Bo Svensmark

Analysis of acidic pesticides using in situ derivatization with alkylchloroformate and solid-phase microextraction (SPME) for GC-MS.

A solid-phase microextraction (SPME) method was developed for the analysis of acidic pesticide residues in water. The method utilizes in situ derivatization with butylchloroformate (BuCF), followed by on-line SPME extraction using a PDMS fibre, and analysis by GC-MS. Derivatives of the phenoxy acids mechlorprop (MCPP), dichlorprop (DCPP), MCPA and 2,4-D and their phenol degradation products 4-chloro-2-methylphenol and 2,4-dichlorophenol (DCP) were identified. Detection limits at 0.16-2.3 microg/l were achieved. Optimization of derivatization, ion strength, extraction time, SPME-fibre, desorption time and temperature are described. Standard curves in the range 0.5-10.0 microg/l were fitted to a second-degree polynomial. Standard deviation (n = 5) was below 10% for the phenol derivatives, but 20-50% for the phenoxy acids. For method verification groundwater samples from a field experiment were screened for content of MCPP and compared to the results from the HPLC analysis. A good agreement was obtained with respect to identification of positive samples, even though concentrations measured by the SPME were lower than with HPLC. Even if the precision and accuracy do not meet the demands for a strictly quantitative analysis, the SPME method is suitable for screening, because it is cheap, it can be automated, and uses smaller amounts of potential harmful solvents. Also, the method is less labour-intensive, as it requires a minimum of sample preparation when compared to traditional analyses. The acidic pesticides bentazon, dicamba, bromoxynil, ioxynil, dinoseb and DNOC were included in the study but could not be analysed by the current method.

Fate and availability of glyphosate and AMPA in agricultural soil

The fate of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) was studied in soil. Labeled glyphosate was used to be able to distinguish the measured quantities of glyphosate and AMPA from the background values since the soil was sampled in a field where glyphosate had been used formerly. After addition of labeled glyphosate, the disappearance of glyphosate and the formation and disappearance of AMPA were monitored. The resulting curves were fitted according to a new EU guideline. The best fit of the glyphosate degradation data was obtained using a first-order multi compartment (FOMC) model. DT50 values of 9 days (glyphosate) and 32 days (AMPA) indicated relatively rapid degradation. After an aging period of 6 months, the leaching risk of each residue was determined by treating the soil with pure water or a phosphate solution (pH 6), to simulate rain over a non-fertilized or fertilized field, respectively. Significantly larger (p < 0.05) amounts of aged glyphosate and AMPA were extracted from the soil when phosphate solution was used as an extraction agent, compared with pure water. This indicates that the risk of leaching of aged glyphosate and AMPA residues from soil is greater in fertilized soil. The blank soil, to which 252 g glyphosate/ha was applied 21 months before this study, contained 0.81 ng glyphosate/g dry soil and 10.46 ng AMPA/g dry soil at the start of the study. Blank soil samples were used as controls without glyphosate addition. After incubation of the blank soil samples for 6 months, a significantly larger amount of AMPA was extracted from the soil treated with phosphate solution than from that treated with pure water. To determine the degree of uptake of aged glyphosate residues by crops growing in the soil, 14C-labeled glyphosate was applied to soil 6.5 months prior to sowing rape and barley seeds. After 41 days, 0.006 ± 0.002% and 0.005 ± 0.001% of the applied radioactivity was measured in rape and barley, respectively.

Formation of chloroform in spruce forest soil : results from laboratory incubation studies

The release of chloroform, 1,1,1-trichloroethane, tetrachloromethane, trichloroethene and tetrachloroethene from an organic rich spruce forest soil was studied in laboratory incubation experiments by dynamic headspace analysis, thermodesorption and gas chromatography. Performance parameters are presented for the dynamic headspace system. For spruce forest soil, the results showed a significant increase in chloroform concentration in the headspace under aerobic conditions over a period of seven days, whereas the concentration of the other compounds remained fairly constant. A biogenic formation of chloroform is suggested, whereas for the other compounds anthropogenic sources are assumed. The addition of trichloroacetic acid to the soil increased the release of chloroform from the soil. It is, therefore, suggested that trichloroacetic acid also contributed to the formation of chloroform. Under the experimental conditions, the spruce forest soil released chloroform concentrations corresponding to a rate of 12 microg m(-2) day(-1). Data on chloroform production rates are presented and compared with literature results, and possible formation mechanisms for chloroform are discussed.

