Browsing by Author "Surleva O."

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    Comparative study of soil test methods for determination of plant available potassium in Bulgarian arable soils
    (2021-01-01) Angelova L.; Genova N.; Stoyanova S.; Surleva O.; Nekov I.H.; Ilieva D.; Surleva A.
    This comparative study was aimed at estimating analytical behavior of methods for determination of plant available potassium applied to Bulgarian arable soils and to reveal the relationship between the amount of extractable K. Twenty-four samples from two traditional agricultural regions in Bulgaria were studied. Soil potassium was extracted by NH4OAc/HOAc pH 4.5 (AA), diluted double acid (Mehlich 1), CaCl2, BaCl2 and a modified acetate/lactate method (ALM) and determined by Flame AES. The factors influencing the methods accuracy were identified and uncertainty was estimated. The expanded uncertainty was (in mg K2O (100 g dry soil)-1): 0.10 (ALM), 0.64 (Mehlich 1), 0.17 (CaCl2) and 1.1 (AA). The study revealed that the factor which mainly influence the uncertainty of the applied analytical methods for plant available potassium in soil was the calibration of Flame AES determination. The obtained results showed that extractable potassium lowered in the following order KALM ≥ KAA > KMechlich1 > KBaCl2 > KCaCl2. Soil potassium extracted by ALM procedure correlated with AA, BaCl2-K, CaCl2 –K and Mehlich 1 - K at 0.05 level of significance. ALM extracted between 1.2 to 5.8 times more soil K than other methods did. The obtained results provided a base for further study on correlation between extractable K and soil fertility indices for particular soil types and climatic regions in Bulgaria.
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    Ensuring the Quality of the Analytical Process in a Research Laboratory
    (2024-04-01) Surleva A.; Angelova L.; Ilieva D.; Ivanova V.; Surleva O.; Chavdarova K.
    Featured Application: The approaches for estimation of the analytical behavior of measuring methods could be applied in a research laboratory aiming at the characterization of new materials or a new method for analysis. The limitations of well-known approaches are described, and the alternatives are discussed. This paper discusses approaches for verification of methods of measurements of chemical and physical characteristics of specific samples. The limitations of well-known approaches are discussed. Some examples of alternatives are given to demonstrate specific issues encountered in the research laboratory analyzing new materials or characterizing new properties of materials. Application of sequential procedure using lower quantities of samples and reagents is presented. A standard addition to solid samples is discussed. The approach of control charts for estimation of method uncertainty for determination of plant available phosphorus is presented. The method comparison is applied as an approach to verification of alkaline reactivity by inductively coupled plasma–optical emission spectroscopy (ICP-OES) measurement, as well as density of newly synthesized chalcogenide glass materials. The presented examples demonstrated that alternative approaches are needed in order to verify the methods applied due to the great variety of activities and corresponding tasks in a research laboratory.