The spectrophotometric determination of trace molybdenum (VI) after collection and elution as molybdate ion on protonated chitin

Collection and elution method for inorganic anion on protonated chitin has been applied to the spectrophotometric determination of molybdenum (VI). The molybdenum (VI) is collected as molybdate ion on a column of chitin in weak acidic medium which is easily eluted with a small volume of 0.1 M ammonia buffer solution (pH 10). The molybdenum (VI) in the eluent is determined by bromopyrogallol red-Zephiramine method spectrophotometrically. Beer's law is obeyed over the concentration range of 0.1-0.8 mug of molybdenum (VI) in 1 ml of eluent at 634 nm. The apparent molar absorptivity is 6x10(4) dm(3) mol(-1) cm(-1). The tolerance limits for WO(4)(2-), VO(3)(-), CrO(4)(2-) and Fe (III) is low, that is, 1-100 times that of molybdenum (VI), but some metal ions and common inorganic anions do not interfere in concentration range of 1000-5000 times that of molybdenum (VI). The present method can be applied to the determination of molybdenum (VI) in natural water samples.