Coupling of SPME with MCC/UV–IMS as a tool for rapid on-site detection of groundwater and surface water contamination

The combination of headspace solid phase microextraction (HS-SPME) [1] with fast chromatographic pre-separation by means of multi-capillary columns (MCC) coupled to an ion mobility spectrometer equipped with a 10.6 eV photoionisation source was applied to rapid on-site monitoring of ground and surface water contaminations. Under field conditions, water contaminants were directly detectable down to the upper microg/L range. The potential of the developed method is illustrated by measurements of BTEX, naphthalene, chlorinated alkenes and chlorinated benzenes in water. Practical results from investigations of contaminated groundwater at a former gasworks site and groundwater from the site of a metal processing plant, focusing on the key substances benzene, naphthalene and tetrachloroethene, demonstrate the feasibility of the system for field studies.

Application of infrared spectroscopy to monitoring gas insulated high-voltage equipment: electrode material-dependent SF(6) decomposition

Sulfur hexafluoride is a chemically inert gas which is used in gas insulated substations (GIS) and other high-voltage equipment, leading to a significant enhancement of apparatus lifetime and reductions in installation size and maintenance requirements compared to conventional air insulated substations. However, component failures due to aging of the gas through electrical discharges may occur, and on-site monitoring for risk assessment is needed. Infrared spectroscopy was used for the analysis of gaseous by-products generated from electrical discharges in sulfur hexafluoride gas. An infrared monitoring system was developed using a micro-cell coupled to an FTIR spectrometer by silver halide fibers. Partial least-squares calibration was applied by using a limited number of optimally selected spectral variables. Emphasis was placed on the determination of main decomposition products, such as SOF(2), SOF(4), and SO(2)F(2). Besides the different electrical conditions, the material of the plane counter electrode of the discharge chamber was also varied between silver, aluminum, copper, tungsten, or tungsten/copper alloy. For the spark experiments the point electrode was the same material as chosen for the plane electrode, whereas for partial discharges a stainless steel needle was employed. Complementary investigations on the chemical composition within the solid counter electrode material by secondary neutral mass spectrometry (SNMS) were also carried out. Under sparking conditions, the electrode material plays an important role in the decomposition rates of the gas-phase, but no relevant material dependence could be observed under partial discharge conditions.

On-site characterization of humic-rich hydrocolloids and their metal loading by means of mobile size-fractionation and exchange techniques

Humic-rich hydrocolloids and their metal loading in selected German bog-waters have been characterized by a novel on-site approach. By use of an on-line multistage ultrafiltration (MST-UF) unit equipped with conventional polyethersulfone (PES)-based flat membranes (nominal cut-off 0.45, 0.22, and 0.1 microm, or 100, 50, 10, 5, 3 kDa) the hydrocolloids could be fractionated on-site in both sub-particulate and macromolecular size ranges. Characterization (dissolved organic carbon (DOC), metals) of the colloid fractions obtained this way was performed off-site by use of conventional instrumental methods (carbon analyzer, AAS, ICP-OES, and TXRF (total reflection X-ray fluorescence)). Major DOC fractions of the hydrocolloids studied were found to be in the size range <5 kDa. The assessed metals (Al, Cu, Fe, Mn, Pb, and Zn) were, however, predominantly enriched in the macromolecular and sub-particulate range, depending on the metal and the sample, respectively. In addition, metal species bound to these hydrocolloids were kinetically characterized on-site by use of competitive ligand (EDTA (ethylenediaminetetraacetate)) and metal (Cu(II)) exchange; the EDTA complexes formed and the metal ions exchanged were separated by means of a small time-controlled tangential-flow UF unit (cut-off 1 kDa). Bound metal fractions, in particular Al and Fe, reacted only slowly (500 to 1000 min) with EDTA; the conditional availability was 60-99%, depending on the hydrocolloid. In contrast, the Cu(II) exchange of colloid-bound metal species approached equilibrium within 5-10 min, with characteristic exchange constants, Kex, of the order of 0.01 to 90 for the metals (Fe<Al<Zn<Mn approximately/= Ca approximately/= Mg). The results were clearly dependent on the water investigated. Thus detailed information on the conditional kinetic and thermodynamic stability of colloid-bound metal species could be obtained from competitive EDTA and Cu(II) exchange under on-site conditions.

Phase transfer and freezing processes investigated on acoustically levitated aqueous droplets

An acoustic trap was designed and constructed to investigate, on a microscale, physicochemical processes relevant to the troposphere, mainly focusing on the temperature range below 0 degrees C. Droplets ranging from 0.5 nL to 4 microliter (0.1 to 2 mm in diameter) were introduced into the cooled reaction chamber by means of a piezo-driven micro pump with a reproducibility better than 5%. Up-take of H2O2 from the gas phase by the levitated droplet was measured and calibrated by in-situ chemiluminescence. Freezing of stably positioned droplets was observed and documented by means of a microscope and a video camera; this demonstrated the usefulness of the technique for simulation and investigation of cloud processes. Ex-situ microanalysis of sub-microliter droplets by use of a fiber optic luminometer was also shown to be a suitable means of investigating relevant physicochemical processes on a micro scale.

