Boron determination

SPh boron detenuination in form of complex with Azomethine-H is the reliable microanalytical method for boronorganic compounds, carboranes, metallacarboranes, etc. Before boron determination the samples should be melted with KOH at 900°C. 

The stereoselectivity of the P-carboethoxyallylic boronate derived from the endo-phenyl auxiliary A (p. 803) toward R- and. S -glyccraldchydc acetonide has been investigated. One enantiomer gives the anti product in 98 2 ratio, whereas the other favors the syn product by a 65 35 ratio. Based on the proposed transition structure for this boronate, determine which combination leads to the higher stereoselectivity and which to the lower. Propose the favored transition structure in each case. 

The effect of those ions most frequently present in soils on the boron determinations is shown in Table 12.1. The interference of iron at concentrations higher than 7xlO 5M can be eliminated as the chloro complex by extraction with methyl isobutyl ketone. The total elimination of iron III was not necessary as the phosphoric acid masked the residual iron III in the boric acid-curcumin reaction. 

The results of boron determinations in soils by the Spectrophotometric method are shown in Table 12.2. Soil samples were provided by Aula Dei, Experimental Station of the Consejo Superior de Investigaciones Cientificas (CSIC), and correspond to alluvial ground or soils with a high limestone content (35-45% of calcium carbonate). 

Table 12.1 Effect of foreign ions on boron determination... 

An interesting example of the contamination risks which may be caused by a laboratory vessel is that of boron. Determination of very low boron concentrations, involves a prior separation by distillation and subsequent analysis by spectrometry, with a suitable reagent such a curcumin or carminic acid. The use of laboratory vessels made of borosilicate glass (such as Duran or Pyrex) could lead to very large errors in the boron content found. Such errors are caused by sample contamination from the boron present in the glassware. 

Gassaway, J.D. (1967) New method for boron determination in sea water and some preliminary results. Int. J. Oceanogr. Limnol., 1, 85—90. 

Use Dye for cotton, stain for microscopy, reagent for boron determination, manufacture of acid and chrome dyes. 

A gold-lined bomb was studied for use in preparing samples for boron determination. White oil spiked with boron sulfonate yielded high recoveries, indicating contamination. 

USE Used with boric acid in the manuf of dry electrolytic condensers for radio applications in making artificial resins and plasticizers in pharmacy as excipient and diluent for solids and liqs in analytical chemistry for boron determinations in the manuf of mannitol hexanitrate. Used in the food industry as anticaking and free f]ow agent flavoring agent, Lubricant and release agent, stabilizer and thickener and nutritive sweetener,... 

Laakso et al. (2001) developed a method for boron determination that uses inductively coupled plasma atomic emission spectrometry and protein removal with trichloroacetic acid before analysis. This method is feasible, accurate, and one of the fastest for boron determination during BNCT and enables a more reliable estimation of the irradiation dose. Yoshida et al. (2002) used flow cytometry to sort the cells by phases, and the boron concentration in each fraction was measured with inductively coupled plasma atomic emission spectroscopy. Obtained results revealed that sodium borocaptate and boronophenylalanine were associated with different rates of boron uptake in different phases. 

Hyperfine field (HF), quadrupole splitting (QS) and isomer shifts (IS) relative to a-Fe at the six different iron sites 16k, 4c and at the metalloid site 4g occupied by carbon or boron determined from Mossbauer and nuclear magnetic resonance (NMR) spectra (Erdmann et al. 1988, 1989). All these data were determined... 

Classical reagents such as azomethine-H and curcu-min are frequently used in boron determination. Azomethine-H is used, for example, in boron determination in plants, geochemical materials, and soils. Curcumin is used in determination of boron as an impurity in silicon-doped galHum arsenide used in electronics and in high-purity molybdenum. The microgram per gram limit of detection (LOD) is attained when curcumin or 4-methoxy-azomethine-H (420 nm) is used. However, boron is also determined by the formation of the macrobicyclic complex Fe(Nx) (3) (BOH) (2) in the nioxime-boric acid-Fe(II) system (447 nm). 

PGAA has been employed for quantitative analysis of boron in boron-containing tumor drugs used for boron neutron-capture therapy. To study the distribution of such drugs in the mouse model, Cho et al. (2007) determined boron in tumors and other tissues of mice that had been injected with boronophenylalanine. Accuracy of the boron determinations at this facility had been established by previous work describing the facility, element standards, and the analysis of several certified reference materials (Cho et al. 2005b). Byun et al. (2004)... 

Elemental boron determined by neutron %ot included in statistical analysis. 

Gupta, U.C. 1967. The boron determination of some piant materiais as determined with and without adding CaO before ashing. Piant Soii 26 202-204. 

Boron analysis by measuring the methyleneblue-BF]j complex after extraction with 1.2-dichlorethane is proposed by Meier et al. (20) as a very sensitive and reliable method for boron determinations in aluminium. 1 g of aluminium is dissolved in sodium hydroxide in a quartz beaker under heating and addition of some sodium peroxide. The solution is cooled, acidified with sulphuric acid and warmed up again until it clarifies. After cooling, the solution is transferred into a 250 ml calibrated quartz flask and diluted to the mark with water. 25 ml of this solution are then mixed with 5 ml hydrofluoric acid (5 %) and 10 ml 0.001 M methyleneblue solution in a plastic beaker and allowed to stand for 1 hour. The pH-value should be 2 + 0.2. The solution is then shaken with 25 ml 1.2-dichlorethane during 1 min. The complete separation of the phases needs 30 min. To eliminate interferences (especially from coextracted methyleneblue fluorohydrate), the extract is washed with 10 ml sodium nitrate solution (3 %), filtered... 

D Orazio, M. (1999). Boron determination in twenty one silicate rock reference materials by isotope dilution ICP-MS. Geostand. Newsl. 23(1), 21. 

Evans, S., and Kraehenbuehl, U. (1994). Improved boron determination in biolt cal material by inductively coupled plasma mass spectrometry J. Anal. At. Spectrom. 9(11), 1249. 

Nyomora, A. M. S., Sah, R. N., Brown, P. H., and Miller, R. O. (1997). Boron determination in biological materials by inductively coupled plasma atomic emission and mass spectrometry Effects of sample dissolution methods. Fresenius J.Anal. Chem. 357(8), 1185. 

Table 4 Electronic Transitions of a-Rhombohedral Boron Determined by the Decomposition of the Absorption Edge...

Boron is one of the difficult elements to analyze with an evaporation step because of its volatility. Since mannitol has been known to contain significant levels of boron, a mixture of hydrofluoric acid and KF has been used instead during preconcentration for boron determination in various high-purity alcohols. The recovery results shown were 100-116% and the concentrations found were in the range of pg/g to ng/g. 

---