Chloroform, as extractant

Fig, 13,5 Schematic diagram of changes in resin content and bittering value of hops during storage.Conductometric analysis using chloroform as extractant — Conductometric analysis using toluene as extractant Polarimetric analysis. 

Sodium acetate reacts with carbon dioxide in aqueous solution to produce acetic anhydride and sodium bicarbonate (49). Under suitable conditions, the sodium bicarbonate precipitates and can be removed by centrifugal separation. Presumably, the cold water solution can be extracted with an organic solvent, eg, chloroform or ethyl acetate, to furnish acetic anhydride. The half-life of aqueous acetic anhydride at 19°C is said to be no more than 1 h (2) and some other data suggests a 6 min half-life at 20°C (50). The free energy of acetic anhydride hydrolysis is given as —65.7 kJ/mol (—15.7 kcal/mol) (51) in water. In wet chloroform, an extractant for anhydride, the free energy of hydrolysis is strangely much lower, —50.0 kJ/mol (—12.0 kcal/mol) (51). Half-life of anhydride in moist chloroform maybe as much as 120 min. Ethyl acetate, chloroform, isooctane, and / -octane may have promise for extraction of acetic anhydride. Benzene extracts acetic anhydride from acetic acid—water solutions (52). 

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. 

A solution of 18 g of 2-thienyl bromide in 30 ml of tetrahydrofuran Is gradually added to a mixture of 2.6 g of magnesium and 80 ml of tetrahydrofuran under stirring at 50°C. The mixture is stirred for 5 hours at room temperature until the magnesium is entirely dissolved in the solution. 6.2 g of methyl N-methyl-5-methoxy-nipecotinate are added to the mixture. Then, the mixture is refluxed for 4 hours. After the reaction Is completed, tetrahydrofuran is distilled off under reduced pressure. An aqueous ammonium chloride solution is added to the residue, and the solution is extracted with chloroform. The extract is dried and then evaporated to remove chloroform. The viscous oil thus obtained is recrystallired from a mixture of benzene and ether. 7 g of di-(2-thienyl) -(N-methyl-5-methoxy-3-piperidyl)-carbinol are obtained as crystals. Melting point 142°C to 146°C. 

If copper is known to be absent or present only in negligible proportions, dilute the solution with water to 50 mL in a graduated flask, and continue as detailed below. Otherwise, transfer the solution to a small separatory funnel and add 5 mL of the diethylammonium diethyldithiocarbamate in chloroform reagent (diluted 1 20 with chloroform when required). Shake and run off the chloroform layer, extract the aqueous layer with successive 1 mL portions of the reagent until the chloroform layer is colourless finally, wash the aqueous layer with a few mL of chloroform. Dilute the aqueous solution with water to 50 mL in a graduated flask. 

The two-phase titration is based on the reaction of anionic surfactants with cations—normally large cationic surfactants—to form an ion pair. The preferred cationic is benzethonium chloride (Hyamine 1622, 1) because of the purity of the commercially available product. On neutralization of the ionic charges, the ion pair has nonpolar character and can be extracted continuously into the organic phase, e.g., chloroform, as it is formed. The reaction is monitored by addition of a water-soluble cationic dye, dimidium bromide (2), and a water-soluble anionic dye, disulfine blue (3). The cationic dye forms an extractable... 

TLC spectrophotometry is used to determine zirconium in Mg-Al alloy. For this purpose, the alloy sample (2 g) is dissolved in HNO3 (20 ml, 6 M), and zirconium is extracted in 6 ml of 0.02-M diantipyrilmethane (DAM) solution in chloroform. The extract was concentrated to 0.4 ml and an aliquot (10 p,l) was chromatographed on silica gel LS plate using 4-M HCl -f dimethylformamide (1 2) as the mobile phase. After development, the portion of the sorbent layer containing the zirconium-DAM complex was removed, and the metal was extracted with 6-M HCl. The zirconium present in this solution was determined in the form of a xylenol orange complex (Amax, 540 nm) by spectrophotometry [22]. 

