Boron isotope dilution in cellular fractions of coffee leaves evaluated by inductively coupled plasma mass spectrometry with direct injection nebulization (DIN-ICP-MS)

Enriched B-10 (94.14 atom %) was supplied to coffee plantlets for three months. Then boron isotope ratios were determined in the leaf cell compartments, cell wall, nuclei and chloroplast, after a sub-cellular fractionation procedure. The isotopic measurements were performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) provided with a direct injection nebulizer (DIN), introducing a sample volume of 50 muL. Isotopic ratios from 1.002 to 1.326 were determined with precision characterized by RSD lower than 1.5% for the enriched cell fractions with B concentrations ranging from 3.3 to 10.8 mug g(-1). The detection limit (3sigma) was 0.5 ng B mL(-1). The average enrichments in B-10 atom % found in the cell walls, nuclei and chloroplasts were 46.7, 44.5 and 48.8, respectively.