Determination Of Molybdenum In Water Research Articles

Voltammetric Determination of Molybdenum Using Polymer Film Modified Pencil Graphite Electrodes

A new indirect voltammetric method for the determination of molybdenum in water samples and food supplements using various polymer film modified pencil graphite electrodes (PFMPGEs) was described. Poly Eriochrome black T film modified pencil graphite electrodes (p-EBT/PGE), poly xylenol orange modified pencil graphite electrodes (p-XO/PGE) and poly methyl red modified pencil graphite electrodes (p-MR/PGE) were used for this purpose. The electrodes were characterized by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The method is based on measuring the oxidation current of Tiron in the Mo-Tiron complex at the PFMPGEs. The limits of detection and analytical ranges for p-EBT/PGE, p-XO/PGE, and p-MR/PGE were estimated to be 2.60, 3.50, and 1.56 μg/L and 8.66 to 100, 11.68 to 100, and 5.20 to 100 μg/L, respectively. The averages of relative standard deviation values for low, medium and high molybdenum content for p-EBT/PGE, p-XO/PGE and p-MR/PGE were 5.46%, 6.30%, and 4.69%, respectively. Selectivity studies were also performed for all electrodes. The method was applied to the determination of molybdenum in water and food supplement samples. The results were statistically evaluated, and the accuracy of the proposed method was demonstrated.

The determination of molybdenum in water and biological samples by graphite furnace atomic spectrometry after polyurethane foam column separation and preconcentration

A system for molybdenum separation and enrichment aiming its determination in water and biological samples by graphite furnace atomic absorption spectrometry (GFAAS) is proposed. The procedure is based on the sorption of the molybdenum (VI) thiocyanate complex onto a mini-column packed with polyurethane foam (PUF). The elution is accomplished by a 3.0 mol l −1 nitric acid solution. Flow variables were optimized and an enrichment factor of 10 as well as a limit of detection (LOD) (3 s) of 0.08 μg l −1 in the sample solution were achieved. The coefficient of variation showed values of 3 and 2% for molybdenum solutions of 2.0 and 10.0 μg l −1, respectively. The accuracy of the method was confirmed by the good concordance between found and certified values in the analysis of certified reference materials (CRMs) (CASS-3 Nearshore Seawater, NIST 1547 Peach Leaves, NIST 1515 Apple Leaves and NIST 1572 Citrus Leaves). The procedure was also applied for the molybdenum determination in mineral waters as well as in produced water samples. The results obtained for the mineral water samples compared well with those obtained by ICP-MS. Concerning the produced water samples, in spite of their large salinity, recoveries of 90 to 120% at the 1 μg l −1 were observed.

Electrothermal atomic absorption spectrometric determination of molybdenum in water, human hair and high-purity reagents with flow injection on-line coprecipitation preconcentration

A flow injection (FI) on-line coprecipitation preconcentration system has been developed for the electrothermal atomic absorption spectrometric determination of trace or ultratrace amounts of molybdenum in water, human hair and high-purity sodium chloride. Molybdenum was coprecipitated with FeII–pyrrolidin-1-yldithioformate (pyrrolidinedithiocarbamate) in 0.4 mol l–1 HCl medium and collected on the walls of a knitted reactor. After washing, the precipitate was dissolved with 50 µl of isobutyl methyl ketone (IBMK) and the IBMK concentrate zone was directly introduced into the graphite tube from the FI system. Electrothermal atomic absorption spectrometric determination of the concentrated analyte was carried out in parallel with the next preconcentration cycle. An enrichment factor of 22 was achieved with a 30 s loading time at a sample flow rate of 2.3 ml min–1. The detection limit (3s) was 0.04 µg l–1 for a 30 s sample loading time and 0.02 µg l–1 for a 60 s loading time. A precision of 3.1% relative standard deviation was obtained at the 1.3 µg l–1 level. Recoveries of spiked molybdenum in tap water, sea-water and sodium chloride reagent were in the range 94–104%. The result obtained for a human hair certified reference material was in good agreement with the certified value.

Polarographic determination of molybdenum in water

AbstractA direct method for determination of Mo(VI) at trace levels in water samples is described. The reaction used, between salycilaldoxime, bromate, and Mo(VI), produces a differential pulse catalytic peak proportional to the Mo(VI) concentration. A detection limit of 0.12 μg/L can be achieved. The procedure, which has been applied to several natural and tap water samples by means of a standard additions method, achieved satisfactory results. A computer‐based system that controls these experiments is also discussed.