Diuron extraction from soil using

Diuron from soil Diuron spiked Tama soil was the extraction example used in the six vessel multi-vessel extractor. As is illustrated in Table III, the average recovery for these samples was 97.3% and the relative standard deviation was 6.6%. When these results are compared to those obtained with the classical extraction techniques, equivalent recoveries were achieved. However, the precision associated with the classical extraction was typically 20%. Acceptable recovery ranges in classical residue analysis are from 70 to 125%. Comparing these precisions with those obtained with a one vessel SFE device, the... 

Cumulative Results for the Extraction of Freshly Spiked Diuron From Tama Soil Using the Multi-vessel Extractor... 

The density stepping method was then run on a spiked soil sample. Five grams of soil were spiked with the same solution of herbicide standards used to spike the celite sample and the solvent was allowed to evaporate. The spiked sample was then placed into an extraction thimble and extracted. The results were different than those obtained from the spiked celite. Even at a high density of C02 the herbicides were not extracted. Previous experience showed that using water as a modifier aided in the extraction of diuron from soils (6)(7). Therefore 1 ml. of water was added to the spiked soil and the sample rerun at a density of 0.9 g/ml of C02. The results showed a significant increase in recovery of the herbicides with the addition of water. This demonstrates that the addition of a modifier added to the extraction cell can have a significant effect upon the extraction recoveries (8)(9). The results are summarized in Table VIII. 

A limitation to the use of modifiers in SFC has been the detector compatibility of the specific modifier. For example, most modifiers (i.e. methanol) provide a flame ionization detector response preventing use at a large concentration. In SFE, however, this limitation does not exist since modifiers can be used in a mixed mode with CCb and the sample. Figure 1 (taken from reference 25) shows an example of the use or modifiers in SFE. Here the comparison of extraction efficiencies obtained using CO and CO2 modified with methanol is shown. The matrices extracted in these SFE experiments were an XAD-2 sorbent resin and soils. The target analytes were dibenzo[a,i]-carbazole, diuron, 2,3,7,8-tetrachorodibenzo-p-dioxin (TCDD) and linear alkylbenzenesulfonate (LAS) detergent. For each of these respective analytes the extraction efficiency increased dramatically with the use of C02/methanol modifier compared to pure CO2 only as the extracting fluid. This was even the case for the ionic compounds namely, the linear alkylbenzenesulfonates (LAS), which were quantitatively recovered. 

The separation of Diuron using the Pye 104 chromatographic is shown in Fig. 9.10 and, although greater sensitivity was obtained compared with the much older Perkin-Elmer instrument, both gave satisfactory results with adequate sensitivity. The response due to 0.04ng of Diuron is shown in (a), together with that from a soil extract (b) and a recovery on the same soil (c). 

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