A novel separation/preconcentration technique based on ultrasonic dispersion liquid-liquid microextraction for determination of trace cobalt by flame atomic absorption spectrometry

Abstract

ABSTRACT. An improved method for the determination of trace cobalt in water samples has been developed using ultrasonic dispersion liquid-liquid microextraction (US-DLLME) prior to flame atomic absorption spectrometry (FAAS) analysis. In this method, cobalt was extracted into the fine droplets of carbon tetrachloride after chelate formation with the water soluble ligand, ammonium pyrrolidine dithiocarbamate (APDC). The fine droplets of carbon tetrachloride were formed and dispersed in the aqueous sample with the help of ultrasonic waves which accelerated the formation of the fine cloudy solution without using disperser solvents. Under optimum conditions, the calibration curve was linear in the range of 2.5-500 µg L -1 , with a detection limit of 0.8 µg L -1 . The relative standard deviation (RSD) for ten replicate measurements of 20 and 500 µg L -1 of cobalt were 3.3 and 2.2%. This proposed method was successfully applied to tap water, river water, and sea water, and accuracy was assessed through the analysis of certified reference water or recovery experiments. Operation simplicity, low cost, high enrichment factor, and low consumption of the extraction solvent are the main advantages of the proposed method.

Determination of Trace Amount of Lead in Industrial and Municipal Effluent Water Samples Based on Dispersive Liquid-Liquid Extraction

“…Limit of detection (lod) was calculated as 3 sb/m, where sb is the standard deviation of the blank and m is slope of the linear section of calibration graph; the lod value was 0.8 μg L −1 . The limit of quantification (loq) was 3.0 μg L −1 (obtained for S/N = 10).The enrichment factor of proposed method was 135 and it was calculated by the ratio of angular coefficients of the calibration curves with and without preconcentration [25]. The precision, expressed as a relative standard deviation (R.S.D, n = 10), was 2.8% for lead solution containing 50 ng mL −1 and 3.2% for a lead solution having 120 ng mL −1 .…”

“…In addition, Pb concentrations in imew samples are near or below the limit of detection of faas. Therefore, preconcentration and separation methods such as cloud point [24], microextraction [25], liquid-liquid extraction [26], solid phase extraction [27], single-drop microextraction [28,29] and dispersive liquid-liquid microextraction (dllme) [30] can solve the problems above and lead to simplified lead determination by faas. Dispersive liquid-liquid microextraction (dllme) is a miniaturization of the traditional lle technique, where the extractant phase is a water-immiscible solvent that can be directly immersed in the sample and dispersed by organic solvents or ultrasonic heating.…”