Determination of some metal ions by flame-AAS after their preconcentration using sodium dodecyl sulfate coated alumina modified with 2-hydroxy-(3-((1-H-indol 3-yle)phenyl) methyl) 1-H-indol (2-HIYPMI)

Highly Blue-fluorescent Carbon Quantum Dots Obtained from Medlar Seed for Hg2+ Determination in Real Water Samples

The carbon quantum dots (CQDs) have been prepared from medlar seeds with pyrolysis method in an oven at 300 °C. UV-vis absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR) spectroscopy, x-ray diffraction (XRD) technique, x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used in the characterization of CQDs. CQDs, give a strong blue fluorescence under UV lamp (at 365 nm), have a quantum yield of 12.2%. The influence of metal ions such as K+, Mg2+, Ca2+, Be2+, Cr3+, Mn2+, Ni2+, Ag+, Hg2+, and Al3+ on the fluorescence properties of the CQDs was investigated by means of emission spectrophotometry. CQDs altering fluorescence characteristics depending on the excitation wavelength show selectivity for Hg2+ ions with outstanding fluorescence quenching among the tested metal ions. Based on these results, a new fluorimetric method has been developed for the determination of Hg2+ in real water samples. The linear range of method is 1.0 to 5.0 mgL- 1. Limit of detection and limit of quantification are 0.26 and 0.79 mgL- 1, respectively. The proposed method has been successfully used in determination of Hg2+ ions in tap, sea, and stream water samples with application of addition-recovery experiments.

Application of a novel poly(SMAm)-Tris-Fe3O4 nanocomposite for selective extraction and enrichment of Cu(I) /Cu(II) from beer, soft drinks and wine samples, and speciation analysis by micro-volume UV-Vis spectrophotometry

In this study, a novel functional nanocomposite was synthesized, characterized and selectively used in pH-controlled separation, pre-concentration and speciation analysis of Cu(I) and Cu(II) from sample matrices where extraction is assisted, facilitated and greatly enhanced by ultrasound energy. The hydrophilic composite material functionalized with tris(2-hydroxymethyl)aminomethane (Tris) and Fe₃O₄ NPs was characterized in detail by ATR-FT-IR, ¹H NMR, XRD, EDX peaks and SEM images. After optimization of the main variables influencing extraction efficiency such as pH, volumes of buffer, modified copolymer in acetone, CTAB and Triton X-114 at fixed concentrations including sonication conditions, the Cu(I) and Cu(II) were monitored against a blank at 347 nm by micro-volume UV-vis spectrophotometer. A good linearity was obtained in the range of 2-140 and 5-150 μg L^-1 for Cu(II) and Cu(I) with r² ≥ 0.993. The limits of detection (LODs) of 0.66 and 1.60 μg L^-1 for each analyte, were obtained from a pre-concentration of 70-fold. After validation, the method was applied to speciation of Cu(I), Cu(II), and total Cu in the pre-treated and diluted beverage samples before and after pre-oxidation of Cu(I) to Cu(II) due to be more sensitive of extraction process to Cu(II) at pH 6.0. The results were also compared with those obtained by FAAS analysis to ensure the reliability of the results. It was observed that there was a statistically good agreement between the results of both methods.

Solid phase extraction of Cd, Pb, Ni, Cu, and Zn in environmental samples on multiwalled carbon nanotubes

A simple and sensitive solid phase extraction (SPE) method on multiwalled carbon nanotubes (MWCNTs) is presented for the determination of cadmium, lead, nickel, copper, and zinc at trace levels combined with flame atomic absorption spectrometry. The effects of parameters like pH, sample volume, sample and eluent flow rates, eluent concentration, and volume and type of eluent on the recovery of trace elements was examined. The metals retained on the nanotube at pH 6.5 as α-benzoin oxime complexes were eluted by 10 mL 2 M HNO3 in acetone. The influence of matrix ions on the developed method was also evaluated. The preconcentration factor of the method was found to be 50. The detection limits for Cd(II), Pb(II), Ni(II), Cu(II), and Zn(II) were found as 1.7, 5.5, 6.0, 2.3, and 2.4 μg L(-1), respectively. To test the accuracy of the method, the method was applied to TMDA-70 fortified lake water and Spinach 1570A standard reference materials. Addition recovery studies were applied to tap water and cracked wheat samples, and determination of the analyte elements was carried out in some food samples with good results.

Preconcentration procedures for the determination of chromium using atomic spectrometric techniques: A review

Chromium is one of the regulated toxic metals in the environment. Naturally, this element exists mainly in two oxidation: Cr(III) and Cr(VI). In general, Cr(VI) is more toxic than Cr(III). Cr(VI) affects human physiology, accumulates in the food chain and causes severe health problems ranging from simple skin irritation to lung carcinoma. Hence, the determination of chromium traces as well as its speciation in environmental samples is a very important task. In recent years, several preconcentration methods such as coprecipitation, liquid-liquid extraction, dispersive liquid-liquid microextraction, cloud point extraction, and solid phase extraction have been developed and widely used. The aim of this study is to review the recent literature (mainly last 5 years) on the preconcentration technologies those have been used in chromium removal before the determination step by atomic spectrometric techniques. Their advantages and limitations in application are also evaluated.