IODINE DETERMINATION IN PLANT MATERIALS

Germany is reported to be an iodine deficient region of the world. The refore investigations of the iodine concentration in plants and soils are of particular importance. The low concentration of iodine (mu g an d ng levels) in plant and soil samples, can be determined by photometr y based on the SANDELL-KOLTHOFF-Reaction, the reduction of Ce(IV) by A s(III) catalysed by iodine. The reaction, essentially depending on tim e and temperature, can also be affected by the ions, such as: Cl-, NO2 -, SCN-, Fe2+, BrO3-, MnO4-, Ag+, CN-, Hg+ and metals like Os. Using t he alkaline dry ashing method by adding KOH and ZnSO4, the digestion w ith the calorimetric bomb and the SCHONIGER digestion are gives reliab le results for iodine determination for use in conjunction with photom etric analytical techniques. For this investigation, the influence of iodine fertilisation on the iodine concentration of cress (Lepidium sa tivum) was determined by a pot experiment in which different amounts o f iodine were added. The iodine fertiliser used was natural Caliche. T he results show a very close correlation between iodine supply and the iodine concentration in cress which increased to more than 30 mg/kg d ry matter.