Spectrophotometric determination of molybdenum based on charge transfer complex in PVA medium

Determination of molybdenum in environmental samples

Determination of molybdenum in different kinds of environmental samples is often a challenging task for analysts. Its concentration is usually very low and the sample matrix may cause serious interferences during measurement. Therefore, preconcentration and separation methods should be used to solve these problems and render more sensitive, accurate and interference-free determination. Recent developments in sample treatment, such as solid phase and liquid-liquid extraction as well as coprecipitation are presented, including flow-based methodology. In addition, important extension and improvements in analytical methods for determinations of molybdenum are updated. Some examples of speciation analysis are also presented.

Kinetic Spectrophotometric Determination of Traces of Molybdenum(VI) by Its Inhibitory Effect on the Oxidation of 4-Hydroxycoumarine by Potassium Permanganate

The present paper describes a simple, selective and sensitive kinetic method for the determination of trace amounts of molybdenum(VI) based on its inhibitory effect on the reaction oxidation of 4-hydroxycoumarine by KMnO(4) in the presence of hydrochloric acid, at pH 1.75 at 25 degrees C. The rate of the indicator reaction was followed spectrophotometrically by measuring the decrease in the absorbance of KMnO(4) at 525 nm. The development method includes optimization of the reagent concentration and temperature. The calibration graph was linear in the range of concentrations from 20 to 200 ng/cm(3) of molybdenum(VI). The probable relative error was in the interval 3.10 - 10.52% for the concentration range of 200 - 20 ng/cm(3) molybdenum(VI), respectively. The interference effects of the foreign ions were determined to assess the selectivity of the method. The developed method was found to have relatively good selectivity, sensitivity, simplicity and rapidity. The proposed method was applied to the determination of molybdenum(VI) in a particular type of steel and alloy (hastelloy).

A novel spectrophotometric determination of trace copper based on charge transfer complex

A new type of colored complex, the charge transfer complex, was used to develop the spectrophotometric determination of copper. The method was based on the formation of a colored product, the charge transfer complex of copper substituted tungstophosphate with 3,3',5,5'-tetramethybenzidine (TMB), which was stabilized and sensitized by the addition of polyvinyl alcohol (PVA) in aqueous solution. The structure of copper substituted tungstophosphate was Keggin-type according to the results of infrared (IR) spectra. The optimum reaction conditions and other important analytic parameters had been investigated. Beer's law was obeyed in the copper(II) concentration range of 0.003-0.1 microg mL(-1), and the molar absorptivity at 660 nm is 2.54 x 10(5) L mol(-1) cm(-1). The proposed method was simple, selective, and sensitive. It was applied to the analytic samples with satisfactory results.