Evaporation residue, determination

A 50-g soil sample is homogenized with 200 mL of water (if the solution pH is <6, adjust to pH 6-8 using 1M NaOH). A 100-mL aliquot portion of the soil/water supernatant is extracted with a 2-g Cig cartridge followed by a 5-g Cig cartridge and the eluate is evaporated to dryness. The residue of trinexapac is dissolved in 4 mL of water-phosphate buffer (pH 7)-ACN-TBABr (90 5 5 0.3). Residue determination is performed using HPLC/UV with a two-column switching system. 

The hot extraction method is a variation of this procedure. The aqueous pigment suspension, prepared as above, is refluxed for a certain time, usually 5 minutes, cooled rapidly, and filtered. A known amount of extract is then dried by evaporation and the weight of the residue determined, or the extracted pigment weighed and the dissolved portion determined by calculating the difference. 

Deproteinization with hydrochloric acid and MeCN was reported for OTC, TC, and CTC residue determination in milk samples. The filtrate was extracted with hexane and dichlorometh-ane, followed by partial evaporation of the aqueous layer. An addition of f-butyl alcohol to the aqueous layer during evaporation prevented foaming and bumping. Recoveries greater than 90% were achieved, and TCs were separated using the ion-pair chromatographic system (48). 

Perhydropyrido[l,2-a]pyrimidin-4-one 349 was prepared by first reacting pyrido[l,2-a]pyrimidin-4-one 347 with methyl iodide in acetone in a sealed tube at 150°C for 24 hours, then dissolving the evaporated residue in methanol, and treating the methanolic solution with sodium borohydride (81USP4291036). Perhydro derivative 349 was isolated as its hydrochloride salt. The stereochemistry of the product was not determined. 

To check for completeness of extraction, add 20 mL of dichloromethane to the column, and collect the eluate in a second tared flask. Evaporate the contents of the second flask to dryness, and examine it for residue. Determine the weight of the residue (IVR1), if present. If residue is present, repeat the procedure with an additional 20 mL of dichloromethane. 

The povidone remains in the aqueous phase and can then be determined by the general method. Ethyl papaverine and diphenhydramine hydrochloride can be extracted with cyclohexanol from the alkaline aqueous solution monophenylbutazone can be extracted from neutral aqueous solutions with the same solvent. Phenyldimethylpyrazolone can be removed from alkaline aqueous solutions by extraction with chloroform. Unlike povidone, starch is insoluble in methanol. The evaporation residue of a solution containing starch and povidone is therefore treated with methanol povidone can then be determined by the general method in the methanolic solution after filtration. 

The total quantity of all substances (the sum of all dissolved and suspended solids) present in water is determined by evaporation of a water sample, drying of the evaporation residue at 105°C to a constant weight and weighing of the dry residue. Dissolved and suspended solids are separated (mostly by filtration) and the quantity of dissolved solids is then determined according to the amount of dry residue of the filtrate. 

X 0.5mL/g tissue). The hexane wash is discarded. The aqueous methanol phase is dried by nitrogen stream (1-3 g samples) or by rotary evaporation (larger samples). The resulting residue is suspended in water (1.0 mL/g tissue) and extracted with chloroform (3 x 0.5 mL/g tissue). The water phase is discarded and the chloroform phase is dried under a stream of nitrogen or by rotary evaporation. Residue weight is determined for successive steps in the protocol. 

DIN 53172, Solvents fm paints and varnishes determination of evaporation residue, 1993. 

Matter extractable by diethyl ether from plasticized cellulose acetate has been normal-lized. " Two grams of plasticized cellulose acetate is extracted in Soxhlet apparatns for 3 h the solvent is evaporated and the residue determined gravimetrically. 

Qualitative spectral analysis of the evaporation residue in order to confirm the presence of toxic heavy metals in relevant concentrations. If appropriate, the heavy metals detected must be determined quantitatively in the seepage water extracts. 

The procedure for determining the evaporation residue is the same as for the determination of the total residue, with the exception that a filtered water sample is used. Take a sufficiently large volume of the filtered sample to provide an evaporation residue of at least 20 mg but not more... 

Tranquillizers and beta-blockers are important potential contaminants in edible tissues, particularly of pigs, where they may be used to counteract the stress susceptibility of some breeds during transport, which results in poor quality meat and even mortality. Some of these substances are prohibited for use in food-producing animals while others have MRL values set. A simple method for seven of these compounds (azaperol, azaperone, carazolol, chlorpromazine, acepromazine, propionylpromazine, xylazine) involves extraction of kidney or muscle samples with acetonitrile, modification of the extract with a sodium chloride solution (10%), and SPE on an Oasis Hlb cartridge. The eluate (acetonitrile) is evaporated, reconstituted in aqueous acetonitrile, and residues determined by LC-MS/MS, with atmospheric pressure chemical ionization. Two additional steps are incorporated into this method to increase the numbers of sample extracts that may be analyzed without affecting the mass spectrometer source first, an inline column (Biomatrix ) is used ahead of the analytical column to remove any macromolecules in the sample extracts and, second, a switching value is... 

Combine all of the aqueous layers and determine the pH with pHydrion paper. Adjust the pH to approximately 7 with either solid sodium carbonate or 3 M HCl. Flush all filtrates down the drain. Pour the recovered diethyl ether and the heptane in a container for nonhalogenated organic liquids. Spread the sodium sulfate and the alumina on a tray in the hood to evaporate residual solvent, and then put them in the container for nonhazardous solids. 

The thiocyanate test for iron fails or is unreliable when applied to concentrated nitric acid (or after the latter has been diluted). The thiocyanic acid is oxidized and yields orange ether-soluble decomposition products. The usual procedure for testing concentrated nitric acid for traces of iron for their colorimetric determination has been to evaporate 7 ml of the acid, take up the evaporation residue in dilute hydrochloric acid, oxidize with persulfate, and then apply the thiocyanate reaction. The rapid procedure given here is based on the production and fixing of hydrous ferric... 

The residue on evaporation is the percentage by weight of the oil that remains after evaporation when determined in a heat-resistant glass-evaporating basin. 

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