X-Ray Fluorescence in Biological Sciences. Группа авторов

X-Ray Fluorescence in Biological Sciences - Группа авторов


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the tea matrix, confirmed by studies of samples of biological origin [13, 89]. In addition, for P, S, and K, the effect of inhomogeneity in the sample distribution on the carrier was more significant when the suspension was used. It should also be noted that the determination of Cl and Br using the acid decomposition method is difficult due to the volatility of these elements, and therefore the use of suspension is recommended for them. The best measurement results for most elements are obtained by analyzing solutions after acid decomposition of tea leaves, whereby this sample preparation method is used to analyze samples of Krasnodar tea. To determine Cl and Br, samples were prepared as suspensions. The average value of the relative standard deviation of the analysis results from the certified values of the CRM for the method used in the verification was not more than 6% for Mg, P, S, Mn, Ni, Cu, Zn, Br, Rb; for K, Ca, Sr, Ba, and Pb – not more than 16%. The largest discrepancies were obtained by determining Ti and Fe. The total uncertainty of TXRF results, considering all stages of analysis (sample preparation and measurement), for all elements except for Ti was on average no more than 16% (n = 3). The uncertainty of applying a sample onto the carrier averaged 7% (n = 7).

      The Student's test was used to evaluate the two quantitative data sets obtained by TXRF and wavelength dispersive X‐ray fluorescence (WDXRF). Good results convergence was obtained for Cl, K, Ca, Mn, Fe, Cu, Zn, Rb, Sr, and Ba. However, the concentrations of P, S, Ni observed in the data had relatively low convergence (74% on average), which is explained by the possible influence of unconsidered factors, which demands further research. Advantages of TXRF over WDXRF include using fewer CRM to quantify data, reducing detection limits for most elements by about an order of magnitude, and not having matrix effects when emitters meet the thin layer criterion.

      The present level of development of the theory of X‐ray fluorescence excitation allows researchers to accurately calculate fluorescence intensities for homogeneous samples. In this case software enables us to take into account different matrix effects: the effect of enhancement of element atoms, primary and fluorescent radiation scattered from the sample atoms, enhancement by sample Auger‐ and photoelectrons, cascade transitions, etc. [7790–92].

Element Concentrations in tea leaves, mg/kg
Range Mean and standard deviation
P 2497–5083 3629 ± 616
S 3057–4822 3830 ± 496
K 13 202–29 710 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
Zna 20–40.7 33 ± 7.0
Brb 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/dc–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.

      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].


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