This enables quantitative measurements of elements and elemental ratios with μm-scale resolution, in-situ, in ferromanganese concretions.
We accounted for error variation inherent in measurement of element concentrations in the samples, with both quality control and twin samples contributing to the maximum-likelihood estimation of and adjustment for day effects [see Supplemental Material (doi 10.1289/ehp.0901541) for additional details].
In the latter case, the appropriate method of measurement would be snap-back timing, which involves separate measurements of elements of work (Bergstrand 1987; Jourgholami et al. 2013; Yoshida and Sakai 2015).
We did not measure, and our study does not present, specific quantitative data regarding these factors because we feel the method we employed represents routine anesthesiology practice, in which the overall impression is used more than specific numeric measurements of elements of the airway exam.
Table 8 Measurement uncertainty of elements determination in plant aqueous extracts and plant dry mass Element Measurement uncertainty, % (k = 2) Plant aqueous extracts Plant dry mass Cd 5.8 8.7 Cr 7.5 8.8 Cu 5.7 8.9 Fe 8.2 8.3 Mn 6.2 6.4 Ni 6.6 8.8 Zn 5.9 6.3 As 7.7 9.8.
Quantitative measurements of element ratios should also provide a useful tool for studying regional environmental changes reflected in the composition of ferromanganese concretions.
To demonstrate the capability of the micro-XRF setup for in-vivo measurement of trace elements in biological samples, we measured cobalt (Co) accumulated in leaves of duckweed floating on a Co solution surface.
Current analytical methods allow the simultaneous measurement of multiple elements in biological samples, including both the potentially toxic ones already mentioned and essential elements including copper (Cu), selenium (Se), and zinc (Zn).
