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L Wennrich

Publications and source records attributed to L Wennrich.

3 recordsLinked to original sources
PubMed2000

Determination of chlorophenols in soils using accelerated solvent extraction combined with solid-phase microextraction.

A method for the determination of chlorophenols in soil samples using accelerated solvent extraction (ASE) with water as the solvent combined with solid-phase microextraction (SPME) and GC/MS has been developed. Important ASE parameters, such as extraction temperature and time, were optimized using a spiked wetland soil. The effect of small amounts of organic modifiers on the extraction yields was studied. An extraction temperature of 125 degrees C and 10 min extractions performed three times proved optimal. Two ASE-SPME procedures without and with an organic modifier (5% acetonitrile) were evaluated with respect to precision and detection limits (LOD). The reproducibility of replicate water extractions/SPME determinations (n = 6) was in the range 7-20% relative standard deviation for the nine chlorophenols investigated. LOD values in the low-ppb range were achieved for all chlorophenols. The ASE-SPME procedure presented here was applied to the determination of chlorophenols in soil samples taken from contaminated areas near Bitterfeld, Germany.

Chlorophenols↗
PubMedDate not supplied

Determination of organochlorine pesticides and chlorobenzenes in strawberries by using accelerated solvent extraction combined with sorptive enrichment and gas chromatography/mass spectrometry.

An analytical scheme for the determination of several organochlorine pesticides like hexachlorocyclohexanes (HCHs) and DDX compounds (p,p'-DDE, p,p'-DDD, and p,p'-DDT) as well as chlorobenzenes in strawberries has been developed. The procedure is based on aqueous accelerated solvent extraction (ASE) followed by solid-phase microextraction (SPME) or stir bar sorptive extraction (SBSE) and subsequent thermodesorption-gas chromatography/mass spectrometry analysis. A 65 microm polydimethylsiloxane/ divinylbenzene fiber was chosen for the SPME experiments. Significant SPME and ASE parameters were optimized using spiked water and strawberry samples. For the ASE of the organochlorine compounds, a water-acetone mixture (90 + 10, v/v) as the extraction solvent, an extraction temperature of 120 degrees C, and 2 cycles of 10 min extraction proved optimal. The developed method was evaluated with respect to precision and limits of detection (LOD). The relative standard deviations of replicate ASE-SPME determinations (n = 5) were in the range of 4-24%. LOD values between 1 and 10 microg/kg were achieved with the exception of DDT and DDE (40 microg/kg). Using SBSE, the LOD of these compounds could be improved (2 and 5 microg/kg). The main advantages of this method are the avoidance of cleanup and concentration procedures as well as the significant reduction of the required volume of organic solvents. The described method was applied to the determination of the pollutants in strawberry samples collected from different allotment gardens in a potentially polluted area, the Bitterfeld-Wolfen region (Germany).

Chlorobenzenes↗