Comparison of two different types of sodium standard for electron-probe analysis of soft tissue

Abstract

Standards prepared from sodium-bearing plastic were examined with an electron probe and compared with standards prepared from freeze-dried, plastic-embedded 20% albumin solution. The calibration coefficients for sodium were 3.062 ± 0.038 mequiv l^–1 count^–1 S^–1 with plastic standards and 2.66 ± 0.11 mequiv l^–1 count^–1 s^–1 with albumin standards. The accelerating voltage was 10 kV and counting rates were normalised to 7 605 ± 29 count S^–1 for sodium chloride crystals. The difference in calibration factors is compatible with independent measurements, which indicate shrinkage of the albumin standards as a result of freeze drying.