Speciation of organotin compounds in waters and marine sediments using purge-and-trap capillary gas chromatography with atomic emission detection

A procedure for the simultaneous determination of six organotin compounds, including methyl-, butyl- and phenyltins, in waters and marine sediments is developed. The analytes were leached from the solid samples into an acetic acid:methanol mixture by using an ultrasonic probe. The organotins were derivatized with sodium tetraethylborate (NaBEt₄) in the aqueous phase, stripped by a flow of helium, pre-concentrated in a trap and thermally desorbed. This was followed by capillary gas chromatography with microwave-induced plasma atomic emission spectrometry as the detection system (GC-AED). Each chromatographic run took 22 min, including the purge time. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients for linear calibration were at least 0.9991. Detection limits ranged from 11 to 50 ng Sn l⁻¹ for tributyltin and tetramethyltin, respectively. The seawater samples analyzed contained variable concentrations of mono-, di- and tributyl- and monophenyltin, ranging from 0.05 to 0.48 μg Sn l⁻¹, depending on the compound. Some of the sediments analyzed contained concentrations of dibutyl- and tributyltin of between 6.0 and 13.0 ng Sn g⁻¹. Analysis of the certified reference material PACS-2, as well as of spiked water and sediment samples showed the accuracy of the method. The proposed method is selective and reproducible, and is considered suitable for monitoring organotin compounds in water and sediment samples.     

Speciation of arsenic using capillary gas chromatography with atomic emission detection

A gas chromatography method with atomic emission detection (GC-AED) for the determination of dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and inorganic arsenic was optimized. The analytes were derivatized in the sample solutions with methyl thioglycolate (TGM) and the products were extracted into cyclohexane before an aliquot of this organic phase was directly injected into the chromatograph. The procedure was applied to the analysis of seawaters, wines, beers and infant foods, the last requiring an additional enzymatic reaction prior to analyte derivatization. Detection limits in seawaters and beverages were 0.05, 0.15 and 0.8 ng mL⁻¹ for DMA, MMA and inorganic arsenic, respectively. In infant foods the detection limits were 1, 10 and 25 ng g⁻¹ for DMA, MMA and inorganic arsenic, respectively. Inorganic arsenic was detected in some of the seawater samples and three of the wines analyzed at concentration levels in the range 1-40 ng mL⁻¹, and DMA in several of the infant foods in the range 20-80 ng g⁻¹. The method was validated by analyzing a certified reference material and by recovery studies. All the samples were also analyzed by hydride generation and atomic fluorescence spectrometry (HG-AFS), which provided data for the total arsenic content.     

Speciation of organotin compounds in water and sediments by gas chromatography/atomic absorption spectrometry (GC-AAS)

A commercially available atomic absorption detector coupled to a wide-bore column-containing gas Chromatograph (GC-AAS) was utilized to detect organotin compounds. Speciation was performed by pentane extraction of the organotin species as the corresponding sodium diethyldithiocarbamate complexes, enrichment by rotary evaporation, derivatization with Grignard reagent and finally the extracted water and sediment samples were separated and detected on the GC-AAS system.     

Speciation of organotin compounds in water by gas chromatography/atomic absorption spectrometry

Summary A reproducible and interference-free method is presented for simultaneous determination of individual tri-, di- and monoalkyltin species present in aqueous systems. The ionic methyltin and butyltin compounds are extracted from water into pentane as diethyldithiocarbamate complexes at pH 5. The organic phase is then evaporated to dryness under reduced pressure, after which derivatization withn-pentyl (Pe) Grignard reagent is carried out in a microvolume ofn-octane to form pentylated alkyltin compounds R _n SnPe_(4-n) (R = Methyl, Me or Butyl, Bu). The quantitation is subsequently performed by gas chromatography with quartz furnace atomic absorption spectrometric detection (GC-AAS). Absolute detection limits range between 0.16 ng and 0.40 ng Sn for the various organotin species, allowing speciation in natural water down to the 4-10 ng 1^–1 level.

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Speziation von organischen Zinnverbindungen in Wasser durch GC/AAS

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Determination of organotin compounds in environmental samples by supercritical fluid extraction and gas chromatography with atomic emission detection

The extraction of six tetraalkyltin and seven ionic organotin compounds from spiked topsoil samples with supercritical carbon dioxide and carbon dioxide modified with 5 percent methanol was investigated. Analysis of the soil extracts was performed by gas chromatography with atomic emission detection. Retention times, minimum detectable concentrations, and detector linear ranges are included for nine organotin compounds (seven of the nine compounds were derivatized with n-pentylmagnesium bromide prior to gas chromatographic analysis). A 2³ factorial experimental design was used to study the effect of three variables (pressure, temperature, and extraction time) on compound recovery. The results indicate that the tetraalkyltin compounds are extracted from topsoil samples with recoveries ranging from 90 to 110 percent. Recoveries for the ionic organotin compounds ranged from 50 to 75 percent for trimethyltin chloride, triethyltin bromide, and tributyltin iodide; they were below 20 percent for dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, and butyltin trichloride. When sodium diethyldithiocarbamate was added to the soil samples prior to extraction, followed by extraction with carbon dioxide modified with 5 percent methanol, recoveries ranged from 70 to 90 percent for trimethyltin chloride, triethyltin bromide, dimethyltin dichloride, tributyltin iodide, and dibutyltin dichloride; recoveries were approximately 40 percent for butyltin trichloride and diphenyltin dichloride.     

