Optimization of a Sample Preparation Procedure for the Speciation of Organotin Compounds in Sediment Samples Using GC-AED

Abstract

Results of a comprehensive study of all analytical steps involved in the sample preparation procedure for the speciation of butyl- and phenyltin compounds in sediments are presented. The proposed method is based on acid leaching (using aqueous acetic acid) and simultaneous extraction of the ionic species into an organic solvent (n-hexane/ethyl acetate) with the addition of a complexing agent (diethyl dithiocarbamic acid). After evaporation to dryness, the residue is derivatized with sodium tetraethylborate in an aqueous buffer solution (acetate buffer, 0.1 M, pH 5) and extracted into n-hexane. Cleanup is performed over basic alumina and the ethylated organotin species are analyzed with a gas chromatograph coupled to a microwave-induced helium plasma atomic emission detector (GC-AED). The optimized method was validated within an interlaboratory study for the certification of tributyltin, triphenyltin and their degradation products in a freshwater sediment, the BCR candidate reference material 646.     

Determination of methyl-and ethylmercury compounds using gas chromatography atomic fluorescence spectrometry following aqueous derivatization with sodium tetraphenylborate

Summary An analytical procedure is described for the determination of methylmercury and ethylmercury compounds in fish and sediment samples, using gas chromatography atomic fluorescence spectrometry following aqueous phenylation with sodium tetraphenylborate. The derivatization products were identified by gas chromatography mass spectrometry. The advantages of using phenylation with sodium tetraphenylborate over ethylation with sodium tetraethylborate are discussed. The validation of the analytical procedure was performed by analyzing standard reference material (DORM-2). Applications for the analysis of fish and sediment samples were carried out and compared to other techniques.     

Speciation for analysis of organotin compounds by GC AA and GC MS after ethylation by sodium tetraethylborate

A range of organotin compounds has been ethylated using the reagent sodium tetraethylborate in a simple one-step procedure. Analysis of the volatile, fully alkylated derivatives has been achieved by GC AA with confirmation of the identity of the resulting ethylated derivatives by GC MS. Conditions for the GC AA and GC MS analysis of the organometallic ethyl derivatives are given.     

Comparison of Derivatization Methods for the Determination of Butyl- and Phenyl-tin Compounds in Mussels by Gas Chromatography

Two different derivatization methods, alkylation with Grignard reagents, and ethylation with sodium tetraethylborate, were compared for the determination of organotin compounds, viz. tributyltin, dibutyltin, monobutyltin, triphenyltin, diphenyltin and monophenyltin, in mussel samples. Temperature, reaction time and concentration of Grignard reagents were optimized in the former method; in the latter the effect of pH, concentration of sodium tetraethylborate and reaction time were studied. In the derivatization with Grignard reagents hexyl, pentyl, propyl, ethyl and methyl were used as alkyl Grignard groups. A critical evaluation of the different derivatization methods is presented. © 1997 John Wiley & Sons, Ltd.     

Determination of butyltin stabilizers in PVC using Liquid-Phase microextraction with electrothermal atomic absorption spectrometry

A rapid and highly sensitive method is described for the extraction and determination of di- and tributyltin in PVC samples using headspace liquid phase microextraction followed by an analysis with graphite furnace atomic absorption spectrometry (HSLPME/ GFAAS). The analytes were derivatized in situ with sodium tetraethylborate and concentrated in a 2 ??l microdrop of benzyl alcohol suspended from the tip of a conventional GC microsyringe. The ethylated species then were directly transferred into a graphite furnace and quantified. The extractions were carried out for 5 ml sample solution (8 ml vial) adjusted at pH 5, with derivatization at 22 °C for 15 min in a 2% sodium tetraethylborate. The experimental parameters impacting the performance of HS-LPME were also investigated. According to the analysis, the linearity range was from 5.0 to 250.0 ng l^-1 with a detection limit of 0.5 ng l^-1 for dibutyltin and from 1.7 to 170.0 ng l^-1 with a detection limit of 0.17 ng l^-1 for tributyltin. Method RSD values were below 1.5%. Finally, the analysis of spiked PVC and water samples revealed that matrix had little effect upon extraction.     

Vibrational spectra and molecular conformations of unbranched dialkyl selenides

The IR and Raman spectra of six unbranched dialkyl selenides, namely ethylmethyl selenide, methylpropyl selenide, butylmethyl selenide, diethyl selenide, ethylpropyl selenide and dipropyl selenide, have been systematically investigated. The spectra are analysed on the basis of the spectral examination and the normal coordinate treatment. The CH₂-Se stretching wavenumbers of the dialkyl selenides correlate well with the conformation about the CSe-C-C bond axes. The molecular conformation in the solid and liquid states is studied by utilizing this correlation in conjunction with the wave-numbers of the CH₂ rocking and skeletal deformation vibrations. The conformational stability in the liquid state is also examined and the enthalpy difference between the trans and gauche forms of ethylmethyl selenide is obtained as 0.22 ± 0.05 kcal mol^?1, the gauche form being more stable. The conformational stability of dialkyl ethers, sulphides and selenides are comparatively discussed.     

