Fast, safe, and reliable methods for extraction of major inorganic cations from small quantities of woody plant tissues

Abstract

Two simple and fast methods for the extraction of major inorganic cations (Ca, Mg, Mn, K) from small quantities of stemwood and needles of woody plants were developed. A 3.2- or 6.4-mm cobalt drill bit was used to shave samples from disks and increment cores of stemwood. For ion extraction, wood (ground or shavings) or needles were either homogenzied using a Tekmar Tissumizer or frozen and thawed (three times) in 0.01 M HCl. After filtration through a 0.45-μm nylon filter, the extract was analyzed for ion content using direct current plasma atomic emission spectrometry. Quality control samples of pine needles obtained from the National Institute of Standards and Technology, and individually pooled wood samples of red spruce (Picearubens Sarg.) and red oak (Quercusrubra L.), were used to compare these two methods of extraction with the most commonly used method of wet ash digestion. The results of either method of extraction (freezing–thawing or homogenization) were higher than or similar to those obtained by wet digestion. Direct use of drill shavings eliminates the need for making wood chips by hand and grinding in a Wiley mill. Moreover, both approaches are relatively safe, since they do not require the use of hot concentrated acids and strong oxidizing agents. These methods may be particularly useful for the analysis of major inorganic cations from extremely small size samples (25 mg) such as individual annual growth rings of mature trees.