Dispersive liquid-liquid microextraction technique based on Solidification of floating organic drop for preconcentration and determination of molybdenum in water samples prior to Uv-Visible spectrophotometry

Molybdenum is a biologically and environmentally relevant trace element. It possesses variableoxidation states, ranging from +۲ to +۶, easily convertible into each other. However, the concentration levels inthese kinds of samples are usually low, in the μg kg range. Thus, highly sensitive techniques are required, namely,electrothermal atomic absorption spectrometry associated with a preconcentration step, in order to achieve betterdetection limits [۱]. In this work, a novel method based on dispersive liquid-liquid microextraction technique basedon solidification of a floating organic drop prior to UV-Vis spectrophotometry for determination of molybdenum attrace levels in environmental samples is proposed. The method is based on the reaction of Mo with thiocyanate(SCN-) as a chelating agent for formation of Mo(SCN)۵ in acidic medium. An appropriate mixture of acetone and ۱-undecanol was rapidly injected into an aqueous sample and the color red complex of molybdenum is then extractedwith ۱-undecanol. After centrifugation, the test tube was cooled for ۵ min and the solidified ۱-undecanol dropformed on the top of the solution was transferred into a micro-cuvette to be determined by UV-Visspectrophotometry. Absorbance of the complex was measured at ۴۷۰ nm. Several important relevant parameterssuch as the amount of ۱-undecanol and acetone, concentration of sulfuric acid and extraction time have beeninvestigated. Under optimum operating conditions, the calibration curve was plotted which was linear in theconcentration range of ۱۲ to ۱۰۰ ng mL-۱ of Mo. The limit of detection (LOD) of the method was obtained to be ۳.۸ng mL-۱ based on ۳sb/m. The relative standard deviation (RSD%) of the method was found to be ۳.۳% for tenreplicate measurement.The proposed method has been successfully applied for the determination of theMolybdenum in tap and well water samples with recoveries in the range of ۹۵-۱۰۳%.