Interferences in ultratrace speciation of organolead and organotin by gas chromatography with atomic spectrometric detection

Interferences in trace and ultratrace speciation analysis of organotin and organolead compounds in various samples by gas chromatography coupled with atomic absorption spectrometry (AAS) and/or microwave induced plasma atomic emission spectrometry (MIP AES) are investigated. Particular attention is given to the effects of matrix co-extractives and reagents impurities introduced during sample preparation. Their influence on the detection limits is discussed in terms of baseline noise level, blank value, formation of artefacts and signal suppression. Loss of column resolution during the analysis of some matrices is observed.     

Volatile organo-selenium speciation in biological matter by solid phase microextraction-moderate temperature multicapillary gas chromatography with microwave induced plasma atomic emission spectrometry detection

Microwave induced plasma atomic emission spectrometry (MIP-AES) in combination with multicapillary (MC) gas chromatography could be proven to be useful for element specific detection of volatile species. Solid phase microextraction (SPME) was used for preconcentration and sample-matrix separation. The fiber desorption unit as well as the heating control for the MC column were in-house developed and multicapillary column was operated at moderate temperatures (30-100 °C). The method was optimized for organo-selenium species (dimethylselenide (DMSe), diethylselenide (DEtSe) and dimethyldiselenide (DMDSe)), using a chemometric approach. Stationary phases for the separation column were optimized using a conventional GC and contrasted with the results obtained with the MC. Application was focussed on selenium accumulating biological matter, such as lupine, yeast, Indian mustard and garlic. These samples were grown in hydroponic solution containing inorganic selenium (Na₂SeO₃ and Na₂SeO₄). SPME sampling was carried out in fixed volume flow boxes in headspace above the living plants and in vials using treated samples. Results demonstrate inorganic selenium transformation into volatile organic species during metabolism. Separation is fast, a chromatogram can be obtained in less than 3 min and detection limits were at sub-ppb level for all investigated species. The system is independent from the use of a conventional gas chromatographic oven and can be used as a versatile alternative to highly cost intensive methods such as GC-ICP-MS.     

Element-selective detection using capillary gas chromatography with atomic emission detection

Capillary GC coupled to an atomic emission detector (AED) provides a powerful new hyphenated technique for the separation and characterization of complex mixtures and compounds. The AED provides simultaneous and truly specific multi-element detection. The specificity of detection reduces the need for the complex sample pretreatment procedures which are necessary to reduce the interference from co-eluted substances which is experienced with detectors such as the FID and the ECD. A range of environmentally significant problems has been studied, including PCB analysis, the characterization of the reaction products of a novel waste treatment process, and the profiling of sulfur-containing species formed by the pyrolysis of various types of coal.     

Speciation of organotin compounds by complex chromatography and reaction detection

Summary The conditions for complex chromatography of organotin compounds have been studied. On-column complex formation with mobile phases containing oxine as reagent is a suitable method for the determination of mono- and di-organotin compounds. Owing to the weak interactions between tri-organotin compounds and oxine and the non-ionic nature of tetra-organotin compounds these species need to be decomposed to lower substituted fragments after their liquid chromatographic separation. This can be achieved by means of photodegradation in a simple nonsegmented post-column-photo-reactor. With the systems investigated sub-g sensitivities and linearitiy of the calibration curves over several orders of magnitude were found.

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Bestimmung von Organozinnverbindungen durch Komplex-Chromatographie und Reaktions-Detektion

Zusammenfassung Zur Bestimmung von Organozinnverbindungen wurde eine komplexchromatographische Methode entwickelt. On-column Komplexbildung mit Oxin als Reagens in der mobilen Phase erweist sich als einfaches und zuverlässiges Verfahren zur Analyse von mono- und di-Organozinnverbindungen. Tri- und tetra-Organozinnverbindungen, die nur mehr bedingt oder gar nicht Komplexe mit Oxin bilden, werden nach ihrer flüssigkeits-chromato-graphischen Auftrennung in einem einfachen, nichtsegmentierten Photoreaktor in niedriger substitutierte, mit Oxin gut reagierende Fragmente zerlegt. Die Empfindlichkeit dieser Systeme reicht in den Submikrogrammbereich und die Eichkurven weisen Linearität über mehrere Zehnerpotenzen auf.

