Ethyl-acetate extracts

Aminocephalosporanic acid (5.00 g) which passed through a 100-mesh sieve was suspended in boiling ethyl acetate (200 ml), and 2-thienylacetyl chloride (Cagniant, Bull. Soc. Chim. France, 1949,847) (4.42 g, 1.5 equiv.) was added in ethyl acetate (20 ml). The mixture was boiled under reflux for 40 minutes, cooled, and filtered. Aniline (5.03 ml) was added, and after 1 hour the mixture was extracted with 3% sodium hydrogen carbonate solution (1 x 150 ml, 2 X 100 ml, 1 x 50 ml) and the alkaline extracts washed with ethyl acetate (3 x 100 ml). The aqueous solution was acidified to pH 1.2, and extracted with ethyl acetate (2 x 150 ml). The ethyl acetate extract was washed with water (4 x 40 ml), dried (MgS04), and concentrated in vacuo to low volume. The crude 7-2 -thienylacetamidocephalosporanic acid (2.5 g) which separated was collected by filtration. Evaporation of the filtrate gave a further 2.68 g (71%) of the product, which was purified by crystallization from ethyl acetate, then aqueous acetone, MP 150°Cto 157°C (decomp.). 

Two hundred milligrams of the diacetate of (dl)-reg.-1-phenyl-2-dichloroacetamidopropane-1,3-dioi is added to a mixture consisting of 0.25 cc of concentrated nitric acid and 0.25 cc of concentrated sulfuric acid at 0°C. The reaction mixture is stirred until solution is complete, poured onto 25 g of ice and the mixture extracted with ethyl acetate. The ethyl acetate extracts are evaporated under reduced pressure and the diacetate of (dl)-reg.-l-p-nitrophenyl-2-dichloroacetamidopropane-1,3-diol so produced purified by recrystallization from ethanol MP 134°C. 

K Fe(CN)6 oxidation Compound F is stoichiometrically inactivated by oxidation with K.3Fe(CN)6 (Shimomura and Johnson, 1967) thus, it is possible to estimate the molecular extinction coefficient (e) of the 388-390 nm absorption peak by titrating F with K.3Fe(CN)6- The e value obtained by the titration in 50% ethanol was 15,400 (assuming the reaction to be one-electron oxidation) or 30,800 (assuming two-electron oxidation). Two other methods of lesser precision were used to determine the true s value 1) the dry weight of the ethyl acetate extract of an acidified solution of F gave an e value of 14,100 2) the comparison of NMR signal intensities gave a value of 11,400 2,000 in water (H. Nakamura, Y. Oba, and A. Murai, 1995, personal... 

When a photoprotein solution (1.3 ml) was shaken with ethanol (0.7 ml) containing one drop of concentrated HC1 and then the mixture was extracted twice with 2 ml each of ethyl acetate, about 75% of the chromophore was extracted into the ethyl acetate extract. The chromophore isolated showed an absorption peak at 398 nm in neutral methanol (Fig. 10.2.5). The isolated chromophore was practically non-fluorescent, like the native photoprotein. However, the acidification of a methanolic solution with HC1 resulted in a sharpening and two-fold increase of the 398 nm absorption peak, accompanied by the appearance of fluorescence. In aqueous 0.1 M HC1, two fluorescence emission peaks (595 nm and 650 nm) were found, together with a corresponding excitation peak (400 nm). Treatment of the 398 nm absorbing chromophore with 0.1 M NaOH resulted in a rapid loss of the 398 nm absorption peak. Dithionite did not affect the 398 peak, suggesting that the chromophore does not contain Fe3+. 

The methods EN 1528 1996 and EN 12393 1998 comprise a range of old multiresidue methods of equal status, which are widely accepted throughout Europe. These are, e.g., the Luke method and the German Deutsche Forschungsgemeinschaft (DFG) methods S8 and S19 ° (all based on extraction with acetone), the Association of Official Analytical Chemists (AOAC) method 970.52 (using acetonitrile extraction and liquid-liquid partition combined with Horisil column cleanup) and the Dutch ethyl acetate extraction combined with GPC. All methods have been subjected to inter-laboratory studies, although not with all pesticide/matrix combinations, which would be impossible to achieve. 

Each individual method collection comprises a large number of methods, which often have different validation statuses. For instance, the most important Swedish multi-residue method (based on ethyl acetate extraction, GPC and GC) is validated for many pesticides by four laboratories, but other methods are presented with singlelaboratory validation data. Some methods in the Dutch and German manuals were tested in inter-laboratory method validation studies, but others by an independent laboratory or in a single laboratory only. 

T. Pihlstrom, B- Kajrap, and A. Valverde, ValidationdataforlSpesticidesincludedinthemulti-residue method for analysis of pesitddes in fruit and vegetable using ethyl acetate extraction, GPC cleanup and GC determination, in Pesticide Analytical Methods in Sweden , Part 1, Rapport 17/98, National Food Administration, Uppsala (1998). 

