Ionic liquid based dispersive liquid–liquid microextraction procedure for the spectrophotometric determination of copper using 3-dimethylamino rhodanine as a chelating agent in natural waters

Imidazolium-Modified Silica Gel for Highly Selective Preconcentration of Ag(I) from the Nitric Acid Medium

The ion-exchange behavior of an organomineral material with an imidazolium (1-methyl-3-(prop-2-yn-1-yl)-1H-imidazol-3-ium bromide)-modified silica gel was studied for the extraction of Ag(I) from nitric acid media. The extraction from multicomponent systems containing Fe(III), Co(II), Ni(II), Cu(II), Pb(II), and Mn(II) in 100- and 1000-fold molar excesses with respect to Ag(I) was shown to occur with high selectivity. Based on the data of X-ray diffraction and X-ray fluorescence spectroscopy for samples of modified silica gel, a mixed ion exchange–adsorption mechanism for the extraction of Ag(I) was proposed. The effect of the phase contact time and the concentration of nitric acid on the distribution coefficient of Ag(I) was studied. The selectivity factors of the extraction of Ag(I) from multicomponent systems containing foreign cations in 100- and 1000-fold molar excesses under steady-state and dynamic concentration conditions were calculated.

A simple and rapid technique for the determination of copper based on air-assisted liquid-liquid microextraction and image colorimetric analysis

In this study, a new, cheap, simple and rapid method for the determination of copper in water and food samples using air-assisted liquid-liquid microextraction and digital image decomposition into the primary colors Red (R), Green (G) and Blue (B) is introduced. In the proposed method, sodium diethyl-dithiocarbamate (Na-DDTC) and carbon tetrachloride (CCl4) were used as the chelating agent and extraction solvent, respectively. The digital images of the extraction phase were obtained using an Android mobile phone and analyzed using a free app (Color Grab). Then the value of the B channel was taken as the analytical signal. The effects of different parameters influencing the extraction efficiency were investigated and optimized. Under the optimal conditions, the limit of detection (LOD) and quantitation (LOQ) were 1.5 and 5 μg L-1, respectively. The repeatability of the proposed method, expressed as the relative standard deviation (RSD), was 4.53% for intra-day (n = 8, C = 100 μg L-1) and 5.66% for inter-day (n = 5) precision. The proposed method was applied for the determination of trace amounts of copper in rice, lettuce and water samples with satisfactory results validated by the Graphite Furnace Atomic Absorption Spectrometry technique.

Green Approaches to Sample Preparation Based on Extraction Techniques

Preparing a sample for analysis is a crucial step of many analytical procedures. The goal of sample preparation is to provide a representative, homogenous sample that is free of interferences and compatible with the intended analytical method. Green approaches to sample preparation require that the consumption of hazardous organic solvents and energy be minimized or even eliminated in the analytical process. While no sample preparation is clearly the most environmentally friendly approach, complete elimination of this step is not always practical. In such cases, the extraction techniques which use low amounts of solvents or no solvents are considered ideal alternatives. This paper presents an overview of green extraction procedures and sample preparation methodologies, briefly introduces their theoretical principles, and describes the recent developments in food, pharmaceutical, environmental and bioanalytical chemistry applications.

Evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets for the determination of triazole fungicides in water samples by high-performance liquid chromatography

A simple, rapid, and effective analytical procedure for determining three triazole fungicides (myclobutanil, epoxiconazole, and tebuconazole) in water samples is developed by high-performance liquid chromatography-diode array detection after evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets. The extraction procedure involves the sequential addition of the extraction solvent 1-dodecanol (low density), volatile solvent dichloromethane (high density), and calcium oxide to the aqueous sample (the latter reacting exothermically). The CaO reaction can promote the volatilization of the dichloromethane which disperses the 1-dodecanol as fine droplets in the aqueous sample due to the bubbles generated. Therefore, a dispersive solvent is not required. Then, the floating 1-dodecanol is solidified using an ice bath for easy separation from the sample. The variables (the volumes of extraction and volatile solvents, amounts of calcium oxide and sodium chloride, pH values, and extraction time) in the extraction procedure are further optimized. Under optimized conditions, the linearity ranges are 0.05-5 μg mL^-1 with correlation coefficients greater than 0.99. The limits of detection and quantification are 0.0051-0.0090 μg mL^-1 and 0.0169-0.0299 μg mL^-1, respectively. The recoveries of myclobutanil, epoxiconazole, and tebuconazole in tap, reservoir, and river water range between 77.6% and 104.4% with relative standard deviations ranging from 0.6% to 7.8%. Hence, the method was reliable for analysis of myclobutanil, epoxiconazole, and tebuconazole in water samples.