     

Determination of pesticides in waters by capillary gas chromatography with atomic emission detection

Capillary gas chromatography with atomic emission detection (GC-AED) was successfully used to separate and quantify 14 pesticides (organochlorines, organophosphorus compounds and pyrethrins) in water samples after liquid-liquid extraction with ethyl acetate. Monitoring the emission lines for elements such as chlorine, bromine and sulfur ensures nearly specific chromatograms for these elements, and markedly increases selectivity. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients relating to linearity were at least 0.999. Each chromatographic separation takes 21 min and, since two injections are necessary, it requires approximately 1 h to analyze one sample. The method shows a precision of 4.3-8.2% (RSD), depending on the compound. The application of liquid-liquid extraction with ethyl acetate led to recoveries from spiked samples ranging from 76 to 113%. The sensitivity and linearity for the elements chlorine, sulfur, nitrogen and phosphorus were checked under the optimized conditions at their customary emission wavelength. The sensitivity and linearity for these compounds decreased in the order (atom and emission wavelength) Cl (479 nm)>S (181 nm)>P (178 nm)>N (174 nm). A study of the GC-AED system's response to chlorine concentration in eight pesticide molecules was performed and a linear relationship was found with a correlation coefficient of 0.987.     

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.     

Analysis of atmospheric sulfur gases by capillary gas chromatography with atomic emission detection

The atomic emission detector (AED) has been found to be a sensitive and selective instrument for analysis of atmospheric sulfur gases by capillary gas chromatography. It was possible to determine atmospheric dimethyl sulfide at concentrations below 0.3 nmol/m³ typical of the remote marine environment in winter. Sample analyses from the Australian Baseline Air Pollution Station, Cape Grim, are used to illustrate this. In comparison with other sulfur-specific detectors previously used for this work, the AED has been found to exhibit the best combination of specificity and sensitivity. A configuration comprising a series of valves, gas calibration loops, and a cryogenic trap prior to the GC-AED was used for sample analysis. Standard addition of sulfur hexafluoride was found to assist determination of carbonyl sulfide, as it could be used to take into account the magnitude of signal quenching from coeluting gases. The AED was also found to be a selective detector for the direct injection of water-soluble dimethyl sulfide oxidation products.     

Speciation analysis of triethyl-lead and tributyl-tin compounds in human urine by liquid-liquid extraction and gas chromatography microwave-induced plasma atomic emission detection

This work describes the development of a fast method for speciation analysis of triethyl-lead and tributyl-tin species in urine samples after in situ derivatization by tetraethyl- or tetrapropyl-borate reagents. The alkylation reaction is done in the aqueous and urine medium and the less-polar derivatives are extracted in hexane by liquid-liquid extraction. The species were extracted and the extract was efficiently collected from the aqueous phase after centrifugation. Finally, the organometallic species are separated by gas chromatography and determined from the emission signals of elemental lead and tin. Atomic lead and tin are formed from the organolead and organotin compounds during atomization of the column eluate in a microwave-induced helium plasma source. The simultaneous measurement of lead (Pb) at 405.780 nm and tin (Sn) at 303.419 nm was achieved by an atomic emission detector. Finally, the analytes were determined with satisfactory precision (<5%) and detection limits of 0.05 μg Pb/L and 0.48 μg Sn/L, respectively, when 10 mL of urine is extracted with 1 mL of hexane and 1 μL of extract is injected.     

Determination of triclosan in human dental plaque by gas chromatography with atomic emission detection

A validated gas chromatographic method for the determination of triclosan in human dental plaque is described. Based on plaque sample weights of 10 mg, the limit of detection (2 × S/N) is 0.5 μg/g. The method is linear (r = 0.9986) from the limit of detection to 50 μg/g. Recoveries from placebos spiked with 2.0, 25, and 50 μg/g of triclosan were 105.6%±7.5%, 107.2%±3.1%, and 99.1%±1.1%, respectively (n = 3 at each level). Twenty replicate preparations and analyses of a homogenized sample, conducted by two operators over the course of 4 days, showed agreement to within 9% RSD. Analyses of dental plaque collected from patients after brushing with dental cream containing triclosan, shows triclosan to be retained in dental plaque at concentrations above the minimum inhibitory concentration (1 μg/g) after 12 h.     

