Abstract
This study proposes a method of direct and simultaneous determination of the amount of Ca2+ and Mg2+ present in soil extracts using a Calcium Ion-Selective Electrode and by Complexometric Titration (ISE-CT). The results were compared to those obtained by conventional analytical techniques of Complexometric Titration (CT) and Flame Atomic Absorption Spectrometry (FAAS). There were no significant differences in the determination of Ca2+ and Mg2+ in comparison with CT and FAAS, at a 95 % confidence level. Additionally, results of this method were more precise and accurate than of the Interlaboratorial Control (IC).
Highlights
MATERIAL AND METHODSOne of the main problems in laboratory soil analysis is the selection of the determination method of ions of interest in the extracts
Complexometric Titration (CT) analyses were carried out using automatic burette (Jekins, precision of 0.01 mL), titrating 10 mL of soil extract with 0.0125 mol L-1 EDTA solution
The determination method of exchangeable calcium and magnesium in soil extracts using Calcium Ion Selective Electrode and Complexometric Titration (ISE-CT) is accurate, precise and applicable when compared to Complexometric Titration (CT) and Flame Atomic Absorption Spectrometry (FAAS)
Summary
MATERIAL AND METHODSOne of the main problems in laboratory soil analysis is the selection of the determination method of ions of interest in the extracts. Most laboratories determine the exchangeable calcium and magnesium by complexometric titration with EDTA in the presence of metallo-chromic indicators Calcon or Murexide for Ca2+ and Eriochrome Black T for total hardness (Ca2+ + Mg2+), where Mg2+ is obtained by difference (Raij, 1966; Embrapa, 1997; Cantarella et al, 2001; Embrapa, 2005) Another common method is the determination by Flame Atomic Absorption Spectrometry with (FAAS) (Willians et al, 1966; Macphee & Ball, 1967; Boeira et al, 2004, Embrapa, 2005). Potentiometric methods have been used to analyze different compounds in soil, such as boron (Carlson & Paul, 1969), sulfate (Goetzen & Oster, 1972), chloride (Ferreira et al, 1996a), nitrogen (Ferreira et al, 1996b) and potassium (Grygolowicz-Pawlak, 2006) In this case, the analysis takes place by means of ion selective electrodes (ISE). Unlike the classical analytical methods, analyses with these sensors are very fast and cheap and allow the direct determination of electrolytes such as Ca and Mg in aqueous media (Christiansen, 1976; Imato et al, 1989; Beli & Zirino, 1993; Chen & Adams, 1998; Saurina et al, 2002; Simões, 2008; Metrohm, 2010a) and some complex matrices, e.g., milk (Metrohm, 2010b) and rocks (Kotek & Dlezal, 1980)
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