Low-temperature Gas Chromatography Research Articles

HG/LT-GC/ICP-MS coupling for identification of metal(loid) species in human urine after fish consumption.

Human urine samples after fish consumption have been investigated by low-temperature gas chromatography with inductively coupled plasma mass spectrometric detection after sample derivatization by hydride generation (HG/LT-GC/ICP-MS). This analytical technique enabled the identification of organometal(loid) compounds in human urine; species of the six elements germanium, arsenic, selenium, tin, antimony, and mercury were determined. Three different organic selenium species, two germanium species, seven arsenic species, four tin species, five antimony species, and one species of mercury were found; 18 of the 22 species detected could be identified. The relative detection limits ranged between 2 and 12 pg x L(-1) (x=element). These organometal(loid) compounds probably build up in the human body under the influence of micro-organisms, in the presence of hydrogen sulfide and methane, in the human intestine.

Metal(loid)organic compounds in contaminated soil

13 samples of soils contaminated with petrol, coaly residues, shredder and domestic waste have been investigated by low temperature gas chromatography with plasma mass spectrometry detection after sample derivatisation by hydride generation (HG/LT-GC/ICP-MS). 24 organic compounds of 9 elements could be analysed, one fifth of them exceeding the concentration of 1 microg/kg. These results are roughly comparable with those on harbour and river sediments, and are discussed in respect to a preliminary evaluation of the emission potential of solid waste and contaminated soil as well as waste treatment processes.

Volatile Metal and Metalloid Species (Pb, Hg, Se) in a European Urban Atmosphere (Bordeaux, France)

Ambient air measurements of volatile metal and metalloid compounds were conducted in a European urban environment (Bordeaux, France). Air samples were collected with a cryogenic trap and analyzed by low-temperature gas chromatography with ICP/MS detection. Indoor and outdoor sites were studied. Tetraalkyllead compounds (Me4-nEtnPb, n = 0−4) and elemental mercury were found to be the major volatile metal species. Average concentrations of 15.5 and 2.7 ng/m3 as metal have been reported respectively for total alkyllead species and elemental mercury in open area. These results illustrate the general phasing out of atmospheric lead initiated in the past decade. Accumulation of dimethyl selenide has been recorded in a building probably originating from human breath. Volatile metal species distribution in the different sites is discussed with regards to meteorological conditions and automotive traffic parameters. Occurrence of unknown volatile metal and metalloid species likely to occur in urban environment is also reported and discussed.

Potential interferences generated during mercury species determination using acid leaching, aqueous ethylation, cryogenic gas chromatography and atomic spectrometry detection techniques

A careful search for formation of methylmercury (MeHg +) as an artefact and for potential interferences has been carried out using an analytical procedure involving aqueous phase ethylation, cryogenic trapping, low temperature gas chromatography and quartz furnace atomic absorption spectrometry (Eth-CT-GC-QFAAS) for mercury speciation, after open-focused microwave extraction. The results show that spurious MeHg + formation from Hg 2+ can occur mainly in the chromatographic column during the determination step rather than during the extraction step. The silanizing agent, dimethyldisilazane, acting as a methyl donor, appears to be responsible for the EtMeHg formation when high concentrations of Hg 2+ (>1 ppm) are present in the solution during the analysis. On the other hand, the production of several unknown peaks, closely corresponding to Me 2Hg, Et 2Hg etc. in the chromatogram, is the result of impurities in the derivatizing agent, NaBEt 4. The magnitude of these interferences varies with different lots of reagent. The derivatization and determination steps must always be checked following standard QA/QC procedures. Once interference problems are taken into account, reliable understanding of Hg cycling and behaviour in aquatic environments will be achieved.

Metal(loid)organic compounds in geothermal gases and waters

Volatile metal(loid)organic species of geogenic and anthropogenic origin are analyzed by low temperature gas chromatography coupled on-line with plasma mass spectrometry (LTGC/ICP–MS) with detection limits in the higher pg-range (per m 3 gas). In respect to the determination of aqueous samples, this instrumental technique is combined with sample derivatization by the hydride generation technique. Volatile species of As, Sb, Se and I could be detected in gases over hot springs in British Columbia (Canada). Methylated species of Hg, Ge, As, Sb and Te were also determined in concentrations in the ng/kg- to low μg/kg-range in geothermal waters from Ruapehu, Waimangu, Waiotapu and Tokaanu (North Island, New Zealand); up to 1% of the total dissolved metal(loid)s are found in methylated forms. Volatile metal(loid)organic species of geogenic origin are compared with those emanating from anthropogenic sources (waste and sewage gases, river and harbor sediments). Possible formation mechanisms for these compounds are discussed.

Organometal(loid) species in geochemical exploration: preliminary qualitative results

Organic and other volatile metal(loid) species (e.g. hydrides) in environmental gases can be determined with high sensitivity and selectivity by low-temperature gas chromatography coupled on-line to plasma mass spectrometry (LTGC/ICP–MS). A standard reference solution is analysed simultaneously for calibration of the results as well as for monitoring the excitation conditions in the plasma. This highly sensitive analytical method was applied in field screening tests at Cu and Hg deposits in Germany. In some of the soil gas and soil samples investigated, organic compounds of several elements (e.g. As, Hg) could clearly be identified. The implications of these results with respect to potential use of organometal(loid) species in geochemical exploration are discussed.

