection, 0.1-4.0 mumol of 2-mercaptopyrimidine (I) and 0.1-5.0 mumol of 2-thioorotic acid (V) were successfully determined.     

Gas chromatographic determination of organolead compounds with an alternating current plasma detector

The performance of the gas chromatography/alternating current plasma detector as a selective detector for organolead compounds is investigated. The helium make-up flow rate and the spatial position from which the lead emission is viewed, have an effect on the detector response. The detection limit for tetrabutyl lead was established as 130 pg/s and the lead selectivity ratio was found to exceed 13,800. Some applications of organolead determination in complex matrices were also studied in order to demonstrate the selectivity and sensitivity of the alternating current plasma detector.     

Mass spectrometry studies of organolead compounds

The mass spectra of alkyl‐, aryl‐ and chlorinated ‐alkyl, aryl organolead compounds were investigated. Positive and negative ion mass spectra of these compounds were recorded using conventional electron impact conditions. In common with the analogous tetraalkyltin and tetraalkylgermanium compounds, tetrabutyllead produced no negative ion spectra under these conditions. The spectra were also examined by tandem mass spectrometry in order to establish reaction mechanisms for these compounds. Fragmentation patterns of seven organolead compounds, based on precursor–product ion relationships, are proposed. Copyright © 2001 John Wiley & Sons, Ltd.     

IR spectra of organolead acetylenic compounds

Russian Chemical Bulletin -     

High-resolution 207Pb NMR of solid organolead compounds

The combined techniques of high-power decoupling, cross-polarisation and magic-angle rotation have been applied to lead-207 NMR of solid organolead compounds for the first time. Tetra-p-tolyl lead is suitable for spectrometer tuning and matching purposes since a spectrum can be obtained with 5 to 10 transients. Tetraphenyllead was also studied under the same conditions. Solution-to-solid shifts in the resonances for these compounds are modest in magnitude (ca. 40 ppm). Hexa-p-tolyldilead gives a spectrum with a crystallographic splitting of 29 ppm and exhibits a pronounced shielding anisotropy.     

Some spectroscopic properties of cyclic organolead compounds I

The nuclear magnetic resonance and infrared properties of two new cyclic organolead compounds are discussed.     

Ultrasound-assisted emulsification microextraction of organolead and organomanganese compounds from seawater, and their determination by GC-MS

We describe a simple method for the simultaneous determination of organolead and organomanganese compounds in seawater samples. It is based on ultrasound-assisted emulsification microextraction. Trimethyllead, triethyllead, tetraethyllead, cyclopentadienylmanganese tricarbonyl and its methyl derivative were separated and determined using gas chromatography and mass spectrometry. Trimethyllead and triethyllead were derivatized with sodium tetraphenylborate before being submitted to the preconcentration step. Detection limits ranged from 7.0 to 41 ng L^?1 depending on the compound. Recoveries ranged from 84 to 118 %, depending on the compound and the sample analyzed. Seawater samples were collected at different sites of the Cartagena Bay and none of the target analytes were found at levels above the corresponding detection limits.

Toxicity and model membrane modifying properties of organolead compounds

The influence of trialkylleads on haemolysis of red blood cells (RBCs), growth of Spirodela oligorrhiza and stability of planar lipid membranes (PLMs) at different pH of solution has been studied. The results obtained show that the efficiency of trialkylleads (methyl‐, ethyl‐, propyl‐ and butyl‐lead chlorides) in modifying the physiological and mechanical properties of the objects studied depended both on pH of solution and hydrophobicity of the compounds. Namely, it was found that this efficiency increased with pH of solution. The most significant increase was observed in PLM experiments. Also, the hydrophobicity of trialkylleads influenced the properties mentioned. The more hydrophobic a compound the greater was its haemolytic toxicity. The same applies to the physiological toxicity ­of the compounds, whose measure was 50% inhibition of plant growth. Generally, the sequence of modifying possibilities of the compounds studied at any pH of the solution was the following:

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Iodimetric determination of carbon disulphide study of the effect of pH

The effects of pH and time on the error (due to decomposition of xanthate) involved in the iodimetric determination of carbon disulphide have been studied. A pH range of 5.4 to 5.8 (acetatebuffered) is recommended, Carbon disulphide varying in amount from 0.0060 to 0.3240 g can be determined with an error of ± 1.0%.     

Iodimetric determination of hydrazine and hydroquinone with thallium(III) solutions

SeIenium(IV) at trace levels can be determined in hydrochloric and perchloric acid solutions by alternating current and differential pulse polarography. The use of a hanging mercury drop electrode with accumulation of elemental selenium followed by cathodic stripping gives detection limits in the range 0.1–1 p.p.b. With a dropping mercury electrode the detection limit is 8 p.p.b. The possible interferences of Te(IV), Ge(IV), Cu(II), Cd(II) and Pb(II) are discussed. The serious interference of lead(II) can be prevented by addition of EDTA.     

