X-Ray Fluorescence in Biological Sciences. Группа авторов

Чтение книги онлайн.

СКАЧАТЬ 19 984 ± 4385 Ca 4173–6922 5371 ± 787 Mn 480–2007 1222 ± 451 Fe 96.1–327 177 ± 71 Ni 2.96–12.6 7.90 ± 2.45 Cu 10.2–33.8 19.8 ± 6.28 Zn^a 20–40.7 33 ± 7.0 Br^b 1.8–6.23 3.24 ± 1.24 Rb 15.2–166 67.1 ± 46.6 Sr 10.6–51.3 20.8 ± 9.58 Ba 8.89–63.2 40.5 ± 14.2 Pb n/d^c–1.23 0.305 ± 0.316

      ^a ‐ In sample M6 Zn with concentration of 1223 mg/l is found, it was not considered at C _mean estimation.

      ^b ‐ Analysis of suspension

      ^c ‐ n/d – it is not determined.

In the 1970s the contribution the secondary electrons, scattered and fluorescent radiation, and the influence of the divergence of the primary beam to the intensities of X‐ray fluorescence were estimated by Irkutsk X‐ray physicists [77, 93]. The influence of inaccuracies in the fundamental parameters, inaccuracies in the description of the distribution of the energy of the primary radiation, etc. were evaluated [42, 75, 76, 94].

      We must list some Russian researchers who have contributed to the solution to these problems: N.F. Losev, G.V. Pavlinsky, V.P. Afonin, A.G. Revenko, Yu.I. Velichko, B.I. Kitov, V.Ya. Borkhodoev, A.L. Finkel'shtein, et al. At that time, many investigations were conducted by our foreign colleagues. First, one has to mention J. Sherman, H. Ebel, T. Shiraiwa, N. Fujino, L.S. Birks, M. Mantler, J. Criss, J. Gilfrich, B. Vrebos, K. Nielson, and others. These researches are being successfully continued by B. Kanngiesser, B. Beckhoff, W. Malzer, R. Sitko, and others.

      The possibility of the application of theoretical intensities was used in the Analytical Center at Institute of the Earth's Crust SB RAS (Irkutsk) to select specific CRMs suitable for calibration to convert measured intensities of analytical lines into concentrations of analyzed elements for different types of geological samples [3495–99].

The estimates of inter‐elemental effects on the intensity of analytical lines for tea, coffee, and some plants which were used in calibration and validation of XRF were presented by Revenko and Sharykina [15]. Table 3.6 show the estimates of the change of the relative specific intensities (I_rel) calculated by the authors of this chapter for the analytical lines of some elements. Variations of the intensity of coherently and non‐coherently scattered radiation of the Rh Kα‐line anode of the X‐ray tube are also given. The minimum and maximum I_rel values are set in bold. Calculations of the intensities were carried out using the program developed by Finkelstein and Afonin [100]. The program algorithm includes the contributions of secondary and tertiary excitation effects as well as the contribution of the radiation scattered by the sample. CRM of the gabbro SGD‐2 [101], diluted in the ratio of 19 : 1 water was taken to calculate the relative intensities of all analytical lines as the reference sample. The calculated intensities were normalized to the ratio of the concentrations of C_samp/C_ref, where, C_samp and C_ref are the concentrations of the element in the CRM or the sample plants and in a reference sample, respectively. For all analytical lines, I_rel for a reference sample is 1.000.

Table 3.6 The relative specific intensities of I_rel for the analytical lines of some of elements, as well as the intensities of coherently (coh) and incoherently (nc) scattered radiation of the Rh Kα line for a group of samples of plant materials. The minimum and maximum Irel values in Table 3.6 are shown in bold.

Sample	Si Kα	K Kα	Ca Kα	Ti Kα	Fe Kα	Ni Kα	Sr Kα	Rh Kαcoh	Rh Kαnc
Ground coffee	1.015	0.955	0.740	0.649	0.687	0.720	0.705	0.734	0.812
Instant coffee	1.010	0.865	0.733	0.561	0.542	0.566	0.545	0.579	0.703
Tea1	1.034	0.985	0.908	0.880	0.885	0.930	0.932	0.942	0.964
Tea2	0.996	0.964	0.829	0.818	0.784	0.759	0.736	0.761	0.822
GBW 08505	1.041	1.106	0.971	0.973	0.995	1.075	1.088	1.088	1.054
Cinnamon	1.008	1.005	0.911	0.750	0.726	0.725	0.701	0.730	СКАЧАТЬ В начало < 37 38 39 40 41 42 43 44 45 46 > В конец