Methylation of the residues of the ethyl acetate extract prepared in Section 6.2.1 should immediately be performed with trimethylsilyldiazomethane, because bispyribac is unstable under acidic conditions. 

Obana et alP reported a modified ethyl acetate extraction which used a super absorbent polymer instead of sodium sulfate to absorb water. Eollowing cleanup by carbon-based SPE and/or gel permeation chromatography (GPC), recoveries in excess of 70% were achieved for the majority of the 107 pesticides of interest in asparagus, orange, potato and strawberry. The super absorbent polymers are now being incorporated into ASE procedures. 

Pass the solution derived from Section 6.2.2 through a Cig cartridge (conditioned prior to use successively with 5mL of acetonitrile and 10 mL of water), then elute interfering substances with 15 mL of acetonitrile-water (3 17, v/v) and discard the eluate. Elute imibenconazole-debenzyl with 20 mL of acetonitrile-water (2 3, v/v) and collect the eluate in a 100-mL separatory funnel (imibenconazole-debenzyl fraction). Elute imibenconazole with 20 mL of acetonitrile-water (17 3, v/v) and collect the eluate in a 100-mL separatory funnel (imibenconazole fraction). Add 30 mL of 20% sodium chloride aqueous solution and 40 mL of ethyl acetate to each separatory funnel and shake the funnel with a mechanical shaker for 5 min. Collect the ethyl acetate extract, dry the extract with anhydrous sodium sulfate and transfer into a 100-mL round-bottom flask. Concentrate the ethyl acetate extract to near dryness by rotary evaporation and dry with a stream of nitrogen. Dissolve the residue of each fraction in acetone for gas chromatographic determination as in Section 6.3. 

At the termination of the activity period, each participant s hands were held over a bowl and doused with 250 mL of a dilute dioctyl sodium sulfosucci-nate (anionic surfactant) mixture. This soap wash was followed by a 250-mL rinse with deionized water. The soap and water fractions were stored together in the same container. Fifteen grams of sodium chloride were added to the container to facilitate phase separation. The chlorpyrifos was partitioned with 200 mL of ethyl acetate, which was also used to rinse the bowl. The ethyl acetate extract was later analyzed for chlorpyrifos content. The amount of test substance removed was used to assess adult hand exposures and dose and also to assess the theoretical amount of test substance removed when children put their hands in their mouths. 

During rotary evaporation of solvent (from an ethyl acetate extract of a fermentation culture) at 55°C/50 mbar, the flask exploded. (It seems likely that some unsuspected peroxidised material may have been present in the extract, or perhaps the flask was scratched or cracked, and imploded [1].) Several fires and explosions suggest that ethyl acetate may be a worse generator of static electricity than its measured conductivity would indicate [2],... 

The 3,4-dihydrodiol is a major component of the free dihydrodiols formed in mouse skin maintained in short-term culture (28). The optical purities of these dihydrodiols were determined by a CSP-HPLC method (43). The metabolic fates of the enantiomeric DMBA 3,4-dihydrodiols are not yet known. Studies in our laboratory indicate that the products formed in liver microsomal metabolism of DMBA 3,4-dihydrodiol bind extensively to the components of liver microsomes and the expected 1,2,3,4-tetrols of DMBA were not detected in the acetone/ethyl acetate extract of the incubation mixture (unpublished results). It is known that these products bind extensively to DNA... 

Extraction of nalidixic acid with chloroform from utine has also been reported.(40) Another fluorimetric method for chicken liver and muscle containing not less than 100 ppb nalidixic acid was reported by Browning(9) using an ethyl-acetate extraction and alumina column to retain the nalidixic acid. The fluorescence was measured at 325/408 nm. 

Sample extracted with ethyl acetate, extract GC-FID... 

The supernatant was first extracted with dichloromethane (2 x 3 L) to eliminate the remaining IMI. The aqueous fraction was then extracted with ethyl acetate (3 L). The ethyl acetate extract, containing 5-hydroxy IMI, wais dried with 30 g anhydrous sodium sulfate and concentrated to about l/20th of the original volume in a vacuum rotary evaporator and then filtered with 0.22 pm pore size ultrafiltration membranes. The filtered solution was evaporated again until white crystals were produced. The crystals were filtered, washed twice with dichloromethane and then dissolved in 10 mL acetonitrile by heating. At 4 °C, the 5-hydroxy IMI crystallized from the above solution and was filtered and dried under vacuum. A total of 413 mg of 5-hydroxy IMI was obtained. 

Methanolic and ethyl acetate extracts of the fungus had low activity against a battery of Gram-positive and Gram-negative bacteria, but the isolated compound was not shown to be the active component. 

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