Competitive reactivity of vinylchalcogenyl radicals in their reactions with acetylene

The reactivities of vinythinyl and vinulselenyl radicals generated high temperature gasphase reactions of acetylene with diethyl disulfide and diethyl selenide, respectively, were compared. The co-pyrolysis of u mixture of these reagents at 410–510 °C results in a mixture of thionphene and selenophene. The vinylselenyl radical is more reactive; in addition, it appears to stabilize vinylthiyl radicals. Owing to this, co-thermolysis of diethyl disulfide, diethylselenide, and acetylene at 510 °C allows one to obtain simultaneously thiophene and selenophene in 91.0 and 92.5 % yields, respectively.     

IMPROVED SYNTHESIS OF CYANOHYDRIN PHOSPHATES AND ITS REACTION MECHANISM

Cyanohydrin phosphates 2a–2c were prepared in high yield from ketones (or aldehyde), diethyl phosphorochloridate, and sodium cyanide by using acetonitrile as solvent. GC analysis proved that the two reactions of cyanohydrin sodium with diethyl phosphorochloridate and with diethyl phosphorocyanidate resulted in the formation of cyanohydrin phosphates.     

Oxidation and halogenation of divinyl selenide. first synthesis of divinyl selenoxide

Efficient procedure was developed for the preparation of divinyl selenoxide in 92% yield by oxidation of divinyl selenide with sodium periodate. At the action of S-nucleophiles on the divinyl selenoxide it is reduced to divinyl selenide. The reaction of divinyl selenide with an equimolar amount of sulfuryl chloride or bromine led to halogenation products at the selenium atom: divinylselenium dichloride and divinylselenium dibromide. A rearrangement was discovered of divinylselenium dibromide into vinyl(1,2-dibromoethyl)-selenide. The hydrolysis of divinylselenium dichloride results in divinyl selenide.     

Reactions of sodium selenide with ethynyl and bromoethynyl ketones: Stereo- and regioselective synthesis of functionalized divinyl selenides and 1,3-diselenetanes

A method for the preparation of 2,4-dimethylene-1,3-diselenetanes based on the novel reaction of sodium selenide with bromoethynyl ketones has been developed. New functionalized divinyl selenides have been obtained by regio- and stereoselective addition of sodium selenide to ethynyl ketones.     

Determination of butyl- and phenyltin compounds in biological material by gas chromatography-flame photometric detection after ethylation with sodium tetraethylborate

A reliable and rapid speciation method for the simultaneous determination of butyl- and phenyltin species in biological samples has been developed. Three extraction procedures are compared: enzymatic hydrolysis and solubilization by ethanoic and hydrochloric acids. Derivatization is performed by the one-step ethylation/extraction procedure using the sodium tetraethylborate reagent directly in the aqueous phase in the presence of an isooctane layer. Analysis is performed using capillary gas chromatography coupled to flame photometric detection. The detection limits are in the range of a few ng(Sn)/g. Analysis of the environmental samples and the certified reference material demonstrates the accuracy of the analytical method.     

Bis(N,N‐diethyl‐1,1‐di­seleno­carbam­ato‐Se)­selenium, [(Se2CNEt2)2Se]

The poly­seleno title compound, bis(N,N‐diethyl­seleno­carbamoyl) tri­selenide, [(Se₂CNEt₂)₂Se] or C₁₀H₂₀N₂Se₅, is obtained from the disproportion of sodium N,N‐diethyl‐1,1‐di­seleno­carbamate. An Se atom connects two N,N‐diethyl‐1,1‐di­seleno­carbamate groups with Se—Se distances in the range 2.4500 (11)–2.8601 (12) Å     

硒氢化钠亲核加成高收率合成对称硒醚

报道了一种制备对称有机硒醚的新方法:在氮气保护下,以水做溶剂,室温下利用硼氢化钠还原硒粉得到硒氢化钠,与水溶的丙烯酸乙酯发生亲核加成反应,对于水不溶的苯乙炔或其他α,β-不饱和化合物需另加入DMF作溶剂进行反应,共合成了7个对称硒醚产物,其中6个化合物尚未见文献报道,位阻较大的甲基丙烯酸甲酯,可以得到52％的分离收率,其他产物分离收率高达82～94％.     

