Total elemental analysis digestion method evaluation on soils and clays

Abstract

The standard digestion method for total elemental analysis of soil material by the Soil Survey Laboratory (USDA Natural Resources Conservation Service) uses a 2-mL clay suspension with hydrofluoric acid (HF) in a closed Teflon digestion vessel (method HF-SUS). The accuracy and efficiency of elemental recovery by method HF-SUS was compared to: (a) modification of HF-SUS by use of a dried sample (method HF-DRI); (b) modification of HF-SUS by use of a dried sample and HF+aqua regia (method HF+AR); (c) sample digestion by Li metaborate fusion (method FUS); and (d) microwave digestion of samples with HF+aqua regia in Teflon bombs (method MICRO). Three replications of three standard reference materials (SRMs), fine-earth (<2 mm) from 12 soils, and the clay (<2 urn) from 10 of those soils were analyzed. Method HF+AR shows the most consistent statistical agreement with the certified SRM values. Analysis of variance (ANOVA) indicates significant effects (α=0.05) for method of digestion, nonsignificant effects for method times SRM and method times clay, but significant effects for method times fine-earth. Composition and/or variability of material are significant factors in the method of digestion. Method HF+AR yields 1

Major and Trace Elements of Selected Pedons in the USA

“…Following digestion, boric acid was added to neutralize HF (2.5% in 100 mL final volume) and extracts analyzed by ICP–AES, radial mode and cross‐flow nebulizer. This digestion is considered a more rigorous digest than by aqua regia alone, as HF is noted for the efficient dissolution of silicate minerals and is often used in conjunction with aqua regia to ensure the digestion of organic constituents of soils (Sawhney and Stilwell, 1994; Wilson et al, 1997a). Quality assurance samples (blank, duplicate, and Certified Reference Material, CRM) were included for every 28 samples in the digestion process.…”

Decomposição de argilas em forno de microondas e determinação simultânea dos seus constituintes principais por espectrometria de emissão óptica em plasma indutivamente acoplado

“…A decomposição de argilas e solos em forno de microondas já foi estudada [5][6][7][8] . Esses procedimentos foram implementados utilizando frascos fechados de PTFE (politetrafluoretileno) com as seguintes misturas ácidas: HNO 3 + HF 5 , HNO 3 + HCl + HF 6 e HNO 3 + HCl + H 2 O 2 7 .…”

“…Dessa forma, a análise elementar completa de argilas geralmente é efetuada aplicando-se esses dois procedimentos independentes. Apesar da exatidão adequada, essa estratégia consome tempo e depende criticamente da experiência do analista.A decomposição de argilas e solos em forno de microondas já foi estudada [5][6][7][8] . Esses procedimentos foram implementados utilizando frascos fechados de PTFE (politetrafluoretileno) com as seguintes misturas ácidas: HNO 3 + HF 5 , HNO 3 + HCl + HF 6 e HNO 3 + HCl + H 2 O 2 7 .…”