Extraction of boron

Transfer a suitable aliquot of the filtered water sample to a separating funnel and adjust to pH 1 with hydrochloric acid 1 + 1. Treat with 20 ml of 20 % 2-ethyl-l,3-hexanediol solution in MIBK and shake for 1 minute following separation of the phases, drain off the aqueous phase into a second 

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Mahler, R.L., Naylor, D.V. and Frederickson, M.K. (1984) Hot water extraction of boron from soils using sealed plastic pouches. Communications in Soil Science and Plant Analysis 15, 479-A92. 

Abreu, C.A. de, Abreu, M.F. de, Raij, B. van and Bataglia, O.C. (1994) Extraction of boron from soil by microwave heating. Commun. Soil Sci. Plant Anal., 25, 3321-3333. 

COMPARISON OF CONTINUOUS ULTRASONIC-ASSISTED LEACHING AND MANUAL LEACHING FOR THE EXTRACTION OF BORON FROM SOIL SAMPLES ... 

Before its determination, boron is normally separated either as volatile trimethyl borate or by other methods. Carminic acid solutions in cone. H2SO4 and glacial CH3COOH were added directly to the chloroform extract of boron with 2,2,4-trimethyl-1,3-pentanediol [15]. 

The first steps in the extraction of boron from borax are its conversion to boric acid (equation 12.1) and then to the oxide (equation 12.2). 

Following extraction of boron with a solution of 2>ethyl-l,3-hexanediol in methyl isobutyl ketone, boron may also be determined in the organic solution by atomic-absorption spectrophotometry... 

Sometimes a preliminary extraction of boron with organic reagent is necessary for improving the selectivity as well as the use of a specific resin. 

A brief discussion of the necessary steps from sample collection to data collection affords an opportunity to present basic chemical principles applied to the boron isotope paleo-/ H proxy. While extraction of boron from samples is the first step in the procedure, it is useful to discuss the mass spectrometry first, as the extraction method is different for the various mass spectrometric methods used. 

Bromo-4-methoxy-A-homo-estra-2,4,5(10)-trien-17-one (44 0. 2g), is dissolved in formic acid, 2 ml of boron trifluoride etherate is added and the mixture is stirred vigorously at 0° for 2 hr. A brown mass ca. 0.12 g) is obtained after evaporation of the solvents at reduced pressure. This material is diluted with water and extracted with chloroform. The chloroform extracts are washed successively with water and saturated salt solution, dried over anhydrous magnesium sulfate and evaporated at reduced pressure to give 95 mg of a product which is purified by filtration through a column of neutral alumina and crystallization of the residue after evaporation of the solvent from ethyl acetate-petroleum ether. The resulting A-homo-estra-l(10),2,4a-triene-4,17-dione (45), mp 143-146°, is identical to the tropone (45) prepared from monoadduct 17-ketone (43a). 

A solution of 3 g of the nitrile, water (5 moles per mole of nitrile), and 20 g of boron trifluoride-acetic acid complex is heated (mantle or oil bath) at 115-120° for 10 minutes. The solution is cooled in an ice bath with stirring and is carefully made alkaline by the slow addition of 6 A sodium hydroxide (about 100 ml). The mixture is then extracted three times with 100-ml portions of 1 1 ether-ethyl acetate, the extracts are dried over anhydrous sodium sulfate, and the solvent is evaporated on a rotary evaporator to yield the desired amide. The product may be recrystallized from water or aqueous methanol. Examples are given in Table 7.1. 

The following procedure is given in U.S. Patent 3,458,528 78 grams (0.675 mol) of 5-nitroimidazole is dissolved in 1,500 ml of acetic acid upon the addition of 72 ml (0.57 mol) of boron trifluoride etherate. 175 ml (3.5 mols) of ethylene oxide in 175 ml of hexane, in a dropping funnel topped with a cold finger, is added slowly over 1 hour to the above solution maintained at 32° to 35°C with a water cooling bath. The mixture is concentrated under high vacuum to 100 to 150 ml volume. The residue is diluted with 500 ml of water, neutralized to pH 7 with aqueous sodium hydroxide, and extracted with 1.5 liters of ethyl acetate. The extract is dried and evaporated to yield 1-(2 -hydroxyethyl)-5-nitroimidazole. 

Discussion. The method is based upon the complexation of boron as the bis(salicylato)borate(III) anion (A), (borodisalicylate), and the solvent extraction into chloroform of the ion-association complex formed with the ferroin. 

The method has been applied to the determination of boron in river water and sewage,16 the chief sources of interference being copper(II) and zinc ions, and anionic detergents. The latter interfere by forming ion-association complexes with ferroin which are extracted by chloroform this property... 

To a stirred — 78 C solution of 5.85 mL (62.5 mmol) of 3-methoxy-l-prnpene in 25 mL of THf- are added 43.1 mL (50 mmol) of 1.16 M. vcc-butyllithium in cyclohexane over a 20-25 min period. The mixture is stirred at — 78 °C for an additional 10 min, and diisopinocampheyl(methoxy)borane [50 mmol prepared from (+ )-a-pinene] in 50 mL of THF is added. This mixture is stirred for 1 h, then 8.17 mL (66.5 mmol) of boron trifluoride diethyl etherate complex are added dropwise to give a solution of diisopiuocampheyl[(Z)-3-inethoxy-2-propenyl]borane. Immediately. 2.8 mL (50 mmol) of acetaldehyde are added and the mixture is stirred for 3 h at — 78 rC and then allowed to warm to r.t. All volatile components are removed in vacuo, then the residue is dissolved in pentane. The insoluble fraction is washed with additional pentane. The combined pentane extracts are cooled to 0 JC and treated with 3.0 mL (50 mmol) of ethanolamine. The mixture is stirred for 2 h at 0rC and is then seeded with a crystal of the diisopinocampheylborane-ethanolaminc complex. The resulting crystals arc filtered and washed with cold pentane. The filtrate is carefully distilled yield 5.6 g (57%) d.r. (synjanti) >99 1 (2/ ,37 )-isomer 90% ee bp 119-120 C/745 Torr. 