Method development for simultaneous analysis of HBCD, TBBPA, and dimethyl-TBBPA in marine biota from Greenland and the Faroe Islands

The brominated flame retardants hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA) are high-production-volume chemicals. In recent years, their presence has been reported in sediment and biota from the marine environment. In this study, an analytical method was developed for the simultaneous determination of HBCD, TBBPA, and the possible metabolite dimethyl-TBBPA. The method was applied in a preliminary screening of egg, liver, and adipose tissue of marine biota from Greenland and the Faroe Islands. α-HBCD was detected in 35 of 36 analysed samples from the Arctic, indicating a ubiquitous presence of α-HBCD in the environment. β- and γ-HBCD were found in 10 and 14 samples, respectively. TBBPA and dimethyl-TBBPA were not detected in any of the samples indicating limited or no transport of these compounds to remote areas.

Analysis of Metribuzin and transformation products in soil by pressurized liquid extraction and liquid chromatographic-tandem mass spectrometry

A method developed for study of metribuzin degradation in soil is presented. LC-MS-MS and electrospray ionisation was used for analysis of metribuzin and the metabolites deaminometribuzin (DA), diketometribuzin (DK) and deaminodiketometribuzin (DADK). Soil samples were extracted by pressurized liquid extraction using methanol-water (75:25) at 60 degrees C. In general, recoveries were about 75% for metribuzin, DA and DADK and their detection limit in soil was 1.25 microg/kg. Lower sensitivity was observed for DK, with detection limit at 12.5 microg/kg and recovery about 50%.

Biodegradation of chlorinated solvents in a water unsaturated topsoil

In order to investigate topsoils as potential sinks for chlorinated solvents from the atmosphere, the degradation of trichloromethane (CHCl(3)), 1,1,1-trichloroethane (CH(3)CCl(3)), tetrachloromethane (CCl(4)), trichloroethene (C(2)HCl(3)) and tetrachloroethene (C(2)Cl(4)) was studied in anoxic laboratory experiments designed to simulate denitrifying conditions in water unsaturated topsoil. Active denitrification was demonstrated by measuring the release of 15N in N(2) to the headspace from added 15N labeled nitrate. The degradation of chlorinated aliphatic compounds was followed by measuring their concentrations in the headspace above the soil. The headspace concentrations of all the chlorinated solvents except CH(3)CCl(3) were significantly (P<or=0.05) lower after 41 days in biologically active batches as compared to sterile batches. For the compounds with significantly decreasing headspace concentrations, the decline was the least for CHCl(3) within the 41 days of incubation. The headspace concentrations of trichloro- and tetrachloroethene decreased more than 50% during the first 20 days with no considerable indication of abiotic transformation. While slow abiotic removal was observed, tetrachloromethane was completely biotransformed after 16 days. Based on the results in this study, we conclude that anaerobic topsoils are potential sinks for these contaminants, and that a natural attenuation potential exists, even in water unsaturated topsoils.

Quantification of compositional changes of petroleum hydrocarbons by GC/FID and GC/MS during a long-term bioremediation experiment.

