Cloud Point Extraction Preconcentration of Trace Cadmium as 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone Complex and Determination by Flame Atomic Absorption Spectrometry

A novel cyclic non-ligand dual-cloud point extraction for the preconcentration of cadmium(ii) through pH regulation in food and environmental matrices

Cd²⁺ was extracted through pH regulation instead of adding a complexant and the position of Cd²⁺ in the micelles was verified.

Adsorption of cadmium(II) ions from aqueous solution on exfoliated graphene nanosheets and its determination by flame atomic absorption spectrometry

In this study, we investigated the enrichment ability of exfoliated graphene nanosheets for determination of trace cadmium in water and vegetable samples with flame atomic absorption spectrometry. Various experimental parameters that could affect the extraction efficiency have been investigated. Under the optimum conditions, the enrichment factor of the method for the target analyte was 100. A liner response was achieved in the concentration range of 0.3–28.8 ng mL−1. The detection limit and precision of the method were 0.2 ng mL−1 and 0.8%, respectively. The proposed method was applied to determine the cadmium in water, onion, and tomato samples and recoveries of target analyte were in the range 97.6%–98.5%. All of these experimental results indicated that this new procedure could be applied for the determination of trace cadmium in real samples.

Complex-forming organic ligands in cloud-point extraction of metal ions: a review

Cloud-point extraction (CPE), an easy, safe, environmentally friendly, rapid and inexpensive methodology for preconcentration and separation of trace metals from aqueous solutions has recently become an attractive area of research and an alternative to liquid-liquid extraction. Moreover, it provides results comparable to those obtained with other separation techniques and has a greater potential to be explored in improving detection limits and other analytical characteristics over other methods. A few reviews have been published covering different aspects of the CPE procedure and its relevant applications, such as the phenomenon of clouding, the application in the extraction of trace inorganic and organic materials, as well as pesticides and protein substrates from different sources, or incorporation of CPE into an FIA system. This review focuses on general properties of the most frequently used organic ligands in cloud-point extraction and on literature data (from 2000 to 2012) concerning the use of modern techniques in determination of metal ions' content in various materials. The article is divided according to the class of organic ligands to be used in CPE.

Vortex-assisted ionic liquid microextraction coupled to flame atomic absorption spectrometry for determination of trace levels of cadmium in real samples

A simple and rapid vortex assisted ionic liquid based liquid-liquid microextraction technique (VALLME) was proposed for preconcentration of trace levels of cadmium. According to this method, the extraction solvent was dispersed into the aqueous samples by the assistance of vortex agitator. Cadmium preconcentration was mediated by chelation with the 8-hydroxyquinoline (oxine) reagent and an IL, 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim][PF6]) was chosen as the extraction solvent to extract the hydrophobic complex. Several variables such as sample pH, concentration of oxine, volume of [Omim][PF6] and extraction time were investigated in details and optimum conditions were selected. Under the optimum conditions, the limit of detection (LOD) was 2.9 μg L(-1) for Cd (ІІ) and relative standard deviation (RSD%) for five replicate determinations of 125 μg L(-1) was 4.1%. The method was successfully applied to the determination of cadmium in tap water, apple and rice samples.

Solid phase selective separation and green preconcentration of Cu, Zn, Pb and Cd in drinking water by using novel functionalized resin

A new solid — phase extraction sorbent was developed based on stepwise anchoring of two ligand molecules for the determination of copper, zinc, lead and cadmium in drinking water by flame AAS. Amberlite XAD-2 functionalized with 4′-(2-hydroxyphenylazo)-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one (HPAPyr) was utilized for preconcentration/separation of these elements. The sorbent was prepared by two successive azo coupling reactions. First, 2-aminophenol was anchored to the amino groups in the resin resulted from nitration followed by reduction. Then, the resulted 2-aminophenol functionalized resin was further diazotized and coupled to the pyrazolone compound and the final product HPAPyr-XAD-2 was characterized by IR and elemental analysis. The optimum pH range for sorption, shaking time, exchange capacity, sample flow rate, preconcentration factor and interference from co-existing ions were investigated. All metal ions were quantitatively desorbed from the resin by 4.5 mol L−1 nitric acid solution. The sorbent provides limit of detection within the range 0.9–3.3 µg L−1 and concentration factor up to 250. The procedure was validated by analysis of certified material NIST-SRM 1577b. Application to drinking water showed satisfactory results with relative standard deviation RSD ≤ 8.5%.

Application of multiwalled carbon nanotubes treated by potassium permanganate for determination of trace cadmium prior to flame atomic absorption spectrometry

In this study we investigated the enrichment ability of oxidized multiwalled carbon nanotubes (MWCNTs) and established a new method for the determination of trace cadmium in environment with flame atomic absorption spectrometry. The MWCNTs were oxidized by potassium permanganate under appropriate conditions before use as preconcentration packing. Parameters influencing the recoveries of target analytes were optimized. Under optimal conditions, the target analyte exhibited a good linearity (R2=0.9992) over the concentration range 0.5-50 ng/ml. The detection limit and precision of the proposed method were 0.15 ng/ml and 2.06%, respectively. The proposed method was applied to the determination of cadmium in real-world environmental samples and the recoveries were in the range of 91.3%-108.0%. All these experimental results indicated that this new procedure could be applied to the determination of trace cadmium in environmental waters.