Degradation of alpha-pinene on Tenax during sample storage: effects of daylight radiation and temperature

The behavior of alpha-pinene sampled on adsorption cartridges filled with Tenax TA has been investigated in relation to different storage conditions, focusing on daylight radiation and temperature. After sampling, the respective cartridges containing the terpene were placed in sunlight on the windowsill for up to 1 month. Corresponding samples have been wrapped in aluminum foil to prevent the influence of daylight radiation. Additional sample cartridges with alpha-pinene were stored in the refrigerator at 4 degrees C and a freezer at -18 degrees C. All cartridges were analyzed using thermodesorption injection onto a gas chromatograph, and the compounds were detected using either a cryocondensation-interface to a Fourier transform infrared-spectrometer (GC/FT-IR) or the flame ionization detector (FID). In summary, 12 compounds were detected and identified, from which eight were products that were formed on Tenax through different mechanisms. Two compounds seemed to be formed under the influence of daylight radiation, while the others appear to be mainly autoxidation products. Estimates after 1 month of storage showed recoveries of over 99% for wrapped samples, while for unwrapped cartridges only about 88% of alpha-pinene was found. A pattern of up to five compounds was found that can be used as an indicator for storage reactions.

Determination of soluble and insoluble nickel compounds in airborne particulate matter by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry

An extraction procedure for the determination of soluble and insoluble nickel and its compounds in ambient air dust was investigated employing a special device for the generation of test aerosols and using water-soluble NiCl2, partly water-soluble NiCO3 and water-insoluble NiO as model compounds. Additionally, results of the separation and determination of different nickel species down to some ng/m3 in ambient aerosols are discussed. The extraction was carried out with a solution containing 0.01 mol/L EDTA in order to determine partly water-soluble compounds such as NiCO3 and water-soluble, non-toxic nickel compounds in one step. Airborne dust was sampled on filters at locations close to two metallurgical plants in Northrhine-Westphalia (Germany), and first results on the nickel concentration (mean (median) values over a period of 4 months: 8.6+/-6.5 ng/m3 (6.7 ng/m3) and 27.7+/-36 ng/m3 (10.8 ng/m3), respectively) in the collected dust are presented. For EDTA-soluble nickel compounds the maximum and mean fractions of total nickel were found to be 77.1% and 18.6+/-12%, respectively.

Application of gas chromatography-cryocondensation-Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry to the identification of gas phase reaction products from the alpha-pinene/ozone reaction

The gas phase reaction of alpha-pinene with the atmospheric oxidant ozone was investigated by using the capabilities of both gas chromatography-cryocondensation-Fourier transform infrared spectroscopy (GC-FT-IR) and gas chromatography-mass spectrometry (GC-MS), for the identification of the reaction products formed. The reaction was carried out in a flow reaction chamber from where the compounds were sampled on Tenax-containing adsorption cartridges. The reaction mixture was injected onto the column after thermodesorption and analyzed using both GC-IR and GC-MS. Twenty compounds could be detected, including the reactant alpha-pinene and it's impurities tricyclene and camphene. Eleven compounds were identified by spectra comparison with either reference data or spectra obtained from commercial standards. Four compounds were tentatively identified from their IR and MS spectra, while from the remaining two compounds the nature of basic functional groups could be established.

Determination of acrylic acid in air by using diffusion denuder tubes combined with HPLC technique

A procedure for the determination of atmospheric acrylic acid in air at the microgram m-3 to mg m-3 level is described. Diffusion-based sampling, designed to discriminate gaseous analytes from their particulate counterparts, has been used. Acrylic acid is collected with an efficiency of > 98% in tubular denuders coated with sodium hydroxide-barium hydroxide-hydroquinone monomethyl ether, and analyzed by high performance liquid chromatography with UV absorbance detection. The detection limit is 2.9 micrograms m-3 at a flow rate of 0.5 L min-1 and 30 min sampling time. A precision (p = 0.95, n = 10) of 7.5% of the overall procedure was achieved at the 100 micrograms m-3 level. Results of laboratory studies concerning the effect of the coating reagent and the relative humidity on the sampling efficiency as well as possible interferences, in particular by ozone, and the elimination of these interferences are discussed. This method was developed to monitor workplace atmospheres as well as ambient air in industrial environments.

Mutagenic properties of 1,2,3,4-tetrahydronaphthaline-1-hydroperoxide, a model compound for organic peroxides in Diesel exhaust

The genotoxicity of the organic peroxide 1,2,3,4-tetrahydronaphthaline-1-hydroperoxide (or tetraline-1-hydroperoxide, THP) was investigated in the Ames assay without a metabolic activating system using Salmonella typhimurium strains TA 98, TA 100, and TA 102. THP served as a model compound for higher organic peroxides, which can arise from autoxidation of hydrocarbons, e.g. in Diesel exhaust. While THP induced no mutagenic response in S. typhimurium TA 98, it was directly mutagenic in strains TA 100 and TA 102. These data, along with findings on mutagenic properties of other alkyl hydroperoxides, suggest that such compounds deserve further investigation regarding their genotoxic potential and occurrence in the environment.

Application of competitive reaction systems to catalytic kinetic analysis-determination of phosphate

A technique is described for the determination of catalytically active substances, in which a slow catalysed reaction is coupled to a fast competitive reaction. One reactant, which at the same time serves as the indicator substance, is removed by the slow reaction as well as by the competitor added to the system from outside. Under suitable conditions the time for the complete removal of the indicator substance is dependent only on the rate of the catalysed reaction and consequently on the catalyst concentration. The technique is illustrated by means of the phosphate-catalysed reduction of Mo(VI) by ascorbic acid.