PROZA and CALIBRATION CURVES for quantitative X-ray microanalysis of biological samples

The main scope of our work was to investigate the usefulness of the PROZA correction method and CALIBRATION CURVE construction for quantitative X-ray microanalysis of biological soft, freeze-dried tissues. The test samples with a known elemental concentration of NaCl, MgCl2, KH2PO4 and Na2SO4 were prepared on the basis of 20% porcine skin gelatine. A control sample containing 20% gelatine was used for sulphur subtraction. Dissolved gelatine solutions were cooled with liquid nitrogen and then cut in cryomicrotome into 16 mum thick slices. The sections were lyophilised, coated with carbon and analysed by means of a scanning electron microscope combined with an energy dispersive (ED) spectrometer. The homogeneity of the prepared samples was verified using the Fisher's test. Only homogenous samples were used for calibration. The significance of the phi(rhoz) (PROZA) correction method for biological sample analysis was verified by comparing the prepared standard and entering it into the Voyager computer program memory with the remaining samples of a known elemental content. The differences between the standard and the samples were noted for all elements analysed. There was no sample matching the standard after the PROZA correction procedure. A high correlation r factor (above 0.99) for all analysed elements indicates that CALIBRATION CURVES construction could be suitable for quantitative X-ray microanalysis of biological samples.