In other experiments, PVC/plasticiser extracts (n-hexane) were separated by SEC using THF or chloroform as the mobile phase. Similarly, PE film was immersed in THF for several hours and the extract was concentrated by a factor of 20 prior to injection into a SEC system [51]. However, use of extraction techniques followed by injection into a SEC system for separation of low-MW additives is not the most obvious analytical approach in view of the relatively low resolution of conventional SEC in the low molecular mass range. For this purpose efficient column packing materials with small pore sizes are to be used. 

Nickel has been determined spectrophotometrically in seawater in amounts down to 0.5 xg/l as the dimethylglyoxime complex [521,522], In one procedure [521] dimethylglyoxime is added to a 750 ml sample and the pH adjusted to 9 -10. The nickel complex is extracted into chloroform. After extraction into 1M hydrochloric acid, it is oxidised with aqueous bromine, adjusted to pH 10.4, and dimethylglyoxime reagent added. It is made up to 50 ml and the extinction of the nickel complex measured at 442 nm. There is no serious interference from iron, cobalt, copper, or zinc but manganese may cause low results. 

Aliphatic amines have been determined by a number of methods. Batley et al. [290] extracted the amines into chloroform as ion-association complexes with chromate, then determined the chromium in the complex colorimetri-cally with diphenylcarbazide. The chromium might also be determined, with fewer steps, by atomic absorption. With the colorimetric method, the limit of detection of a commercial tertiary amine mixture was 15ppb. The sensitivity was extended to 0.2 ppb by extracting into organic solvent the complex formed by the amine and Eosin Yellow. The concentration of the complex was measured fluorometrically. Gas chromatography, with the separations taking place on a modified carbon black column, was used by Di Corcia and Samperi [291] to measure aliphatic amines. 

Indium, cadmium and silver can be extracted into chloroform as their 8-hydroxyquinoline complexes, and the pH1/2 values for these metals are 2.1, 6.3 and 8.8 respectively. Plot a graph of theoretical percent extraction against pH over the range 0 to 9 for each metal. Deduce the pH of incipient extraction (0.01%) and complete extraction (99.99%) for each metal, and comment on the feasibility of separating each from the other assuming that all the distribution coefficients are sufficiently high. 

Shearken (1968) adopted a modified method of assay by using chloroform as an extracting medium, but instead of the carbonyl band measured the N—H stretching band at 3436 cm-1. However, this particular method essentially requires the complete removal of both water and ethanol the latter is present in CHC13 as a stabilizer which is required to be eliminated completely to avoid interference from O—H stretching bands. To achieve this objective activated alumina columns have been used extensively. However, Zappala and Post... 

Example 4 Cl- ion serves as an appropriate anion that favourably combines with many aromatic amines and alkaloids which may ultimately be extracted from the corresponding aqueous solutions into chloroform as their respective chlorides. ... 

In the past, minor releases may have resulted from the use of consumer products (e.g., certain air deodorizers and cleaning products) that contained chloroform as a component or residual product (Bayer et al. 1988 Wallace et al. 1987a). Chloroform is widely used in laboratory work as an extractant. It is also still used in certain medical procedures, such as dental root canal surgeries (McDonald and Vire 1992), and in combination with aspirin as an experimental treatment for serious cases of herpes zoster (King 1993). These medical uses are extremely limited and would contribute very minor amounts of chloroform as releases to the air. 

Early in 1970, Few et al. [10] radiolabelled polystyrene particles for a mucociliaiy clearance study. The radiolabelled aerosols were produced by a spinning-disk generator. The technique involves the key steps of extracting sodium pertechnetate (Na " Tc04) into chloroform as tetraphenylarsonium pertechnetate, followed by evaporation of the chloroform. A solution of polystyrene is added to the radioactive residue and dispersed Scheme 1). This technique has subsequently been adopted by... 

The bomb tubes are returned to the dry ice-acetone bath. After cooling thusly, the tubes are drawn out to a fine capillary to allow the ammonia to escape, and the entire reaction mixture is immediately collected in an excess of dilute HCl acid solution. Evaporate the acidic solution to dryness on a steam bath, desiccate the residue, and extract in a soxhlet extractor for 12 hours using chloroform as the solvent (dry chloroform) and taking care to exclude all H2O. Distill off the chloroform and if separation is not important to you, then you can use the combination of all three amines in a synthesis calling for any one of the three. 

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