Utilization of Cloud-Point Preconcentration for Spectrophotometric Determination of Trace Amounts of Molybdenum(VI) in Plants and Water Samples

A cloud-point preconcentration process using micelle of the non-ionic surfactant Triton X-114 to extract Mo(VI) from aqueous solutions was investigated. The method is based on the color reaction of molybdenum with 5-(2-benzothiazolyl-azo)8-hydroxy-quinoline (BTAHQ) in the presence of potassium bromide at pH 1.75 glycine/HCl buffer media and micelle-mediated extraction of complex. The optimal extraction and reaction conditions (e.g., surfactant concentration, reagent concentration and effect of time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration and improvement factors) were obtained. Linearity was obeyed in the range of 0.2–180 ng/mL of molybdenum(VI) ion and the detection limit of the method was 0.06 ng/mL. The relative standard deviation (RSD) and relative error for six replicate measurements of 100 ng/mL Mo(VI) were 0.88 % and 1.5 %, respectively. Preconcentration and improvement factors were found to be 250 and 5.0, respectively. The interference effect of some anions and cations was also tested. The method was applied to the determination of molybdenum(VI) in plants and water samples.