Simultaneous microdetermination of carbon,hydrogen and lead in organolead compounds

The straight emtpy-tube method of Korshun and Klimova has been successfully extended to the simultaneous microdetermination of carbon, hydrogen and lead in organolead compounds. In all cases, the lead content was calculated from the weight of the plumbous oxide residue left behind in the fused-silica capsule used to hold the sample. Sulphur could also be determined in the same analysis. Satisfactory results were obtained for all compounds with a standard deviation not exceeding 0.1%.     

Electrochemical behaviour of organolead compounds: Part I. Triphenyl-lead acetate

The electrochemical behaviour of triphenyl-lead acetate in 50% (v/v) ethanol has been investigated using various electrochemical techniques including polarography, cyclic voltammetry and controlled potential coulometry. It has been found to give three/four polarographic waves. The first normal wave involves an one-electron irreversible reduction of triphenyl-lead ions giving triphenyl-lead free radicals which are strongly adsorbed at the DME giving rise to an adsorption prewave. The triphenyl-lead free radicals produced in the normal reduction step immediately react with mercury of the DME producing phenylmercury radicals and metallic lead. Wave II has been ascribed to the simultaneous reduction of triphenyl-lead free radicals and phenylmercury free radicals. The metallic lead produced in these processes undergoes oxidation at the electrode and “distorts” the “normal” adsorption prewave of step I. A mechanism of reduction is proposed and polarographic methods have been developed for determining triphenyl-lead compounds at ordinary level and down to submicromolar level.     

The effects of organolead compounds on a freshwater and a marine alga

There are conflicting reports concerning the toxicity of tetraalkyllead (TAL) compounds to algae. A number of groups have found the TAL's to be comparable in toxicity with the trialkyllead compounds (R₃Pb⁺), whereas in a recent report it is suggested that the TAL's themselves are completely non-toxic and any apparent toxicity is due to R₃Pb⁺ breakdown products. With the object of identifying the toxic agent, the effect of Et₄Pb (TEL) on two algal species was re-examined. Analyses were carried out during the course of the incubations to establish the nature and concentrations of organoleads present in both media and algae, and hence evaluate their relative contributions to total toxicity. Algae were also cultured in the presence of Me₄Pb (TML), Me₃PbCl, Et₃PbCl, Bu₃PbCl and Et₂PbCl₂ to assess relationships between alkyl chain length and degree of substitution around the lead on algal activity. Additions of selenide and sulphide were made to the Et₃Pb⁺ and Et₂Pb²⁺ systems to see if these environmentally abundant species reduced or enhanced organolead toxicity. Problems were encountered in the analysis of the heterogeneous TEL containing media. Regardless of the analytical problems, the results confirm the previous findings that TAL's are non-toxic to algae and it is the R₃Pb⁺ breakdown products which are responsible for the apparent toxicity of the TAL's. The trialkylleads were the most toxic of the several alkyllead species studied, and within the trialkyl series toxicity increased with alkyl chain length. Neither selenide or sulphide had any significant ameliorative effect on alkyllead toxicity. It was found that the ionic organoleads were complexed on the TAL's and this complexing led to a number of unexpected results.     

Determination of organolead compounds and of chromate beside Cr(III)

A procedure for the preconcentration and determination of ionic alkyllead compounds in surface waters and human urine and tetraalkyllead compounds in ambient air is described.Concentration ranges are given and difficulties arising in the validation of TriML and DiML in some matrices are discussed.A chromium(VI) speciation procedure consisting of a selective biosampling step by using human erythrocytes and two subsequent determination methods (GFAAS and reverse-FIA) is introduced.     

Simultaneous determination of organotin,organolead, and organomercury compounds in environmental samples using capillary gas chromatography with atomic emission detection

As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organolead, and organomercury compounds in environmental samples was investigated. Pentylmagnesium bromide was used to pentylate ionic organotin, organolead, and organomercury compounds; the pentyl derivatives were then separated by GC and determined by AED. Several important GC-AED parameters, including the type of injector inlet, carrier gas flow rate, and helium make-up gas flow rate, were optimized for the simultaneous determination of these organometallic compounds. Their minimum detectable concentrations were approximately 1.0 to 2.5 ng/mL using a 0.5-μL on-column injection. The calibration curves exhibited good linearity between 2.5 and 2500 ng/mL for organotin and organolead compounds, and between 2.5 and 10000 ng/mL for organomercury compounds.