Quantification of deep soil carbon by a wet digestion technique

Abstract

Two wet digestion methods were evaluated using pure kaolinite as background for quantifying small concentrations of carbon (<0.05% total organic carbon (TOC)) in deep kaolinitic regolith in south-western Australia. The limit of detection and limit of quantification of the Walkley–Black method (0.015 and 0.050% TOC respectively) were approximately five times lower than those of the Heanes method (0.085 and 0.281% TOC respectively). Both methods showed excellent linearity (R2>0.99) using prepared standards (lignin, humic acid, cellulose and chitin mixed with kaolinite and their combinations), in the concentration range 0.008–1.000% TOC. However, the percentage carbon recovery values were underestimated for chitin. The Walkley–Black method (TOCWB, %) was evaluated with 94 calibration and 27 validation deep soil samples (1–35m soil depth) and compared with a dry combustion (Elementar) technique (TOCactual, %). The predictive equation (TOCactual=1.66TOCWB+0.018) (R2=0.91) obtained from the calibration set agreed well with the benchmark dry combustion values (root mean square error=0.017) and is recommended for quantification of deep soil carbon in other kaolinitic regoliths.

Determination and Analysis of Trace Elements in Five Kinds of Traditional Chinese Medicine in High Blood Pressure Medicinal Food by ICP-AES

“…So microelements have a close association with high blood pressure. One of the traditional sample treatment methods in analysis of constants and trace elements is mainly wet digestion processing; the disadvantages of this approach is long digestion time, high sample consumption, and serious environmental pollution [4][5][6]. In recent years, microwave digestion technology has been widely used in almost every field of sample digestion processing, such as food, beverage, and human and animal organs for digestion; its advantages are mainly manifested in the low sample and reagent dosage, a short reaction time, and low environmental pollution [7][8][9].…”