Investigation into the determination of trimethylarsine in natural gas and its partitioning into gas and condensate phases using (cryotrapping)/gas chromatography coupled to inductively coupled plasma mass spectrometry and liquid/solid sorption techniques

Speciation of trialkylated arsenic compunds in natural gas, pressurized and stable condensate samples from the same gas well was performed using (Cryotrapping) Gas Chromatography-Inductively Coupled Plasma Mass Spectrometry. The major species in all phases investigated was found to be trimethylarsine with a highest concentration of 17.8 ng/L (As) in the gas phase and 33.2 μg/L (As) in the stable condensate phase. The highest amount of trimethylarsine (121 μg/L (As)) was found in the pressurized condensate, along with trace amounts of non-identified higher alkylated arsines. Volatile arsenic species in natural gas and its related products cause concern with regards to environment, safety, occupational health and gas processing. Therefore, interest lies in a fast and simple field method for the determination of volatile arsenicals. Here, we use simple liquid and solid sorption techniques, namely absorption in silver nitrate solution and adsorption on silver nitrate impregnated silica gel tubes followed by total arsenic determination as a promising tool for field monitoring of volatile arsenicals in natural gas and gas condensates. Preliminary results obtained for the sorption-based methods show that around 70% of the arsenic is determined with these methods in comparison to volatile arsenic determination using GC-ICP-MS. Furthermore, an inter-laboratory- and inter-method comparison was performed using silver nitrate impregnated silica tubes on 14 different gas samples with concentrations varying from below 1 to 1000 μg As/m³ natural gas. The results obtained from the two laboratories differ in a range of 10 to 60%, but agree within the order of magnitude, which is satisfactory for our purposes.     

GC–ICP–MS法测定丙烯中的痕量砷化氢

建立GC–ICP–MS直接进样法测定丙烯中痕量砷化氢的方法。采用GS Gaspro毛细柱进行分离,气相色谱载气流速为3.5 mL/min,分流比为6∶1,ICP–MS积分时间为0.5 s,载气流速为0.83 L/min,增敏气为含有20%(体积分数)氮气的氩气,压力为206.85 kPa。砷化氢的检出限为0.09 nL/L,在5 nL/L和80 nL/L加标水平下的回收率分别为102%和104%,测定结果的相对标准偏差小于3%(n=6)。结果表明该方法简单快速,可用于丙烯中痕量砷化氢的测定。     

Environmental application of elemental speciation analysis based on liquid or gas chromatography hyphenated to inductively coupled plasma mass spectrometry—A review

In recent years the number of environmental applications of elemental speciation analysis using inductively coupled plasma mass spectrometry (ICP-MS) as detector has increased significantly. The analytical characteristics, such as extremely low detection limits (LOD) for almost all elements, the wide linear range, the possibility for multi-elemental analysis and the possibility to apply isotope dilution mass spectrometry (IDMS) make ICP-MS an attractive tool for elemental speciation analysis. Two methodological approaches, i.e. the combination of ICP-MS with high performance liquid chromatography (HPLC) and gas chromatography (GC), dominate the field. Besides the investigation of metals and metalloids and their species (e.g. Sn, Hg, As), representing “classic” elements in environmental science, more recently other elements (e.g. P, S, Br, I) amenable to ICP-MS determination were addressed. In addition, the introduction of isotope dilution analysis and the development of isotopically labeled species-specific standards have contributed to the success of ICP-MS in the field. The aim of this review is to summarize these developments and to highlight recent trends in the environmental application of ICP-MS coupled to GC and HPLC.     