Simplified sample preparation for GC speciation analysis of organotin in marine biomaterials

Two simple sample preparation methods for the speciation analysis of triphenyltin and butyltin compounds in marine biotissues, using tetramethylammonium hydroxide (TMAH) solubilization and enzymic hydrolysis, have been developed and compared with conventional acid digestion. Derivatization was carried out in situ using sodium tetraethylborate (NaBEt₄) without prior separation of the analytes from the tissue matrix. Separation and detection was performed using capillary gas chromatography (GC) coupled to microwave-induced plasma atomic emission spectrometry (MIP AE) allowing detection limits of 2 ng g^?1 (as tin) to be reached. The accuracy of the presented methods was demonstrated by the analysis of a fish reference material (NIES No. 11). the necessity for sample clean-up is discussed and examples of the analysis of mussel tissue are shown.     

Studies on the disproportionation of trichloromethyltin

The rate of disproportionation of trichloromethyltin in various solvents was studied by two methods, derivatization with sodium tetraethylborate and ¹³C NMR measurements, which gave similar results. The reaction followed second‐order kinetics and was more rapid in coordinating solvents than in uncoordinating ones. Moreover, it was catalyzed by nucleophiles, such as amines or alcohols, which is in favor of a nucleophile‐assisted electrophilic reaction. Copyright © 2003 John Wiley & Sons, Ltd.     

Comparison of tetraethylborate and tetraphenylborate for selenite determination in human urine by gas chromatography mass spectrometry, after headspace solid phase microextraction

Two different derivatizing reagents were tested for the development of a fast and sensitive method for the determination of selenites (Se^IV) in human urine. The reagents were sodium tetraethylborate (NaBEt₄) and tetraphenylborate (NaBPh₄), respectively, and the procedure is based on in situ derivatization of selenites in aqueous medium. Selenite ions are converted to diethylselenide (DESe) or diphenylselenide (DPhSe) and subsequently collected from the headspace by solid phase microextraction using a silica fiber coated with polydimethylsiloxane (HS-SPME). Finally, they are quantitated by GC/MS in SIM mode. Ethylation over phenylation was proved preferable for the headspace extraction because of the higher volatility of the diethyl-derivative of selenites. The optimization of the HS-SPME conditions was performed both in aqueous and urinary solutions. Under the optimum conditions for HS-SPME, the gas chromatographic conditions were also optimized. Between the two alkylation reagents tetraethylborate was proved more efficient and the quantitation was satisfactory. Aqueous certified reference materials were analyzed to evaluate the accuracy of the method. The precision of the method was 4.2% and the calculated detection limit was 0.05 μg L⁻¹ for human urine.     

Stereospecific synthesis of divinyl diselenides from vinyl acetyl selenides

Vinyl halides react with MeSeLi in DMF to afford vinyl methyl selenides which are demethylated by the excess of the MeSeLi; the vinyl selenide anions thus obtained react with acetyl chloride to give vinyl acetyl selenides. This three steps one pot synthesis occurs with complete retention of configuration. The vinyl acetyl selenides are cleanly fragmented by electron transfer to the vinyl selenide anions; addition of iodine to the resulting solutions produced the divinyl diselenides with retention of configuration. The transformation of vinyl acetyl selenides into divinyl diselenides can also be induced by catalytic amounts of a solution of sodium in HMPA or of sodium methanethiolate.     

硒化银纳米枝晶的合成与表征(英)

Silver selenide nanodendrites were synthesized by the reaction of AgNO₃ and sodium selenosulfate in the presence of cetyltrimethyl ammonium bromide (CTAB). The as-synthesized sivler selenide samples were characterized by XRD, TEM and SAED. The results showed that Ag₂Se nanodendrites were of single crystalline with diameters ranging from 60～150 nm.     

Synthesis of [3-(trimethylsilyl)prop-2-yn-1-yl] selenides

Efficient and selective methods have been developed for the synthesis of previously unknown organyl [3-(trimethylsilyl)prop-2-yn-1-yl] selenides, organyl prop-2-yn-1-yl selenides, and bis[3-(trimethylsilyl) prop-2-yn-1-yl] selenide by reactions of 3-bromo-1-(trimethylsilyl)prop-1-yne with the corresponding organylselenolates and sodium selenide generated from diorganyl diselenides or elemental selenium by the action of sodium tetrahydridoborate.     

Substoichiometric determination of trace impurities in zinc selenide

Determination of trace impurities in zinc selenide was carried out by substoichiometric neutron activation analysis. Trace impurities were separated from matrix elements by suitable procedures and determined by substoichiometric methods, i.e., Au was extracted with rhodamine-B, Ag and Cu with dithizone, Cr with sodium diethyldithiocarbamate, Co with 1-nitroso-2-naphthol, and Sb with cupferron. Two sorts of zinc selenide single crystals were supplied for analysis and the following values were obtained as impurity concentration; Au 0.36, 0.076 ppb, Ag 42, 32 ppb, Cr. 1.8, 0.63 ppm, Co 0.16, 0.0079 ppm, Sb 8.5, 5.9 ppb and Cu 1.4, 0.44 ppm. The behavior of copper by heat-treatment of zinc selenide was also studied by means of substoichiometric isotope dilution analysis.