Calcium resonance

Flame atomic absorption spectrometry FAAS measurements are performed at the calcium resonance line at 422.7 nm using an air-acetylene flame. SrCli may be used as the internal standard. Before analysis, samples are diluted and the viscosity of the analytical portion and of the calibrator solution is adjusted. Phosphate ions form thermally stable calcium salts, which then escape atomization and measurement. For this reason. Lads is added, which binds phosphate ions enabling accurate calcium measurements independent of the (varying) phosphate concentration. FAAS is considered to be the most reliable technique for total calcium determination, and therefore it has been chosen as the reference method. 

With regard to position within the flame, it can be shown that in certain cases the concentration of atoms may vary widely if the flame is moved either vertically or laterally relative to the light path from the resonance line source. Rann and Hambly42 have shown that with certain metals (e.g. calcium and... 

Procedure (ii). Make certain that the instrument is fitted with the correct burner for an acetylene-nitrous oxide flame, then set the instrument up with the calcium hollow cathode lamp, select the resonance line of wavelength 422.7 nm, and adjust the gas controls as specified in the instrument manual to give a fuel-rich flame. Take measurements with the blank, and the standard solutions, and with the test solution, all of which contain the ionisation buffer the need, mentioned under procedure (i), for adequate treatment with de-ionised water after each measurement applies with equal force in this case. Plot the calibration graph and ascertain the concentration of the unknown solution. 

To the solution is added 900 ml. of water, and the resulting mixture is washed with four 500-ml. portions of ether. The ether layers are combined and washed with 200 ml. of aqueous 10% potassium carbonate and then twice with 200-ml. portions of water (Note 9). The ether layer is dried for 1 hour over 200 g. of anhydrous calcium chloride (Note 10) and the solvent is removed on a rotary evaporator at room temperature to give 145-158 g. of crude product (Note 11). Distillation under reduced pressure through a Vigreux column gives 115-128 g. of a fraction, b.p. 83-86° (54 mm.), w22 d 1.4620-1.4640, containing 95% of l-bromo-3-methyl-2-butanone as established by proton magnetic resonance measurements (Note 11). 

Johnson, K., Sutcliffe, L., Edwards, RH.T. and Jackson, M.J. (1988). Calcium ionophore enhances the electron spin resonance signal from isolated skeletal muscle. Bitxhim. Biophys. Acta 964, 285-288. 

The binding of calcium ion to calmodulin, a major biochemical regulator of ion pumps and receptors, occurs on a time scale about a thousand times shorter than that observed for RNA conformational change. This Ca2+-calmodulin binding, which can be followed successfully by nuclear magnetic resonance (NMR), occurs in about ten milliseconds. 

K. B. Seamon, Calcium- and magnesium-dependent conformational states of calmodulin as determined by nuclear magnetic resonance, Biochemistry 19, 207-215 (1980). 

One also sees that at room temperature the two peaks of the quadru-pole split pattern are different in intensity. This difference disappears at 77°K. It is an example of what is known as the Gordanskii effect 10) and is caused by the fact that the amplitude of vibration is different, parallel to the surface and normal to the surface, so that the effective resonant fraction is different for the two halves of the quadrupole splitting. This effect has been extensively studied by the Russians. In a recent paper, Suzdalev and others report a study of tin in the surface of silica gel 18), They put calcium ions in the surface of silica gel, then replaced them with divalent tin by ion exchange. The result was a mixture of stannous and stannic ions, and of course, the use of the Mossbauer effect made it possible to determine accurately the relative amounts of the two. They studied the amplitude of vibration of the two kinds of atoms and found, for example, for the stannous ions, the r.m.s. amplitude of vibration parallel to the surface was 0.07 A., and the r.m.s. amplitude of vibration perpendicular to the surface was about twice as great—about 0.13 A. Karasev and others have also worked on the chemistry of adsorbed... 

J. P. Yesinowski, Nuclear magnetic resonance spectroscopy of calcium phosphates, in Z. Amjad (Ed.), Calcium Phosphates in Biological and Industrial Systems, Kluwer Academic Publishers, Norwell, MA, 1998, pp. 103-143. 

K. A. Smith, D.P. Burum, Application of Fluorine-19 CRAMPS to the analysis of calcium fluoride/fluorapatite mixtures, J. Magn. Reson. 84 (1989) 85-94. 

Y. Pan, P- F rotational-echo double resonance nuclear magnetic resonance experiment on fluoridated hydroxyapatite. Solid State Nucl. Magn. Reson. 5 (1995) 263-268. L. Wu, W. Forsling, P.W. Schindler, Surface complexation of calcium mineral in aqueous solution, surface protonation at fluorapatite surface, J. Colloid Interface Sci. 147 (1991) 178-185. 

K. J. D. MacKenzie and R. H. Meinhold, Thermal decomposition of dolomite (calcium magnesium carbonate) studied by Mg solid-state nuclear magnetic resonance. Ther-mochim. Acta, 1993, 230,331-337. 

Yabusaki, K. K., Wells, M. Binding of Calcium to phosphatidyl cholines as determined hy proton magnetic resonance and infrared spectroscopy. Biochemistry 14, 162 (1975)... 

---