Boron is mined as borax and kernite, Na2B407-xH20, with x = 10 and 4, respectively. Large deposits from ancient hot springs are found in volcanic regions, such as the Mojave Desert region of California. In the extraction process, the ore is converted into boron oxide with acid and then reduced with magnesium to an impure brown, amorphous form of boron ... 

Synthesis of Derivatizing Reagent III. We placed 50 mL of methanol, which had been previously dried over 4-S molecular sieves, in a 100-mL round-bottom flask and added 6.0 g of 2-hydroxynicotinic acid and 3 mL of boron trifluoride etherate. The solution was heated to reflux for 24 h and the solvent was removed under reduced pressure. The residue was dissolved in 50 mL of 0.1-ff sodium hydroxide and extracted with 60 mL of chloroform. The chloroform extract was concentrated under reduced pressure and the residue crystallized from isopropyl alcohol. The yield of 3-carbomethoxy-2(lH)pyridone was 5.0 g mp 152.5-154°C NMR (CDCI3) 6 3.85 (s, 3, -CH3), 6.34 (t, 1,... 

Crude chloroform-methanol-water (30 60 8, v/v) extracts of immunostainedTLC bands were analyzed without further purification by nanoelectrospray low-energy mass spectrometry. The authors showed that this effective PLC/MS-joined procedure offers a wide range of applications for any carbohydrate-binding agents such as bacterial toxins, plant lectins, and others. Phenyl-boronic acid (PBA) immobilized on stationary support phases can be put to similar applications. This technology, named boronate affinity chromatography (BAC), consists of a chemical reaction of 1,2- and 1,3-diols with the bonded-phase PBA to form a stable... 

Aznarez et al. [2] have described a Spectrophotometric method using curcumin as chromopore for the determination of boron in soil. Boron is extracted from the soil into methyl isobutyl ketone with 2-methylpentane-2,4-diol. In this method 0.2-lg of finely ground soil is digested with 5ml concentrated nitric-perchloric acid (3 + 1) in a polytetrafluoroethylene lined pressure pump for 2h at 150°C. The filtrate is neutralized with 6M sodium hydroxide and diluted to 100ml with hydrochloric acid 1+l.This solution is triple extracted with 10ml of methyl isobutyl ketone to remove iron interference. This solution is then extracted with 10ml 2-methyl pentane-2,4 diol and this extract dried over anhydrous sodium sulphate. 

In addition to the spectrophotometric method discussed in section 12.1.1.1 Aznarez et al. [2] have described a method based on the molecular fluorescence of boron with dibenzoylmethane. The preliminary soil digestion and extraction procedures are identical to those described earlier. The reactive fluorescence intensity of the boron complex is measured at 400nm with excitation at 390nm and quinine sulphate as reference. 

Kiss [8] examined various techniques for the efficient separation and preconcentration of boron from marine sediments. Alkaline fusion with potassium carbonate was used to render boron reactive, even in the most resistant silicate minerals. Fusion cakes were extracted with water and borate was isolated by Amberlite XE-243 boron-selective resin. Borate was determined spectrophotometrically, following elution with 2 mol L 1 hydrochloric acid. Either the carminic acid complex (620nm), formed in sulphuric acid (94%) or sulphuric acetic acid (1 4), or the azomethine hydrogen ion association complex (415nm) formed at pH5.2, were used for borate measurement. 

McCaulay, D., Shoemaker, B., and lien, A. (1950) Hydrogen fluoride-boron trifluoride extraction of xylene isomers. Ind. Eng. Chem., 42 (10), 2103-2107. 

Whatman No. 2 filter paper, collecting the filtrate in a boron-free tube inside the filter flask. Terminate the filtration after 5 min, and retain the filtered extract for the determination of boron. Carry out a blank determination. 

The B2O3 content of borax may be determined by extraction into HCl solution followed by complexation with mannitol and titration with dUute NaOH. The Na20 content of horax may he measured by titration of an aqueous solution with dUute HCl. Boron and sodium metals in the acid extract of horax may be analyzed by atomic absorption or emission spectroscopy after appropriate dUution of the extract. In the solid phase B2O3 and Na20 may he measured nondestructively by x-ray techniques. 

Method A A solution of 0.5 mmol of (2/ /S ,3R/S )-2,3-dialkyl-1,4-diarylbutane and 0.125 mL (1.0 mmol) of boron trifluoride-diethyl ether complex in 2 mL of trifluoroacctic acid is added to a suspension of 0.12 g (0.26 mmol) of thallium(III) oxide in 2 mL of trifluoroacetic acid at — 40°C to +25CC under an argon atmosphere. The dark colored solution is stirred until the reaction is complete, diluted with ethyl acetate, then washed successively with water (twice) and sat. aq NaCl. Evaporation of the dried extract gives the crude product. In a variant of this method the boron trifluoride-diethyl ether complex can be omitted. 

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