Determination and characterization of molybdenum in natural water by solvent extraction

A rapid, sensitive and selective method is described for the determination of molybdenum in natural waters and environmental materials by polarized Zeeman atomic absorption spectrometry with a pyrolytic graphite-coated graphite furnace. For the separation and concentration of trace amounts of molybdenum(VI), the extraction behavior of molybdenum(VI)-8-quinolinolate complex with diisobutyl ketone(DIBK) was investigated. The high extractability of molybdenum with DIBK allows molybdenum to be concentrated about 200 fold or more with a single extraction at pH 3.5. The molybdenum absorbance was measured at the wavelength of 313.3 nm by using 20 mm3 of organic phase. The optimum conditions obtained at heating stages were as follows: drying for 30 s programmed from 150 to 200 deg C, charring at 500 deg C for 30 s, atomizing at 2800 deg C for 15 s and cleaning at 2900 deg C for 10 s. The detection limit, defined as twice the standard deviation of the blank value, was found to be 0.05 ng of molybdenum and the relative standard deviation was 1.5 % for 2 ng of molybdenum. Interferences of many metal ions can be effectively reduced by masking with EDTA and sodium fluoride. (author)