A direct and rapid leaf water extraction method for isotopic analysis

Abstract

Isotopic measurements of leaf water have provided insights into a range of ecophysiological and biogeochemical processes, but require an extraction step which often constitutes the major analytical bottleneck in large-scale studies. Current standard procedures for leaf water analysis are based on cryogenic vacuum or azeotrophic distillation, and are laborious, require sophisticated distillation lines and the use of toxic materials. We report a rapid technique based on centrifugation/filtration of leaf samples pulverised in their original sampling tubes, using a specifically adapted, simple apparatus. The leaf water extracts produced are suitable for isotopic analysis via pyrolysis gas chromatography isotope ratio mass spectrometry (PYR/GC/IRMS). The new method was validated against cryogenic vacuum distillation and showed an overall accuracy of +/-0.5 per thousand (nine grouped comparisons, n = 110) over a range of 21 per thousand. Effects due to the presence of soluble carbohydrates were near the detection limits for most samples analysed, and these effects could be corrected for (the extracted soluble organics could also be used for isotopic analysis). The extraction time for a routine eight-sample subset was reduced from 4 h (cryogenic distillation) to 45 min, limited only by the size of the centrifuge(s) used. This method provides a rapid, low-cost and reliable alternative to conventional vacuum and other distillation methods that can alleviate current restrictions on ecosystem- and global-scale studies that require high-throughput leaf water isotopic analysis.

Validation and application of a cryogenic vacuum extraction system for soil and plant water extraction for isotope analysis

“…Our extraction duration of 180 min exceeded the extraction times of the abovementioned studies. The same was true for the applied pressure level (0.3 Pa), which was at the lower end of other vacuum extraction procedures ranging from 13 Pa (Goebel and Lascano, 2012), 8.0 Pa (West et al, 2006), 3.07 Pa (Koeniger et al, 2011), 1.3 Pa (Vendramini andSternberg, 2007) to 0.13 Pa (Peters and Yakir, 2008). We conclude that either longer extraction times (> 180 min), or higher extraction temperatures (> 90…”

“…To determine the isotopic signature of water, it is necessary to separate or extract the water from other components of the sample material (plant roots, stems and leaves, soil). In recent decades, several extraction methods have been developed: azeotropic distillation with various toxic substances such as toluene, hexane, and kerosene (Revesz and Woods, 1990;Thorburn et al, 1993), mechanical squeezing (Wershaw et al, 1966;White et al, 1985), cryogenic vacuum extraction (Dalton, 1988;Dawson and Ehleringer, 1993;Sala et al, 2000;West et al, 2006;Goebel and Lascano, 2012), the batch-method for stem water extraction (Vendramini and Sternberg, 2007), the modified vacuum extraction technique of Koeniger et al (2011), centrifugation with or without immiscible heavy liquids (Mubarak and Olsen, 1976;Batley and Giles, 1979;Barrow and Whelan, 1980;Peters and Yakir, 2008) as well as different equilibrium techniques especially for soil samples (Scrimgeour, 1995;Hsieh et al, 1998;McConville et al, 1999;Koehler et al, 2000;. Out of these, cryogenic vacuum extraction is the most widely utilized method (Ingraham and Shadel, 1992;West et al, 2006;Vendramini and Sternberg, 2007;Koeniger et al, 2011).…”

Stable Isotope Techniques and Applications for Primatologists

“…Collecting plant water in the field is a difficult task and is beyond the scope of this paper. Details about collecting and extracting plant water are available elsewhere (Cernusak et al 2004;Peters and Yakir 2008). Fortunately, the δ 18 O values of dried plant material and plant water are correlated (Barbour 2007;Cernusak et al 2004).…”

Intercomparison of soil pore water extraction methods for stable isotope analysis

“…Orlowski et al,1 Many plant species also expel alcohols along with the extracted water and can subsequently only be analyzed on IRMS (costly and time consuming) instead of the faster, less expensive OA-ICOS (West et al, 2010). Also, thus far, none of the isotope effects associated with soils have been observed during plant water extractions (Koeniger et al, 2011;Munksgaard et al, 2014;Peters and Yakir, 2008). Therefore, plant water extractions are assumed not to be problematic in this regard.…”

“…Further, soil water isotopic composition can be determined via direct equilibration techniques. Laboratory methods include: azeotropic distillation (Revesz and Woods, 1990;Thorburn et al, 1993), microdistillation (Kendall and Coplen, 1985), mechanical squeezing (Böttcher et al, 1997;Wershaw et al, 1966;White et al, 1985), cryogenic vacuum extraction (Dalton, 1988;Goebel and Lascano, 2012;Orlowski et al, 2013;Dawson and Ehleringer, 1993;West et al, 2006;Ehleringer et al, 2000), a modified vacuum extraction technique (Koeniger et al, 2011), centrifugation with or without immiscible heavy liquids (Mubarak and Olsen, 1976;Batley and Giles, 1979;Barrow and Whelan, 1980;Peters and Yakir, 2008), Picarro's Induction Module (Picarro, 2015), microwave extraction (Munksgaard et al, 2014), or the accelerated solvent extraction technique (Zhu et al, 2014). Field-based methods include: wick samplers (e.g.…”