COMPARATIVE STUDY OF SOIL TEST METHODS FOR DETERMINATION OF PLANT AVAILABLE POTASSIUM IN BULGARIAN ARABLE SOILS

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 . 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.Keywords: available potassium, extraction methods, Flame AES, uncertainty, arable soils DOI: http://dx.doi.org/10.15826/analitika.2021.25.3.00

Comparative study of soil test methods for determination of plant available potassium in Bulgarian arable soils

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 K ALM ≥ K AA > K M ehlich 1> K BaCl2> K CaCl2 . 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.The authors of this study were thankful to prof. Margarita Nikolova for the idea and discussions; to Mr. Vencislav Nekov (Sembodja, Ltd., Sofia, Bulgaria) for providing soil samples. Lyudmila Angelova acknowledged the financial support of the National Program for Support of Young Researchers 2018–2020 funded by the Bulgarian Ministry of Education and Science. The authors are thankful to Ms. Yulia Ivanova for making some of the laboratory experiments

Composition and Antioxidant Activity of Aronia Melanocarpa Fruit Juice

Aronia melanocarpa is a woody shrub of the Rosaceae family. Its fruits are used for consumption either fresh, or as juice, jam and wine. The aim of the present study was to measure the concentration of some biologically active substances and the antioxidant activity of two samples of Aronia melanocarpa fruit juice (AMFJ). The juice was prepared from fresh fruits. One of the samples was produced using a juice centrifuge and was preserved with potassium sorbate (1.0 g/l). The other sample was produced by crushing and squeezing of fruits after which the juice was filtered and sterilized at 100 °C for 10 min. The contents of biologically active substances in the juice samples were measured by spectrophotometric and high-performance liquid chromatography methods. The antioxidant activity of the two juice samples was measured by the ORAC (oxygen radical absorbance capacity) and HORAC (hydroxyl radical аverting capacity) methods. The results showed that both samples were extremely rich in polyphenolic substances, amongst which the highest was the concentration of procyanidins followed by phenolic acids (chlorogenic and neochlorogenic) and anthocyanins. Sample 1 had higher concentration of total phenolics and contained higher quantities of most polyphenolic substances with the exception of anthocyanins. It also contained micro-quantities of cyanogens. The variations in the composition of the two samples could be attributed to the different methods of juice production and conservation. Both juice samples showed very high ORAC and HORAC values which were higher for sample 1 (the sample with the higher concentration of polyphenolic substances). The high antioxidant activity of the two AMFJ samples could be attributed to their polyphenolic ingredients

Nanoscale Potentiometry

Potentiometric sensors share unique characteristics that set them apart from other electrochemical sensors. Potentiometric nanoelectrodes have been reported and successfully used for many decades, and we review these developments. Current research chiefly focuses on nanoscale films at the outer or the inner side of the membrane, with outer layers for increasing biocompatibility, expanding the sensor response, or improving the limit of detection (LOD). Inner layers are mainly used for stabilizing the response and eliminating inner aqueous contacts or undesired nanoscale layers of water. We also discuss the ultimate detectability of ions with such sensors and the power of coupling the ultra-low LODs of ion-selective electrodes with nanoparticle labels to give attractive bioassays that can compete with state-of-the-art electrochemical detection

Ensuring the Quality of the Analytical Process in a Research Laboratory

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

Determination of Bromide and Bromate Ions in the Presence of Standard Ions by Suppressed Ion Chromatography

An ion chromatographic method for determination of bromide and bromate in the presence of standard anions in drinking water was described. The method was based on separation on Metrosep A Supp 7-250 (250 x 4 mm) column with 3.6 mmol/L Na2CO3 as eluent and conductivity detection after sequential chemical and carbon dioxide suppression. The influence of flow rate and column temperature was studied and optimal experimental conditions for simultaneous determination of eight anions were chosen. Analytical characteristics of the ion chromatographic method were assessed for simultaneous determination of bromide, bromate, fluoride, chloride, nitrate, nitrite, phosphate and sulfate. The calibration curves were linear (r2=1, N=7) in the concentration ranges: 0.4-12 mg/L BrO3- and 0.3-11 mg/L Br-. Recovery test was performed on a spiked certified reference material for soft drinking water. The obtained recoveries for bromate and bromide were 96.0 and 101.0 %, respectively. The repeatability and intermediate precision were between 5.1 and 0.14 % (RSD) depending on the analytes concentration. The limits of detection were 20 μg/L BrO3- and 10 μg/L Br-</jats:p

THE USE OF FLUORIDE CONTAINING MINERAL WATER IN WORT PRODUCTION

The present work aims to study the quality of wort produced using fluoride containing mineral water. The results show that the mineral water has a negative impact on the enzymatic destruction of starch, proteins, color intensity and pH of the wort. The changes of pH during mashing process using tap and mineral water was studied. The lower acidity of wort obtained using mineral water didn’t change during the brewing process. The fluoride content of beer is lower than 5 mg.L-1 when wort is produced using mineral and tap water in 1:1 ratio and citric acid for pH correction. At the same time, the final degree of fermentation, α-amine nitrogen content and the intensity of color of produced wort are close to the control sample. The changes in fluoride ion concentration are monitored using ion-selective potentiometry. The fluoride content is decreased from 5.7 to 4.75 mg.L-1, the most intense change is observed during the mashing process