Quantitative Microchemical and Histochemical Analysis of Elements by X-rays

Abstract

A METHOD of X-ray absorption analysis has been developed which permits the quantitative determination of elements with low atomic numbers in extremely small quantities of a biological tissue. It is based upon the measurement of the absorption of monochromatic X-ray radiation, within a very small area of an object, for example, a microscopic section of a tissue. The measuring procedure, either ionometrically or photographic-photometrically, is repeated in a series of wave-lengths lying on each side of a long-wave X-ray absorption edge of the element sought for. From these experimental data the quantity of the element in question can be calculated. Localization of the area in the specimen to be analysed is secured by taking monochromatic X-ray radio-micrographs. The method permits of the determination in a tissue of elements of atomic number above 6. Thus with the exception of hydrogen, all elements of biological interest can be determined. Analysis may be made upon a volume of tissue corresponding to that of a mammalian cell. In analyses of calcium and phosphorus in biological material, quantities of 10^{â 10}–10^{â 11} gm. have been determined by the method with an error of 10 per cent.