Extraction procedure, efficiency

Microwave extraction realized at 120 °C for 30 min with Hexane -Acetone (3 2 V/V) as the extraction solvent was identified as the most effective extraction procedure for isolation of TPH from biotic matrices. The aim of this research is to develop a silica gel and alumina fractionation procedure for plant sample extraction. Column chromatography with two solvents (chloroform and hexane dichloromethane) as a mobile phase were used for clean-up of extract. In this research the efficiency of recovery received from chloroform as a mobile phase. 

In the second and following passes through the press, water was added to the pulp to increase the efficiency of the extraction procedure. The crude juice was screened to remove the coarse particles. Hydrogen sulfide gas was bled into the collected juice to partially saturate it. 

The separation was carried out on a bonded phase LC-PCN column carrying cyanopropylmethyl moieties on the surface. Thus, in contrast to the extraction process, which appears to be based on ionic interactions with the weak ion exchange material, the LC separation appears to be based on a mixture of interactions. There will be dispersive interactions of the drugs with the hydrocarbon chains of the bonded moiety and also weakly polar interactions with the cyano group. It is seen that the extraction procedures are very efficient and all the tricyclic antidepressant drugs are eluted discretely. 

In contrast to the quantity of solvent 1 used during the reaction, the quantity of extraction solvent 2 (work up) increases during scale up (Laboratory 100% Operation 103%), especially when it is related to substrate 2 (Laboratory 100% Operation 169%). Compared to the yield obtained from the literature protocol in which an extraction procedure is missing, an efficient extraction seems to be important in order to achieve sufficient product accumulation. However, as the mass index and the environmental factor demonstrate with respect to the possibility for reducing the volume of water used (see above), solvent 2 demand should be able to be reduced as well, since less water use means less solvent is required for extraction. StiU, at least the recycle rate of solvent 2 is as high as 72.8% (from 169% to 46%, Table 5.1), regarding the current data of the technical operation scale. 

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. 

Specifically for triazines in water, multi-residue methods incorporating SPE and LC/MS/MS will soon be available that are capable of measuring numerous parent compounds and all their relevant degradates (including the hydroxytriazines) in one analysis. Continued increases in liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/API-MS/MS) sensitivity will lead to methods requiring no aqueous sample preparation at all, and portions of water samples will be injected directly into the LC column. The use of SPE and GC or LC coupled with MS and MS/MS systems will also be applied routinely to the analysis of more complex sample matrices such as soil and crop and animal tissues. However, the analyte(s) must first be removed from the sample matrix, and additional research is needed to develop more efficient extraction procedures. Increased selectivity during extraction also simplifies the sample purification requirements prior to injection. Certainly, miniaturization of all aspects of the analysis (sample extraction, purification, and instrumentation) will continue, and some of this may involve SEE, subcritical and microwave extraction, sonication, others or even combinations of these techniques for the initial isolation of the analyte(s) from the bulk of the sample matrix. 

The extraction efficiencies using a blender and a shaker were compared and both methods gave similar results. A corn sample treated with radiolabeled carfentrazone-ethyl and collected from a metabolism study was used for comparison. Multiple samples can be extracted simultaneously if extraction is performed by shaking. In addition, since the extraction procedures in the residue study closely followed the extraction scheme in the metabolism study, the resulting extraction efficiencies from both studies were almost identical. 

The fundamental issue is to describe how much of the residue can be characterized accurately and whether an accounting of the applied mass of pesticide can be maintained throughout the course of the experiment. A series of environmental fate studies is required for pesticide registration in order to characterize the degradation pathways and formation and decline patterns of each major degradate. These studies are typically conducted in the laboratory under controlled conditions, applying radiolabeled pesticides to evaluate the extraction efficiency of various procedures. When standard extraction methods fail to release a significant amount of the applied radioactivity, more efficient and exhaustive extraction procedures are tried in a stepwise fashion... 

Because the protein analyte is endogenous to the plant, it can be difficult to demonstrate the efficiency of the extraction procedure. Ideally, an alternative detection method (e.g., Western blotting) is used for comparison with the immunoassay results. Another approach to addressing extraction efficiency is to demonstrate the recovery of each type of protein analyte from each type of food fraction by exhaustive extraction, i.e., repeatedly extracting the sample until no more of the protein is detected. " ... 

An efficient and reproducible extraction procedure is mandatory when analyzing agrochemicals in soil. An overview of common soil extraction techniques is given below. 

The efficiency of the extraction procedure was tested using seawater spiked with iron-59, which gave a recovery of 97%, and with stable iron, which gave a recovery of 86%. 