Determination of trimethylsilanol in the environment by LT-GC/ICP-OES and GC-MS

The combination of element-specific investigation by low temperature gas chromatography coupled on-line with inductively coupled plasma optical emission spectroscopy (LT-GC/ICP-OES) and gas chromatography using mass spectrometry detection (GC-MS), as an additional analytical technique for molecular identification, was employed for the determination of volatile organosilicon species. Gaseous and liquid samples from waste deposit sites, waste composting tanks and sewage-disposal plants were investigated. It was frequently possible to identify the labile silanol compound trimethylsilanol as a dominant silicon species in waste disposal and waste composting gases. The results presented give rise to the assumption that trimethylsilanol is a volatile product of the degradation of organosilicon materials under special environmental conditions.

Determination of organometallics in intra-oral air by LT-GC/ICP-MS.

Low temperature gas chromatography (LT-GC) coupled on-line with inductively coupled plasma mass spectrometry (ICP-MS) has been used to identify volatile metal and metalloid compounds in human breath. After cryogenic sampling, the gas sample has been separated without any clean-up by increasing the temperature (-100 to +200 degrees C). Simultaneous determination of 11 elements with ICP-MS was used for screening analysis. The detection limits of volatile compounds in intra-oral air are in the range of ng m(-3). Dimethyl selenium has been determined in each gas sample from six test persons in the range of 0.08 to 0.98 microg m(-3).

Sorption, separation, and conversion of hydrogen nuclear spin isomers on zeolites, alumina, and silicagel

Sorption of ortho- and para-hydrogen as well as -deuterium on silica, alumina, and different types of zeolites is investigated by low-temperature gas chromatography. Adsorption isotherms and thermodynamic properties are determined from their elution profiles (first statistical moment ), temperature, and coverage dependence. Separation factors on alumina over a wide temperature range are evaluated and compared to calculated values. On zeolites a slight conversion is observed. The conversion rates due to different mechanisms are presented and discussed.

Determination of volatile mercury species at the picogram level by low-temperature gas chromatography with cold-vapour atomic fluorescence detection

Alkylmercury compounds were preconcentrated from air on a Carbotrap (graphitized carbon black) column at room temperature. The species were then transferred by thermal desorption to a U-tube chromatographic column packed with 15% OV-3 on Chromosorb WAW-DMSC, held at −196°C in liquid nitrogen. The compounds were clearly separated and eluted in order of increasing polarity using a simple, ramped heating step to 180°C over 20 min. After thermal decomposition of the eluant, the resultant mercury vapour was detected by cold-vapour atomic fluorescence spectrometry. The detection limits (as Hg) for the system were approximately 0.3 pg for mercury and dimethylmercury, 0.4 pg for diethylmercury, and 2.0 pg for methylmercury chloride. A study of the Long Island Sound atmosphere showed Hg 0 to account for 95–100% of the total mercury present, with the remainder being monomethylmercury.

Vapor Pressures of Some Deuterated Propylenes

The deuterium vapor pressure isotope effect has been measured for CH3CDCH2, CH2DCHCH2, CH3CHCD2, and CD2CDCD2 using mercury manometry. The samples were of high isotopic purity and were chemically purified using low temperature gas chromatography. Substitution at the ethylenic end of the molecule results in an inverse isotope effect of 0.5% per D near 240°K falling off to a normal effect of 1% per D near 150°K. At the higher temperatures the law of the mean was nearly obeyed but deviations, of course, occur around the crossover. The monodeuteromethyl compound shows an inverse effect of about 1% per D at 240°K and displays a very broad maximum around 1.3% per D near 160°K. The perduetero compound also displays a broad maximum. Its effect is larger than that predicted from the approximate theory.

Vapor Pressure Isotope Effects of the Deuterated Acetylenes

The vapor pressures of the isotopic acetylenes: C2H2, C2HD, and C2D2, have been investigated by mercury manometry. Samples of relatively pure C2HD were prepared for this purpose by low-temperature gas chromatography. The vapor pressure measurements were made from 0.5 to 800 mm pressure (125–190°K) with a precision of ∼0.01 mm. The vapor pressure isotope effects were normal with the isotope effect for C2HD being slightly larger than the rule of the mean value. The data for C2D2 showed a sharp change in the temperature dependence at 147.4°K which has been interpreted as a result of a solid–solid phase transition in C2D2. The experimental results have been considered in the light of the statistical theory of isotope effects in condensed systems. A model calculation made within the framework of this theory is in agreement with the experimental data.

Gas chromatography of monoterpene hydrocarbons from etheric oils on packed separation columns with low content of fluid stationary phase. Terpenes and related compounds. V

In the hydrocarbon fraction of the essential oil of leaves of Abies alba Mill. 28 volatile terpenes could be demonstrated by low–temperature gas chromatography on low–load columns; 19 could be identified.

Low Temperature Gas Chromatography

Low Temperature Gas Chromatography

The krypton and xenon contents of atmospheric air

The proportion of krypton and xenon in dry air has been measured by a method using distillation and low-temperature gas-chromatography for the isolation of krypton and xenon. The separation has been controlled by the use of radioactive 85 Kr tracer. The krypton content of dry air is 1⋅139 ± 0⋅01 x 10 -6 by volume. The xenon content of dry air is 0⋅086 ± 0⋅001 x 10 -6 by volume.