CORRECTION OF IRON INTERFACE IN THE SPECTROPHOTOMETRIC FLOW-INJECTIONCATALYTIC DETERMINATION OF MOLYBDENUM IN PLANTS

Iron interference in the spectrophotometric catalytic determination of molybdenum based on the iodide-hydrogen peroxide reaction can be corr ected by using sulphosalicylic acid as masking and color-forming reage nt. The catalytic influence of iron ions is circumvented to the extent of about 90% and correction of any remaining iron ions is possible by monitoring the colored iron(III)-salicylate complex at 490 nm. In thi s way, iron is also determined. With the proposed system, molybdenum c an be determined in plant and food digests within the 0-100 mu g Mo l( -1) range in the presence of up to 25 mg Fe l(-1), at a sampling rate of about 50 determinations h(-1). The relative standard deviation of 1 0 consecutive measurements was estimated as <2%. Results for samples w ere comparable with those obtained by graphite furnace atomic absorpti on spectrometry. In addition, recoveries within the range 94-100% were calculated.