In this method volatile organic matter in seawater is concentrated on a Tenax GC solid adsorbent trap and dry-ice trap in series. The trapped organic material is then desorbed and oxidised to carbon dioxide, which is measured with a non-dispersive infrared analyser. A dynamic headspace method was used for the extraction with the assistance of nitrogen purging. Dynamic headspace analysis [184] is an efficient extraction procedure. The efficiency of extraction... 

Matrix effect is a phrase normally used to describe the effect of some portion of a sample matrix that causes erroneous assay results if care is not taken to avoid the problem or correct for it by some mechanism. The most common matrix effects are those that result in ion suppression and subsequent false negative results. Ion enhancement may lead to false positive results.126 127 Several reports about matrix effects include suggestions on what can cause them and how to avoid them.126-147 While various ways to detect matrix effects have been reported, Matuszewski et al.140 described a clear way to measure the matrix effect (ME) for an analyte, recovery (RE) from the extraction procedure, and overall process efficiency (PE) of a procedure. Their method is to prepare three sets of samples and assay them using the planned HPLC/MS/MS method. The first set is the neat solution standards diluted into the mobile phase before injection to obtain the A results. The second set is the analyte spiked into the blank plasma extract (after extraction) to obtain the B results. The third set is the analyte spiked into the blank plasma before the extraction step (C results) these samples are extracted and assayed along with the two other sets. The three data sets allow for the following calculations ... 

Immunoaffinity procedures have also been developed to selectively extract corticosteroids from different sample matrices. Thus, Seymour et al. demonstrated the higher efficiency of the immunoaffinity methods compared with the conventional extraction procedures using organic solvents [177]. Immunosorbents have also been used for online procedures followed by HLPC-UV [178, 179], HPLC-APCI-MS [179,180], GC-MS [176,181], or capillary electrophoresis [182]. Poly(hydroxyethyl methacrylate) (HEMA) was evaluated as a support material for the anti-dexamethasone antibodies used in IAC. The online IAC-HPLC-MS allowed determination of dexamethasone and flumethasone in equine urine with LODs in the range 3-4 ng mL-1 [180]. The cross-reactivity values obtained in the ELISA and the recoveries of an IAC-HPLC procedure are presented in Table 7. Bagnati et al. developed an immunoaffinity extraction... 

McIntyre et al. [58, 59] conclude that the extraction of polychlorobiphenyls and organochlorine insecticides is most efficient at a total solids concentration of lg L-l, using the extraction procedure described above. The recovery of p,p -DDE from subsamples was always found to be the lowest of the four determinands considered (61.8%), while recoveries of Aroclor 1260, 7-HCH, and Dieldrin from the diluted sample averaged 96.3, 89.4 and 82.9% respectively at lg L-l total solids. 

Keith et al. [36] and Reijnders et al. [37] reviewed applications of gas chromatography-mass spectrometry to sediment analysis. Lopez-Avila et al. [38] investigated the efficiency of dichloromethane extraction procedures for the isolation of organic compounds from sediments prior to gas chromatography-mass spectrometry. The compounds investigated were the 51 priority pollutants listed by the Environmental Protection Agency, USA. 

Particle size reduction makes dissolving procedures more efficient and extracting procedures more accurate because of the improved contact of the solvent with the sample. If accompanied by thorough mixing, particle size reduction also results in more homogeneous samples, which are more representative. 

Matrix effects can influence significantly the extraction efficiency and signal intensity. For heavily contaminated samples such as sewage sludge, this problem is particularly relevant, and therefore the use of internal standards is essential in these applications. Internal standards applied in the extraction procedures for non-ionic surfactants include perinaphtenone [8], 4-fluoro-4,-hydroxyl-benzophenone [5] and 4-bro-mophenyl acetic acid [9]. More appropriate are internal standards from the same compound class butylphenol [10], heptylphenol [11],... 

Extraction Procedure. We modified the extraction procedure of Nelson et al (10). Brie acidified with 2 ml of 5% trichloracetic acid (TCA) was extracted 3 times with 20 ml of petroleum ether. The combined extracts were reduced to 5 ml in a rotating evaporator, returned to the separatory funnel, and combined with 60 ml each of acetonitrile and distilled water. The acetonitrile-water-insecticide mixture was extracted twice with 60 ml of petroleum ether and anhydrous Na2S04 was added to the combined 120 ml extract. The extract was evaporated just to dryness and the residue was dissolved in benzene for analysis by gas-liquid chromatography (GLC). Extraction efficiencies in spiked experiments were 73% (aldrin) and 83% (dieldrin). 

---