Samples from a long-term bioremediation experiment contaminated with two crude oils, Arabian Heavy and Gullfax, was used to analyze the compositional change of petroleum hydrocarbons. A time course of five different homologous series of petroleum hydrocarbons were analysed by GC/FID and GC/MS. The homologous series were n-alkanes, acyclic isoprenoids, alkylated naphthalenes, alkylated phenanthrenes, and alkylated dibenzothiophenes. Several biomarker compounds were monitored during the experiment to evaluate the possible use as conserved reference compounds for the quantification of other oil compounds, that is, nor-hopanes, hopanes, methyl-hopanes, steranes, mono- og triaromatic steranes. The 17α(H),21β(H)-hopane was found to be stable toward biodegradation and was used as reference compound. The internal standard quantification method was used to quantify changes of the homologous series of oil compounds, and a graphic presentation was used to compare the decrease of the individual compounds. This was found to be an easy way of comparing relative changes in oil. The disappearance of the compounds was extensive and in 6 to 7 months less than 6% remained. The decrease of the n-alkanes (>C15) and acyclic isoprenoids was almost uniform within each homologous series and thus independent of physical-chemical characteristics. Evaporation affected compounds with boiling points lower than n-C15. The alkylated aromatic and sulfur-aromatic compounds decreased according to the degree of alkylation and the decrease showed to be delayed by 10 to 20% by each additional alkyl group. The lack of isomeric-specific degradation of most of the aromatic and sulfur-aromatic compounds, until extensive decrease in concentration had occurred, suggests these compounds have to be dissolved, before any biodegradation occurs.

Gas Chromatography Interfaced with Atmospheric Pressure Ionization-Quadrupole Time-of-Flight-Mass Spectrometry by Low-Temperature Plasma Ionization

A low temperature plasma (LTP) ionization interface between a gas chromatograph (GC) and an atmospheric pressure inlet mass spectrometer, was constructed. This enabled time-of-flight mass spectrometric detection of GC-eluting compounds. The performance of the setup was evaluated by injection of mixtures of common volatile organic compounds. Amounts down to ca. 0.5 ng (on column) could be detected for most compounds and with a chromatographic performance comparable to that of GC/EIMS. In the positive mode, LTP ionization resulted in a compound specific formation of molecular ions M(+•), protonated molecules [M + H](+), and adduct ions such as [(M + O) + H](+) and [M + NO](+). The ion patterns seemed unique for each of the analyzed compound classes and can therefore be useful for identification of functional groups. A total of 20 different compounds within 8 functional groups were analyzed.

Determination of volatilization (dissipation) and secondary deposition of pesticides in a field study using passive dosimeters

The volatilization and secondary deposition of the herbicides prosulfocarb and pendimethalin were measured using passive dosimeters with Chinese cabbage and soil as collective material. Passive dosimeters were placed in the field before spraying and at three distances downwind after spraying. The volatilization of prosulfocarb and pendimethalin determined as dissipation was 80 and 60% of the applied amount from the cabbage surface, while no significant loss was measured from soil surfaces after 48 h. The secondary deposition of prosulfocarb and pendimethalin 25 m from the spray zone was 2 and 4% on the leaf surface as well as on the soil surface. At 5 m distance, 6 and 10% of the field dose of prosulfocarb and pendimethalin could be determined on dosimeters with leaves, and 4 and 8% of the field dose could be determined on soil surfaces.

Extraction and determination of the potato glycoalkaloid α -solanine in soil

The toxic glycoalkaloids α-solanine and α-chaconine are produced in all parts of the potato plant, and post-harvest potato tubers may represent a source of soil and water contamination. A new method was developed for extraction and purification of α-solanine in soil samples. Soil samples were extracted with THF : H2O : ACN : CH3COOH (50 : 30 : 20 : 1) and the extract purified by SPE before HPLC determination of α-solanine. The limit of detection was 2.4 mg of α-solanine kg−1 soil. The new procedure was used for determination of α-solanine in spiked soils with varying content of organic matter and texture. Recovery for soil samples spiked with α-solanine 1 h before extraction was 61–68% for soils low in organic carbon (<2.2% C), and to 47% for soil high in organic carbon. Similar recoveries were obtained for α-chaconine. The reproducibility of the method shown by the relative standard deviation varied from 1.7 to 10.1%, depending on the soil type. No decrease in extractable α-solanine was observed until day 17 for soil samples spiked with pure α-solanine kept at 5°C, while the content in samples spiked with potato materials showed a faster decline. This indicates that the degradation and/or ageing processes proceed relatively slowly for glycoalkaloids in soil matrices. This is the first method reported for determination of potato glycoalkaloids in soil.