Comparison with solvent extraction experiment

Validation of true extraction efficiency normally requires the identification and quantitation of field-applied radiolabeled analyte(s), including resulting metabolites and all other degradation products. The manufacturer of a new pesticide has to perform such experiments and is able to determine the extraction efficiency of aged residues. Without any identification of residue components the calculation of the ratio between extracted radioactivity and total radioactivity inside the sample before extraction gives a first impression of the extraction efficiency of solvents. At best, this ratio is nearly 1 (i.e., a traceability of about 100%) and no further information is required. Such an efficient extraction solvent may serve as a reference solvent for any comparison with other extraction procedures. 

At first, the reaction was investigated in batch mode, by use of different ionic liquids with wealdy coordinating anions as the catalyst medium and compressed CO2 as simultaneous extraction solvent. These experiments revealed that the activation of Wilke s catalyst by the ionic liquid medium was clearly highly dependent on the nature of the ionic liquid s anion. Comparison of the results in different ionic liquids with [EMIM] as the common cation showed that the catalyst s activity drops in the order [BARF] > [Al OC(CF3)2Ph 4] > [(CF3S02)2N] > [BFJ . This trend is consistent with the estimated nucleophilicity/coordination strength of the anions. 

In this chapter, Section 10.2 gives an overview of the operation of the Argonne centrifugal contactor. Section 10.3 focuses on the design principles for this contactor. Section 10.4 discusses the worldwide applications of this contactor to solvent-extraction processes of interest to the nuclear and other industries. Comparisons with other types of contactors are made throughout the text, and a separate section is devoted to them in Section 10.4. However, because of their widespread use and the author s particular experience with them, the ANL contactor and its variations remain the primary focus. 

As an extraction technique, SFE proved to give comparable recoveries to those of Soxhlet extraction. In all cases, SFE dramatically shortened extraction times and minimized most environmental hazards, solvent concentration steps, and waste disposal costs. A summary of this comparison is included as Table XII and is a projected cost comparison of SFE to Soxhlet extraction, based on our experiences with the SFE system used in these studies (Isco SFE System 1200). The projected cost per extraction was determined to be 15.85(SFE) vs. 22.60(Soxhlet). 

The recovery experiment carried out for this assay resembles somehow the sum of two potential effects The loss of compound during the sample preparation process (in this case on-line extraction) and a potential matrix effect during sample analysis. However, since an online sample clean up procedure is used here, these two potential effects cannot be separated in the usual way (One experiment would be the comparison of a processed spiked plasma sample with a blank plasma sample spiked post sample processing in order to determine the recovery of the sample preparation step. In a second experiment, again a processed blank plasma sample would be spiked post processing and the result would be compared with the response of a spiked solvent sample in order to reveal a potential matrix effect during analysis). 

The use of supercritical CO2 to extract AR from cereal material was only recently presented (49). Pure supercritical CO2 was not able to extract AR even at pressures as high as 35 MPa and SS C. This result was attributed to the amphiphilic character of the AR and the non polar character of the supercritical CO2. With the addition of 10% of ethanol or methanol, it was possible to obtain extracts even at near the critical pressure (8 MPa). The optimal pressure was determined to be 3SMPa at S5°C when ethanol or methanol acted as co-solvent. The co-solvent was added as 10%wAv of the CO2. The CO2 flow was kept constant at Sg/min during the experiments. A comparison of the supercritical CO2 extraction with die addition of ethanol and classical extraction methods was made. For the classical method, pure acetone extraction at O.IMPa and 20°C was used. Between 15 and 30 MPa at 55°C, 8 to 80%w/w higher yields of AR crude extracts for the extraction with supercritical CO2 with co-solvents were obtained than for pure acetone extraction (refer to figure 2). However, the HPLC analysis of the extracts showed similar composition (49). 

Pilavakis (20, 29) investigated the esterification of methanol by acetic acid in a packed column. He assumed the reaction to be pseudo-first-order with respect to either methanol or acid over certain specified concentration ranges and incorporated the effect of heat of reaction not only in the enthalpy balances but also in the flux equations. The column was calculated by numerical solution of a set of differential equations. The top product was an azeotropic mixture of methanol and ester which could, however, be broken by introduction of acetic acid high up in the column rather than further down as a mixed feed with methanol. Consequently, in practice such a column will consist of a rectifying section, an extractive distillation section with acetic acid as the extractive solvent and a distillation reactor section. Good agreement was obtained between theory and experiment which, however, suffered from the fact that the hold-up of liquid in the column was small in comparison to the reboiler hold-up so that most of the reaction occurred in the latter location. 

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