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Standards for quantification of elements in the otolithic membrane by electron probe X‐ray microanalysis: Calibration curves and electron beam sensitivity
Author(s) -
LÓPEZESCÁMEZ J. A.,
CRESPO P. V.,
CAÑIZARES F. J.,
CAMPOS A.
Publication year - 1993
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1993.tb03378.x
Subject(s) - saccule , utricle , analytical chemistry (journal) , acceleration voltage , chemistry , cathode ray , calibration , electron , materials science , optics , atomic physics , physics , chromatography , vestibular system , medicine , quantum mechanics , radiology
Summary An absolute quantitative standardization technique has been developed to measure Ca and K weight fractions (WF) in the otolithic membrane of the saccule and utricle by scanning electron microscopy and electron probe X‐ray analysis using the peak‐to‐background ( P/B ) ratio method. Microcrystalline salt standards were used to calibrate Ca and K Kα P/B or Y = ( P/B ) · Z 2 / A ( Z = atomic number; A = atomic weight) against WF at 10, 15, 20 and 25 kV accelerating voltage. The effect of voltage on the calibration, plotting the coefficient of correlation ( r ) as a function of voltage, was not dependent on the voltage in the range 10–25 kV for Ca standards. K standards were also independent when P/B was corrected for Z 2 / A . Background counts in the otoconia ( B o ) were obtained at 5, 25, 50, 100, 200 and 500 s and used to test the electron beam sensitivity of saccular and utricular otoconia. B o was not dependent on the spectra acquisition time, with the exception of B o under Kα K peak in the saccule at 10 kV. Ca and K WF were determined at 10, 15, 20 and 25 kV in the saccule and utricle, showing similar values regardless of the voltage used. This method of calibration offers several advantages, such as stability, homogeneity, known composition of the standards, high reproducibility at different voltages even without Z 2 / A correction and the similarity between the otoconia and crystal standards. We recommend the application of this method for other elements and biomineral systems.