Monica Waldebäck

Pressurised fluid extraction (PFE) as an alternative general method for the determination of pesticide residues in rape seed.

A pressurised fluid extraction (PFE) multi-method has been developed for the determination of pesticide residues in rape seed. The method was validated for 25 different pesticides and metabolites. The reliability and efficiency of PFE for extracting pesticide residues from rape seed was investigated. The traditional extraction solvent, hexane saturated with acetonitrile, was used at elevated temperature and pressure. With increased temperature, the extraction kinetics were improved but at the same time more co-extractives were obtained in the form of lipids. When 1 g of rape seed was extracted at temperatures from 60 degrees C to 150 degrees C, the lipid content extracted was found to be as high as 17-26%. An additional clean-up step was therefore required and lipid co-extractives were effectively removed by gel permeation chromatography. The interpretation of the chromatograms and the quantification of the results were satisfactorily improved by the removal of interfering lipids. The developed method was used to extract vinclozolin and iprodione from incurred samples, resulting in a concentration in accordance with the results using conventional liquid-liquid extraction (LLE) between hexane and acetonitrile and also supercritical fluid extraction (SFE) using carbon dioxide. The results of the present study suggest that PEE is a good alternative extraction technique for the determination of pesticide residues in oil seed. Despite the necessity for a lipid-removal clean-up step, the PFE technique facilitated the extraction process by faster extractions and the possibility of automated analysis.

Screening for Organic Phosphorus Compounds in Aquatic Sediments by Liquid Chromatography Coupled to ICP-AES and ESI-MS/MS

The structures of organic phosphorous (P) compounds in aquatic sediments are to a large extent unknown although these compounds are considered to play an important role in regulating lake trophic status. To enhance identification of these compounds, a liquid chromatography (LC) method for their separation was developed. The stationary phase was porous graphitic carbon (PGC), and the mobile phases used in the gradient elution were compatible with both inductive coupled plasma atomic emission spectroscopy (ICP-AES) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). With LC-ICP-AES, eight different P containing peaks could be observed in the P chromatogram indicating that at least eight different P compounds were separated. With the setup of an information dependent acquisition (IDA) with ESI-MS/MS, the mass over charge ( m/ z) of compounds containing a phosphate group (H 2PO 3 (-), m/ z 97) could be measured and further fragmentation experiments gave additional information on the structure of almost 40 separated P compounds, several were verified to be nucleotides. ICP-AES was very suitable in the development of the LC method and allowed screening and quantification of P compounds. The presented LC-ESI-MS/MS technique was able to identify several sediment organic P compounds.

Use of accelerated solvent extraction for determination of ecological important phosphorus in lake sediments

Abstract Phosphorus has been identified as one of the most important elements in eutrophication of lakes, and the bulk of phosphorus compounds stored in lake sediment contribute to a large extent to this process. It is therefore of great interest to get an adequate estimate of the amount of potentially mobile phosphorus for future release from lake sediment. The traditional analytical technique, which is both labour and time consuming, consists of different steps of liquid/solid extractions. The total extraction time for the procedure used today is as long as three days. The recently developed accelerated solvent extraction technique has in this study been applied to effectively extract the mobile forms of phosphorus in sediments. By using a buffered dithionite solution at 25 °C followed by water at 100°C as solvents in sequential extractions, the total extraction process was completed within 90 minutes. The feasibility of using aqueous solutions and water as solvents with this technique is demonstrated h...

Sediment extraction and clean-up for organic phosphorus analysis by electrospray ionization tandem mass spectrometry

A method to prepare NaOH sediment extracts for organic P compound analysis with electrospray ionization tandem mass spectrometry (ESI-MS-MS) was developed on natural samples. Ion exchange, rotary evaporation and mass cut-off filtering proved to be suitable for sample preparation. Samples were analyzed with ESI-MS-MS, and reproducibility and repeatability of the method was calculated. In addition, (31)P-nuclear magnetic resonance spectroscopy ((31)P NMR) was used to measure recovery of different P compound groups such as orthophosphate (Ortho-P), orthophosphate monoesters (Monoester-P), orthophosphate diesters (Diester-P) and pyrophosphates (Pyro-P). The developed sample preparation method resulted in an easy-to-spray liquid for the ESI-MS-MS instrumentation. The overall P recovery was 65% and (31)P NMR showed that Diester-P, possibly in the form of DNA, was apparently lost through the filtering step most likely due to their size. Variances in the total intensities of the MS scans (relative standard deviation (R.S.D.) 35-54%) were for about 50% due to repeated MS runs. Covariances of the peaks in the MS spectra were calculated to be for about 30% due to the sample preparation procedure. Finally, with the ESI-MS-MS approach, 11 peaks in the mass spectra were found likely to represent phosphate containing compounds.