A highly sensitive and selective spectrofluorimetric method for the determination of molybdenum at pico-trace levels in various matrices using N-(pyridin-2-yl)-quinoline-2-carbothioamide

Abstract

A new spectrofluorimetric reagent N-(pyridin-2-yl)-quinoline-2-carbothioamide (PQTA) has been synthesized and characterized. A very simple, ultra-sensitive, and highly selective, and non-extractive new spectrofluorimetric method for the determination of molybdenum at pico-trace levels using PQTA has been developed. This novel fluorimetric reagent PQTA, becomes oxidized in a slightly acidic (0.0025-0.05 M H2SO4) solution with molybdenum (VI) in absolute ethanol to produce a highly fluorescent oxidized product (λex = 300 nm; λem= 377 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity (0.0025-0.0500 M H2SO4) for the period between 2 min and 24 h. Linear calibration graphs were obtained for 0.001-600 μg/L of Mo having a detection limit of 0.15 ng/L; the quantification limit of the reaction system was found to be 1.5 ng/L and the RSD was 0-2%. A large excess of over 60 cations, anions, and complexing agents like chloride, phosphate, azide, tartrate, oxalate, and SCN- etc. do not interfere in the determination. The developed method was successfully used in the determination of molybdenum in several Certified Reference Materials (Alloys, steel, serum, bovine liver, drinking water, soil, and sediments) as well as in some environmental waters (Potable and polluted), biological fluids (Human blood, urine, hair, and milk), soil samples and food samples (Vegetables, rice, and wheat) solutions containing both molybdenum (VI) and molybdenum (V) ions. The results of the proposed method for assessing biological, food and vegetable samples were comparable with ICP-OES and AAS were found to be in excellent agreement.

Development of a new highly sensitive and selective spectrophotometric method for the determination of selenium at nano-trace levels in various complex matrices using salicylaldehyde-orthoaminophenol

“…Therefore, this method will be successfully applied to the routine monitoring of trace and ultra-trace amounts of selenium in real, environmental, biological, soil, food and pharmaceutical samples. It is a new method needs neither heating nor extraction to organic phase, works satisfactorily and could be an alternative method for the rapid determination of selenium in a wide variety of sample solutions and found superior to spectrophotometric methods described in different literature [73][74][75][76][77][78][79][80][81][82].…”

A new simple, highly sensitive and selective spectrofluorimetric method for the speciation of thallium at pico-trace levels in various complex matrices usingN-(pyridin-2-yl)-quinoline-2-carbothioamide

“…PQCTA has been reported as a spectrouorimetric reagent but, to our knowledge, it has not been used previously for the simultaneous determination of Tl I and Tl III in a uorescence system. The method possesses distinct advantages over existing methods, [25][26][27][28][29][30][31][32][44][45][46][47][48][49] as shown in Table 1, with respect to several analytical parameters (Table 1). The method is based on the oxidative reaction of non-uorescent PQCTA in a slightly acidic (0.0025-0.05 M H 2 SO 4 ) solution with Tl III in the presence of ethanol to produce a highly uorescent oxidized product, followed by the direct measurement of the uorescence intensity in an aqueous solution at room temperature.…”