Analytical methods and quality assurance

Abstract

A wet digestion method of soil samples has been developed for analysis of "total" concentration (acid extraction) of elements by inductively coupled plasma emission spectrometry (ICP-AES). This HNO 3 -H 2 O 2 wet digestion method is a simple, fast and safe sample preparation method with satisfactory accuracy and precision. The first examined condition was the applied digestion acid or acid mixture (HNO 3 , HNO 3 -H 2 O 2 , HCl-H 2 O 2 , HNO 3 -HClO 4 , H 2 SO 4 -H 2 O 2 ), and the volume of concentrated nitric acid (65% HNO 3 ). Temperature and duration of predigestion, volume of concentrated hydrogen-peroxide (30 % H 2 O 2 ), temperature and duration of digestion were also investigated. Two different kind of soil samples (a sandy soil with low humus content, calcareous chernozem with relatively high humus content), three different dry weight values and three different values for each parameters were chosen to investigate soil sample digestion in order to select the best parameters. A LABOR MIM Electronic Block Digest Apparatus was applied for sample preparation and numerous elements (e.g. Al, As, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, S, Sr, Zn) have been measured by a LABTAM 8440M Inductively Coupled Plasma Emission Spectrometer. The optimum values of parameters to digest soil sample in an electronic block digest apparatus are: a) 1 g dry weight, b) 5 cm 3 HNO 3 as digestion acid, c) 30°C-60°C temperature range for 30-60 minutes predigestion, d) 5 cm 3 30% H 2 O 2 , e) 120 C temperature for 270 minutes digestion. Two soil samples were digested with four methods (block digestion, Milestone microwave, Prolabo focused microwave and Hungarian standard). Results of the two microwaves and detailed block digestion methods are in well agreement in the two soil samples. Finally three Standard Reference Materials were applied to compare the appropriate results. These results showed well agreement for all elements except for aluminium and iron content. The difference between certified and measured results is dependent on their concentrations in soil.

Assessing the Accuracy of Soil and Water Quality Characterization Using Remote Sensing

“…Decision trees: (i) handle non-parametric data where the predictors are not characterized as having a specific distribution, (ii) are insensitive to missing data, to inclusion of irrelevant predictors, or to the presence of outliers, (iii) effectively operate Nelson andSommers (1982, 1996) pH probe Peech (1965), Thomas (1996) Electrical conductivity probe Lal, (1996), Peech (1965) P, K, Ca, Mg, Al, B, Cu, Fe, Mn,,Ni, Pb, S Inductively coupled plasma analysis Kovacs et al (2000) F, Cl, Br, Cl − , NO 3 -N, PO 4 -P, SO 4 -S Ion chromatograph Zhang et al (2013) using numerical, ordinal, binary, and categorical classes; and (iv) identify complex hierarchical relationships between predictors and response variables (Heung et al 2014). Practically, the decision tree algorithms iteratively split the data into mutually exclusive subsets, minimizing the sum of squares, and creating homogeneous groups (Breiman et al 1984).…”

Extractable aluminium in New Zealand Andisols and Inceptisols

“…Soil pH was measured using the 1:2.5 soil to water ratio (ASPAC 4A1), Total Carbon was analysed using no soil pre-treatment (ASPAC 6B2) and CEC and BS were determined by extraction using 1M ammonium acetate at pH 7; MP-AES analysis for cations, followed by pH change determination for H + (ASPAC 15A1) (Rayment and Lyons, 2011b). Total extractable Al, Fe and Mn concentrations were analysed using microwave digestion at Lincoln University using the method proposed by Kovács et al (2000) (Table A.1, Supporting Information) and were then analysed using inductively coupled plasma-optical emission spectrometery (ICP-OES; Varian 720 ES, Varian Pty Ltd, Melbourne, Australia).…”

Trace metal mobilization by organic soil amendments: insights gained from analyses of solid and solution phase complexation of cadmium, nickel and zinc

“…The digest was then filtered through Whatman no. 52 filter paper (pore size: 7 µm) and diluted with HPW to a volume of 25 mL (Kovács et al, 2000). Certified Reference Materials for soil and plant matter (International Soil analytical Exchange-ISE 921, and International Plant analytical Exchange IPE 100; Wageningen University, The Netherlands) were also analysed to confirm acceptable recovery of the analytes.…”