Water minimization data extraction

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

In this paper we present for the first time a test that combines heat extraction and heat injection pulses in one experiment. It is expected that differences in the ground thermal conductivity, when different data windows are used to obtain an estimate, can be related to advection and convection of ground water. The real ground conductivity should be derived from the experimental data where the response is close to or lower than the natural ground temperature, minimizing effects of advection and convection. First results, for a case of no ground water flow, show that estimates of ground thermal conductivity are very comparable for the different data windows. 

Preparation of Apple CWM and AIR and Extraction of Pectin Fractions. Apples ( Granny Smith variety) were cored and peeled and the resulting pulp (2 kg batches) was stored in ethanol suspension to minimize enzymic oxidation. Separate batches of pulp were processed, as described for carrot preparations, to furnish apple CWM (32.5 g) and apple AIR (39.8 g) for which analytical data are recorded in Table VI. Polysaccharide fractions B (4 g) and C (2.5 g) were extracted from CWM with water at 80° and aqueous 1% ammonium oxalate at 80°. Likewise polysaccharide fractions A (2.1 g), B (5.2 g), and C (4.5 g) were Isolated from AIR by extraction with water at room temperature, 80°, and with aqueous 1% ammonium oxalate... 

The addition of Na2C03 serves the dual purpose of stopping the reaction and maximizing the fluorescence of the product, MU, as described above. The initial levels of fluorescence in the extract (at time=0) are often largely contributed by the traces of pre-hydrolyzed substrate (i.e., methyl umbelliferone) in commercial substrate preparations, or coumarins in the extract. It should be pointed out, in fact, that the GUS produced by one transformed plant cell can easily be measured using unpurified commercial MUG and a relatively low-tech fluorimeter (Jefferson et al., unpublished data). To minimize the levels of zero-time fluorescence (the MU in the MUG) the solid stocks of MUG should be kept frozen and dessicated, and the bottle not opened when it is still cold (condensation of water from the air will stimulate hydrolysis in the bottle). The MUG in extraction buffer is fine in the refrigerator for a couple of weeks, but will eventually begin to show increased fluorescence. 

Thirteen urinary anabolics and corticoids (e.g., cortisone, 11-ketotestosterone, hydroxyprogesterone, epitestosterone, androstenolone) and synthetic anabolics (bolderone, bolasterone) were extracted from urine and analyzed on a C g column X = 200 nm) and 245 nm) using a 60/40 water/acetonitrile mobile phase [1507]. Baseline resolution was not achieved for all compounds and elution was complete in 24 min. Calibration data for each compound were generated from 2 to 10 (ig/mL. Detection limits were reported as 0.05 (ig/mL. It is interesting to note that the authors used an optimization triangle approach to maximize resolution and minimize analysis time. For 10 of the compounds, a <20 min analysis was achieved using a 56.7/20/13.3/10 water/methanol/acetonitrile/THF mobile phase. 

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