Occurrence of Volatile Metal and Metalloid Species in Landfill and Sewage Gases

Abstract

Speciation of volatile metals and metalloids in the environment is extensively described in literature. In order to investigate unstable volatile organometallics, on-line coupling of GC with ICP-MS was used. Preliminary results for gases of sewage sludge fermentation at thermophilic and mesophilic conditions are compared with the metal and metalloid speciation in landfill gases. In each case 20 L gas were sampled by cryogenic trapping. The species were identified by element-specific detection either by retention time of standards or by calculation of the boiling point correlation. Characteristic of the separation is the linear correlation of boiling point (bp/°C) versus retention time (rt/min) (bp = 6.39?rt -109.2, r² = 0.9926). The amounts of total volatile elements are estimated by semi-quantification. Cd, Sn. Hg, Pb (sewage gas) and Se, Te, Hg, Pb (landfill gas) were determined in the range of ng m^?3 level; As, Sb, Te and Bi (sewage gas) and As, Sn, Sb and Bi (landfill gas) in the μg m^?3 level range.     

Isotope dilution analysis mass spectrometry for the routine measurement of butyltin compounds in marine environmental and biological samples

The highly qualified primary method of species-specific isotope dilution analysis has been employed in this work to evaluate for the first time the levels of butyltin compounds in the estuary of the river Eo (Northwest Spain) where there is, since many years, a high oyster farming activity. A spike solution containing mono-, di- and tributyltin enriched in ¹¹⁹Sn allowed the simultaneous determination of the three compounds in different marine environmental and biological samples collected in this area (seawater samples, sediments and biological tissues of four different marine species). The results obtained in this work showed toxic TBT levels for many marine species in 45% of the seawater samples analyzed whereas significant organotin concentrations were found to be obtained only in one of the sediments analyzed. On the other hand, TBT levels ranging from 20 to almost 200 ng g^− 1 (dry weight) were obtained in the different biological tissues analyzed demonstrating the bioaccumulation of organotin compounds in certain marine species.     

Development of a species-specific isotope dilution GC-ICP-MS method for the determination of thiophene derivates in petroleum products

A species-specific isotope dilution technique for accurate determination of sulfur species in low- and high-boiling petroleum products was developed by coupling capillary gas chromatography with quadrupole ICP-MS (GC-ICP-IDMS). For the isotope dilution step ³⁴S-labeled thiophene, dibenzothiophene, and mixed dibenzothiophene/4-methyldibenzothiophene spike compounds were synthesized on the milligram scale from elemental ³⁴S-enriched sulfur. Thiophene was determined in gasoline, ‘sulfur-free’ gasoline, and naphtha. By analyzing reference material NIST SRM 2296, the accuracy of species-specific GC-ICP-IDMS was demonstrated by an excellent agreement with the certified value. The detection limit is always limited by the background noise of the isotope chromatograms and was determined for thiophene to be 7 pg absolute, which corresponds to 7 ng sulfur/g sample under the experimental conditions used. Dibenzothiophene and 4-methyldibenzothiophene were determined in different high-boiling petroleum products like gas oil, diesel fuel, and heating oil. In this case a large concentration range from about < 0.04 to more than 2,000 μg g⁻¹ was covered for both sulfur species. By parallel GC-ICP-MS and GC-EI-MS experiments (EI-MS electron impact ionization mass spectrometry) the substantial influence of co-eluting hydrocarbons on the ICP-MS sulfur signal was demonstrated, which can significantly affect results obtained by external calibration but not those by the isotope dilution technique.     

Sample preparation methods for subsequent determination of metals and non-metals in crude oil—A review

In this review sample preparation strategies used for crude oil digestion in last ten years are discussed focusing on further metals and non-metals determination. One of the main challenges of proposed methods has been to overcome the difficulty to bring crude oil samples into solution, which should be compatible with analytical techniques used for element determination. On this aspect, this review summarizes the sample preparation methods for metals and non metals determination in crude oil including those based on wet digestion, combustion, emulsification, extraction, sample dilution with organic solvents, among others. Conventional methods related to wet digestion with concentrated acids or combustion are also covered, with special emphasis to closed systems. Trends in sample digestion, such as microwave-assisted digestion using diluted acids combined with high-efficiency decomposition systems are discussed. On the other hand, strategies based on sample dilution in organic solvents and procedures recommended for speciation analysis are reported as well as the use of direct analysis in view of the recent importance for crude oil field. A compilation concerning sample preparation for crude oil provided by official methods as well as certified reference materials available for accuracy evaluation is also presented and discussed.