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Abstract
An analytical method employing hydrophobic interaction chromatography (HIC) combined with parallel detectors, provided a quantitative method for the determination of soluble carbohydrates in conifer needle tissues. Evaporative light‐scattering detection (ELSD), in parallel with atmospheric pressure chemical ionization mass spectrometry (APCI‐MS), yielded excellent quantitative and spectral data. Non‐linear detector responses of the ELSD were overcome by performing a simple exponential transformation of the detector response data. The transformation allowed for single‐point calibrations that yielded quantitative results with excellent accuracy and precision. Method recovery and precision were determined from maltose‐fortified conifer tissues. Maltose recovery was 101.7% [relative standard deviation (RSD) = 9.74%] for homogenized Douglas‐fir (Pseudotsuga menziesii) needle tissue fortified at 1.01 mg/g and 107.8% (RSD = 2.47%) for tissue fortified at 10.1 mg/g. Maltose recovery from fortified western redcedar (Thuja plicata) tissues (7.60 mg/g) was 93.0% (RSD = 3.0%). The method limit of detection (MLOD) was 0.24 mg/g for maltose in Douglas‐fir. The method was employed for the quantitative analysis of soluble carbohydrates in Douglas‐fir needles, collected from new and previous‐year's growth for 7 weeks after the emergence of new growth (bud break). Needles collected from dormant trees were also analyzed. The concentrations of fructose and glucose were consistently greater in previous‐year's growth vs. new and dormant growth.
Acknowledgments
Mention of specific products does not constitute endorsement by the United States Department of Agriculture. The authors thank Julia Figuerora for her assistance with sample preparation.