A miniaturized curcumin method for the determination of boron in solutionsand biological samples

Methods for the determination of boron require either sophisticated and exp ensive equipment (e.g. ICP-OES or ICP-MS) or a relatively large sample volu me (e.g. spectrophotometric methods). A modified and miniaturized spectroph otometric curcumin method is presented which allows the determination of bo ron in sample volumes of 50-150 mu l with a detection limit of 0.010 mg B l (-1). The calibration curve is linear up to a concentration of 3 mg B l(-1) . Interferences with other ions are eliminated by extraction of boron with 2-ethyl-1,3-hexanediol in chloroform Simultaneously, enrichment of boron in the sample can be performed within the same extraction step. Results show good reproducibility with a relative standard deviation of 1-5% at B concen trations between 0.05 and 0.40 mg B l(-1). In different types of solutions, recovery of added boron was in the range of 98 to 99%. For several plant m aterials containing from 18 to 58 mu g B (g dw)(-1), an overall relative st andard deviation of 4.5% was established. So far, the method has been succe ssfully applied to determine boron in waters, nutrient solutions, different plant parts (roots, stems an leaves) as well as in phloem sap and apoplast ic washing fluid of several plant species.