Pesticide analysis in herbal infusions by solid-phase microextraction and gas chromatography with atomic emission detection

A direct immersion solid-phase microextraction (SPME) procedure was used in combination with capillary gas chromatography with atomic emission detection (GC-AED) for the determination of 10 pesticides (organochlorines, organophosphorus compounds and pyrethrins) in herbal and tea infusions. Ionic strength, sample dilution and time and temperature of the absorption and desorption stages were some of the parameters investigated in order to select the optimum conditions for SPME with a 100 μm PDMS fiber-coating. Element-specific detection and quantification was carried out by monitoring the chlorine (479 nm) and bromine (478 nm) emission lines, which provided nearly specific chromatograms. Calibration was carried out by using a spiked sample infusion. The detection limits varied between 11.9 ng ml⁻¹ for deltamethrin and 0.03 ng ml⁻¹ for p,p′-DDE and p,p′-DDD. The recoveries ranged from 73.5% for deltamethrin to 108.3% for p,p′-DDT in a spiked white tea infusion. Two of the eight samples analyzed contained low levels of some the pesticides considered.     

Measurements using gas chromatography with coelution and dual-isotope atomic emission detection.

Dual-isotope measurements by gas chromatography (GC)-atomic emission detection (AED) may enhance results for quantitative analyses. Adding a known amount of an isotopically labelled form of target analytes in each sample can compensate for irreproducibilities or uncertainties associated with sample pretreatments and sample loading. Similarly, fluctuations in AED temperatures, flows and interferants can be compensated via the added labelled forms if each target analyte and its isotopically labelled form coelute. Under these conditions they are subject to identical excitation environments and are measured from the same viewed volumes. Consequently, improved quantitative results may be attained by coelution in GC-AED methods which mimic isotope dilution.     

Speciation of tin in sediments and soils by leaching

For the evaluation of the speciation of Sn in solid samples, a leaching sequence is presented, which takes into account the special properties of the element investigated. The sample is leached with ethanol (organics), 25% acetic acid (carbonates), oxalate (coprecipitation upon Fe/Mn-hydroxides), then oxidized with KMnO₄ (sulfides), and finally sublimed with NH₄I (cassiterite); the silicate fraction is found as the difference to the total decomposition value (e.g. LiBO₂).Final determinations are done by hydride AAS from tartaric acid-solutions, except the ethanol fraction which is submitted to ETA-AAS. In the furnace, addition of HNO₃ and H₂O₂ and rapid heating in the gas-stop mode results in equal sensitivity of organic and inorganic tin in the ethanol extract. The proposed method is checked by coprecipitation/adsorption experiments and by addition of tin-bearing minerals to a natural sediment.The method was applied to fresh water sediments. In sediment cores, the KMnO₄ fraction was dominant, whereas in an oxic surface sediment NH₄I releases the main fraction (cassiterite).     

Speciation analysis of mercury by solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight-mass spectrometry

This paper reports the development of an analytical approach for speciation analysis of mercury at ultra-trace levels on the basis of solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight mass spectrometry. Headspace solid-phase microextraction with a carboxen/polydimethylsyloxane fiber is used for extraction/preconcentration of mercury species after derivatization with sodium tetraethylborate and subsequent volatilization. Isothermal separation of methylmercury (MeHg), inorganic mercury (Hg2+) and propylmercury (PrHg) used as internal standard is achieved within a chromatographic run below 45 s without the introduction of spectral skew. Method detection limits (3 x standard deviation criteria) calculated for 10 successive injections of the analytical reagent blank are 0.027 pg g(-1) (as metal) for MeHg and 0.27 pg g(-1) for Hg2+. The repeatability (R.S.D., %) is 3.3% for MeHg and 3.8% for Hg2+ for 10 successive injections of a standard mixture of 10pg. The method accuracy for MeHg and total mercury is validated through the analysis of marine and estuarine sediment reference materials. A comparison of the sediment data with those obtained by a purge-and-trap injection (PTI) method is also addressed. The analytical procedure is illustrated with some results for the ultra-trace level analysis of ice from Antarctica for which the accuracy is assessed by spike recovery experiments.     

Using gas chromatography with atomic emission detection for determining organic pollutants in water

The efficiency of gas chromatography with atomic emission detection (AED) for determining the composition of complex mixtures of organic water pollutants was studied by the example of 13 compounds of different classes. It was found that the correlation between the ratio of AED signals for single element atoms of the compound in the sample and their predetermined ratio in individual solutions additionally supports the identification of impurities in water at a trace level. The determination of a compound by the concentration of one or two elements in its molecule allows the evaluation of the effect of interfering impurities on the results of analysis.     

Determination of monomethylmercury in low- and high-polluted sediments by microwave extraction and gas chromatography with atomic fluorescence detection

Laser tomography techniques were used in order to make visible the flow patterns induced by ascending bubbles in flutes poured with champagne. The stability of flow patterns was investigated in flutes showing natural (without any specific surface treatment) as well as artificial effervescence (i.e., engraved at their bottom), all along the first 15 min after pouring. Engravement conditions were found to strongly influence the kinetics and the stability with time of the mixing flow phenomena found in champagne glasses.