Organic samples, extraction with

Sediment, fish (TAL) Homogenization offish addition of EDTAto sample extraction with hexane centrifugation isolation off organic layer for analysis. GC/AAS 0.01 pg/g (sediment) 0.025 pg/g 81-85 72-76 Chau et al. 1979... 

For identification of other organic rubber compounding ingredients such as waxes, and most antioxidants/antiozonants, sample extraction with diethyl ether, followed by GC-MS of the resulting extract is commonly employed. Examination of volatile species can also provide information on the nature of curatives employed. 

Pressurized fluid Sample extracted with Organic compounds in solid... 

Extraction/deproteinization has been performed by either vortexing liquid samples or homogenizing semisolid samples with acetonitrile (227, 382, 383, 386-392), methanol (14, 393-395), methanol/water mixtures (396-401), ethyl acetate (384,402-406), dichloromethane (379,380,407), and acetone (408,409). Nonpolar organic solvents, such as isooctane (410, 411) and toluene (407), have also been reported to work extremely well for extracting salinomycin and dimetridazole from chicken tissues, respectively. Sample extraction with these nonpolar solvents yields a cleaner extract and an easier workup than extraction with commonly used polar solvents. However, selecting an extraction solvent is critical in establishing an analytical method because it is closely related to the cleanup systems. 

LLE sample extracted with extraction mixture diethyl ether/n-hexane (8 2, v/v) then dried organic residue was reconstituted with 250 [A mixture of 5 mM ammonium formate/MeOH (20 80)... 

Aqueous samples extracted with chloroform chloroform extract further extracted with 1 M HjSO, the acid extract buffered with 0.4 M sodium tribasic phosphate and then pH adjusted between 6 and 7 using NaOH the neutralized extract then treated with chloroform organic layer separated and concentrated benzidine analyzed by HPLC using an electrochemical detector (i.e., glassy carbon electrode). 

A measured quantity of soil, sediment, or solid waste sample extracted with a measured volume of water, aqueous solution pH adjusted to >11 and serially extracted with methylene chloride pyridine partitions into the organic phase, which is then concentrated and analyzed as above. 

The analysis of samples extracted with various solvents will provide information on the most easily removed metal species, the less available, and the most refractory metal content, which is dissolved only by the strongest acid extractants. There are at least a dozen different published speciation schemes for metals in soils and sediments. Many are based on the pioneering work by Tessier et al. [125]. Most include releasing metals from carbonates and hydrous oxides with acids, and an oxidation step to destroy organic... 

Determination of the intact CW agents in urine or blood may proceed by the methods commonly applied to water samples. Extraction with an organic solvent and subsequent cleanup with a Florisil column is a well-established procedure. Rather volatile, scheduled compounds can often be successfully recovered and purified from biological materials by means of dynamic headspace stripping and subsequent adsorption on Tenax tubes these tubes are then subjected to GC/MS analysis. 

Karl-Fischer titration for total H 2O in original sample NH 3 in original sample by Kjeldahl distillation total N2 in original sample by decomposition and Kjeldahl distillation original sample extracted with a saturated NaCI solution in a calibrated vessel infrared spectrum of organic phase from 4 recorded... 

LEE extracting solvent diethyl ether ethyl acetate = 1 1 Sample extracted with extracting solvent. The upper organic layer was then separated and evaporated at 30 °C under nitrogen. Residue then dissolved in mobile phase... 

Sample extracted with diethyl ether dichloromethane = 70 30. Upper organic layer was transferred and evaporated at 40 °C under nitrogen. The residue was dissolved in mobile phase... 

Add NaCl/acetic acid solution to sample extract with toluene add water evaporate organic phase combine aqueous phase with acetonitrile-containing internal standard filter... 

Liquid-liquid partitioning is employed either to extract the analytes from an organic sample extract into an aqueous solution or to wash out interfering substances from the organic or aqueous sample extracts. In general, quinolones are partitioned from chloroform or ethyl acetate sample extracts into alkaline aqueous buffers, to be then back-extracted into the organic solvent under acidic conditions. To remove lipids, sample extracts are often also partitioned with -hexane or diethyl ether. ° ... 

What must a solute s distribution ratio be if 99% of the solut in a 50.0-mF sample is to be extracted with a single 50.0-mF portion of an organic solvent Repeat for the case where two 25.0-mF portions of the organic solvent are used. 

A sample contains a weak acid analyte, HA, and a weak acid interferent, HB. The acid dissociation constants and partition coefficients for the weak acids are as follows Ra.HA = 1.0 X 10 Ra HB = 1.0 X f0 , RpjHA D,HB 500. (a) Calculate the extraction efficiency for HA and HB when 50.0 mF of sampk buffered to a pH of 7.0, is extracted with 50.0 mF of the organic solvent, (b) Which phase is enriched in the analyte (c) What are the recoveries for the analyte and interferent in this phase (d) What is the separation factor (e) A quantitative analysis is conducted on the contents of the phase enriched in analyte. What is the expected relative erroi if the selectivity coefficient, Rha.hb> is 0.500 and the initial ratio ofHB/HA was lO.O ... 

An on-line concentration, isolation, and Hquid chromatographic separation method for the analysis of trace organics in natural waters has been described (63). Concentration and isolation are accompHshed with two precolumns connected in series the first acts as a filter for removal of interferences the second actually concentrates target solutes. The technique is appHcable even if no selective sorbent is available for the specific analyte of interest. Detection limits of less than 0.1 ppb were achieved for polar herbicides (qv) in the chlorotriazine and phenylurea classes. A novel method for deterrnination of tetracyclines in animal tissues and fluids was developed with sample extraction and cleanup based on tendency of tetracyclines to chelate with divalent metal ions (64). The metal chelate affinity precolumn was connected on-line to reversed-phase hplc column, and detection limits for several different tetracyclines in a variety of matrices were in the 10—50 ppb range. 

Recent publications indicate the cloud-point extraction by phases of nonionic surfactant as an effective procedure for preconcentrating and separation of metal ions, organic pollutants and biologically active compounds. The effectiveness of the cloud-point extraction is due to its high selectivity and the possibility to obtain high coefficients of absolute preconcentrating while analyzing small volumes of the sample. Besides, the cloud-point extraction with non-ionic surfactants insures the low-cost, simple and accurate analytic procedures. 

A total of 3 g (0.13 moles) of sodium hydride is added to a solution consisting of 10 g of 17 -hydroxy-5a-androstan-3-one (36 mmoles) in 200 ml of benzene and 10 ml of ethyl formate. The reaction mixture is allowed to stand under nitrogen for 3 days followed by dropwise addition of 10 ml of methanol to decompose the excess of sodium hydride. The solution is then diluted with 300 ml water and the layers are separated. The basic aqueous solution is extracted with ether to remove neutral material. The aqueous layer is acidified with 80 ml of 3 A hydrochloric acid and the hydroxymethylene steroid is extracted with benzene and ether. The combined organic extracts are washed with water and saturated sodium chloride solution and then dried over magnesium sulfate and concentrated. The residue, a reddish-yellow oil, crystallized from 10 ml of ether to yield 9.12 g (83%) of 17 -hydroxy-2-hydroxymethylene-5a-androstan-3-one mp 162-162.5°. Recrystallization from chloroform-ether gives an analytical sample mp 165-165.5° [a]o 53° (ethanol) 2 ° 252 mjj. (g 11,500), 307 m u (e 5,800). 

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