COLUMN PRECONCENTRATION IN THE SPECTROPHOTOMETRIC DETERMINATION OF PHOSPHORUS IN HUMAN HAIR, CHLORELLA, MUSSEL AND NATURAL-WATERS USING MOLYBDATE AND BRILLIANT GREEN WITH NAPHTHALENE AS AN ABSORBENT

A column preconcentration method has been established for the spectrop hotometric determination of phosphorus with the retention of the ion a ssociation complex produced from molybdophosphate and Brilliant Green on naphthalene packed in a simple glass-tipped tube. The phosphate ion reacts with molybdate to form an anionic molybdophosphate. This anion produces a water-insoluble ion association complex with cationic Bril liant Green in 0.45 hi H2SO4 medium, which is quantitatively retained on naphthalene. The solid mass is extracted from the column with 5 mt of dimethylformamide (DMF) and the absorbance was measured at 632 nm a gainst a reagent blank. A calibration curve was linear over the concen tration range 0.0.5-1.20 mu g of phosphorus in 5 mt of the final DMF s olution. Molar absorptivity and Sandell sensitivity were calculated to be 9.75 x 10(4) I mol(-1) cm(-1) and 3.18 x 10(-4) mu g cm(-2), respe ctively. Seven replicate determinations of solution containing 0.62 mu g of phosphorus gave a mean absorbance of 0.390 with a relative stand ard deviation of 0.49%. Interference due to various foreign ions has b een studied and the method has been applied to the determination of ph osphorus in standard biological materials and natural waters.