Boron-10, detection

In contrast to many chemotherapeutic agents in cancer therapy, boron compounds for BNCT do not require a tumoricidal action in their own right. For their successful application in the therapy of patients, it is important to deliver, to the tumor, a radiation dose which is higher than the radiation dose to the surrounding tissue. The demonstration that this is actually achieved lies ultimately in the treatment of the tumor in question. Because of the short range of the particles produced in the 10B(n,a)7Li reaction, it is very important where, on a cellular and subcellular dimension, the neutron capture reaction takes place. Different methods for boron detection and quantification give different resolution of the boron distribution. It is instructive to compare these methods, both for their precision and lower detection limits, as well as for their ability to yield an image of the boron distribution in tissue (Table 2.2-1). 

Tab. 2.2-1. Selected methods for boron detection and quantification in tissue. 

Cobalt and Nitrogen—Cobalti-hexa-nitrites—Cobalti-tetra-nitrites—Cobalti-tri-nitrites—Cobalt and Phosphorus, Arsenio, and Antimony—Cobalt and Carbon—Cobalto-oyanides—Cobalti-oyanides—Cobalt Nitro-oyanides—Cobalt and Silicon—Smalt—Cobalt and Tin—Cobalt and- Boron—Detection and Estimation of Cobalt. 

Niokel and Carbon—Niokel, Silicon, and Tin—Niokel and Boron—Detection and Estimation of Niokel. 

Curcumin is a sensitive reagent for boron, detecting 0.01-0.1 ppm of B by absorbance at 555 nm. Fluoride, nitrate, and nitrite interfere but can be eliminated by separating the boron from the sample by distillation of B as a methyl borate ester. 

The isotope boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons. Boron nitride has remarkable properties and can be used to make a material as hard as diamond. The nitride also behaves like an electrical insulator but conducts heat like a metal. 

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

One of the first applications of this technique was to the enrichment of and "B isotopes, present as 18.7 and 81.3 per cent, respectively, in natural abundance. Boron trichloride, BCI3, dissociates when irradiated with a pulsed CO2 laser in the 3g vibrational band at 958 cm (vj is an e vibration of the planar, D j, molecule). One of the products of dissociation was detected by reaction with O2 to form BO which then produced chemiluminescence (emission of radiation as a result of energy gained by chemical reaction) in the visible region due to A U — fluorescence. Irradiation in the 3g band of BCls or "BCI3 resulted in °BO or BO chemiluminescence. The fluorescence of °BO is easily resolved from that of "BO. 

Radiometric ore sorting has been used successfully for some uranium ores because uranium minerals emit gamma rays which may be detected by a scintillation counter (2). In this appHcation, the distribution of uranium is such that a large fraction of the ore containing less than some specified cut-off grade can be discarded with tittle loss of uranium values. Radioactivity can also be induced in certain minerals, eg, boron and beryllium ores, by bombarding with neutrons or gamma rays. 

The high cross-section for thermal neutrons results in the use of boron and boron compounds for radiation shielding (14). The ease of detecting the a-particle produced when boron absorbs thermal neutrons results in the use of boron for neutron counters as weU. 

Borate reacts with curcumin [458-37-7] C2 H2qO, in the presence of a mineral acid to give a colored 1 2 bore acid curcumin complex that has been used to determine microamounts of boron. Carrninic acid [1260-17-9J, C22H2QO23, (98) and azomethine-H (99) also form a colored complex usehil for low level detection of borates. Boron compounds give a characteristic green color when burned in a flame. 

InP, in the range 10 —10 cm . Boron, phosphorus, and other shallow impurities can be detected in silicon in concentrations approaching 10 cm . Copper contamination at Si surfaces has been detected down to 10 cm levels. ... 

The boron trihalides are volatile, highly reactive, monomeric molecular compounds which show no detectable tendency to dimerize (except perhaps in Kr matrix-isolation experiments at 20K). In... 

The energy of the detected neutrons has an epithermal component because a high percentage of the incoming thermal neutron flux is absorbed as it passes through a 1 in. of drill collar steel. Furthermore, a wrap of cadmium under the detector banks shields them from the thermal neutron arriving from the inner mud channel. This mainly epithermal detection practically eliminates adverse effects caused by thermal neutron absorbers in the borehole or in the formation, such as boron. 

Therefore we should expect in the gaseous state to find molecules such as BeH2 and BeF2. These molecules have been detected. On the other hand, beryllium has the trouble boron has, only in a double dose. It has two vacant valence orbitals. As a result, BeH2 and BeF2 molecules, as such, are obtained only at extremely high temperatures (say, above 1000°K). At lower temperatures these vacant valence orbitals cause a condensation to a solid in which these orbitals can participate in bonding. We shall discuss these solids in the next chapter. 

The reaction of Na with B, detectable at 850°C, becomes complete at 900°C after 24 h. At 1000°C, the reaction rate is independent of the variety of boron (a- or -rh), if the particle size is the same. The B-Na system contains two borides with the... 

Note It is reported that the use of chlorobenzene as solvent is essential when the reagent is to be used to detect aromatic amines [1]. In the case of steroids, penicillins, diuretics and alkaloids the reaction should be accelerated and intensified by spraying afterwards with dimethylsulfoxide (DMSO) or dimethylformamide (DMF), indeed this step makes it possible to detect some substances when this would not otherwise be possible [5,9-11] this latter treatment can, like heating, cause color changes [5,9]. Penicillins and diuretics only exhibit weak reactions if not treated afterwards with DMF [10, 11]. Steroids alone also yield colored derivatives with DMSO [9]. Tlreatment afterwards with diluted sulfuric acid (c = 2 mol/L) also leads to an improvement in detection sensitivity in the case of a range of alkaloids. In the case of pyrrolizidine alkaloids it is possible to use o-chloranil as an alternative detection reagent however, in this case it is recommended that the plate be treated afterwards with a solution of 2 g 4-(dimethyl-amino)-benzaldehyde and 2 ml boron trifluoride etherate in 100 ml anhydrous ethanol because otherwise the colors initially produced with o-chloranil rapidly fade [12]. 

Boronic Ester Relative Retention Minimum Detectable Quantity (pg of pinacol) Optimum Detector Temperature ( C)... 

PIGE is a rapid, non-destructive technique that is employed in the analysis of light elements such as lithium (10-100 ppm limit of detection), boron (500-1000 ppm limit of detection), and fluorine (1-10 ppm limit of detection), which are often difficult to determine by other analytical means. Because the technique is based upon specific nuclear reactions, the sensitivity of PIGE varies greatly from isotope to isotope, and this non-uniformity of sensitivity has limited its widespread use as a complementary technique to micro-PIXE. 

WDSs have excellent resolving power, and the peak-to-background ratio of each line is much higher than can be achieved with a crystal detector. With a suitable crystal of large lattice spacing it is possible to detect and count X-rays as soft as boron K or even beryllium K , and this type of spectrometer is widely used when... 

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